Our results reveal a significant increase (P< or =0.05) in the level of the ZENK mRNA in MNH and Field L, and in the two forebrain hemispheres; no increase was seen in the ectostriatum, which is a visual projection area.  

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. ectostriatum-lesioned pigeons were unimpaired and behaved similar to controls. 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.  

In SF birds, the density of Fos-like immunoreactive (Fos-lir) cells was elevated in the bed nucleus stria terminalis, medial portion (BSTm), and ectostriatum (E).  

The ectostriatum is a large visual structure in the avian telencephalon. Part of the tectofugal pathway, the ectostriatum receives a large ascending thalamic input from the nucleus rotundus, the homolog of the mammalian pulvinar complex. We investigated the effects of bilateral lesions of the ectostriatum in pigeons on visual motion and spatial-pattern perception tasks. Pigeons with lesions to the caudal ectostriatum showed a performance deficit on the motion task but not the grating task. In contrast, pigeons with lesions to the rostral ectostriatum showed a performance deficit on the grating task but not the motion task.  

In situ hybridisation analysis of chicken brain showed strong expression in neurons of granular layers of cerebellum, optic tectum and ectostriatum.  

In birds the entopallium (formerly known as the core region of ectostriatum) is the major thalamorecipient zone, within the telencephalon, of the tectofugal visual system.  

Labelled fibres and terminals were also found in the ipsilateral ectostriatum (Ect).  

It is an important center of visual information processing and conveys information from the optic tectum to the ectostriatum in the telencephalon.  

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.  

This coincidence is found in areas of the avian ventral and lateral pallium (ventral hyperstriatum, neostriatum, and ectostriatum) and in a part of the archistriatum, which is of pallial origin.  

However, little is known about exactly how the visual information is processed in this pathway, especially at the core region of the ectostriatum (Ec) in the telencephalon.  

The avian ectostriatum is the telencephalic recipient zone of the tectofugal pathway, which may be homologous to the colliculo-pulvinar-cortical pathway in mammals. These response properties and receptive field organization may reflect the possible roles of the ectostriatum in stimulus discrimination and visual cognition..  

Melatonin affected daytime 2DG uptake within visual suprachiasmatic nucleus and ectostriatum only.  

Primary sensory areas such as the ectostriatum, layer L2 of field L, and the rostral part of the nucleus basalis displayed very few 5-HT+ fibers.  

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. Control and ectostriatum-lesioned pigeons learned the task well, and orientated appropriately during the first trial of the last three training sessions and after a phase-shift manipulation.  

Although the optic nerve in birds crosses completely, visual information from the ipsilateral eye also reaches the ectostriatum, the telencephalic statibon of the tectofugal pathway, by recrossing fibers. These recrossing projections connect the contralateral tectum opticum with the ipsilateral nucleus rotundus, which in turn projects to the ectostriatum. The ectostriatum itself projects to the overlying lateral neostriatum, an area which serves an important role in sexual imprinting. The strength of ipsilateral responses is rather weak within the nucleus rotundus and ectostriatum, but shows a sharp increase in the lateral neostriatum. For most neurons of nucleus rotundus and ectostriatum, an additional ipsilateral stimulus did not significantly affect the response to a contralateral one.  

In birds, the thalamic nucleus rotundus relays visual information from the midbrain optic tectum to the forebrain ectostriatum.  

We recorded from 71 neurons in the ectostriatum of awake behaving pigeons performing the delayed matching-to-sample task. The ectostriatum is considered to be equivalent to the primate extrastriate cortex.  

The projection of the nucleus rotundus upon the ectostriatum is equivalent to that of the pulvinar nucleus upon the extrastriate cortex in mammals. In this system, the optic tectum relays retinal input to the nucleus rotundus, which then ascends to the ectostriatum of the telencephalon. We used multiple injections of cholera toxin B subunit (CTb) in the ectostriatum of chick embryos to retrogradely trace projections to the nucleus rotundus. It was noted that the time of this initial connection between the nucleus rotundus and the ectostriatum is nearly synchronous with that of the retinotectal and tectorotundal pathways, respectively (Crossland et al., 1975; Thanos & Bonhoeffer, 1987; Wu et al., 2000).  

