Centrifugal organization of direction preferences in the cat's lateral suprasylvian visual cortex and its relation to flow field processing

Abstract

The cerebral cortex of the cat contains between 1 and 2 dozen representations of the visual field with different functional specializations. Six visual field maps lie along both banks of the suprasylvian sulcus, lateral and anterior to the visual areas in the occipital cortex. We have studied single-unit receptive field properties and their global organization across the visual field in 2 of these lateral suprasylvian areas, PMLS (essentially the Clare-Bishop area) and PLLS. Most neurons in PMLS and PLLS display selectivity for the direction of a light stimulus moving across their receptive fields with various degrees of directional tuning. We have used light spots of different size and velocity projected on a tangent screen in order to determine the direction preference of cells in these 2 areas. A strong tendency was found for neurons to respond best to centrifugal directions, i.e., to movement away from the area centralis. Thus, for these cells direction preference depends on the location of their receptive fields within the visual field. Velocity preference and binocular interaction in these neurons is also globally organized: Velocity preference increases with eccentricity, binocular synergism is strongest in the center of the visual field. Cluster analysis of recording tracks with respect to "radial" and "circular" cell categories reveals a grouping of cells with like properties in the lateral suprasylvian cortex. These new categories are formed by combining "centrifugal" and "centripetal" cells on the one hand and cells with direction preferences orthogonal to these on the other. The radial or centrifugal organization of direction preferences in conjunction with the global arrangement of velocity preference and binocular interaction suggests that PMLS and PLLS are involved in the processing of expanding visual flow fields of motion. Such flow fields are commonly encountered when a visual object moves towards an observer or during forward locomotion.

Synchronization of oscillatory neuronal responses between striate and extrastriate visual cortical areas of the cat.

“…The average of the oscillation frequency was 52 Hz (SD = ±12 Hz; n = 19) and thus in the same range as that of responses in area 17 (11)(12)(13). In agreement with previous reports (18)(19)(20), most of the cell clusters (17 out of 25) showed a clear directional selectivity. Oscillatory responses occurred in both directionally selective and nonselective cells.…”

“…This enabled us to verify the location of the electrode array in area PMLS by two additional criteria: (i) The spatial arrangement of the receptive fields agreed with the characteristic retinotopy of area PMLS; i.e., during electrode penetrations at the AP level chosen, the receptive fields moved toward the center of the visual field along the horizontal meridian (16). (ii) The receptive field properties of the cells encountered were characteristic of area PMLS; i.e., the cells had large directionally selective receptive fields, exhibited pronounced binocularity, and showed broad velocity tuning but poor orientation selectivity (18)(19)(20) Our methods for data processing have been described in detail (13). Auto-and cross-correlation functions were computed for all spike trains.…”

“…These two areas presumably process different aspects of visual stimuli in parallel. Area 17 appears to be devoted to the fine grain analysis of objects in the visual field (17), whereas area PMLS is considered as a visual association area involved in analysis ofglobal motion and of the global structure of patterns (17)(18)(19)(20). Therefore, we were interested in investigating (i) whether oscillatory responses occur in this extrastriate visual area, (ii) whether response synchronization can be observed between areas 17 and PMLS, and (iii) whether synchronization, if it occurs, depends on features of the visual stimuli used.…”

Subthreshold auditory inputs to extrastriate visual neurons are responsive to parametric changes in stimulus quality: Sensory-specific versus non-specific coding

“…Collectively, the present results and their implications indicate that subthreshold auditory influences observed in visual PLLS neurons are sensory in nature and undoubtedly contribute to the role of the retinotopically-organized region (Palmer et al, 1978) in visual motion processing (Rauschecker et al, 1987). These observations are also consistent with the receptive field-based sensory processing that occurs in bimodal multisensory neurons.…”

Radial motion bias in macaque frontal eye field

“…These results suggest that projections to FEF from posterior visual areas preserve the radial motion bias seen in MT and posterior parietal cortex~Steinmetz et al, 1987;Albright, 1989!, and that this bias is incorporated into motor commands for saccades. A radial motion bias has also been reported for cells in the lateral suprasylvian cortex of cats~LS; Rauschecker et al, 1987!, and recent studies have found evidence for an explicit representation of optic flow in cat LS~Li et al, 2000;Sherk & Fowler, 2001!. The preferred orientation of neurons in V1 also shows a radial bias~Bauer & Dow, 1989;Bauer et al, 1983;Leventhal, 1983;Vidyasagar & Henry, 1990!, suggesting that this form of representational bias may be ubiquitous in visual cortex.…”