The avian visual "Wulst" is a target of the ascending thalamofugal visual pathway. In pigeons (Columba livia), lesion damage to the Wulst has little effect on simple visual discriminations, but impairs performance on tasks such as reversal learning. We recorded the responses of single Wulst neurons as pigeons were trained on the acquisition and subsequent reversal of a visual discrimination. As such, responses of pigeon Wulst neurons indicate a role in representing aspects of learning as much as the physical/perceptual properties of visual stimuli..  

The Wulst of birds, which is generally considered homologous with the isocortex of mammals, is an elevation on the dorsum of the telencephalon that is particularly prominent in predatory species, especially those with large, frontally placed eyes, such as owls. The Wulst, therefore, is largely visual, but a relatively small rostral portion is somatosensory in nature. In barn owls, this rostral somatosensory part of the Wulst forms a unique physical protuberance dedicated to the representation of the contralateral claw. These results indicate the existence in this species of a "classical" trisynaptic somatosensory pathway from the body periphery to the telencephalic Wulst, via the dorsal thalamus, one that is likely involved in the barn owl's predatory behavior.  

A significant number of neurons in the rostral dorsal cortex followed a deep (earlier arising) to superficial (later arising) pattern of neurogenesis, similar to that in the avian Wulst or in the mammalian isocortex.  

Using both conventional statistics and modern comparative methods, we tested whether the relative size of the Wulst and optic tectum (TeO) were significantly correlated with orbit orientation, binocular visual field width and eye size in birds using a large, multi-species data set. In addition, we tested whether relative Wulst and TeO volumes were correlated with axial length of the eye. The relative size of the Wulst was significantly correlated with orbit orientation and the width of the binocular field such that species with more frontal orbits and broader binocular fields have relatively large Wulst volumes. In addition, both relative Wulst and TeO volume were weakly correlated with relative axial length of the eye, but these were not corroborated by independent contrasts. Overall, our results indicate that relative Wulst volume reflects orbit orientation and possibly binocular visual field, but not eye size..  

Endocranial morphology of the moa species examined was similar to that for non-New Zealand ratites, with proportionally similar sizes of the olfactory bulb, Wulst, vagal and maxillomandibular foramina, suggesting that the moa occupied similar diurnal niches with comparable sensory specializations to the emu, rhea and ostrich.  

The avian retinothalamofugal pathway reaches the telencephalon in an area known as visual Wulst. The goal of the present study was to assess quantitatively the directional selectivity and motion integration capability of visual Wulst neurones, aspects that have not been previously investigated. Overall, our data suggest that, as in the mammalian primary visual cortex, the visual Wulst neurones of owls signal the local orientated features of a moving object.  

Furthermore, Cluster N seems to be a specialized part of the visual Wulst.  

Imprinting object is recognized and processed in the visual Wulst, and the memory is stored in the intermediate medial mesopallium in the dorsal pallium of the telencephalon. These results suggest that the activation of CCK cells in the visual Wulst as well as in the intermediate medial mesopallium by visual stimuli is indispensable for the acquisition of visual imprinting..  

RESULTS: A lesion in the visual Wulst, which is similar functionally to the mammalian visual cortex, caused anterograde amnesia in visual imprinting behavior. Since the color of an object was one of the important cues for imprinting, we investigated color information processing in the visual Wulst. Intrinsic optical signals from the visual Wulst were detected in the early posthatch period and the peak regions of responses to red, green, and blue were spatially organized from the caudal to the nasal regions in dark-reared chicks. This spatial representation of color recognition showed plastic changes, and the response pattern along the antero-posterior axis of the visual Wulst altered according to the color the chick was imprinted to. CONCLUSION: These results indicate that the thalamofugal pathway is critical for learning the imprinting stimulus and that the visual Wulst shows learning-related plasticity and may relay processed visual information to indicate the color of the imprint stimulus to the memory storage region, e.g., the intermediate medial mesopallium..  

Here, we present data on species variation in brain and telencephalon size and features of the Wulst, the neuroanatomical substrate that subserves stereopsis, in a putative sister-group to owls, the order Caprimulgiformes. The owlet-nightjars and frogmouths shared almost identical relative brain, telencephalic and Wulst volumes as well as overall brain morphology and Wulst morphology with owls. Specifically, the owls, frogmouths and owlet-nightjars possess relatively large brains and telencephalic and Wulst volumes, had a characteristic brain shape and displayed prominent laminae in the Wulst. In contrast, potoos and nightjars both had relatively small brains and telencephala, and Wulst volumes that are typical for similarly sized birds from other orders. The Oilbird had a large brain, telencephalon and Wulst, although these measures were not quite as large as those of the owls. This gradation of owl-like versus nightjar-like brains within caprimulgiforms has significant implications for understanding the evolution of stereopsis and the Wulst both within the order and birds in general..  

Unilateral injections of RITC made into the telencephalic visual Wulst resulted in the retrograde (1) first-order labeling (FOL) of dorsal thalamic (n.  

Advances in our understanding of comparative neuroanatomy and the genesis of mammalian SWs suggest that the absence of SWs in reptiles is due to limited connectivity within the pallium, the dorsal portion of the telencephalon that includes the mammalian neocortex, reptilian dorsal cortex and avian Wulst (hyperpallium), as well as the dorsal ventricular ridge in birds and reptiles and the mammalian claustrum and pallial amygdala.  

Retrograde tracer injections into the VLT revealed an ipsilateral forebrain input from the visual Wulst, from subregions of the arcopallium, and bilateral afferents from the optic tectum.  

The rostral dorsolateral aspect of nucleus dorsomedialis anterior thalami and the dorsal aspect of nucleus dorsolateralis pars medialis are partially comparable to the mammalian intralaminar nuclei, sharing connections to non-limbic 'corticoid' areas (the Wulst), and the reticular thalamic nuclei..  

Previous studies in pigeons using anterograde tracers have shown that both nBOR and LM receive input from the visual Wulst, the putative homolog of mammalian primary visual cortex. After injections of the retrograde tracer cholera toxin subunit B (CTB) into either LM or nBOR, retrograde labeling in the telencephalon was restricted to the hyperpallium apicale (HA) of the Wulst. In summary, our results suggest that the nBOR and LM receive input from different areas of the Wulst.  

Whereas some telencephalic areas that have not been regarded as limbic were also LAMP-rich (e.g., the hyperpallium intercalatum and densocellulare of the Wulst, the mesopallium, and the intrapeduncular nucleus), most nonlimbic telencephalic areas were LAMP-poor (e.g., field L, the lateral nidopallium, and somatic basal ganglia).  

By injecting a single 60 microg dose of corticosterone into the eggs of domestic chicks on day 18 of incubation, we have shown that elevated levels of this hormone affect the development of asymmetry in the visual projections from the thalamus to the Wulst regions in the left and right hemispheres of the forebrain. Pre-hatching exposure to light leads to more projections from the left side of the thalamus to the right Wulst than from the right side of the thalamus to the left Wulst, as confirmed here by injection of the tracers Fluorogold and Rhodamine into the left and right Wulst followed by counting the number of labelled cell bodies in the thalamus (asymmetry greater in males than females). The corticosterone-treated group had fewer projections from the left side of the thalamus to the right Wulst than did the controls.  

A third type is composed of two species, the tawny frogmouth (Podargus strigoides) and an owl, both of which share extremely large Wulst volumes.  

Because lidocaine injections into the visual Wulst produced a significant reduction of late response components only, neurons with long latencies were probably activated via a top-down telencephalotectorotundal system.  

Experiment 1 examined the role of the visual Wulst and the ectostriatum in a far-field pattern discrimination task in a large open arena. Control pigeons, pigeons with ectostriatum lesions, and pigeons with Wulst lesions were trained to discriminate between four patterns within the arena. By contrast, Wulst-lesioned pigeons were severely impaired in the pattern discrimination task in the open arena and performed poorer than control pigeons and pigeons with ectostriatum lesions. Statistical analyses of regional contributions to the observed impairment identified the left visual Wulst and bilateral hyperstriatum ventrale, which lies outside the Wulst, as interesting areas. Wulst-lesioned pigeons were able to learn the task and performed at a level no different from control pigeons. The results of these experiments support the proposal that the Wulst may be important for processing far-field information..  

