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. 
NCL receives telencephalic projections from the hyperstriatum accessorium, cells along the border of hyperstriatum dorsale and hyperstriatum ventrale, anterolateral hyperstriatum adjacent to the vallecula, confined cell groups within the anterior neostriatum, and subdivisions of the archistriatum.
In particular, efferent pathways from the granular layer (Intercalated nucleus of the hyperstriatum accessorium, IHA), supragranular layer (hyperstriatum accessorium, HA), and infragranular layers (hyperstriatum intercalatus superior and/or hyperstriatum dorsale, HIS/HD) were investigated.
In contrast, in the hyperstriatum dorsale and hyperstriatum ventrale, numerous PPE mRNA-expressing cells were detected in the chicken but not in the pigeon.
In the E19 groups metabolic activity in visual regions of the hyperstriatum accessorium (HA) was significantly higher than that in the hyperstriatum dorsale (HD), the region which receives the thalamofugal visual projections.
The piriform cortex also connects reciprocally with a large portion of the anterior telencephalon, including the cortex prepiriformis and hyperstriatum dorsale.
It was possible to localize these changes in Na+,K(+)-ATPase activity into forebrain structures contained within the dorsal ventricular ridge comprising the hyperstriatum accessorium (HA), hyperstriatum ventrale (HV), hyperstriatum dorsale (HD), and parts of neostriatum (N).
There were decreases in binding in the hyperstriatum dorsale of the left hemisphere (14%) and a decrease in binding in the lateral hyperstriatum ventrale of the right hemisphere (14%).
In 2 experiments we explored the effects of lateral versus medial laminar lesions of the hyperstriatum in pigeons (Columba livia); medical lesions were largely confined to the hyperstriatum accessorium, and lateral lesions to the hyperstriatum dorsale and hyperstriatum ventrale.
On the other hand, a raised level of activity in the hyperstriatum dorsale (HD) appeared in chicks viewing the rotating stripes, indicating that at this age the thalamo-hyperstriatal pathway may be involved in processing whole-field visual movement.
The highest densities of binding sites were observed in the hyperstriatum dorsale, archistriatum, auditory field L of neostriatum, area corticoidea dorsolateralis and temporo-parieto-occipitalis, area parahippocampalis, tectum opticum, nucleus dorsomedialis anterior thalami, and in the periventricular area of the hypothalamus. Fibers and terminals were observed in the area corticoidea dorsolateralis, area parahippocampalis, hippocampus, hyperstriatum accessorium, hyperstriatum dorsale, archistriatum, tuberculum olfactorium, nuclei dorsolateralis and dorsomedialis of the thalamus, and throughout the hypothalamus and the median eminence. A qualitatively good matching was found in the area corticoidea dorsolateralis, hyperstriatum dorsale, hyperstriatum accessorium, nucleus septi lateralis, nuclei dorsomedialis and dorsolateralis thalami, and in some hypothalamic areas.
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.
Contralateral visual information arrives in the hyperstriatum dorsale (HD) and is processed further to the hyperstriatum accessorium (HA).
Telencephalic afferents of the DLP came from the hyperstriatum accessorium (HA) and a group of cells at the borderline between the hyperstriatum intercalatus superior (HIS) and the hyperstriatum dorsale (HD).
In the telencephalon, identifiable groups of progestin-accumulating cells were found in the hyperstriatum dorsale, at the medial edge of the lobus parolfactorius, and in the medial septum.
The highest staining intensity was found in the nonprimary sensory regions of the telencephalon such as the hyperstriatum dorsale, hyperstriatum ventrale, hippocampus, palaeostriatum augmentatum, lobus parolfactorius and caudal parts of neostriatum.
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.
Among the forebrain regions, the greatest levels of opiate binding were found in hyperstriatum dorsale, hyperstriatum ventrale, hyperstriatum intercalatum supremum and neostriatum.
3 and 4, but not in 1 and 2: part of the neostriatum intermedium; part of the lateral neostriatum, both with adjacent parts of the hyperstriatum ventrale, hyperstriatum accessorium and hyperstriatum dorsale, a portion of the caudal neo/archistriatum.
Pallial derivatives including the hyperstriatum dorsale, hyperstriatum ventrale, dorsal archistriatum, and hippocampus also receive projections from AVT and TPc neurons, although these projections are much sparser than those reaching subpallial structures.