The ectostriatum was characterized by intensely and diffusely stained neuropil.  

Testosterone-treated males (both captive and free-living) had a smaller telencephalon and nucleus rotundus, but not a smaller HF or ectostriatum, than controls.  

Forebrain areas devoid of immunoreactivity were the basal nucleus, ectostriatum, rostral archistriatum, most of the paleostriatum augmentatum and the lateral bed nucleus of the stria terminalis.  

The possible participation of basal ganglia and associated structures [ dorsal striato-pallidum, nucleus spiriformis lateralis (SpL), ectostriatum] in the elaboration of the optocollic reflex (OCR) was investigated by making bilateral chemical lesions (ibotenic acid). Extensive lesions (including the striato-pallidum, ectostriatum and a part of the neostriatum), as well as SpL lesions, provoked a greater SPV decrease over a longer time than lesions restricted to the striato-pallidum or the ectostriatum.  

In a control region, the primary sensory forebrain area ectostriatum, spine density and dendritic length remained unchanged.  

The ectostriatum is a major visual component of the avian telencephalon. The core region of the ectostriatum (Ec) receives visual input from the optic tectum through thalamic nuclei. In the present study, the efferent projections of the ectostriatum were investigated by using the anterograde tracers Phaseolus vulgaris leucoagglutinin and biotinylated dextran amine. When anterograde tracers were injected in Ec, primary projections were seen traveling dorsolaterally to the belt region of the ectostriatum (Ep) and the neostriatal area immediately surrounding Ep (Ep2).  

No direct connection was found between the visual Wulst and the ectostriatum or the telencephalic centres of the tectofugal and thalamofugal pathways. 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 lateral part of the hyperstriatum ventrale sent a few efferent fibres toward the diencephalon and brainstem, but projected massively to the ectostriatum periphericum, neostriatum intermedium pars laterale, the ventral part of the neostriatum caudale and the archistriatum dorsale.  

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.  

The distribution of GFAP-immunopositive astrocytes in the post-hatch telencephalon is like that found in adult chicken, except for the ectostriatum, in which an adult-like GFAP-immunostaining only develops during week three.  

In doves with bilateral electrolytic lesion of nucleus ectostriatum (E), the mean number of proliferating cells in the lateral ventricular zone (LVZ) and newborn neurons in the forebrain increased by 1.95 times and 2.38 times respectively as compared with that in intact doves. The most remarkable increase of neurogenesis induced by nucleus ectostriatum lesions was found at the anterior-posterior level 3 (L3), where the lesion site was located.  

High levels of hybridization were detected in the cortex piriformis, ectostriatum, hippocampus, cerebellum and in a range of discrete nuclei throughout the brain, including the ovoidalis, isthmo-opticus and spiriformis lateralis nuclei.  

Lesions of ectostriatum (the telencephalic target of the avian tectofugal visual pathway) impaired the ability of pigeons to learn a color-reversal task.  

Thus, only the rho1-subunit gene is expressed in the deep cerebellar nuclei, the dorsal thalamus, the ectostriatum and the tractus vestibulomesencephalicus, while only the rho2-subunit gene is transcribed in the nucleus habenularis lateralis and the nucleus isthmo-opticus.  

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).  

The reverse pattern of asymmetry was found for all 3 ligands in regions such as the ectostriatum of chicks that had their LES exposed to light, while asymmetry of muscimol and AMPA binding, present in many regions in right eye system chicks was not present in chicks that had the left eye system exposed to light during incubation.  

By contrast, glutamate injections of the left ectostriatum affected only the attack behavior and not performance in the pebble-floor test or copulation responses. Glutamate treatment of the right ectostriatum had no affect on any of the behaviours tested and this was also the case for glutamate treatment of both the left and right neostriata.  