The sectors of the hyperstriatum composing the Wulst (i.e., the hyperstriatum accessorium intermedium, and dorsale), the hyperstriatum ventrale, the neostriatum, and the archistriatum have been renamed (respectively) the hyperpallium (hypertrophied pallium), the mesopallium (middle pallium), the nidopallium (nest pallium), and the arcopallium (arched pallium).  

In addition to retinal afferentation, both the nBOR and LM receive afferents from the Wulst, which is thought to be the avian homolog of the primary visual cortex. We examined the effects of Wulst electrical stimulation on the activity of LM neurons and recorded the directional and spatiotemporal tuning of LM neurons in pigeons before, during, and after the Wulst was temporarily inactivated by lidocaine injection. In response to Wulst electrical stimulation, LM neurons showed either short-latency excitation followed by longer-latency inhibition (W+ cells), or only a longer-latency inhibition (W- cells). The effects of Wulst stimulation did not correlate with either the directional or spatiotemporal tuning of the LM neurons. When the Wulst was temporarily inactivated by lidocaine neither the directional nor spatiotemporal response properties of LM neurons were affected. The possible functions of the projection from the Wulst to the LM are discussed..  

Optic transmission by these cells may be modulated by the GABA-immunopositive terminals from various local circuit neurons, and very probably from GABAergic myelinated fibres as well, which may originate from the contralateral nLMmc and/or the visual Wulst..  

However, the pigeon and rat HF reside in different forebrain environments characterized by a Wulst and neocortex, respectively.  

The avian telencephalon has two visual areas, (1) a 'Wulst' that consists of hyperstriatum accessorium, hyperstriatum intercalatus superior and hyperstriatum dorsale, and (2) the ectostriatum. Deficits in visual discrimination have been observed after ectostratal lesions but not after Wulst lesions. In the present experiments, the cognitive functions of the Wulst in pigeons were examined. The Wulst lesions disrupted the acquisition of discrimination, while the ectostriatal lesions did not..  

The present study shows that the enhancement of ipsilateral responses in white zebra finches is detectable in all areas of the tectofugal pathway, and also in the visual Wulst, the only station of the thalamofugal pathway examined so far in white zebra finches.  

The projections of the DMA covered the rostrobasal forebrain, ventral paleostriatum, nucleus accumbens, septal nuclei, Wulst, hyperstriatum ventrale, neostriatal areas, archistriatal subdivisions, dorsolateral corticoid area, numerous hypothalamic nuclei, and dorsal thalamic nuclei.  

Using the technique of intrinsic signal optical imaging, orientation preference maps were obtained from the Wulst of the barn owl in the area that represents central vision, and from the visual cortices (V1 and V2) of cat and marmoset monkey. Iso-orientation domains in barn owl's visual Wulst were patch-like structures with an inter-patch distance of approximately 0.9 mm, arranged in a pinwheel-like manner around singularity points. Superficial layers of the owl visual Wulst may be equivalent to extra-striate visual areas of primates and carnivores, as already suggested by electrophysiologists discussing the much increased radial dimensions of the Wulst compared with neocortex in mammals..  

Light-exposure of the chick embryo induces development of asymmetry in the thalamofugal visual projections to the Wulst regions of the forebrain since the embryo is turned so that it occludes its left and not its right eye.  

Multiunit mapping techniques were used to examine the representation of the specialized receptor surface of the claw in the anterior Wulst. The mutability and multiple representations indicates that the Wulst provides the owl with sensory processing capabilities analogous to those in mammals..  

We revealed functional lateralization of the chick visual system by placing injections of monosodium glutamate (0.5 microl, 100 mM) into the left or right Wulst regions of the hemispheres, and examined the effects of light experience before hatching on this lateralization. Following exposure of the left or right eye to light for 24 h beginning on day 18 of incubation, the chick's ability to categorize grain as distinct from pebbles was impaired by glutamate treatment of the Wulst contralateral to the exposed eye. Following incubation of the eggs in darkness or with both eyes exposed to light, treatment of neither the left or right Wulst affected performance on the pebble-grain task: showing that either the left and right Wulst can assume control of this function. Treatment of either the left or right Wulst of these chicks elevates attack and copulation. However, examination of the distribution of attack scores revealed a bimodality in the attack scores of the chicks treated with glutamate in the right Wulst and not those treated in the left Wulst. In summary, light stimulation of one eye during a critical period of embryonic development causes the visual Wulst contralateral to the light exposed eye to develop dominance over its equivalent region in the other hemisphere. Without this lateralized stimulation of light both the left and right Wulst regions are largely but not exactly equivalent..  

Most parts of the forebrain, such as the different subdivisions of the visual Wulst and the neostriatum, displayed a rather uniform, moderate to dense innervation of serotonergic (5-HT+) fibers.  

The ascending thalamofugal visual pathway in pigeons (Columba livia) terminates in the telencephalic Wulst. To determine whether this pathway, and in particular the Wulst, may participate in sun-compass-guided behaviour in homing pigeons, intact, ectostriatum-lesioned or Wulst-lesioned pigeons were trained to use their sun compass to locate the direction of a food reward in an outdoor, octagonal arena. In contrast, the Wulst-lesioned pigeons learned the task but they took more sessions to learn, and their directional choices were more scattered during the first trial of the last three training sessions and after the phase-shift manipulation. A subsequent regression analysis indicated that deeper layers of the Wulst might have made more of a contribution to the observed behavioural impairments. The data indicate that the homing pigeon Wulst participates in visually guided behaviour when the sun compass is used to learn the directional location of a goal..  

In this study, neuronal activity in the visual forebrain (visual Wulst) of behaving barn owls to vertical disparity was investigated.  

Much of the Wulst and dorsal ventricular ridge (DVR) in birds, which together make up the part of the avian telencephalon functionally resembling mammalian cerebral cortex, projects to the striatum.  

To address this issue, we labeled cells in the dorsolateral anterior thalamus (DLA) using retrograde fluorescent tracers injected into visual Wulst, counted the labeled cell number, and compared the anatomical asymmetry of DLA between the left eye occluded and the right eye occluded chickens.  

Within the pallium, the major cortical domains (Wulst and caudolateral, parahippocampal, and hippocampal cortices) appear posterior to the dorsal ventricular ridge.  

All four species showed a similar distribution of SP throughout the brain with the exception of two areas, the hippocampal complex (including hippocampus (Hp) and parahippocampus (APH)) and the Wulst (including the hyperstriatum accessorium (HA)).  

To address this issue, tuning data during stimulation with correlated and anticorrelated random-dot stereograms (a-RDS) were obtained from 52 disparity-sensitive visual Wulst neurons in three behaving owls.  

Considering that the archistriatum is also connected indirectly to the Wulst, the movements are able to be guided by well processed visual information..  

In simple correlations, size of the Wulst and the striatopallidal complex is associated with feeding innovation rate, but the two structures are eliminated from the multiple regressions.  

Most importantly, the cells born on day 6 in the avian Wulst, the likely homolog of mammalian neocortex, end up homogeneously distributed throughout the Wulst, which suggests that many of them are migrating past older cells.  

If one assumes that the antecedent of superior and temporal neocortex in stem amniotes was one continuous field that histologically resembled dorsal cortex in living reptiles, the first hypothesis provides basis for a parsimonious account of the origin of superior and temporal neocortex and their considerable resemblance to dorsal cortex and DVR in reptiles, as well as to Wulst and DVR in birds..  

