Pupillary constriction evoked from the posterior medial lateral suprasylvian (PMLS) area in cats

Pupillary constriction was evoked by systematic stimulation using a microelectrode in the upper medial bank of the middle suprasylvian sulcus in the parieto-occipital cortex of the cat. The pupillo-constrictor area corresponded to the rostral and middle parts of the posterior medial lateral suprasylvian (PMLS) area. This pupillo-constrictor area extended by 2-3 mm along the middle suprasylvian sulcus. It is suggested that this pupillo-constrictor area overlaps or lies in close proximity of a part of the region in PMLS area related to lens accommodation, in which unit activity temporally related to lens accommodation was recorded and from which lens accommodation was evoked by electric stimulation.     

A comparison of magnification functions in area 19 and the lateral suprasylvian visual area in the cat

A retinotopic map can be described by a magnification function that relates magnification factor to visual field eccentricity. Magnification factor for primary visual cortex (VI) in both the cat and the macaque monkey is directly proportional to retinal ganglion cell density. However, among those extrastriate areas for which a magnification function has been described, this is often not the case. Deviations from the pattern established in V1 are of considerable interest because they may provide insight into an extrastriate area's role in visual processing. The present study explored the magnification function for the lateral suprasylvian area (LS) in the cat. Because of its complex retinotopic organization, magnification was calculated indirectly using the known magnification function for area 19. Small tracer injections were made in area 17, and the extent of anterograde label in LS and in area 19 was measured. Using the ratio of cortical area labeled in LS to that in area 19, and the known magnification factor for area 19 at the corresponding retinotopic location, we were able to calculate magnification factor for LS. We found that the magnification function for LS differed substantially from that for area 19: central visual field was expanded, and peripheral field compressed in LS compared with area 19. Additionally, we found that the lower vertical meridian's representation was compressed relative to that of the horizontal meridian. We also examined receptive field size in areas 17, 19, and LS and found that, for all three areas, receptive field size was inversely proportional to magnification factor.     

Callosal connections of suprasylvian visual areas in the cat

After horseradish peroxidase injections in cat's lateral suprasylvian visual area and in areas 17 and 18, labeled callosal neurons are found within the various subdivisions of the lateral suprasylvian area, mostly in regions where the area centralis and vertical meridian are represented. The homotopic callosal projections from lateral suprasylvian area to lateral suprasylvian area originate almost exclusively from layer III. The heterotopic callosal projections from the lateral suprasylvian area to areas 17 and 18 originate mainly from layer VI but also from layer III. Callosal neurons in the lateral suprasylvian area are pyramidal cells (layers III and VI), fusiform and triangular cells (layer VI).The distribution of callosal neurons in the lateral suprasylvian area is similar to that previously found in areas 17 and 18 in the sense that in all these areas callosal neurons are preferentially located near the vertical meridian representation within two radially separated laminae. However, the preponderance of layer VI neurons in the projection from the lateral suprasylvian area to contralateral areas 17 and 18 is different from what was observed in other callosal connections. Since layer VI usually gives rise to corticothalamic projections it is possible that similar feed-back mechanisms may modulate the information sent to the lateral suprasylvian area from the thalamus and the primary visual areas.     

Representation of both visual hemifields in the lateral suprasylvian area of one hemisphere

Clusters of neurons of the lateral suprasylvian area are shown to be able to respond to stimulation of symmetrical areas of the ipsi- and contralateral visual hemifields. Neuron clusters with such symmetrical receptive fields have a retinotopic organization.Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 68, No. 6, pp. 763–766, June, 1982.     