Within the telencephalon, the following neural structures receive input from neurons in the LoC and subcoeruleus cell groups: the paleostriatal complex including the paleostriatum augmentatum and lobus parolfactorius, septal nuclei, nucleus accumbens, olfactory tubercle, hippocampus and parahippocampal area, nucleus taeniae, dorsal archistriatum, lateral neostriatum, hyperstriatum dorsale, hyperstriatum ventrale, and preoptic area.
Only Hp received input from the contralateral Hp while only APH received input from the ipsilateral hyperstriatum dorsale and archistriatum, pars ventralis. Only Hp appeared to send efferents to the contralateral septum and Hp, while only APH sent efferents to the hyperstriatum dorsale and the archistriatum.
Increased 2-deoxyglucose incorporation were found in 3 rostral forebrain areas of separated chicks, namely the hyperstriatum accessorium/hyperstriatum dorsale, the lateral neostriatum/hyperstriatum ventrale and the medial neostriatum/hyperstriatum ventrale.
Aromatase activity was measured and found to be present in the anterior pituitary gland, the anterior/preoptic hypothalamus, the posterior hypothalamus and the hyperstriatum dorsale. It was higher in the hypothalamus than in the hyperstriatum dorsale and higher in the posterior than in the anterior/preoptic hypothalamus.
Numerous fibers leave the LPO region and course dorsally into the deep layer of the Wulst, hyperstriatum dorsale (HD).
The metabolism of testosterone to reduced derivatives was studied in the pituitary gland, the hypothalamus, and the hyperstriatum dorsale of thyroidectomized, sham-operated, and thyroxine (T4)-injected immature cockerels. Irrespective of thyroid state 5 beta-DHT and 5 beta-3 alpha-diol were produced to the greatest extent by the hyperstriatum dorsale whereas androstenedione was maximally produced in the pituitary gland. In comparison with the hyperstriatum dorsale and the hypothalamus only small quantities of 5 beta-DHT were produced in the pituitary gland. In the hyperstriatum dorsale of thyroidectomized birds both 5 beta-DHT (P less than 0.05) and 5 beta-3 alpha-diol (P less than 0.1) were formed to a greater extent than in sham-operated birds.
Little enkephalinlike immunoreactivity was observed dorsal to the paleostriatal complex except in the hyperstriatum dorsale. Within the hyperstriatum dorsale, a band of enkephalinergic neurons appeared to give rise to an overlying parallel band of dense enkephalinergic fibers.
In some of the chicks, after penetrating through HA, discharges evoked by diffuse retinal illumination were monitored and the zona hyperstriatum intercalatus/hyperstriatum dorsale (HI/HD) below HA was classified as being a visually responsive lamina (VRL) if responses were obtained to greater than or equal to 20 consecutive light flashes.
The metabolism in vitro of [ 4-14C]testosterone to reduced derivatives was studied in the pituitary gland, hypothalamus and hyperstriatum dorsale of cockerels from hatch to sexual maturity. At all ages studied, 5 beta-DHT was formed to the greatest extent by the hyperstriatum dorsale, to a lesser extent by the hypothalamus and in the smallest quantities by the pituitary gland.
In the laying hen, progesterone was shown to be converted in vitro in the pituitary gland and the hypothalamus to 5 beta-pregnane-3,20-dione (5 beta-pregnane-3 alpha-ol-20-one (5 beta,3 alpha-ol) and 5 alpha-pregnane-3,20-dione (5 alpha-DHP) and in the hyperstriatum dorsale to 5 beta-DHP and 5 beta,3 alpha-ol. The conversion of progesterone to 5 beta-reduced metabolites was greater in the hyperstriatum dorsale than in the hypothalamus (P < 0.001) and greater in the hypothalamus than in the pituitary gland (P < 0.01).
No labelling was observed in hyperstriatum dorsale.
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).
The brains of the swift Streptoprocne zonaris, the flycatcher Tyrannus melancholicus, the tanager Ramphocelus dimidiatus and the finch Oryzoborus angolensis were compared with respect to the hyperstriatum accessorium, hyperstriatum dorsale, hyperstriatum ventrale, neostriatum, ectostriatum, paleostriatum augmentatum and paleostriatum primitivum.
The damage to hyperstriatum dorsale, another component of the visual Wulst, made no contribution to the initial deficit.
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