Golgi-stained preparations were processed with computerized morphometry to study the effect of the deprivation (eyes covered with nontransparent caps) on the development of neurons in the Wulst (the structure analogous to mammalian visual cortex) of pied flycatcher nestlings. In the previous paper [ Korneeva et al., 1994] in was shown that the Wulst of 6-day-old nestlings consisted of non-differentiated neurons and stellate-like cells at different stages of maturation; the latter group was subdivided into more- and less-mature cells.  

In the current study, responses of 160 visual Wulst neurons to static random-dot stereograms (RDS) were recorded via radiotelemetry in awake, fixating barn owls. Only a minority of neurons were clustered according to their disparity-tuning properties, suggesting that neurons in the visual Wulst are not organized into columns by preferred disparity. Our study emphasizes the significance of visual Wulst neurons in analyzing stereoscopic depth information and introduces the barn owl as a second model system to study stereopsis in awake, behaving animals..  

The avian visual Wulst, said to be the equivalent of the striate cortex in mammals, is the telencephalic visual area of the thalamofugal visual pathway. In this study, by means of retrograde labelling with fluorescent tracers injected into the Wulst regions in the left and right hemispheres, we have investigated the organization of the intratelencephalic projections to the visual Wulst in chicks. After injecting Fluorogold (FG), True blue (TB) or rhodamine into the visual Wulst, fluorescent-labelled neurones were found in the ipsilateral neostriatum frontale, pars lateralis (NFl), the ipsilateral neostriatum intermedium (NI) and the ipsilateral dorso-lateral neostriatum. In addition, some neurones in the archistriatum were double-labelled, which indicates that these archistriatal neurones have axon collaterals projecting to the visual Wulst on both sides of the forebrain. Through these intratelencephalic afferents to the visual Wulst, visual information transmitted in the thalamofugal pathway may be modulated by other telencephalic areas.  

The rostral Wulst of birds, like the somatosensory cortex of mammals, receives somatosensory information from the thalamus and projects to the brainstem and spinal cord via a pyramidal-like tract. Using anterograde and retrograde tract-tracers, we show here, in adult zebra finches, that the rostral Wulst also projects directly to the cerebellar cortex and deep nuclei.  

An avian "pyramidal tract" was defined in zebra finches and green finches by making injections of neuronal tracers into the hyperstriatum accessorium (HA) of the rostral Wulst. There was also a sparse projection to the dorsal thalamic nucleus intermedius ventralis anterior, which supplies the somatosensory input to the rostral Wulst, and distinct projections to the intercollicular region surrounding the central nucleus of the inferior colliculus, where they partly overlapped the projections of the dorsal column nuclei.  

Recent data on the expression of several homeobox genes in the embryonic telencephalon of mammals, birds and reptiles support the homology of a part of the avian pallium, named the Wulst, and at least the more-medial and superior parts of mammalian neocortex. Furthermore, new evidence on the connections and electrophysiological properties of specific subfields within the avian Wulst, and on the thalamic territories that project to these fields, supports the more-specific conclusion that a primary visual area and a primary somatosensory-somatomotor area are present in the avian Wulst; these areas are likely to be homologous to their counterparts in mammals. In spite of this, developmental, morphological and comparative evidence indicate that some structural and physiological traits that appear to be similar in the Wulst and neocortex (such as the lamination or binocularity) evolved independently in birds and mammals..  

These androgen-induced effects were limited to fledgling and juvenile periods and were spatially restricted, in that androgens did not accelerate developmental changes in NMDA-EPSCs recorded in a nonsong area, the Wulst.  

We have previously shown that the hyperstriatum accessorium (HA) of the rostral Wulst in zebra finches and green finches is the origin of a pyramidal-like tract with substantial projections to the brainstem and cervical spinal cord.  

Rhodamine B Isothiocyanate (RITC), Fluorogold (FG) and True blue (TB) were injected into either the visual Wulst (thalamofugal pathway) or the nucleus rotundus (Rt; tectofugal pathway) and the retrogradely labelled neurones in the nucleus geniculatus lateralis pars dorsalis (GLd) or the optic tectum, respectively, were counted.  

Golgi preparations of the pied flycatcher Wulst region (the structure analogous to the mammalian visual cortex) were analyzed using the method of computerized morphometry, to study the influence of visual deprivation on the development of different types of neurons selected previously. A large number of tree-like neurons were revealed in the Wulst in the deprived 10-day-old nestlings while in the control age-matched nestlings they were virtually never found.  

Moreover, single-neuron recordings from visual forebrain (visual Wulst) of awake, behaving birds revealed a high proportion of neurons signaling such subjective contours, independent of local stimulus attributes. These data suggest that the visual Wulst is important in contour-based form perception and exhibits a functional complexity analogous to mammalian extrastriate cortex..  

Our results indicate that avian basal ganglia appear to control movement through major projections to several premotor pretectal and tegmental centres which innervate the tectum, and through a minor projection to a possible motor thalamic centre which innervates the Wulst.  

The forebrains of reptiles and mammals are similar in that the dorsal surface of their cerebral hemisphere is formed by a pallium with three major segments: (a) an olfactory, lateral cortex; (b) a 'limbic' cortex that forms the dorsomedial wall of the hemisphere, and (c) an intermediate cortex that is composed entirely of isocortex in mammals, but in reptiles (and birds) consists of at least part of the dorsal cortex (in birds the Wulst) and a large intraventricular protrusion, i.e.  

Retrograde tracing also demonstrated further afferents from the deep layers of the Wulst and from the frontolateral neostriatum as well as the sources of thalamic input.  

No direct connection was found between the visual Wulst and the ectostriatum or the telencephalic centres of the tectofugal and thalamofugal pathways. Besides other projections, the visual Wulst emitted fibres also to the middle and lateral parts of the hyperstriatum ventrale. Further experiments revealed that the middle part of the hyperstriatum ventrale projected to the ectostriatum centrale and periphericum and established an indirect connection between the visual Wulst and the ectostriatum.  

The distribution of beta-adrenoceptors was fairly similar in the areas of the visual Wulst of all five species studied while striking differences were found in the ectostriatum, the higher centre of the tectofugal pathway.  

Neurons of the Wulst area (analogous to mammalian visual cortex) were studied with the method of computerized morphometry (6 parameters) in frontal Golgi-stained sections of pied flycatcher nestlings which were binocularly deprived since the age of 1-1.5 days post-hatching.  

By means of a double-labeling technique, we have investigated the organization of the bilateral thalamo-Wulst and tecto-rotundal projections in 2-day old chicks. After injecting fluorogold (FG) into one side of the visual Wulst and rhodamine B isothiocyanate (RITC) into the other side of the visual Wulst, the labeled neurons in the nucleus geniculatus lateralis pars dorsalis (GLd) were examined. This suggests that the ipsilateral and contralateral projections to the Wulst come from different neuronal populations of the thalamus.  

Connections of the thalamo-hyperstriatal system of hatchling chicks were investigated using multiple injections of cholera toxin B subunit (CTb) in the Wulst. Moreover, efferent projections of the Wulst were evident in the most ventral half of the optic tectum and the pretectal areas. Additionally, efferent projections from the Wulst to the diencephalic, mesencephalic, and pretectal structures are evident..  

An examination of the pattern of sparing and loss of performance on this task after lesions of various components of the ascending visual pathways suggests that deficits in color-reversal learning observed after lesions of the visual Wulst are not due to the Wulst's connections with the thalamofugal pathway. Instead, the data suggest that the visual Wulst maintains a role in color-reversal learning through its connections with the tectofugal pathway..  

Previous lesion studies of color-reversal learning in pigeons show that an impairment results when (1) the tectofugal visual pathway is damaged at either the thalamic level (nucleus rotundus) or the telencephalic level (ectostriatum), or (2) the thalamofugal visual pathway is damaged at the telencephalic level (the visual Wulst). opticus principalis thalami or OPT) to the visual Wulst is damaged. These results suggest that the visual Wulst plays a role in color-reversal learning as a consequence of visual information routed from the tectofugal pathway via other visual areas in the telencephalon. An impairment in color-reversal learning resulted from combined damage to lateral HV and the fronto-thalamic tract (FT), which carries ascending visual input from OPT to the visual Wulst. These findings suggest that both the thalamofugal and tectofugal pathways provide the visual Wulst with visual input relevant to color-reversal learning..  

