Perinatal-lesion-induced reorganization of cerebral functions revealed using reversible cooling deactivation and attentional tasks

We tested the concept that lesions of primary visual cortical areas 17 and 18 sustained on the day of birth induce a redistribution of cerebral operat ions underlying the ability to disengage visual attention and then redirect it to a new location. In cats, these operations are normally highly locali zable to posterior middle suprasylvian (pMS) cortex. Three stimulation para digms were used: ill movement of a high contrast visual stimulus into the v isual field: (ii) illumination of a static light-emitting diode (LED) stimu lus; and (iii) a control static auditory stimulus. To test for the redistri bution of critical neural operations, cryoloops were implanted bilaterally in the pMS sulcus and in contact with ventral posterior suprasylvian (VPS) cortex. Separate and combined deactivations of pMS and vPS cortices in cats with early lesions of primary visual cortex showed that full, unilateral d eactivation of pMS cortex only partially impaired the ability to detect and orient to stimuli moved into the contracooled hemifield. Much more complet e impairment required the additional deactivation of ipsilateral vPS cortex . Bilateral pMS deactivation alone, or in combination with bilateral vPS de activation, largely reversed the unilateral contracooled neglect. For the o rienting to static, illuminated LED stimuli, unilateral deactivation of pMS cortex was sufficient to fully impair orienting to stimuli presented in th e contracooled hemifield. Bilateral pMS deactivation induced an almost comp lete visual-field-wide neglect of stimuli. On its own, unilateral deactivat ion of vPS cortex was without effect on either task, although bilateral vPS deactivations introduced inconsistencies into the performance. Termination of cooling reversed all deficits. Finally, neither the initial lesion of a reas 17 and 18 nor cooling of either the MS or vPS cortex alone, or in comb ination, interfered with orienting to sound stimuli. Overall, our results p rovide evidence that at least one highly localizable visual function of nor mal cerebral cortex is remapped across the cortical surface following the e arly lesion of primary visual cortical areas 17 and 18. Moreover, the redis tribution has spread the essential neural operations from the visual pariet al cortex to a normally functionally distinct type of cortex in the visual temporal system.