Grip Constancy but Not Perceptual Size Constancy Survives Lesions of Early Visual Cortex.

Grip Constancy but Not Perceptual Size Constancy Survives Lesions of Early Visual Cortex. Curr Biol. 2020 Jul 29;: Authors: Whitwell RL, Sperandio I, Buckingham G, Chouinard PA, Goodale MA Abstract Object constancies are central constructs in theories of visual phenomenology. A powerful example is "size constancy," in which the perceived size of an object remains stable despite changes in viewing distance [1-4]. Evidence from neuropsychology [5], neuroimaging [6-11], transcranial magnetic stimulation [12, 13], single-unit and lesion studies in monkey [14-20], and computational modeling [21] suggests that re-entrant processes involving reciprocal interactions between primary visual cortex (V1) and extrastriate visual areas [22-26] play an essential role in mediating size constancy. It is seldom appreciated, however, that object constancies must also operate for the visual guidance of goal-directed action. For example, when reaching out to pick up an object, the hand's in-flight aperture scales with size of the goal object [27-30] and is refractory to the decrease in retinal-image size with increased viewing distance [31-41] (Figure 1), a phenomenon we call "grip constancy." Does grip constancy, like perceptual constancy, depend on V1 or can it be mediated by pathways that bypass it altogether? We tested these possibilities in an individual, M.C., who has bilateral lesions encompassing V1 and much of the ventral visual stream. We show...
Source: Current Biology - Category: Biology Authors: Tags: Curr Biol Source Type: research