To investigate whether any of the dorsal thalamic nuclei receiving pallidal input project to a motor cortical field, injections of the retrograde tracer Fluoro-Gold were placed into the rostral Wulst. Our results indicate that neurons in the rostral ventrointermediate area, but not in the nucleus subrotundus, the dorsointermediate posterior nucleus, or the intermediate or caudal parts of the ventrointermediate area, project to the rostral Wulst.  

The organization of the wing component of the dorsal column-medial lemniscal pathway, and somatosensory projections from the thalamus to the Wulst, are described for an oscine member of the major group of birds, the Passeriformes. DIVA projects to the ipsilateral rostral Wulst where it terminates in the intercalated hyperstriatum accessorium, in a distinct, regular patchy fashion.  

Then the ectostriatum or the Wulst was bilaterally damaged. The Wulst lesions did not cause deficits in any tasks.  

Metabolic activity of the terminal nucleus (ectostriatum) of the tectofugal pathway increased significantly by day 18, but in the terminal nuclei (the Wulst) of the thalamofugal visual pathway activity did not change significantly.  

The visual Wulst is the telencephalic target of the thalamofugal visual pathway of birds, and thus the avian equivalent of the striate cortex of mammals. The anterograde tracer Phaseolus vulgaris leucoagglutinin was used to follow the intratelencephalic connections of the major constituents of the visual Wulst in pigeons.  

This expanse includes the Wulst and archistriatum as well as the entire outer rind of the pallium intervening between Wulst and archistriatum, termed by us the pallium externum (PE). Such "limbic" pallial areas also project to medialmost LPO and lateralmost PA, while the hyperstriatum accessorium portion of the Wulst, the PE, and the dorsal parts of the archistriatum were found to project primarily to the remainder of LPO (the lateral two-thirds) and PA (the medial four-fifths). The extensive corticostriatal system in both birds and mammals appears to include two types of pallial neurons: 1) those that project to both striatum and brainstem (i.e., those in the Wulst and the archistriatum) and 2) those that project to striatum but not to brainstem (i.e., those in the PE).  

No IMEL binding could be demonstrated in the pineal gland, the hippocampus, the nucleus suprachiasmaticus, the visual Wulst or the pituitary..  

Since the n.SPC has also been shown to project upon the visual Wulst, different fluorescent dyes were injected concomitantly into the latter and the hippocampus and the distribution of retrograde somatic labeling within the thalamus was compared. Direct retinal projections upon the n.SPC were also demonstrated and terminated within the same regions of the nucleus containing relay cells projecting to both the hippocampus and the Wulst.  

The study shows the contribution of visual Wulst efferents, to visual processing in the ectostriatum by recordings of visually evoked slow field potentials. Suppression of visual Wulst activity resulted in a selective reduction of distinct potential components in contralaterally evoked slow field potentials. The results showed that the visual Wulst has a significant, most likely facilitatory, influence on the processing of contralateral visual information in the ectostriatum. Ipsilateral stimulus processing was partly independent from visual Wulst activity.  

The primary sensory areas of the pallium of the avian telencephalon (Wulst and dorsal ventricular ridge) tended to be low in all three binding sites, while the surrounding second order belt regions of the pallium were typically high in all three.  

The lateral part forms striate cortex in mammals and the lateral part of dorsal cortex (or pallial thickening or visual Wulst) in non-synapsid amniotes.  

Shimizu and Hodos (1989) had reported that lesions of two laminae in the visual Wulst (IHA and HD), both targets of the avian thalamofugal pathway, resulted in increased errors in a color-reversal learning task in pigeons. We suggest that the color-reversal learning deficits after Wulst lesions are not due to the Wulst's connections with the thalamofugal pathway, but rather to its connections with the tectofugal pathway..  

One region, the intermediate and medial part of the hyperstriatum ventrale (IMHV), is probably a site of long-term memory; the other, the Wulst, contains somatic sensory and visual projection areas. A significant negative partial correlation between preference score and F1/GAP-43 phosphorylation in the right Wulst was observed.  

In normal adult brains, SS-positive cells and processes were present in the optic tectum, the nucleus of the basal optic root, the visual Wulst, and the ectostriatum.  

isthmi parvocellularis (Ipc) and the hyperstriatum accessorium (HA) subdivision of the telencephalic visual Wulst.  

Extracellular recordings were made in the prosencephalon (Wulst) and in the mesencephalon (optic tectum) of paralysed animals.  

Using a larger sample size and a double-labelling procedure, projections to the visual Wulst were labelled with the retrograde tracers True Blue and Fluoro-gold and the ratio of contralateral projections to ipsilateral projections was calculated.  

In 79 pigeons, unit discharges of Wulst neurons responding to bilateral stimulation of N. These results suggest that the Wulst may function as an important centre for integrating visual and somatic sensory information..  

A greater development of the Wulst and low values of olfactory bulbs suggest that Eudromia and Rhynchotus are progressive species.  

The results show that a sparse and diffuse projection to the red nucleus arises from deep regions of the hyperstriatum accessorium (HA) of the anterior Wulst, and that a much more dense projection arises from the caudal part of the nucleus principalis precommissuralis and the medial part of the medial spiriform nucleus (SpMm). These last two sources were themselves shown to receive a substantial projection from HA of the anterior Wulst.  

The visual projections from the thalamus to the Wulst of the chick forebrain are asymmetrically organized.  

The Wulst of the avian brain needs further investigation to discover how it could give birds the consciousness that they seem to have..  

After the pigeons had accomplished the discrimination tasks, they received lesions of the Wulst or the ectostriatum. While damage to the Wulst did not disrupt either task, the ectostriatal damage caused deficits selectively in individual discrimination.  

Differences in visual discrimination ability between the left and right eyes of chicks, which are most prominent in young males, may result from a structural asymmetry in the organization of the visual projections from the thalamus to the visual Wulst.  

The somatic and visual response areas of the Wulst were investigated electrophysiologically in pigeons. In the Wulst, the somatic response area overlaps the visual area and there is somatosensory-visual convergence..  

In normal adult brains, neuropeptide Y-positive cells and processes were present in the nucleus pretectalis, the nucleus of the basal optic root, the nucleus of the marginal optic tract, and the visual Wulst. Substance P-positive cells and processes were found in the optic tectum and in the visual Wulst. Choline acetyltransferase-positive cells and processes were located in the optic tectum, visual Wulst, the nucleus isthmo opticus, nucleus isthmi and certain visual thalamic nuclei.  

The efferent projections from the Wulst were studied in the little owl, Athene noctua, using anterograde migration of wheat-germ-agglutinin conjugated horseradish peroxidase (WGA-HRP). Wulst projections were distributed to telencephalic, diencephalic and mesencephalic targets in a general pattern similar to that previously described in other avian species. Our results on the organization of the Wulst-optic tectum pathway in the little owl reveal well defined and laminarly arranged terminal projections into the superficial tectal layers, with a distribution suggestive of topographical relationships between neurons of origin in the Wulst and termination fields in the optic tectum. In addition, the anterior and posterior Wulst differentially contribute to the ipsilateral and contralateral projections to the optic tectum. This differential organization of Wulst efferents, as well as the presence of substantial contralateral projections, might be related to the high degree of binocular overlap typical of frontal-eyed birds. After Wulst ablation, the amplitude of these potentials was significantly reduced, indicating that Wulst efferents may influence visually-evoked activity in the optic tectum..  

In reptiles and especially in birds, although there was also an increase in brain size (associated with higher cognitive capacities), the optic tectum grew in size and complexity and the forebrain grew largely as a nonlaminar structure (except the Wulst in birds).  

Transmitter-specific projections onto the visual Wulst and the optic tectum were studied by simultaneous double-labelling of retrograde tracer molecules and immunocytochemical labelling. Three subnuclei (DLL, DLAmc, SpRt) were shown to project to the visual Wulst.  