We also demonstrate that while the beta 2S- and beta 2L-subunit messenger RNAs frequently co-localize in many brain areas, certain structures (e.g., the ectostriatum, the hippocampus, the nucleus solitarius, the nucleus isthmi, pars parvocellularis, the nucleus isthmi, pars magnocellularis, the paleostriatum primitivum, the Purkinje cell layer, and the deep cerebellar nuclei) exclusively or predominantly contain either the beta 2S- or the beta 2L-subunit transcript.  

Then the ectostriatum or the Wulst was bilaterally damaged.  

The binding of IMEL to the HVC and to visual areas, e.g., the ectostriatum and the optic tectum, was saturable and showed a single class of high-affinity binding sites with binding affinities (Kds) in the range of 5-20 pM.  

Picrotoxin-induced blockade of inhibitory synapses in the ectostriatum reveals remarkable differences between wild type and white zebra finches.  

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.  

Low but significant levels of receptors were also present in the medial preoptic area at the level of the sexually dimorphic medial preoptic nucleus and throughout the infundibulum, as well as in the ectostriatum, medial and lateral septum, and nucleus accumbens.  

Immunoreactivity for a monoclonal sequence-specific antipeptide antibody was widespread and most prominent in Purkinje cell perikarya and their dendrites, neuronal cell bodies of the ectostriatum, and the deep optic tectum.  

The endogenous cytochrome oxidase activity of the pigeon's ectostriatum, the primary telencephalic structure of the tectofugal visual pathway, was histochemically demonstrated and a heterogeneous distribution of the reaction product was observed. In cross-sections the medial, central and ventrolateral parts of the ectostriatum showed high levels of activity while the centroventral and dorsolateral ectostriatum remained weakly labelled.  

PKC gamma-stained cells were distributed widely in the telencephalon, including all hyperstriatal structures (including the IMHV), the hippocampus, neostriatum, ectostriatum and archistriatum.  

No volumetric differences were observed in ectostriatum, which served as a control brain region.  

Additionally, IMEL binding sites were detected in the ectostriatum, the thalamus, the mesencephalon and the limbic system.  

Anterograde degeneration was also noted in nuclei and tracts related to the visual tectofugal system-the brachium of the superior colliculus, nucleus rotundus, pretectal nuclei, and the ectostriatum.  

An unexpected consequence of ONX was that 2-[ 125I]- iodomelatonin binding was decreased in certain secondary (nucleus rotundus, isthmi nuclei) and tertiary level (ectostriatum) nuclei along the prominent tectofugal visual pathway.  

Volumetric analysis was carried out to measure the hippocampal region, ectostriatum, and telencephalon of experienced and control birds. No volumetric differences were observed in ectostriatum, which served as a control brain region.  

A comparable pattern of visual connections has been found: the ectostriatum has reciprocal connections with the intermediate neostriatum (Ni) and HV.  

The study shows the contribution of visual wulst efferents, to visual processing in the ectostriatum by recordings of visually 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. A model for thalamo- and tectofugal connectivity in the ectostriatum is suggested..  

The smallest proportional difference in regional CBF between control and submerged ducks occurred in the ectostriatum (+141%) and the largest in the locus ceruleus (+241%).  

Some regions, such as the ectostriatum and the hippocampus, had no positive elements.  

Experimental lesions of the ectostriatum in pigeons caused deficits in the artificial pattern recognition, arbitrary classification of natural objects, conspecific individual recognition and discrimination of two different avian species.  

In contrast, Na+,K(+)-ATPase activity in the ectostriatum (E), the medial neostriatum (NM), and the paleostriatal complex were unaffected.  

The terminals of rotundal fibers labelled with Phaseolus Lectin anterograde tracer were studied in ectostriatum periphericum and neostriatum intermedium laterale with EM. These terminals belong to the fibers which cross the ectostriatum centrale before they enter the ectostriatum periphericum and neostriatum intermedium laterale. The EM results prove the connections of ectostriatum periphericum and neostriatum intermedium laterale with the visual system..  

