Prestriate Cortex Research Articles

Recency effects and lesion effects in delayed non-matching to randomly baited samples by monkeys

Monkeys' memory for 3-dimensional junk objects was tested in a task which required them to discriminate objects which had recently been presented in an acquisition list from new objects which had not. The accuracy of this discrimination was shown to depend on the recency of presentation of the old object. The discrimination was not significantly affected by lesions of either the foveal pre-striate cortex, the fundus of the superior temporal sulcus, or the anterior inferior temporal area. A substantial impairment was caused by transection of the formix.

A tectocortical visual pathway in the rat

Injections of tritiated leucine into the superior colliculus of the rat were used to study the efferents of the colliculus. The superficial layers of the colliculus project to the lateral posterior nucleus, the lateral geniculate nucleus and the pretectum. Two distinct subdivisions of the lateral posterior nucleus were found, a caudomedial region which receives a bilateral projection from the superior colliculus and an anterolateral region which receives a unilateral projection from the superior colliculus. Injections of horseradish peroxidase into the lateral prestriate visual cortex showed that the lateral posterior nucleus sends a dense projection to this area. There was no evidence that the caudomedial and anterolateral parts of the lateral posterior nucleus project to different regions of the lateral prestriate cortex. The tectothalamocortical pathway in the rat provides a major route outside the geniculostriate projection by which visual information from the retina can reach the cortex.

Prestriate afferents to inferior temporal cortex: an HRP study

The inferior temporal (IT) cortex of 6 macaques was injected with horseradish peroxidase. HRP-labeled cells were found throughout IT cortex itself (outside the injection area) but were not found in the polysensory areas that surround IT dorsally, anteriorly and ventrally. Posterior to IT, labeled cells were found in the anterior parts of prestriate cortex. In one animal, the anterior prestriate region was injected with HRP. Labeled cells were then found in the regions of posterior prestriate cortex that receive direct projections from striate cortex. These results suggest that IT cortex receives information from striate cortex after at least two stages of processing in prestriate cortex.

The striate projection zone in the superior temporal sulcus of Macaca mulatta: location and topographic organization.

In the rhesus monkey, the caudal portion of the superior temporal sulcus (STS) receives a direct projection from lateral striate cortex, the striate are representing central vision. The present study was undertaken to determine whether STS also receives a direct projection from areas of striate cortex representing peripheral vision, with the intent of defining the entire striate projection zone in STS as well as providing information regarding a possible topographic organization within this secondary visual area. A series of five rhesus monkeys was prepared with unilateral lesions of lateral, posterior, or medial striate cortex, such that, collectively, the lesions in the series included all of striate cortex with little or no invasion of prestriate cortex. The monkeys were sacrificed seven days after surgery and their brains were processed by the Fink-Heimer procedure. An analysis of the distribution of terminal degeneration within STS indicated: (1) All areas of striate cortex project to a restricted region along the caudal portion of STS. The ventral limit of this region can be demarcated by an imaginary line connecting the ventral tips of the lunate and intraparietal sulci; from this limit the region extends dorsocaudally for approximately 12 mm to the point at which STS frequently bifurcates, sending one spur forward into the inferior parietal lobule. (2) Within this portion of STS there is an orderly mapping of the visual field; progression from central vision to the far periphery is represented by a progression down the posterior bank of STS and continuing along the entire floor, or insula-like portion, of the sulcus. (3) Projections from striate cortex to STS terminate predominantly in layer IV and the deep part of layer III. (4) There is a distinctive pattern of myelination contained within the striate projection zone of STS. These anatomical findings concerning the striate projection zone of STS in the rhesus monkey are remarkably similar to those that have been described for the middle temporal visual area (MT) in New World monkeys, and thus support earlier proposals that the two areas are homologous.

Evoked potential evidence for differences in binocularity between striate and prestriate regions of human visual cortex.