The projections from thalamus to visual Wulst in chicks are asymmetrical and their development is determined by exposure to light just before and after hatching.  

Electrical stimulation of the visual Wulst (considered to be the equivalent of the visual cortex) produced mainly inhibitory effects on units with downward preferences (among 123 units, 47% were inhibited, 24% were excited and 29% were not affected), and mixed effects on units with upward preferences (among 70 cells, 30% were excited, 36% were inhibited and 34% were not affected).  

Pigeons with lesions of the lateral part of the telencephalon, visual Wulst, and fronto-archistriatal tract were compared with sham-operated controls in 2 procedures.  

The avian Wulst, a laminated "bulge" in the dorsal telencephalon, contains several distinct regions. The posterolateral portion (visual Wulst) has been proposed to be an avian equivalent of the mammalian striate cortex. The present study examines specific neurotransmitters and neuropeptides within the visual Wulst by immunohistochemical techniques. Somata and neuropil displaying specific immunoreactivity were generally distributed in accordance with the laminar cytoarchitectonic organization of the Wulst. The superficial layer of the Wulst, the hyperstriatum accessorium, contained the highest densities of TH-, 5-HT-, SP-, NPY-, SRIF-, CRF-, and VIP-positive neuropil in the Wulst, whereas the highest density of CCK- and NT-staining was found in the deepest layer of the Wulst, the hyperstriatum dorsale. In addition to the traditionally defined four laminae of the Wulst, the immunoreactive staining revealed several subregions within each lamina. The most dorsolateral portion of the Wulst contained the highest densities of ChAT- and L-ENK-stained fibers in the Wulst, as well as moderately dense staining of neuropil for 5-HT-, TH-, SP-, and CCK-like immunoreactivity. The nAChR-immunoreactivity was faint and distributed rather uniformly throughout the Wulst. The results suggest that the Wulst consists of multiple regional variations within layers comparable to laminar variations found within different cytoarchitectonic areas of the mammalian neocortex..  

The telencephalic target of the thalamofugal visual pathway in birds, the visual Wulst, is part of the hyperstriatum accessorium/dorsale in the bird's brain. Instead, our results show that ipsilaterally evoked potentials are inhibited at least in part by a projection from the contralateral visual Wulst..  

The distinctive patterns of thalamic input to the rostral (R), intermediate (I) and caudal (C) divisions of the pigeon Wulst were determined using the retrograde multiple label technique following concomitant injections of various fluorescent tracers into different Wulst loci. Major ipsilateral and contralateral projections upon the R and I Wulst stem from the pars lateralis ventralis and dorsalis nuclei, respectively. suprarotundus provide weak bilateral projections to all of the Wulst divisions sampled. dorsolateralis posterior upon the posterior C Wulst were also demonstrated. Based upon their patterns of terminal distribution upon the Wulst, some of these thalamic nuclei are compared to specific components of the mammalian geniculate and extrageniculate visual systems..  

Visual Wulst responses to ipsi- and contralateral visual stimuli were investigated in young zebra finches (Taeniopygia guttata castanotis Gould) of different ages.  

Samples from the left cerebral hemisphere were removed including (i) the intermediate and medial part of the hyperstriatum ventrale (IMHV), a region which is crucial for imprinting, (ii) the posterior neostriatum and (iii) the visual Wulst.  

Visually evoked potentials (VEPs) have been recorded from the Wulst surface of the little owl, Athene noctua, in response to counterphase-reversal of sinusoidal gratings with different contrast, spatial frequency and mean luminance, presented either monocularly or binocularly. These results suggest that a 50% recrossing occurs in thalamic efferents and that different ipsilateral and contralateral regions converge onto the same Wulst sites.  

The efferent projections from the visual thalamus to the Wulst were studied in the little owl, Athene noctua. Cells of origin were identified by retrograde labeling after injections of wheat-germ-agglutinin-conjugated horseradish peroxidase into the Wulst. Projections from the visual thalamus to the Wulst showed a specific and orderly pattern, and retrogradely labeled cells of DLA were distributed equally, in a complementary fashion, on both sides of the brain, with a small region of overlap. Retinal termination fields in DLA largely overlapped relay neurons projecting to either Wulst, although the overlap was not complete.  

The directional selectivity of units within the nucleus of the basal optic root (nBOR) of the accessory optic system (AOS) was studied before and after lesions of the visual telencephalon (visual Wulst) in urethane-anesthetized pigeons. The overall distribution of preferred directions was still bimodal following ipsilateral or bilateral Wulst lesions, with most units showing best responses to a straight temporal or to downward-nasal directions. The contralateral Wulst lesions produced, instead, a marked reduction in downward preferences. These data suggest an involvement of the visual Wulst in the determination of the directional selectivity of nBOR neurons in the pigeon.  

In the Golgi preparation of visual Wulst of chicken four types of projection neurons were found: type 1a, 1b, 1c, and 1d neurons, which are distinguished on the basis of their dendritic ramification pattern and especially on the density of the dendritic spines. In the Wulst short axon cells (interneurons-INs) of different types occur: large, medium-sized and small INs can be observed.  

Following injections of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) into the visual Wulst contralateral to the operated eye, a smaller number of ipsilateral projecting thalamo-Wulst neurons was found as compared with control pigeons. In contrast, the contralateral thalamo-Wulst projections were increased. No changes in thalamo-Wulst projections were found following tracer injections into the opposite Wulst, i.e., ipsilateral to the operated eye.  

Pigeons with lesions of either the Wulst or ectostriatum were compared to controls on reversal of a go/no-go pattern discrimination. The Wulst-lesioned animals were slower to acquire the response to the new S+ but were not different from the other groups on extinction of response to the old S+. The results extend the range of situations in which Wulst-lesioned pigeons have been found to show a reversal deficit and are consistent with the notion that Wulst lesions may disrupt learning..  

Serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels were determined in the visual Wulst, optic lobes, retina, cerebellum and brainstem of the pigeon during embryonic and posthatching periods.  

The effects of bilateral lesions of individual laminae of the Wulst on reversal-learning performance in pigeons were evaluated. A multiple regression analysis indicated that those components of the Wulst that were critical for increasing the numbers of errors on each reversal were the laminae that receive the thalamofugal visual projections, that is, the nucleus intercalatus of the hyperstriatum accessorium and the hyperstriatum dorsale. Lesions in the other laminae of the Wulst (the hyperstriatum accessorium and the hyperstriatum intercalatus superior) had no effect on errors.  

We investigated quantitatively the thalamo-hyperstriatal visual projections of chickens by injecting the fluorescent dye True blue (TB) in either side of the Wulst on day 2 post hatching.  

There are two somatosensory areas in the telencephalon of the pigeon which receive an input from the spinal somatosensory system: one in the rostral Wulst which consists of the three hyperstriatal layers (h. The rostral Wulst area receives somatic signals only through dorsal tracts contralateral to the recording site. Signals transmitted through the lateral pathways were found to elicit the earliest responses (6-13 ms, electrical stimulation) in the caudal forebrain, while signals travelling through the DC arrive later in the caudal area (about 14 ms for wing stimulation) than in the rostral Wulst area (about 9 ms). Combined injections of FB and RITC revealed a topographic projection from the DIVA to the anterior Wulst.(ABSTRACT TRUNCATED AT 400 WORDS).  

One somatosensory area is located rostrally in the hyperstriatum accessorium (HA), rostral to the visual "Wulst".  

High endogenous 5-HT levels in the visual Wulst and brainstem and medium 5-HT content in the optic lobes were found. Similar endogenous 5-HIAA levels were measured in the visual Wulst, optic lobes and brainstem, whereas the 5-HIAA content of the cerebellum and retina was significantly lower. Six days after p-CA treatment, the 5-HT content of the visual Wulst, optic lobes, brainstem and the 5-HIAA content of the optic lobes and cerebellum markedly decreased. Nine days after 5,7-DHT administration, the 5-HT and 5-HIAA content of the visual Wulst and optic lobes was significantly reduced.  