In situ hybridization reveals that the gamma 4-subunit mRNA is abundant in several brain regions, including the ectostriatum, nucleus rotundus and hyperstriatum ventrale, which are involved in visual processing and learning..  

In the telencephalon, the nuclei basalis, accumbens, ectostriatum, paleostriatum primitivum, and the ventral paleostriatum are particularly rich in GFAP-positive cells, whereas the neostriatum, hyperstriatum, and paleostriatum augmentatum are almost devoid of GFAP labelling.  

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.  

High receptor density was detected in the major targets of direct retinal input (optic tectum, nucleus of the optic basal rout, ventrolateral geniculate nucleus), as well as areas representing terminals in the visual pathways (nucleus rotundus, ectostriatum, thalamo-hyperstriatal pathway).  

Near by (but not overlapping) fields in NI and HV receive input from the nucleus dorsomedialis posterior thalami (DMP), the archistriatum and ectostriatum.  

After having iontophoretically injected Phaseolus vulgaris Lectin into nucleus rotundus, labelled terminals were examined in ectostriatum centrale by EM. Some observations completed the already known data on fine structure of the chicken ectostriatum centrale..  

The labelled fibers terminate in ectostriatum centrale, ectostriatum perifericum and neostriatum intermedium.  

Our earlier report of differences in metabolic activity within the visual regions of the hyperstriatum and ectostriatum, in 2-day-old chicks compared with 23-day-old chicks, suggested that two visual pathways within the visual system develop at different rates.  

The amplitude of the peak was increased in constant darkness in all structures, with the exception of the ectostriatum and neostriatum.  

After the pigeons had accomplished the discrimination tasks, they received lesions of the Wulst or the ectostriatum.  

Levels of norepinephrine, epinephrine, dopamine, and serotonin (5-HT) and their precursors [ tyrosine, L-3,4-dihydroxyphenylalanine, tryptophan, and 5-hydroxytryptophan (5-HTP)] and metabolites [ 3,4-dihydroxyphenylacetic acid (DOPAC), 3-methoxytyramine (3-MT), homovanillic acid, 3-methoxy-4-hydroxyphenylglycol, and 5-hydroxyindoleacetic acid (5-HIAA)] were determined concurrently in samples of chick retina, pineal gland, and nine selected areas of the brain (optic lobes, thalamus, hypothalamus, optic chiasm, pons/medulla, cerebellum, neostriatum/ectostriatum, hyperstriatum, and basal forebrain) using HPLC coupled with a coulometric electrode array detection system.  

The effect of barochamber hypoxia on the local blood flow in the pigeon neostriatum caudalum, hypostriatum accessorium, ectostriatum, cerebellum cortex was studied by means of the hydrogen clearance technique.  

Eight brain regions were chosen for binding characterization and pharmacological analysis: optic tectum, Edinger-Westphal nucleus, oculomotor nucleus, nucleus rotundus, ventral supraoptic decussation, ventrolateral geniculate nucleus, neostriatum, and ectostriatum.  

Based on known descriptions of ectostriatal cytoarchitecture and synaptology, it is suggested that the GABA+ cells of chick ectostriatum represent inhibitory interneurons which may be equivalent to GABAergic non-pyramidal neuronal types of mammalian visual cortex. GABA+ axosomatic synapses afferent to large GABA cells are likely to form the structural basis for a disinhibitory mechanism in the avian ectostriatum..  

Then, lesions of the ectostriatum were carried out. These results suggest that the ectostriatum plays a role in task discrimination that requires much visual processing to classify stimuli..  

Very low to background levels of VIP binding were detected in the ectostriatum, paleostriatum primitivum, paleostriatum augmentatum, lobus parolfactorius, nucleus accumbens, most of the brainstem, and the cerebellum. The paleostriatum, lobus parolfactorius, and ectostriatum were virtually devoid of both binding sites and immunoreactive profiles.  

No PPR was observed in either the caudal ectostriatum, or the paleostriatum..  

