Impairments in selective attention to visual stimuli in monkeys with inferotemporal and lateral striate lesions.

Bilateral removal of inferotemporal (IT) cortex in monkeys produces a severe impairment in discrimination learning limited to the visual modality (see Mishkin 12 for a review of these findings). While the visual deficits produced by IT lesions cannot be readily attributed to sensory losses 7,16 the nature of the disorder remains unclear. Chow and Orbach 5 attempted to determine whether IT ablation is associated with losses in selective attention by use of a discrimination task in which visual stimuli are briefly exposed, but found no impairment in IT monkeys in this situation. Subsequently, it was shown that the failure to obtain visual losses in IT monkeys under these conditions could be attributed to preoperative overtraining 6,13. The present experiment reinvestigated the question of selective attention losses in IT monkeys by methods which avoid the problem of preoperative overtraining. In this experiment, monkeys with IT ablation, along with their controls monkeys with lateral striate (LS) ablation and unoperated monkeys were first trained to discriminate between two visual stimuli. Irrelevant features were then added to the stimuli in a series of tests in which the animals were required to relearn the discrimination problem. If the IT animals were to be retarded in relearning the discrimination, this might imply a loss in the ability to selectively attend to or abstract the relevant visual features.