For two components of the visual evoked potential elicited by the onset of a stationary pattern the degree of interocular transfer of the attenuation caused by prior exposure to a similar pattern was measured. The results show almost complete interocular transfer for component CII, thought to originate in prestriate cortex, but only partial transfer of CI, thought to be of striate cortical origin. This suggests that in man, as in monkey, monocularly driven neurones are more common in striate than in prestriate cortex.

Fucntional specialization and binocular interaction in the visual areas of rhesus monkey prestriate cortex.

If is is believed that neural mechanisms mediating stereoscopic vision may be localized in specific areas of the visual cortex, then it becomes necessary to be able to define these areas adequately. This is no easy matter in the rhesus monkey, an animal close to man, where the cytoarchitecturally uniform prestriate cortex is folded into deep sulci with secondary gyri. One way around this awkward problem is to use the callosal connections of the prestriate cortex as the anatomical landmarks. Callosal connections are restricted to regions at which the vertical meridian is represented. Since the visual fields, including the vertical meridian, are separately represented in each area, each has its own callosal connections. These are of great help in defining some of the boundaries of these areas, since the boundaries often coincide with the representation of the vertical meridian. With the visual areas thus defined anatomically, it becomes relatively easy to assign recordings to particular areas. Studies of binocular interactions in these areas reveal that most cells in all prestriate areas are binocularly driven. Hence, theoretically, all of the prestriate areas are candidates for stereoscopic mechanisms. The degree of binocular interaction varies from cell to cell. At the two extremes are cells which either respond to monocular stimulation only and are inhibited by binocular stimulation or ones which respond to binocular stimulation only. Changing, as opposed to fixed, disparity is signalled by two types of cells. In one category are cells activated in opposite directions for the two eyes. Such cells are always binocularly driven. In the other category are cells, some of which are monocularly activated, that are capable of responding to changing image size. In the monkey, both these categories of cells have so far been found in the motion area of the superior temporal sulcus only.

Depth sensitivity of binocular cortical neurons of behaving monkeys.

Activity of neurons if foveal striate and prestriate cortex of trained rhesus monkeys was recorded with metal microelectrodes. While animals fixated a small spot at a given fixation distance (38 or 57 cm), bright or dark bars moving across a frontoparallel plane were presented at different depths in a range of +/- 10 cm about the fixation distance. Almost all cells showed binocular interaction. Neurons with balanced ocularity (approximately equal monocular responses) usually facilitated each other and were tuned to depth around the plane of fixation often with inhibitory flanks nearer and further. Neurons with unbalanced ocularity either inhibited each other or had asymmetric depth sensitivity profiles, i.e. activation by stimuli in front and suppression by stimuli behind the fixation plane (near cells) or vice versa (far cells). Thus striate and prestriate cortex of the monkey contains four subsets of binocular cells which may contribute to depth perception.

A comparison of the organization of the projections of the dorsal lateral geniculate nucleus, the inferior pulvinar and adjacent lateral pulvinar to primary visual cortex (area 17) in the macaque monkey

Both anterograde and retrograde transport tracing methods were used to study the organization of the projections of the dorsal lateral geniculate (DLG), the inferior pulvinar and subdivisions of the lateral pulvinar to primary visual cortex (striate cortex or area 17). The DLG projects only to striate cortex. These projections are retinotopically organized, and do not extend to any cortical layers above layer IVA. In contrast the inferior pulvinar (PI) and the immediately adjacent portion of the lateral pulvinar (PLα 48) project to both striate and prestriate cortex. The projections from these two thalamic areas to the striate cortex are also retinotopically organized and exist in parallel with those from the DLG. In contrast to the DLG, the projections from PI and PLα terminate above layer IVA in striate cortex, i.e. layers I, II and III. In prestriate cortex the layers of termination include layers IV, III and I. The pulvinar terminations in layers II and III of area 17 occur in segregated patches as do the geniculate terminations in layers IVC and IVA. On the other hand the pulvinar terminations in layer I which overlie those in layers II and III of area 17 appeared to be continuous. Control studies show that the remainder of the lateral pulvinar overlying PLα does not project to striate cortex. It is concluded that there are 3 visuotopically organized inputs from the lateral thalamus to primary visual cortex and that each of these inputs have different layers of termination. The inputs from PI and DLG can convey direct retinal inputs while those from PI and PLα can also be involved in intrinsic cortico-thalamocortical connections with prestriate cortex. It remains, then, that it cannot be tacitly assumed that the ascending inputs which influence the response properties of the primary cortical neurons arise solely from the dorsal lateral geniculate nucleus. It is also argued that these inputs to the supragranular layers may be excitatory as those from the DLG to the IVth layer.