The study demonstrates one kind of the afferent fibers in ectostriatum in Golgi preparates. The fiber-networks found in one-day-old and 28-day-old chicken ectostriatum centrale were compared..  

In Golgi impregnated ectostriatum centrale of telencephalon of one-day-old chicken two types of neuron: projection neuron and interneuron with large axonal field and varicose axonal preterminals and terminals, were identified and examined in EM preparates.  

We therefore investigated the development of visually evoked potentials (VEPs) in the ectostriatum, the telencephalic target area of the tectofugal pathway. The relationship of these results to morphological studies and possible mechanisms which may cause the double-peaked development of visual-evoked potentials in the ectostriatum are discussed..  

However, the neostriatum and especially the ectostriatum showed much lower levels.  

The small influence of ipsilaterally evoked potentials is not due to inhibition by the activity of the contralateral eye, as could be demonstrated previously for the ectostriatum.  

ectostriatum and paleostriatum augmentatum displayed lower densities of specific binding.  

Increases in [ K+]e in the ectostriatum (E) of 5-6 mmol/l was found in response to electrical stimulation (30-100 Hz, 5-10 sec) of the contralateral optic nerve, and of about 2 mmol/l by applying pressure to the bulb.  

The activity of these enzymes was studied by a one-point assay in 5 nuclei of the song system (X, MAN, HVc, RA, ICo), 2 nuclei of the visual system (ectostriatum, nucleus rotundus) and in limbic and hypothalamic areas. A few sex-related differences in the activity of the 5 beta-reductase were also observed (higher activity in females than in males for area X and RA, but difference in the opposite direction for the ectostriatum).  

The effects of monocular deprivation, beginning at hatching, were examined in the neuropil of ectostriatum, a visual telencephalic projection area in birds. The volume of ectostriatum, the number of synapses and subsynaptic features like the presynaptic terminal size and the length of the postsynaptic contact zone were quantified in juvenile (20 d) and adult (100 d) zebra finches. Both hemispheres are affected in juvenile birds with respect to the volume of ectostriatum, the length of synaptic contact zones and the presynaptic terminal size when compared to normal values. The only permanent effect caused by monocular deprivation in the ectostriatum is characterized by smaller presynaptic terminals.  

To determine the dynamic level of these processes, the development of perforated synapses at different ages was examined in the neuropil of the ectostriatum, a visual projection area in birds.  

The development of synapses and subsynaptic features in the neuropil of the ectostriatum, a visual projection area in birds, was examined ultrastructurally at 5, 10, 20, and 100 days posthatching. The number of synapses in ectostriatum and the number of specific synaptic types vary with age as does the constellation of subsynaptic structures. This increase is mainly due to an increase of asymmetric synapses, the most common type in the neuropil of ectostriatum (90% of the synapse population).  

Primary sensory projection areas, such as the ectostriatum (visual), hyperstriatum intercalatum superius (visual), nucleus basalis (beak representation), the input layer L2 of the auditory field L and the somatosensory area rostral to field L were selectively left unstained.  

[ 3H]MK-801 binding is generally widespread in the telencephalon but is notably absent from the ectostriatum.  

Pigeons with lesions of either the Wulst or ectostriatum were compared to controls on reversal of a go/no-go pattern discrimination. The ectostriatum-lesioned group was not different from controls.  

It was found that the projection areas of brachial afferents were located within the neostriatum, the hyperstriatum and the ectostriatum.  

Intermediate levels were found throughout the paleostriatal regions, septum, thalamus, archistriatum, hyperstriatum accessorium and area parahippocampalis whilst in hippocampus and ectostriatum the density of [ 3H]naloxone binding sites was low.  

Light and electron microscopic studies have been made on degenerative changes in the nervous tissue induced by experimental destruction of the median brain bulb at the 5th day of incubation, in parts of the tecto-thalamo-telencephalic visual system in 13-day chick embryos (in the visual tectum, round nucleus of the thalamus and ectostriatum of the telencephalon).  