Effects of lesioning the anterior suprasylvian cortex on visuo-motor guidance performance in the cat

Summary Seven cats were trained to press a lever that moved in front of them at an adjustable speed and at random from left to right or from right to left. Efficient presses were reinforced by food. After measuring accuracy and latency of pressing the lever, the animals underwent bilateral ablation of the suprasylvian (SS) cortex; in three animals the lesions involved its anterior aspect; in two animals, they were restricted to its middle portion; two others cats had lesions of both anterior and the middle SS cortex. No long-lasting postoperative deficits were observed in any group when the lever remained immobile. On the other hand, the scores after anterior SS lesions were severely deteriorated, when presses had to be performed on the moving lever. No such deficits were noticed when the ablations were restricted to the middle SS. These results suggest that the cat anterior suprasylvian cortex (that includes parts of areas 5 and 7) plays a determinant role in the spatial adjustment of a visually guided (or visually triggered) forelimb movement.This work was supported by the following grants: ERA - CNRS 411; ATP 36-22; Fondation pour la Recherche Medicale Française     

Thalamo-cortical connections and their correlation with receptive field properties in the cat's lateral suprasylvian visual cortex

Summary Areas PMLS and PLLS of the cat's lateral suprasylvian visual cortex display an interesting global organization of local features in their single unit response properties: direction preference is centrifugally organized and velocity preference increases with eccentricity. In addition it has previously been shown that binocular interactions are strongest around the visual field center. This characterizes the LS areas as apt for the analysis of optic flow fields and for visual processing in various kinds of visuomotor tasks (Rauschecker et al. 1987). In the present study we analysed the types of input to LS from the optic chiasm, the corpus callosum and from two thalamic relay nuclei (lateral posterior and lateral geniculate) that constitute important sources of afferent information to the LS areas. We were interested in learning how the afferent (and efferent) connections between LS and these structures relate to the response properties of LS neurons. Overlap of an RF into the ipsilateral hemifield was virtually always associated with callosal input. Latency differences between responses to electrical stimulation of the optic chiasm and the thalamic sites indicated almost exclusively fast-conducting Y-input to LS. Correlation of response latencies with receptive field properties revealed the following correspondences: A positive correlation was found between LP-latency and RF-size matching the dependence of RF size on laminar origin. The type of correlation found between LP-latency and directional tuning of LS cells suggests that an interaction between thalamic and other inputs may be responsible for direction selectivity in LS. Finally, correlation of LP-latencies with centrifugal direction preference suggests that this specific property is generated by intracortical wiring rather than by thalamic input.     

Neuronal responsiveness to three-dimensional motion in cat posteromedial lateral suprasylvian cortex

The neuronal responsiveness to three-dimensional (3D) motion in cat posteromedial lateral suprasylvian (PMLS) cortex was studied using a computer-controlled, stereoscopic 3D graphic display capable of reproducing the major visual cues for natural 3D motion, including motion disparity, size, texture, and shading changes. The animals were anesthetized with nitrous oxide supplemented with alphaxalone, and paralysis prevented eye movement. Systematic investigation of neuronal responsiveness to 3D motions in 26 different directions revealed that more than half of the PMLS cells were selectively responsive to approaching (AP cells, 112 of 271) or recessive motion (RC cells, 64 of 271). The remaining cells were selectively responsive to frontoparallel motion (FP cells, 49 of 271) or nonselectively responsive to motion in multiple directions (NS cells, 46 of 271). The dependency on these visual cues was investigated as a reduction in the response amplitude or the response selectivity for the removal of a single cue from the motion stimuli containing the full visual cues. The AP and RC cells showed a strong dependency on the motion disparity cue, moderate dependency on the size cue, and weak dependency on the texture and shading cues. The FP cells showed no dependency on those visual cues. The cue dependency analysis indicated the existence of nonlinear interactions between those visual cues. Comparison of the responses to a combination of the motion disparity and size cues with the summed responses to each of the individual cues revealed that the responses to the combined cues are roughly predicted as a linear sum between the preferred responses. This comparison also showed nonlinear summation between the nonpreferred responses, i.e., responses to the combined cues were smaller than the summed responses. A similar quasilinear summation of the preferred responses between the two eyes and a nonlinear summation of the nonpreferred responses were found in the AP and RC cells for the motion disparity stimulus. All of these observations indicate that quasilinear and nonlinear interactions of the responses to various stimulus elements underlie the 3D motion responsiveness of the PMLS cells. Received: 6 January 1998 / Accepted: 23 April 1998     