Role of the inferotemporal cortex in visual selective attention

Electrocortical recordings were made from monkeys performing in a multidimensional visual task. Wave forms dependent on the stimulus presented (irrespective of task required) were recorded immediately following the stimulus primarily from electrodes implanted in the striate and prestriate cortex. Wave forms dependent on the panel pressed (irrespective of the stimulus or of the task) were recorded especially from motor and post-central cortex, and to a lesser extent in anterior frontal cortex, always just prior to or following the time of the response. Wave forms dependent on the task as determined by the reinforcing contingencies (but independent of the particular stimulus presented or the particular panel pressed) were recorded primarily from the inferior temporal cortex, and rarely from prestriate and anterior frontal cortex. While task-related wave forms began to appear shortly after stimulus presentation, they became especially apparent around the time of the response. This response-linking increased in prominence as the subject achieved 90% proficiency in each task, only to drop off with overtraining. Further, the task-related wave form does not change as rapidly as does overt behavior when the reinforcement contingency is shifted from one stimulus dimension to another. The relevance of these results to an understanding of the process of selective attention is discussed.

Columnar cortico-cortical interconnections within the visual system of the squirrel and macaque monkeys

Cortico-cortical interconnections within the visual cortex of squirrel monkeys ( Saimiri sciureus) were studied by means of single or multiple injections of [ 3H]leucine or combined [ 3H]leucine and horseradish peroxidase into the dorsolateral striate and prestriate cortices. Injections of [ 3H]leucine were also made into the dorsolateral striate cortex of a Macaca speciosa for comparison. The results indicated that in Saimiri the dorsolateral prestriate cortex is precisely and reciprocally connected with the striate and peristriate cortex, and with the posterior bank of superior temporal sulcus, including the middle temporal area (MT). The dorsolateral striate area is precisely and reciprocally connected with the prestriate and MT area, but does not project to the perstriate cortex as in the case of the macaque. At each target site, the radioactively labelled terminal fields are distributed in a distinctly columnar fashion, with labelled columns (120–480 μm in diameter, commonly 240 μm) interdigitating with sparsely labelled or unlabelled columns of lesser widths. The HRP-labelled neurons invariably exist within the radioactively labelled columns. For all of the cortical areas examined except area 17, lamina IV is the principal ‘receptive’ layer for associational fibers, while layers III and II, as well as V and VI within the same column, receive progressively less input. As for area 17, associational fibers from the prestriate cortex terminate mainly within lamina I, with laminae II, III, V and VI receiving decreasing amounts of input. The present results indicate that the major visual cortical areas are interconnected in precise, topographical and reciprocal fashion. The columnar arrangement is found to be the basis of both extra- and intercortical connections.

A quantative study of the cells projecting from the lateral geniculate nucleus to the prestriate cortex in the monkey with horseradish peroxidase

A quantative study of the cells projecting from the lateral geniculate nucleus to the prestriate cortex in the monkey with horseradish peroxidase

Visual cortex ablation and thresholds for successively presented stimuli in rhesus monkeys: I. Orientation.

Rhesus monkeys were trained to discriminate gratings of different orientation presented one at a time. The smallest difference they could reliably detect was determined before and after removal of either inferotemporal, foveal prestriate or lateral striate cortex. Four animals with inferotemporal lesions had significantly higher thresholds after operation, which did not improve after extensive practice. Two monkeys with lateral striate ablation, and 1 out of 3 animals with foveal prestriate lesions were also impaired, but improved with practice. Monkeys without inferotemporal cortex may have imprecise internal templates for stimulus orientation, in accordance with the categorisation hypothesis of the inferotemporal defect.