Recent research has demonstrated that ipsilaterally visually evoked potentials (VEPs) can be measured within the ectostriatum, the telencephalic target area of the tectofugal visual pathway in birds. The occurrence of macroscopic sinks and sources and the fact that VEPs can be recorded from the ectostriatum shows that there is a higher degree of order in the ectostriatum than has been previously demonstrated by anatomical methods.  

Pigeons were trained to discriminate visual stimuli that differed in intensity, color, or pattern, after which lesions were made in the ectostriatum, either the core region (EC), the belt region (EB), or both (EC + EB).  

The postnatal development of the main neuron type in the ectostriatum, the telencephalic station of the tectofugal pathway, was followed in normally reared and monocularly deprived zebra finches by using the Golgi method.  

When their performance stabilized, lesions were made in the ectostriatum in 4 birds and in the neostriatum in the remaining 3 birds. After surgery, the pigeons with ectostriatum lesions showed markedly elevated thresholds. A psychophysical scaling analysis showed that the ectostriatum-lesioned pigeons had lost from 50% to 83% of their preoperative capacity to discriminate differences in the intensity of visual stimuli. A multiple-regression analysis based on quantitative reconstructions of the lesions revealed that only damage to the core region of the ectostriatum contributed to the postoperative threshold changes..  

The present study concerns the time course of this sensitive period for the morphological effects of monocular deprivation in two areas of the tectofugal visual pathway of zebra finches, the nucleus rotundus of the thalamus and the telencephalic ectostriatum.  

tectum opticum, nucleus rotundus of thalamus and ectostriatum of telencephalon--of 13-day chick embryos. Being phylogenetically more ancient structures, tectum opticum and nucleus rotundus reveal differentiation earlier than ectostriatum which is phylogenetically younger..  

D1 receptors were in addition enriched in the entire pigeon telencephalon with exception of the ectostriatum.  

This study is the first to demonstrate an excitatory projection from the ipsilateral eye to the telencephalic projection area of the tectofugal pathway by recordings of visually evoked potentials in the ectostriatum. The excitatory projection probably leads from the eye to the contralateral tectum opticum, then recrosses back to the nucleus rotundus of the ipsilateral side where it reaches the ectostriatum. In normal birds, the ipsilateral stimulus responses in the ectostriatum are smaller in amplitude and have a longer latency than responses to contralateral stimuli. In unilaterally enucleated birds, the ipsilateral response is enhanced in the ectostriatum and can be detected in the nucleus rotundus, too.  

Chicken ectostriatum was studied in Golgi preparations. In the two parts of the area (ectostriatum centrale and ectostriatum periphericum) the cell types were analysed. The stellate-like projection neurons in ectostriatum centrale have 4-6 main dendrites, which ramify only slightly, and are densely covered by characteristic spines. The projection neurons in ectostriatum periphericum emit several (7-10) main dendrites, which have numerous bifurcations establishing a dense dendritic tree. The interneurons--in both parts of ectostriatum--have three subtypes.  

After the discrimination tasks were again mastered, a second set of lesions was made, this time in the ectostriatum. 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 after the second operation of the WI-EII group was the same as that of pigeons with lesions of ectostriatum alone; i.e. destruction of ectostriatum first or second resulted in the same duration of impairment.  

The lowest levels of NT binding sites in the telencephalon were observed within the paleostriatum primitivum (PP, considered comparable to mammalian globus pallidus), ectostriatum (comparable to layer IV of mammalian extrastriate visual cortex), field "L" (comparable to layer IV of mammalian auditory cortex), hippocampus, septum, and preoptic area.  

The primary sensory areas (ectostriatum, field L) were active above background in each experiment.  