Influence of the presentation of remote visual stimuli on visual responses of cat area 17 and lateral suprasylvian area

Summary Single units were recorded extracellularly from area 17 and lateral suprasylvian area (LSSA) in curarized cats. Visual stimuli, usually a 10 ° black spot, were introduced abruptly in the visual field remote from the discharge area of a neuron's receptive field and moved at a speed of about 30 °/sec. The effect of these remote stimuli (S₂) on the response to a restricted visual stimulus (S₁) crossing the discharge area was studied.It was found that most units in area 17 were not affected by the presentation of remote stimuli, the remainder being either slightly facilitated or slightly inhibited. In contrast the LSSA neurons were usually inhibited by the presentation of S₂: this effect was strong, was present in all classes of LSSA neurons and was independent of the relative directions of movement of S₁ and S₂.On the basis of these data and those previously obtained from the superior colliculus it is concluded that the way the extrageniculate centres respond to a stimulus abruptly introduced in the visual field is substantially different from that of the striate cortex. Only in the extrageniculate centres a new stimulus, besides exciting the neurons which correspond to the position of the stimulus in the field, concomitantly decreases the responses of neurons located in positions of the visual field remote from that stimulus. Possible behavioral implications of the findings are discussed.     

Retinotopic order is surprisingly good within cell columns in the cat's lateral suprasylvian cortex

Summary The retinotopic map in the striate-recipient region of the cat's lateral suprasylvian cortex (referred to here as the lateral suprasylvian area (LS)) has generally been described as quite disorderly. The disorder is commonly attributed to receptive field scatter within cell columns, reflecting the very large size of receptive fields. However, scatter within columns has never been investigated. In the experiments reported here, we examined the receptive field scatter of cells in columns, and also the scatter of a limited sample of their afferents arising from areas 17 and 18. To measure post-synaptic receptive field scatter, electrode penetrations were made parallel to columns in LS, with the electrode approaching from the medial side, traversing the suprasylvian gyrus and emerging into the suprasylvian sulcus. In all 13 such penetrations, receptive fields were clustered together despite their large size. Their centers were scattered over a region that occupied on average less than 20% of the largest field in the column. In contrast, in columns in areas 17 and 18 receptive field centers reportedly are dispersed over regions about equal to the largest of the fields (Hubel and Wiesel 1962, 1965, 1974).The scatter of afferents' receptive fields was assessed anatomically by measuring the overlap between patches of different anterograde tracers in LS. These patches represented terminal labeling from two adjacent or overlapping tracer injections in area 17. While a large degree of overlap would be predicted if afferents have substantial scatter, we found the overlap to be small unless the two injection sites themselves were highly overlapping.Scatter in afferents' receptive fields was measured more directly by physiological recording. In previous experiments, cells in LS were silenced by the local injection of kainic acid, and responses were recorded from axon terminals arising from areas 17 and 18 (Sherk 1989). We examined the receptive field scatter in three penetrations made approximately normal to the cortical surface. Scatter was modest, much less than predicted by the size of post-synaptic receptive fields. Because the degree of receptive field scatter for postsynaptic cells in LS was similar to that of inputs from areas 17 and 18, the scatter of these inputs might be entirely responsible for that seen postsynaptically. Postsynaptic receptive field scatter, on the other hand, was too small to explain the reported disorder in the map in LS.     

Neurophysiological mechanisms of recovery from visual cortex damage in cats: Properties of lateral suprasylvian visual area neurons following behavioral recovery