Reciprocal connections between striate and prestriate cortex in squirrel monkey as demonstrated by combined peroxidase histochemistry and autoradiography

Reciprocal connections between striate and prestriate cortex in squirrel monkey as demonstrated by combined peroxidase histochemistry and autoradiography

Uniformity and diversity of structure and function in rhesus monkey prestriate visual cortex.

1. Recordings were made from single neurones, or small clusters of cells, in five prestriate visual areas of rhesus monkey cortex. The cells were studied for their binocularity, as well as for their orientational, motion and colour preferences. In all, 1500 cells were studied, 250 cells for each of the areas V2, V3, V3A and the motion area of the posterior bank of the superior temporal sulcus, and 500 cells for V4. All the cells referred to in this study can be placed in one prestriate area or another unambiguously. 2. The great majority of cells in all areas were binocularly driven, without monocular preferences. Within each area, there were cells that either preferred binocular stimulation markedly, or were responsive to binocular stimulation only. The ocular interaction histograms for all areas are remarkably similar when tested at a fixed disparity. 3. Over 70% of the cells in areas V2, V3 and V3A were selective for orientation. The receptive fields of cells were larger in V3 and V3A than in V2. By contrast, less than 50% of the cells in V4 and the motion area of the superior temporal sulcus were orientation selective. 4. Directionally selective cells were found in all areas. But they were present in small numbers (less than 15%) in areas V2, V3, V3A and V4. By contrast, 90% of the cells in the motion area of the superior temporal sulcus were directionally selective. 5. 8% of the cells in V2 had opponent colour properties. Cells with such properties were not found in V3, V3A or in the motion area of the superior temporal sulcus. By contrast, 54% of the cells in the V4 complex had opponent colour properties. 6. It is argued that despite its uniformity in cytoarchitectural appearance and in ocular interaction patterns, there is a functional division of labour within the prestriate cortex. Evidence for this is seen not only in the different concentrations of functional cell types in distinct areas of the prestriate cortex, but also in the differential anatomical and callosal connexions of each area.

The third visual complex of rhesus monkey prestriate cortex.

1. Two independent but neighbouring visual areas, V3 and V3A, sharing a common cytoarchitectural plan, but in each one of which the visual fields are separately represented, have been studied anatomically, functionally, and in combined anatomico-physiological experiments. 2. The properties of single cells in the two areas are so similar, judged by the techniques used in this study, that it is often impossible to tell whether any one penetration was sampling from cells in V3 or V3A. This is especially so if the cells have receptive fields in the lower hemi-quadrants, since the vertical meridian of the lower visual fields is represented along the V3-V3A boundary and since a transition from V3 to V3A along this border is not accompanied by a shift in receptive field positions of cells. 3. Since the visual fields, including the vertical meridian, are separately represented in these two areas, and since regions of vertical meridian representation are callosally connected, a simple and certain method of specifying the boundary between V3 and V3A is to examine the degeneration following section of the callosal splenium. A heavy patch of degeneration then marks the V3-V3A boundary. Within this patch, however, is a sub-patch containing fewer callosal fibres, or none at all. The boundary between V3 and V3A was taken to be at this subpatch. 4. Since the horizontal meridian is represented at the V2-V3 boundary, and since V1 projects to both these areas, sending coarse fibres to V3 and fine fibres to V2, it was found that the boundary between V2 and V3 could be precisely drawn by making a lesion in the horizontal meridian representation in V1 and noting where, in the prestriate cortex, fine fibres give way to coarse ones, without an intervening gap. 5. Double tracer anatomical experiments, in which tritiated proline was injected into V1 of animals whose callosal splenium had been sectioned, showed that whereas V3 receives a direct input from V1, V3A does not. V3A, instead, was found to receive an input from V3. Double tracer anatomical experiments were undertaken to study a possible input from V2 to V3A. Although such experiments did not reveal a direct input from V2 to V3A, they were not entirely conclusive. 6. The vast majority of cells in V3 and V3A were binocularly driven, without obvious monocular preferences. Some cells, however, though responding to stimulation of the individual eyes, summated their responses to binocular stimulation. Others responded only when both eyes were simulataneously stimulated. In any oblique penetration, cells preferring binocular stimulation only occurred either singly or in groups. 7. In an oblique penetration, the shift from a cell responding to binocular stimulation only to one responding equally well to stimulation of either eye was not necessarily accompanied by a shift in orientational preferences, shifts in the former...