In the first experiment, pigeons with lesions of the ectostriatum that spared the medial 15% were unimpaired in their size-discrimination ability. Those cases in which the lesions involved both the medial and lateral regions of the ectostriatum were greatly impaired. In addition, the second study indicated that destruction of the medial ectostriatum with the lateral regions intact had no measurable effect on size-difference thresholds. The medial region of ectostriatum is part of the termination field of a second tectofugal pathway to the telencephalon. This pathway passes from the optic tectum to nucleus dorsolateralis posterior thalami and then to the neostriatum intermedium, including the medial ectostriatum. An examination of the data of the present experiment and those of other behavioral studies of the ectostriatum suggest that the medial ectostriatum may be involved in the processing of visual information with low spatial-frequency components and the lateral ectostriatum may be processing information about the high-frequency composition of stimuli..  

140:35-52, '70) have described an ascending tectofugal visual pathway from the optic tectum to the ectostriatum by way of the nucleus rotundus of the thalamus.  

The effects of different periods of monocular deprivation on cell sizes in the ectostriatum, the telencephalic relay of the tectofugal pathway in zebra finches, were evaluated.  

The postnatal development of two visual areas (nucleus rotundus and ectostriatum) and two song control areas (hyperstriatum ventrale pars caudale, HVc, and nucleus robustus archistriatalis, RA) of the zebra finch brain was followed from birth to adulthood. A similar temporal sequence of development is seen in the ectostriatum, except myelination starts some days later.  

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.  

During conditioning single neurons in the nucleus rotundus and ectostriatum, the thalamic and telencephalic relays of the tectofugal pathway, showed enhancement of their phasic light-evoked responses.  

Highest receptor density was observed in the hyperstriatum ventrale, palaeostriatum augmentatum, septum, and parts of the archistriatum In sites of known sensory input of neostriatum (field L) and ectostriatum low receptor binding was observed.  

The sites of origin of ascending projections to the telencephalon in the pigeon (Columba livia) were studied by means of the retrograde fluorescence technique following the injection of various tracers (Evans Blue, Fast Blue, Nuclear Yellow) concomitantly into different regions of topographically distinct areas of one hemisphere: hyperstriatum (HY), ectostriatum-paleostriatum (EP), posterior neostriatum (PN). Single ipsilateral projections upon either the ectostriatum or the caudal neostriatum arise from the nucleus (n.) rotundus/n.  

In one group, lesions were made in the ectostriatum, which is the telencephalic target of the tectofugal visual pathway.  

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.  

Three of these areas show topographic relationships to primary projection areas in the neighbouring neostriatum (Nucleus basalis, ectostriatum, Feld L), and connections are in part well known.  

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). As in the pigeon or the owl the ectostriatum of the zebra finch receives massive input, which is topographically ordered, from the n. In addition to this pathway the ectostriatum receives additional visual input from the ipsilateral area pretectalis, the n.  

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).  

Each telencephalic structure (based on terminology used by Karten and Hodos, '67) was characterized by a specific range of birthdates: some regions such as the core of the ectostriatum or the paleostriatum primitivum, were generated within a single day, while others, such as the hyperstriatum accessorium, required up to five days for generation of the complete population.  

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.  

TPO neurons, in turn, were found to receive projections from the contralateral ventral archistriatum (Av) and from neurons in the ipsilateral frontal neostriatum adjacent to the rostral portion of the ectostriatum (e).  

As Mogenson and CioĆ© (1977) have assumed that our electrodes aimed at the ectostriatum (Hollard and Davison, 1971) were actually located there, we feel that a presentation of the histological data is necessary. Further work in this laboratory has also found that, using the same coordinates, electrode tips tend to fall in the paleostriatum, rather than in the more dorsal ectostriatum at which they are aimed. The paleostriatal placements tended to sustain self-stimulation, whereas others located in the ectostriatum sustained relatively low or unstable rates..  

To examine the detailed organization of this principal ascending visual pathway, small injections of the marker horseradish peroxidase (HRP) were placed in various sites throughout the ectostriatum (E) or nucleus rotundus (Rt) in pigeons. The various subdivisions of rotundus in turn project upon distinct portions of the ectostriatum. In contrast, the nucleus triangularis, a dorso-medial extension of Rt which receives its input from the deepest of all SGC neurons, sends its efferents to all parts of the ectostriatum..  

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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