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At least 631 records · Page 35Linked to original sources
PubMed1981

Behavioral analyses of visual cortex of the Galago.

For the purpose of examining some of the principles underlying the function of primate visual cortex, the performance of one normal control group and three operated groups of Galagos having bilateral cortical lesions in area 17 (S), the middle temporal area (MT), or areas 18 and 19 (XS) was assessed on tasks measuring visual sensory capacity, search, and learning. Striate lesions produced a reduction in foveal vision and were responsible for deficits only on a complex visual learning task. The lesions of Group MT extended beyond area MT and involved the optic radiations. This resulted in impairments on all visual problems. Animals in Group XS had subtotal lesions of prestriate cortex and were also impaired on each task, but they showed less severe deficits in sensory capacity than animals in Group MT. It is suggested that the Galago's striate cortex plays a major role in the identification and utilization of relevant visual information and that areas 18 and 19 are important in both visual learning and visuospatial analyses. Evidence is provided that area MT is involved in visual search.

Animals↗
PubMed1998

Some effects of representational friction, target size, and memory averaging on memory for vertically moving targets.

Observers viewed an animated ascending or descending target that varied in size and velocity across trials and appeared either (a) in isolation, (b) to slide along one side of a single larger stationary object, or (c) to slide between two larger stationary objects. Targets vanished without warning, and displacements (i.e., differences between actual and remembered final position) along the axis of motion and orthogonal axis were measured. Forward displacement (a) decreased with increases in implied friction, (b) increased with increases in target size for descending targets, and (c) decreased with increases in target size for ascending targets. When a larger stationary object was to one side of the target, orthogonal displacement was toward that object; when no object or objects on both sides were present, orthogonal displacement was near zero. Results are consistent with previous findings and speculation on the effects of representational friction, memory averaging, and target size on memory.

Analysis of Variance↗
PubMed2000

Body image as a visuomotor transformation device revealed in adaptation to reversed vision.

People adapt with remarkable flexibility to reversal of the visual field caused by prism spectacles. With sufficient time, this adaptation restores visually guided behaviour and perceptual harmony between the visible and tactile worlds. Although it has been suggested that seeing one's own body is crucial for adaptation, the underlying mechanisms are unclear. Here we show that a new representation of visuomotor mapping with respect to the hands emerges in a month during adaptation to reversed vision. The subjects become bi-perceptual, or able to use both new and old representations. In a visual task designed to assess the new hand representation, subjects identified visually presented hands as left or right by matching the picture to the representation of their own hands. Functional magnetic resonance imaging showed brain activity in the left posterior frontal cortex (Broca's area) that was unique to the new hand representations of both hands, together with activation in the intraparietal sulcus and prefrontal cortex. The emergence of the new hand representation coincided with the adaptation of perceived location of visible objects in space. These results suggest that the hand representation operates as a visuomotor transformation device that provides an arm-centred frame of reference for space perception.

Adaptation, Physiological↗
PubMed1995

Effects of picture size and placement on memory for written words.

A study investigating the effects of varying size and position of line drawings in combination with written words was conducted with kindergarten students. Subjects were shown written words under four conditions that represented various size and position relationships between line drawings and orthography. After 4 consecutive days of exposure in an incidental learning task, both identification and recognition measures were obtained. Results showed superior performance for word-only and enhanced-word conditions, over those in which small and large line drawings were paired with written words, supporting similar research findings conducted with reading tasks. Implications are drawn for application to individuals with little or no functional speech who use graphic symbols for expressive communication.

Child↗