The first group (WI-EII) received lesions of the visual Wulst and were retested. In the third group (E + W), lesions of both the visual Wulst and ectostriatum were made in a single operation, followed by retesting. the birds with visual-Wulst lesions showed little or no impairment on any of the tasks, whereas the pigeons with ectostriatum lesions showed considerable deficits in intensity and pattern discrimination, which diminished after prolonged retraining. The performance of the EI-WII group after its visual Wulst lesion, however, was similar to that observed in the E + W group.  

The visual Wulst (VW) in the avian telencephalon is thought to be an avian equivalent of the mammalian striate cortex.  

Between 6 and 10 h after chicks had hatched, bilateral lesions were placed in the IMHV (n = 16), and the Wulst (n = 16). While both the sham-operated and the Wulst-lesioned groups had a significant mean preference for the fowl to which they had been exposed during training, the IMHV-lesioned birds had no preference.  

Birds submitted to visual Wulst ablation or supraoptic commissure lesion performed in much the same way.  

The positions of terminals from the retina and visual Wulst upon identified relay neurons in the DLA were examined in Japanese quail with both light and electron microscopic techniques. Injection of horseradish peroxidase (HRP) into the visual Wulst showed that relay neurons projecting ipsilaterally or contralaterally were located in a rostrolateral subdivision (DLAlr) and in Zones A and B of a lateral subdivision (DLL) of the DLA. By contrast, lesions in the visual Wulst produced dense degenerating terminals in Zones A and B of the DLL. The somata and proximal dendrites of relay neurons or terminals from the retina in the DLA were identified electron microscopically following HRP injection into the visual Wulst or optic nerve, respectively. Lesions of the visual Wulst resulted in degeneration of small terminals with spherical vesicles.  

Autoradiographic analysis of their brains revealed 3 well demarcated areas of increased 2DG accumulation in the rostral forebrain of imprinted chicks compared to controls: HAD in the rostral Wulst; MNH, an auditory area in the rostromedial neostriatum and hyperstriatum ventrale; LNH in the rostrolateral neostriatum and hyperstriatum ventrale.  

The efferent projections of the pigeon visual Wulst upon the diencephalon and mesencephalon were investigated using the autoradiographic technique following the combined injection of [ 3H] proline and [ 3H] leucine into the rostral hyperstriatum accessorium. The data showed ipsilateral projections from the visual Wulst and via the tractus septomesencephalicus upon the dorsal thalamus (n.: dorsolateralis anterior superficialis parvocellularis), ventral thalamus (n.: intercalatus, ventrolateralis, geniculatus lateralis pars ventralis--GLv), pretectum (n.: superficialis synencephali, geniculatus pretectalis, griseus tectalis, pretectalis: diffusus, pars lateralis and pars medialis, area pretectalis) as well as to the nucleus of the basal optic root, n. Interspecies variations in the organization of descending visual Wulst projections, related to the terminal distribution and relative size of the crossed components may be linked to differences in the degree of overlap of the binocular fields. Correspondingly, this may reflect the degree of bilateralization upon the Wulst of direct input from the visual thalamus..  

Comparative study has been carried out of factors of organization of visually guided feeding behaviour (observation method) and the degree of maturity of the visual mechanisms by the criterion of Wulst EPs formation and of their recovery cycles in normally developing and visually deprived nestlings.  

Following training, bilateral stereotaxic lesions were made in either the visual Wulst or ectostriatum, which are telencephalic components of the thalamofugal and tectofugal visual pathways, respectively. The performance of the four subjects that received visual Wulst lesions was only mildly and transiently impaired and was equally disrupted on each pattern discrimination.  

Numerous fibers leave the LPO region and course dorsally into the deep layer of the Wulst, hyperstriatum dorsale (HD).  

Noradrenaline concentration was determined in Wulst and medial and basal forebrain samples.  

In particular, the pigeon Wulst, like the mammalian visual cortex, is profusely innervated by CA terminals. These results suggest a possible convergence of NA terminals and visual fibers on common target cells in the Wulst..  

Since the pigeon uses the normally binocular portion of its retina to scan the discriminative stimuli in a key-pecking task and the DSO carries converging binocular input from the retinorecipient zone of the thalamus to the visual Wulst, the results suggest that IOT in the pigeon is the simple consequence of information reaching both hemispheres from a single eye via converging binocular pathways.  

Labelled cells were found (i) ipsilaterally in the visual Wulst, neostriatum pars intermedia and caudalis, the posterior part of the hyperstriatum ventrale, the dorsal part of the archistriatum, paleostriatum augmentatum, dorsomedial part of the thalamus, and (ii) bilaterally in the hippocampus, area septalis, ventromedial part of the thalamus and the stratum album centrale of the tectum opticum.  

The responses of the cells in the pigeon's optic tectum to electrical stimulation of the contralateral optic nerve, the ipsilateral visual Wulst and the opposite optic tectum were intracellularly recorded. Optic nerve or visual Wulst stimulation elicited 3 types of responses: (1) a pure EPSP which gave rise to one or two action potentials; (2) an EPSP which sometimes gave rise to a spike, followed by an IPSP; and (3) a pure IPSP. The latency of the responses of individual cells to optic nerve, visual Wulst and opposite tectum stimulation show that the polysynaptic IPSPs to optic nerve stimulation did not involve relays in the visual Wulst or the opposite tectum..  

At approximately equal to 48 h after hatching each chick was anaesthetized and a microelectrode advanced in 250 micron steps through the left Wulst.  

One microelectrode penetration was made through a region, the intermediate and medial part of the hyperstriatum ventrale (IMHV) known to be critical for imprinting; simultaneously another microelectrode penetration was made through the visual Wulst. The mean firing rate from greater than or equal to 3 sites was calculated for IMHV and for the hyperstriatum accessorium of the Wulst.  

In another group, lesions were made in the visual Wulst, a portion of which receives the ascending fibers of the thalamofugal visual pathway. Within this group, only lesions that were large and included all components of the visual Wulst were effective in decreasing visual acuity to a moderate degree. A partial correlation analysis indicated that the components of the visual Wulst that were responsible for the acuity changes were the accessory hyperstriatum and the hyperstriatum ventrale. Also ineffective were lesions of the granular components of the visual Wulst, which receive the ascending thalamofugal fibers.  

Different results point to the Wulst as a visual structure affected at metabolic, cellular level by an early monocular deprivation. Cholinergic and noradrenergic systems in the Wulst are affected by early visual deprivation..  

Shorter latencies were recorded in this region than in both the classic primary telencephalic visual projection areas, the Wulst and the ectostriatum. Projections from the Wulst and the ectostriatum could also be excluded as sources of the short latency visual evoked potentials from the caudolateral telencephalon.  

In a subsequent experiment, both sham operated control birds and birds with lesions of the visual Wulst homed successfully when released only 800 m from and in full view of their respective home lofts. In an additional experiment, pigeons with Wulst lesions were shown to orient as controls and to successfully return to the home loft when released from two distant sites. This experiment demonstrated that the avian Wulst plays no necessary role in the homing behavior of pigeons..  

The falcon's visual Wulst as detected by the [ 14C] 2-Deoxyglucose labeling, is proportionally larger than that found in the pigeon. This result is consistent with the marked representation of the binocular visual field in the falcon's Wulst..  