Summary Damage to visual cortical areas 17, 18, and 19 in the cat produces severe and long-lasting deficits in performance of form and pattern discriminations. However, with extensive retraining the animals are able to recover their ability to discriminate form and pattern stimuli. Recent behavioral experiments from this laboratory have shown that a nearby region of cortex, the lateral suprasylvian visual area (LS area), plays an important role in this recovery (Wood et al., 1974; Baumann and Spear, 1977b). The present experiment investigated the underlying neurophysiological mechanisms of the recovery by recording from single neurons in the LS area of cats which had recovered from long-term visual cortex damage.Five adult cats received bilateral removal of areas 17, 18, and 19. They were then trained to criterion on two-choice brightness, form, and pattern discriminations. Recording from LS area neurons was carried out after the behavioral training, from 3 to 7 months after the visual cortex lesions. The properties of these neurons were compared to those of LS area neurons in normal cats (Spear and Baumann, 1975) and in cats with acute or short-term visual cortex damage and no behavioral recovery (Spear and Baumann, 1979). The results showed that all of the changes from normal which were produced by acute visual cortex damage were also present after the behavioral recovery. Moreover, all of the response properties of LS area neurons which remain after acute visual cortex damage were present in similar form after the behavioral recovery. There was no evidence for any functional reorganization in the LS area concomitant with its role in the behavioral recovery.These results suggest that functional reorganization plays little or no role in recovery from visual cortex damage in adult cats. Rather, the recovery of form and pattern discrimination ability appears to be based upon the functioning of residual neural processes in the LS area which remain after the visual cortex damage.     

Visual response properties of neurons in the middle and lateral suprasylvian cortices of the behaving cat

Summary The visual response properties of cells in the middle (MS) and lateral (LS) suprasylvian cortices were studied in alert cats, which were trained to fixate a spot of light and maintain fixation when a second test light was introduced in the midst of fixation. This second light served to test for visual sensitivity, and it could be moved at different speeds in any direction under computer control. Over half of the cells exhibited a visual response. With a small spot of light, most cells were directionally selective and responded better to a moving spot than to a stationary one. In some cases movements of the spot in the non-preferred direction revealed an inhibitory process. The visual receptive fields were large and often extended into the ipsilateral hemifield, though the centers of the receptive fields were usually in the contralateral field. We used Fourier analysis to quantify directional selectivity and compared these results to other commonly used measures of directional selectivity. Compared to cells in MS, there was a higher incidence of visual cells in LS and the visual cells were more directional. We also made comparisons between our results and those found in anesthetized cats and awake monkeys.     

Double-opponent-process mechanism underlying RF-structure of directionally specific cells of cat lateral suprasylvian visual area

Summary For the experiments reported in this study, recordings were obtained from 246 single units in the middle lateral suprasylvian visual area (LS) of 13 cats. 49 of these cells were subjected to detailed quantitative analysis. The receptive field (RF) organization was examined for directionally specific cells by presenting moving single spots on large moving random dot backgrounds. A cell's response to an optimal spot (in terms of size, direction, velocity) moving on a stationary background inside the excitatory RF (ERF) was compared to in-phase (same direction, same velocity) and anti-phase (opposite direction, same velocity) movement of spot and background. In-phase movement resulted in inhibition of the cell's response (3–100%) in 94% of the cells, while anti-phase movement led to reduced inhibition in 52% of the cells or to facilitation (0.5–327%) in 39% of the cells. By changing the direction of background motion with respect to that of the spot, the directional tuning of the in-phase inhibition and anti-phase facilitation effects was determined.We were able to manipulate the size of the background effects by masking out the background for various proportions of the ERF, and maximizing them by restricting background stimulation to the large inhibitory RF (IRF) surrounding the ERF. These results could be best accounted for by a double-opponent-process mechanism with both RF center and RF surround being directionally selective, but with opposite polarity. It is suggested that this type of mechanism could be involved in the processing of object motion.Partially supported by an NSERC University Research Fellowship (U 0057) and an ARC equipment grant to M. von Grünau and by an NSERC Grant to B. J. Frost (A 0353)     

Visuomotor interactions in responses of neurons in the middle and lateral suprasylvian cortices of the behaving cat

