The superior colliculus (SC) has been implicated in spatial analyses of the environment, although few behavioral studies have explicitly tested this role. To test its imputed role in spatial analyses, we used a battery of four spatial tasks combined with unilateral and bilateral cooling deactivation of the upper and intermediate layers of the superior colliculus. We tested the abilities of cats to orient to three different stimuli: (1) moving visual, (2) stationary visual, (3) stationary white-noise aural. Furthermore, we tested the ability of the cats to discriminate the relative spatial position of a landmark. Unilateral cooling deactivation of the superficial layers of the SC induced a profound neglect of both moving and stationary visual stimuli presented in, and landmark objects located within, the contralateral hemifield. However, responses to auditory stimuli were unimpaired. Unilateral cooling deactivation of both the superficial and intermediate layers induced a profound contralateral neglect of the auditory stimulus. Additional and equivalent deactivation of the opposite SC largely restored orienting to either moving visual or auditory stimuli, and restored landmark position reporting to normal levels. However, during bilateral SC deactivation, orienting to the static visual stimulus was abolished throughout the entire visual field. Overall, unilateral SC deactivation results show that the upper and intermediate layers of the SC contribute in different ways to guiding behavioral responses to visual and auditory stimuli cues. Finally, bilateral superior colliculus deactivations reveal that other structures are sufficient to support spatial analyses and guide visual behaviors in the absence of neural operations in the superior colliculus, but only under certain circumstances.

We used reversible cooling deactivation to compare the functions of cortices lining the middle suprasylvian (MS) sulcus and forming the ventral portion of the posterior suprasylvian (vPS) gyrus. A battery of attentional, motion and mnemonic processing tasks were used and performance was examined during deactivation of each region. The results show a clear dissociation of functions. Deactivation of MS cortex resulted in profound deficits on a visual orienting task and on the discrimination of direction of motion, whereas deactivation of vPS cortex severely impaired both retention and learning of novel and overlearned object discriminations. In addition, deactivation of either MS or vPS cortex impaired discrimination of learned patterns when components of the patterns were in motion, whereas only deactivation of vPS cortex impaired the discrimination when all components were static. Together, these results show that a region of parietal cortex contributes to the processing of visual motion and to attentional processes, whereas a region of temporal cortex contributes to the learning and recognition of three-dimensional objects and two-dimensional patterns. This functional dissociation is linked to differences in underlying visual pathways, which have many features in common with the parietal and temporal visual processing streams previously identified in monkeys and humans. Furthermore, the broad similarity in neural operations carried out in parietal and temporal cortices of cats, monkeys and humans suggests the existence of a common plan for cortical processing machinery within mammals with well developed cerebral cortices.

Cats that received either marginal or marginal plus extramarginal lesions as 3-day-old kittens were assessed on a series of tests of visually guided behavior. These Ss were not conspicuously different from normal controls in avoiding obstacles or in activity level. Yet these same operated Ss were severely impaired in performance on the visual cliff and in visual discrimination learning, even when lesions were limited to the geniculocortical portion of the visual system. Maximum losses in pattern and form discrimination learning were observed only in Ss with severe retrograde degeneration in both the lateral geniculate nucleus and the complex of the pulvinar and nucleus lateralis posterior. Photically evoked potentials were recorded in the lateral regions of the neocortex more reliably from operated Ss that had made fewer errors in discrimination learning than from more severely debilitated cases; this relation was present even among cases with nearly equivalent amounts of retrograde degeneration in the visual thalamus. These findings suggest that in the cat (a) recovery of vision is incomplete after neonatal lesions of the visual cortex, and (b) a cortical system lateral to the geniculocortical projections may be involved in pattern vision. (29 ref)

Extrarite sual areas on the banks of the middle suprasylvian sulcus were inactivated by cooling to assess the behavioral contribution of this cortical region to the extraction of a stationa figure from a moving mask. Cooling blocked figure-ground separation when the mask was moving but had no influence when the mask was static. This difference provides strong evidence that the areas nding the middle suprasylvian sulcus contribute to the neural separation of stationary from moving visual stimuli.Lesion studies have shown that the visual cortex of cats and monkeys is composed of several regions, each of which plays one or more specific roles in visual processing and cognition (1). This functional division ofcortex is related to the multiple visual maps and to the unique patterns of connections each region possesses (2). In the present study we used cooling to reversibly inactivate the middle suprasylvian (MS) cortex in the behaving cat to investigate the contribution of this cortical region in solving a complex visual perceptual problem that involves movement. Our belief that motion processing is one function of MS cortex is based on the facts that (i) many neurons in this region are highly sensitive to simple motion (3-6) and respond well to differential motion (7); (ii) there is a systematic representation of movement direction (8); and (iii) permanent lesions interfere with movement velocity discrimination (9). By extension, the purported homologous (1) cortical area V5, or MT, contributes in a similar way to vision in primates (10-14). However, most previous behavioral studies have examined motion processing in the absence of any other potentially interactive features. This situation is akin to the rather simple process of identifying the coherence, direction, or speed of flight of a flock of birds in a clear sky. However, under natural conditions there is typically relative motion between figures and either complex foregrounds or complex backgrounds. Our cats were trained to solve a discrimination in which stimuli composed of two geometrical outline patterns are partially obscured by either a moving grid pattern or a moving, nonsystematically arrayed pattern comprised of variable spatial frequencies. In this task the figure remains stationary and the mask moves coherently in the standard directions of up and down. This task is akin to identifying an object either behind a moving mesh (e.g., chain-link fence) or in a wind-driven black-snow storm. Our results show that (i) motion is a visual cue useful to cats for separating a static figure from a moving foreground mask and that the-MS cortex plays a critical role in this separation, and (ii) the perceptual deficits in vision induced by the cooling of this region are completely reversible. EXPERIMENTAL METHODS Three cats (S, Sd, and V) were trained to discriminate between an outline figure I and an outline figure 0 obscured by a multiline grid mask that oscillated up and down across the figures (Fig. 2D). In two ofthe cats (Sd and V) the optic chiasm an...