The concentrations of adrenaline, dopamine and noradrenaline were measured in 3 regions of the domestic chick telencephalon: (a) the Wulst; (b) a medial forebrain sample comprising mainly the intermediate part of the medial hyperstriatum ventrale (IMHV); and (c) a basal forebrain sample comprising mainly paleostriatum augmentatum. Adrenaline was undetectable in the Wulst and medial forebrain samples and only trace amounts were found in the basal forebrain samples of 1-day-old, light-reared chicks. Dopamine concentrations of 9.13 +/- 1.13 (S.E.M.) ng/g were present in the Wulst, 16.66 +/- 2.56 ng/g in the medial forebrain and 121.19 +/- 33.06 ng/g in the basal forebrain samples at hatching. At hatching, noradrenaline concentrations of 35.83 +/- 8.61 ng/g were present in the Wulst, 26.09 +/- 3.75 ng/g in the medial forebrain and 53.13 +/- 7.85 in the basal forebrain samples. The noradrenaline concentrations in the Wulst and medial forebrain samples increased significantly over the first 50 h post-hatch in dark-reared chicks.  

On the contrary, the NE content in the Wulst and cerebellum gradually decreased from hatching to 6 days. After this period, the Wulst NE level did not change significantly. The NE content in the Wulst could be related to noradrenergic afferents originating in the ipsilateral locus coeruleus and substantia grisea centralis, since an electrolytic lesion of the pontine tegmentum caused a 60% reduction in the NE level in the ipsilateral Wulst. In line with the hypothesis that NE plays an important role in cortical plasticity, effects of early monocular deprivation on the Wulst NE content were also observed. After monocular deprivation during the first 6 months of life, the NE level increased by 40% in the Wulst ipsilateral to the deprived eye in comparison to the other side, where the NE level was normal. Monocular deprivation performed in adult animals did not affect the NE content in the Wulst. These results indicate that noradrenergic systems in the Wulst are affected by early, but not late visual deprivation..  

The noradrenergic fibers were mainly concentrated in the Wulst regions which receive visual afferents from the dorsolateral thalamus..  

The projections were found to arise from the hyperstriatum accessorium (HA) of the Wulst, were essentially ipsilateral and topographically organized with respect to the dorsoventral and lateromedial plane of HA.  

Following horseradish peroxidase injections into the pigeon tractus septomesencephalicus, the efferent outflow bundle of the avian Wulst, retrogradely labeled neurons within the Wulst were confined to the superficialmost layer, the hyperstriatum accessorium. These results suggest that the hyperstriatum accessorium is the sole source of Wulst efferent projections. In similarity to the laminar organization of mammalian striate cortex, this efferent layer is juxtaposed to the thalamorecipient layer of Wulst..  

Efferent projections of the visual Wulst upon the nucleus of the basal optic root (nBOR) were investigated using various neuroanatomical approaches: optical and EM orthograde degeneration methods (following visual Wulst ablation), radioautographic and HRP techniques (following injection of various tracers within the visual Wulst). The radioautographic and electron microscope degeneration experiments clearly demonstrated a visual Wulst projection upon the ipsilateral nBORl and the lateral portions of nBORd and nBORp.  

Age dynamics of evoked potentials (EPs) of Wulst area of the dorsal hyperstriatum (functional analogue of mammalian visual cortex) was investigated in 2-7 days old nestlings.  

In birds, efferents from the visual telencephalon (visual Wulst) terminate in the ipsilateral and contralateral optic tectum. This study concerns the influence of a bilateral cryogenic block of the Wulst on the receptive field properties of the visual tectal cells in the pigeon. Tectal units were tested for their responses to static and moving stimuli before, during and after cooling the Wulst. For some units the cryogenic block of the Wulst was repeated twice. The responsiveness to static and moving stimuli was decreased in most of the tectal cells when the neural activity of the Wulst was blocked. In contrast, in some units cooling the Wulst provokes an increase of responsiveness. These results indicate that the Wulst-tectum path is able to convey both excitatory and inhibitory influences. Other receptive field properties such as the spatial location of the light and dark excitatory regions in the field, the effect of the surround, the size and shape of the excitatory region, the relative responsiveness to static and moving stimuli and the 'spontaneous activity' were not affected by Wulst cooling. Directional tuning curves were obtained in 18 directionally selective cells before, during and after Wulst cooling. In two others directionally selective cells, cooling the Wulst provoked a total loss of directional selectivity due to a reduction of the response to the preferred direction together with an increase of the response to the null direction. These results show: (1) that the retinal directional selective input to the tectum is affected by the cryogenic block of the Wulst; and (2) that the visual Wulst provokes a sharpening of the directional tuning at the optic tectum level..  

The afferent connections to the Wulst, a well-defined bulge in the forebrain roof, were studied in the pigeon. Cells of origin were identified by horseradish peroxidase retrograde tracing, after placing multiple injections in the Wulst. The account provides a direct anatomical demonstration of a Wulst input from the basal forebrain, the somatosensory thalamus, and the brainstem.  

The cellular organization of the Wulst was studied in Nissl- and Golgi-stained brain sections in order to identify the visual receptive neurons. Type I neurons, the largest cells in the Wulst, have long, straight dendrites with many spines. Type IV neurons, the smallest cells in the Wulst, have short dendrites with sparse spines. The projections of the nucleus dorsolateralis anterior thalami pars lateralis (DLL) to the Wulst were determined by the Fink-Heimer method.  

Responses to photic stimulation were recorded from the visual Wulst, the stratum opticum and the nucleus rotundus.  

[ 3H]-GABA injection in the pigeon Wulst leads to perikaryal retrograde labeling in the ipsilateral thalamic visual relay, n. This result gives further support to the biochemical evidence of the existence, in the pigeon, of a GABAergic projection from DLLv to the ipsilateral visual Wulst..  

The motor potentials appeared earlier (40 msec before pecking) in the Wulst than in the neo-, ecto- and archistriatum (18-28 msec before pecking).  

Pigeons with ectostriatal lesions made more errors than shams or Wulst-lesioned animals on the pattern problem, but there was no difference among the three groups on the shift to color. The Wulst-lesioned animals, on the other hand, showed a deficit on the shift to pattern but not on the original color problem.  

The drug solution (10 microliters) was locally injected into the telencephalon of a curarized animal under artificial respiration and Wulst EEG was recorded near the administered region.  

Afferent connections of the two main areas in the telencephalon, the visual Wulst and the ectostriatum, were traced in the zebra finch by injection of horseradish peroxidase and staining with tetramethylbenzidine (TMB).  

After mononuclear deprivation during the first 6-11 months, ChAT activity was higher by 40-60% in the dorsolateral visual Wulst contralateral to the deprived eye, as compared to the other side. Mononuclear deprivation performed in adult animals did not affect the ChAT activity in visual Wulst. GAD activity was bilaterally decreased in the visual Wulst after early monocular deprivation.  

Interocular transfer (IOT) of monocularly learned pattern, brightness and color discriminations was studied in normal pigeons and in pigeons with a bilateral ablation of the visual Wulst. Pigeons with a Wulst ablation which had shown a normal capacity for IOT, subsequently lost this capacity following a section of the supra-optic decussation (DSO). It is concluded that IOT in pigeons does not require the presence of the binocular neurons of the visual Wulst, and that in absence of this structure, IOT must rely on other centers for binocular interaction which receive fibers from the DSO..  

The influence of the visual telencephalic projection area (Wulst) upon directional selective cells in the Pigeon's optic tectum was studied through reversible cold block of this telencephalic region. About half of the cells studied were affected during Wulst cooling. These results indicate that the Wulst plays an important role in controlling the directional selectivity in the Pigeon's optic tectum..  

The relative importance of acetylcholine, dopamine, endogenous opiates, gamma-aminobutyric acid (GABA), glutamate, glycine, noradrenaline, and serotonin as transmitters in the pigeon visual system was estimated by measuring the activity of choline acetyltransferase (ChAT), glutamic acid decarboxylase (GAD), and aromatic amino acid decarboxylase (AAD) as well as the binding of dihydroalprenolol, etorphine, kainic acid, muscimol, serotonin, spiroperidol, strychnine, and quinuclidinyl benzilate (QNB) in the tectum opticum, nucleus rotundus, ectostriatum, dorsolateral thalamus, and hyperstriatum (Wulst). As a hypothesis for further investigations, the presence of cholinergic and serotoninergic systems in the Wulst, possibly originating in the dorsolateral thalamus and nucleus raphe, respectively, and of glycinergic and dopaminergic terminals in the paleostriatal complex is proposed..  

