Training ameliorates deficits in visual detection and orienting following lesions of primary visual cortex sustained in adulthood and in infancy

Purpose: Damage of primary visual cortex in adult humans, monkeys and cats severely disrupts vision by disconnecting much of the cognitive processing machinery of extrastriate cortex from its source of visual signals in the r etina. Equivalent lesions sustained early in life result in partial sparing of visual processing functions and evidence from the mature brain suggests that systematic training procedures can ameliorate the impact of remaining deficits. The purpose of the present work was to use two reflex-based, visual detecti on and orienting tasks to test for the therapeutic effects of rehabilitativ e training in cats that sustained lesions of primary cortical areas 17 & 18 in adulthood, and to test whether similar training is of benefit to cats t hat incurred equivalent lesions at one month-of-age (P28) or shortly after birth (P1). Methods: Cats were trained to attend to static visual and auditory cynosure s and tested on their ability to disengage the cynosure and orient towards a target presented in the periphery of the testing arena. Targets were: 1) a high contrast, dark, moved rod; 2) an illuminated static light-emitting d iode (LED); and 3) a broad band, white noise, sound stimulus. Results: On Task 1, cats with lesions of areas 17 & 18 sustained in adultho od are markedly impaired whereas cats that sustained lesions in infancy exh ibit partial sparing of the visual operations underlying this task. With tr aining, the performance of all cats improved. On Task 2, performance by the adult-lesion and the P1-groups were markedly impaired, whereas the P28-gro up exhibited partial sparing. On Task 3, per formance by all groups was uni formly high. No detectable benefits of training were identified on tasks 2 and 3. Conclusions: Overall, the results show that cats incur definite benefits of training following visual cortex lesions regardless of whether the lesions were sustained early in life or later, but the benefits are limited to spe cific types of visual stimuli.