The topographic organization of rhesus monkey prestriate cortex.

1. The topographic organization of prestriate visual cortex in the rhesus monkey has been studied both anatomically, by determining the pattern of termination of fibres passing through the corpus callosum, and physiologically, in the same animals, by plotting receptive field positions for different recording sites. Results are displayed on two-dimensional, "unfolded" maps of the cortex in the dorsal half of the occipital lobe. 2. Transcallosal fibres terminate in a narrow strip of cortex along the boundary between striate and prestriate areas and in a separate, broader, zone occupying much of the anterior bank of the lunate sulcus, the annectant gyrus, and the parietooccipital sulcus. The detailed pattern of inputs is highly complicated but shows considerable similarities from one animal to the next. 3. Physiological recordings confirmed earlier reports that regions where transcallosal fibres terminate correspond to representations of the vertical meridian in the visual field. This relationship is most precise along the striate-prestriate boundary and along the boundary of area V3 farthest from V1; it is less precise within area V4, where the pattern of transcallosal inputs is more complex. 4. A distinct, topographically organized visual area, named V3A, was found in the region between areas V3 and V4 in the lunate and parieto-occipital sulci. Area V3A differs from V2 and V3 in that both superior and inferior visual quadrants are represented in a single region of the dorsal occipital lobe. 5. The contralateral visual field is represented in a suprisingly complex fashion in areas V3A and V4. Within each area there are multiple representations of some, but perhaps not all, parts of the visual hemifield. It is unclear whether V3A and V4 should be more appropriately considered as sets of distinct sub-areas, each representing only a portion of the hemifield, or as larger areas with complicated internal topographies. 6. Most cells in areas V2, V3 and V3A are orientation selective but not selective for stimulus colour or direction of movement. In contrast, area V4 contains a higher incidence of colour selective cells and a lower incidence of orientation selectivity. These results support the notion of a functional division of labour within the prestriate cortex.

The cortical projections of foveal striate cortex in the rhesus monkey.

1. The cortical projections of the foveal and extrafoveal parts of the striate cortex have been compared, using conventional degeneration techniques, as well as combinations of anatomical methods. While both foveal and extrafoveal striate cortex share a common pattern of projections (to areas V2, V3 and the visual area in the medial part of the posterior bank of the superior temporal sulcus), foveal striate cortex was found to have an additional projection (to part of the cortex of the fourth visual areas, V4). The latter projection includes the posterior lip of the inferior occipital sulcus which, on anatomical grounds, is regarded as the ventral extension of V4. 2. Anatomical studies using double tracers were employed to clarify the nature of the projections from the striate cortex and from V2 to V4. In one such experiment, tritiated proline was injected into extra-foveal striate cortex and a small lesion was made in that part of V2 receiving a direct projection from the region of the striate cortex into which the radioactive tracer was injected. Only degenerating fibres (due to the lesion), and no radioactive label, was found in V4. Such an experiment showed that, unlike foveal striate cortex, the projections from extrafoveal striate cortex to V4 are not direct, but through V2. 3. In another type of anatomical experiment using double tracers, the corpus callosum was sectioned and tritiated proline was injected into foveal striate cortex. Such an experiment allowed a more accurate determination of the extent of V4, as judged from its callosal connexions, to which foveal striate cortex projects. 4. Considering the projections of V1 to areas V2, V3 and the visual area in the medial part of the posterior bank of the superior temporal sulcus, and considering the differences in the projections of foveal and extrafoveal striate cortex, it is suggested that, among other functions, the striate cortex acts as a distribution centre for the information coming over the retino-geniculo-cortical pathways, parcelling this information out to different visual areas of the prestriate cortex for further analysis.