An analysis of contrast sensitivity of neurons in the optic tectum of intact and Wulst-ablated pigeons was carried out using moving light bars. (5) The relationship between unit responses and contrast values, as well as the contrast threshold value, did not differ between intact and Wulst-ablated animals..  

After [ 3H]choline injection in the pigeon visual Wulst, only the ipsilateral thalamic relay, of all inputs, showed similar perikaryal retrograde labeling, an observation supporting the suggestion that at least some thalamo-Wulst neurons are cholinergic..  

A study was made of the structure of evoked potentials in the Wulst of the dorsal hyperstriatum in five- to eight-day old nestlings in response to ecologically determined visual stimuli significant for the alimentary behaviour, within the range of their intensity natural fluctuation.  

In the visual Wulst, labeled neurons were confined to the supragranular layers after both tectal and thalamic injections. Corticotectal neurons were found in both ipsilateral and contralateral visual Wulst. Corticotectal neurons were distributed throughout the mediolateral extent of the ipsilateral Wulst and therefore involved both the monocular and binocular representations of the visual field. Corticothalamic neurons, found only in the ipsilateral Wulst, were characterized by smaller cell bodies and fine dendrites.  

The monocular and binocular performance of pigeons with bilateral, unilateral or sham lesions in the telencephalic Wulst was tested with visual discrimination tasks. The reciprocal inhibition of symmetrical visual brain stem centers is thought to have been unbalanced through the one-sided interruption of a known pathway descending from the Wulst..  

The organization of the visual projection to the hyperstriatum, or Wulst, in the domestic chick has been investigated using extracellular recording with microelectrodes. The entire visual field of the contralateral eye projects retinotopically into the Wulst. The projection of the nasal and temporal margins of the visual field is more complex, the superior and inferior parts of the temporal hemi-field being represented in the superficial and deep regions of the Wulst respectively, with an intervening projection of the nasal hemi-field at an intermediate depth. The organization found in the chick is discussed in relation to the previous physiological and anatomical findings of other workers in the visual Wulst of the pigeon and the owl..  

Labelled neurons were observed bilaterally in part of the visual Wulst (Hyperstriatum accessorium and Hyperstriatum intercalatum superior) following unilateral injection of the enzyme horseradish peroxidase into the Tectum opticum of pigeons.  

Following either extensive or restricted injections of the enzyme into different regions of the latter, differential bilateral or unilateral projections onto the Wulst (hyperstriatum accessorium, hyperstriatum intercalatus superior, hyperstriatum dorsale) were demonstrated from the dorsal thalami complex (nucleus dorsolateralis anterior thalami, pars lateralis).  

Single neurons recorded from the owl's visual Wulst are surprisingly similar to those found in mammalian striate cortex. The receptive fields of Wulst neurons are elaborated, in an apparently hierarchical fashion, from those of their monocular, concentrically organized inputs to produce binocular interneurons with increasingly sophisticated requirements for stimulus orientation, movement and binocular disparity. Output neurons located in the superficial laminae of the Wulst are the most sophisticated of all, with absolute requirements for a combination of stimuli, which include binocular presentation at a particular horizontal binocular disparity, and with no response unless all of the stimulus conditions are satisfied simultaneously.  

The influences of visual Wulst and optic tract (OTr) stimulation on units recorded from the pigeon's optic tectum (OT) were studied. On 54 of the OTr-excited units, single-shock visual Wulst stimulation exerted a long-lasting inhibitory effect. No effect was exerted by Wulst stimulation on 24 units. These results are discussed in terms of convergence of Wulst and retinal input on OT neurons, and the role of the integration of visual information from both peripheral and central origins is suggested for the OT neurons..  

In the chick, as soon as hatching, the responses recorded in various areas in the "accessorius hyperstriatum" (Wulst) seem to be very localized in relation with the stimulated region of the contralateral tectum.  

In the latter case, a critical interval (25--60 msec) was necessary to obtain maximal inhibition, when testing Wulst shocks previous to optic tract stimuli. These results show that the higher telencephalic visual area (the so-called Wulst) can modulate tectal activity, and so control the output of this region, by an example, to thalamic nucleus rotundus, second station of the tectofugal visual pathway. The Wulst-tectal relationship is discussed in its possible role in visual information processing and visually guided behaviours in pigeons, and also in comparison to mammalian corticotectal systems..  

Averaged visual evoked potentials (VEPs) from the surface of the Wulst and the electroretinogram (ERG) were recorded simultaneously in curarized cockerels. The polyphasic VEPs were recorded from the dorso-medial region of the Wulst of cockerels at 1 Hz stimulation, while the ERG consisted of the a, b, and c waves.  

The results are discussed in terms of competition between the projections from both eyes in the visual Wulst..  

Particular attention was paid to the discovery of retinotopic projection in the Wulst region. Unit responses in the visual projection zone of the Wulst depend on the intensity of illumination, size, and speed and direction of movement of the test objects across the receptive field. The functional role of the retino--thalamo--telencephalic system in visual interpretation in birds is discussed and it is suggested that the Wulst region is comparable with the striatal and also with the frontal regions of the mammalian cortex..  

Subjects with visual Wulst lesions showed initial postoperative threshold elevations that represented losses of 19%-49% of their preoperative sensory capacity. This initial loss was correlated with the extent of damage to three components of the visual Wulst: nucleus intercalatus hyperstriati accessorii, hyperstriatum intercalatus suprema, and hyperstriatum accessorium. The damage to hyperstriatum dorsale, another component of the visual Wulst, made no contribution to the initial deficit.  

Subjects that sustained extensive or complete damage to the visual Wulst and moderate damage to hyperstriatum ventrale showed a decrease in accuracy of performance to chance levels at all of the delay conditions as well as on simultaneous matching.  

Studies of impulse activity in 452 neurons of the hyperstriatal part of the forebrain in crows revealed visual projectional zone within Wulst. In rostral regions, neurons with the receptive fields in temporal areas of the visual field are located, whereas nasal areas are projected to caudal parts of the Wulst.  

The influence of the visual Wulst on the optic tectum of Columba livia were studied. Single shock visual Wulst stimulation elicited a surface-positive field potential the depth profile of which showed that it is due to the activation of neurons of the deep tectal layers, probably different from those responsible for the P wave. Visual Wulst stimulation depresses the positive component of the field potential elicited by optic nerve stimulation.  

In the chick, polyphasic evoked responses displaying a first negative component have been registered in the superficial part of the "Wulst" after stimulation in the depth of the contra or ipsilateral optic tectum, as early as the first hours following hatching. Moreover, responses on the surface of the tectum have been elicited by contra or ipsilateral stimulation of the Wulst.  

The visual response properties of single neurons in the owl's visual Wulst suggest that this forebrain structure is an analog of the mammalian visual cortex.  

Strychnine spikes in the Wulst EEG were not induced by the same intravenous does of strychnine in both cockerels and adult hens..  

The change in the capacity for extrapolation was studied in crows after ablation of Wulst and the archicortex. After the ablation of Wulst, the number of "refusals" to solve increases, the number of correct responses diminishes, although it remains significantly higher than the number of errors. It is assumed that the archicortex and Wulst play no decisive part in the process of solving problems involving extrapolation; yet Wulst apparently controls the achievement of the final reaction, by-passing the screen..  

Particular attention was given to revealing a retinotopic projection in the region of visual representation in Wulst. Neurons responses of the visual projection of the Wulst region depend on luminosity, size, speed and direction of the movement of the test-objects through the receptive field. The functional role of the retino-thalamo-telencephalic system in the visual integration in birds is discussed and a supposition is advanced on possibility to compare the Wulst region with striatal and frontal visual areas of the mammalian cortex..  

The AMPs appeared significantly earlier (40 msec before pecking) in the Wulst than in the neostriatum, ectostriatum, and archistriatum (18 to 28 msec before pecking).  

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