Summary We studied visuomotor processing in the middle (MS) and lateral suprasylvian (LS) cortices of the alert cat by making single cell recordings while the cat was working in a behavioral task requiring visual fixation and visually guided eye movements. We found responses with three different components: visual sensory, saccaderelated motor, and fixation. Some cells exhibited purely visual responses and all of their activity during visuomotor tasks could be attributed to the sensory aspects of the task. Other cells showed no sensory response properties, but discharged in relation to the saccadic eye movements that the cat made to visual targets. A smaller number of fixation cells displayed increased discharge when the cat fixated a target light and usually only when that target was in a particular region of the visual field.These response components could be present in a variety of combinations in different cells, of which the largest proportion combined visuomotor responses and could take five general forms: simple visuomotor, saccadic enhanced, visually triggered movement (VTM), enhanced VTM, and disenhanced. Simple visuomotor responses had both a visual and saccade-related component. Saccadic enhanced responses had a visual response to the appearance of a spot in the cell's receptive field that became enhanced when the cat subsequently made a saccade to that spot. The VTM responses were synchronized better to the visual stimulus than to the saccade, but they also exhibited properties expected of motor responses. The last two classes of visuomotor responses were rare: one we termed enhanced VTM and the other disenhanced. Cells could combine different visuomotor response components or even sensory, saccade-related and fixation responses in different combinations for different directions of eye movements. Generally, the timing of the saccade-related responses occurred too late to play a role in the initiation of saccades: most (83%) saccade-related responses occurred between 40 ms before to 80 ms after the onset of the eye movement. Cells of all different types could be found in both the MS and LS areas, though in general the responses in LS were more sensory in nature while those in MS were more closely related to the eye movement. About a quarter of the cells were unresponsive during any aspect of our tasks.     

Considerable deficits in the detection performance of the cat after lesion of the suprasylvian visual cortex

Summary The ability of two cats to discriminate between two geometrical outline patterns in the presence of superimposed structured background was tested before and after bilateral removal of the lateral suprasylvian visual areas (PMLS, PLLS, AMLS, ALLS, part of area 7). There were mild deficits when patterns and background were kept stationary; these deficits may be due to a partial undercutting of areas 17, 18 and 19. However, there was a severe impairment in performance when the patterns were moving on a stationary background which may be due to loss of the suprasylvian visual areas. Movement of the background relative to the figure resulted in an intermediate detection deficit.The paper is part of this author's doctoral thesis     

Auditory cortex projections target the peripheral field representation of primary visual cortex

The purpose of the present study was to identify projections from auditory to visual cortex and their organization. Retrograde tracers were used to identify the sources of auditory cortical projections to primary visual cortex (areas 17 and 18) in adult cats. Two groups of animals were studied. In the first group, large deposits were centered on the lower visual field representation of the vertical meridian located along the area 17 and 18 border. Following tissue processing, characteristic patterns of cell body labeling were identified in extrastriate visual cortex and the visual thalamus (LGN, MIN, & LPl). In auditory cortex, of the four tonotopically-organized regions, neuronal labeling was identified in the supragranular layers of the posterior auditory field (PAF). Little to no labeling was evident in the primary auditory cortex, the anterior auditory field, the ventral posterior auditory field or in the remaining six non-tonotopically organized regions of auditory cortex. In the second group, small deposits were made into the central or peripheral visual field representations of primary visual cortex. Labeled cells were identified in PAF following deposits into regions of primary visual cortex representing peripheral, but not central, visual field representations. Furthermore, a coarse topography was identified in PAF, with neurons projecting to the upper field representation being located in the gyral portion of PAF and neurons projecting to the lower field representation located in the sulcal portion of PAF. Therefore, direct projections can be identified from tonotopically organized auditory cortex to the earliest stages of visual cortical processing.     

The role of the lateral suprasylvian visual cortex of the cat in object-background interactions: Permanent deficits following lesions

The contribution of the lateral suprasylvian cortex to pattern recognition was studied by behavioural detection experiments in combination with bilateral lesions of different parts of the lateral suprasylvian areas (LSA) and area 7 in seven cats. In a two-alternatives forced choice task the cats had to discriminate simple outline patterns which were additively superimposed on a structured visual background made up of broadband Gaussian noise. For various stimulus conditions (moving or stationary patterns and/or background) the detection probability (P _D) of the cats was measured as a function of the signal to noise ratio (S/N). Each cat was tested before and after the lesion. Four different types of lesion could be distinguished depending on their extent: (1) lesion of parts of the (LSA); (2) lesion of parts of the LSA with undercutting of areas 17, 18 and 19; (3) lesion of area 7; (4) lesion of area 7 and parts of the LSA.