Topographical projections of the prestriate cortex to the pulvinar nuclei in the macaque monkey: An autoradiographic study

Localized microinjections of tritiated amino acids were made in the prestriate cortex (areas 18 and 19) of macaque monkeys in order to determine the topography of the subcortical projections. It was found that the prestriate cortex projected to the entire inferior pulvinar (PI), lateral pulvinar (PL), dorsolateral nucleus, the lateral posterior nucleus, the reticular nucleus, a portion of the medial pulvinar, superior colliculus, and caudate nucleus but not to the dorsal lateral geniculate nucleus. The projections to the PI were organized according to the topographical representation of the contralateral visual hemifield. The ventral portion of the PL which is immediately adjacent to the PI also received a parallel topographical projection in register with the representation of the visual hemifield and thus is distinguished from the remainder of the PL. The dorsal and caudal portions of the PL (which extend to form the lateral portion of the caudal pole of the pulvinar and are located away from PI) also received projections from prestriate cortex which often appeared as several bands of grains. However, although dorsal prestriate cortex seemed to project to the dorsal portion of caudal PL and ventral prestriate cortex seemed to project to the ventral portion of caudal PL, any further topography in the projections to the dorsal and caudal PL as well as any to the other dorsal group nuclei was difficult to determine. The results point to the conclusion that the PI and the immediately adjacent portion of PL are distinguished from the remainder of the pulvinar by their connectional organization, and each region contains a representation of the visual hemifield. Furthermore, the prestriate projections to these and other regions of the pulvinar form the corticothalamic half of visual and visuomotor cortico-thalamocortical projections which involve all the occipital cortices (areas 17, 18 and 19) as well as inferotemporal, parietal and frontal cortices.

Binocular interaction and depth sensitivity in striate and prestriate cortex of behaving rhesus monkey

Binocular interaction and depth sensitivity in striate and prestriate cortex of behaving rhesus monkey

Connections between the pulvinar nucleus and the prestriate cortex in the squirrel monkey as revealed by peroxidase histochemistry and autoradiography

Summary Connections between the pulvinar nucleus and the dorsolateral prestriate cortex in the squirrel monkeys were demonstrated by means of retrograde axonal transport of horseradish peroxidase (HRP) and orthograde transport of tritiated leucine ([3H]L) in two sets of animals. The HRP experiments showed that a significant portion of both the inferior (PuI) and lateral (PuL) subdivisions of the pulvinar nucleus project to the dorsolateral prestriate cortex. The labeled cells form laminae or slabs which extend in a rostroventrolateral to caudodorsomedial direction, parallel to the external surface of PuI and PuL respectively. The lateral and medial slabs in both PuI and PuL differ in that large labeled neurons are prominently found within the lateral slabs, whereas the medial slabs are composed mainly of densely packed medium-sized neurons (PuL) or small neurons (PuI). There is continuity between the medial slab in PuL and that in PuI so that functionally these two subdivisions may be more closely related than has previously been recognized. The autoradiographic experiments also revealed a laminar or slab-like pattern of distribution of corticopulvinar projections that span again in a rostroventrolateral to caudodorsomedial direction, thus complementing the laminar distribution of pulvinocortical cells. Each slab is interpreted as a composite of rostrolateral to caudomedially oriented parallel columns of labels following a dorsal to ventral row of injections in the dorsal prestriate cortex. The relationship between the prestriate cortex and PuI-PuL complex is topographical, reciprocal and well-organized. This study points to the importance of PuL, in addition to PuI, as a vital subcortical visual center mediating a thalamoprestriate pathway that is parallel to the primary geniculostriate pathway.