The retinotopic distribution of visual callosal projections in the suprasylvian visual areas compared to the classical visual areas (17, 18, 19) in the cat

Summary The distribution of the interhemispheric projection from area 17 and 18 was studied using the anterograde degeneration technique. Besides the classical visual areas (17, 18, 19), area 21 and several visual areas in the middle suprasylvian sulcus also received visual callosal input. In the four terminal areas of the middle suprasylvian sulcus the projection was found to be focused on representations of the vertical meridian including the area centralis, as in the classical visual areas. An increase of the width of visual field represented in the zone of callosal terminations can be seen from area 17 through area 18 to area 19 and possibly this trend continues in the suprasylvian visual areas.     

Types of synapses contacting the soma of corticotectal cells in the visual cortex of the cat

Retrograde transport of horseradish peroxidase has been used to single out a distinct functional cortical cell type for ultrastructural study. Following injection of horseradish peroxidase into the superior colliculus, labelled pyramidal cells were found in layer V of the visual cortex. Examination of the labelled corticotectal cells from the visual cortex showed that their cell bodies received two types of synaptic contacts, one from boutons containing spherical vesicles and one from boutons containing flattened vesicles. The possible functional significance of this dual type of input is pointed out.     

Classification of receptive field properties in cat visual cortex

Summary The properties of the receptive fields of visual cortex neurons of cats were studied manually and by a computer controlled system using single lines, double lines and multiple lines (gratings). The multiple selectivities of each of the receptive fields studied make it necessary to abandon the concept that each cell functions as a feature detector. Instead, an attempt was made to classify the receptive field properties with the aim to delineate the transfer functions (of the total networks) served by each property. When tested with one-line stimulus, cells with simple receptive field properties diffefed from cells with complex receptive field properties as to their velocity selectivity (simple: 1 ° to 3 °/s; complex: 4 ° to 10 °/s), spontaneous activity (lower for cells with simple properties), optimal firing rate (lower for cells with simple properties) and receptive field size (smaller for cells with simple properties) but not for orientation and direction selectivity. When tested with a 2-lines moving stimulus, the responses of cells with simple properties were facilitated by the progressive separation of the lines whereas the responses of cells with complex receptive field properties were inhibited. When multiple lines, i.e. gratings, were used, an equivalence between simple and X properties and complex and Y properties was shown, while the sustained/transient classification proved to be independent of the simple/complex (X/Y) classification. Thus, receptive field properties can be classified into three categories: one reflects the input to the receptive fields; a second deals with the interactive properties of the fields; while a third appears more related to the overall properties of the network.This research was supported by a postdoctoral fellowship from the Medical Research Council of Canada to Maurice Ptito, a predoctoral fellowship from the National Research Council of Canada to Maryse C. Lassende and NIMH Grant MH12970 and NIMH Career Research Award MH15214 to Karl H. Pribram     

Differences in the temporal dynamics of the visual ON and OFF pathways

The temporal structure of spike trains recorded from optic fibers and single units of the lateral geniculate nucleus (LGN) and primary visual cortex of the cat was studied with a novel method of inter-spike interval analysis. ON type relay cells of the LGN exhibited a multimodal interval distribution preferring a distinct interval (fundamental interval) and its multiples during the sustained light response, whereas most OFF cells showed a broad, unimodal distribution. The general pattern of the interval distribution was relatively independent of stimulus size and contrast and the degree of light adaptation. Simultaneously recorded S-potentials originating from the retinal input generally produced only a single peak at the fundamental interval length. Therefore, the multimodal interval distribution of LGN cells seems to be a result of intra-geniculate inhibition. Cortical cells also showed a weak tendency to fire with spike intervals similar to LGN cells. Therefore, the regular firing pattern observed at peripheral stages of the visual pathway can persist at higher levels and might promote the occurrence of oscillatory activity.