Deficits in feature-based control of attention in a patient with a right fronto-temporal lesion.

Three experiments examined feature-based top-down control of search in a patient with right frontal-temporal lobe brain damage (YW), in comparison with normal control participants. In Experiment 1, YW showed normal search functions for single-feature targets. However, he showed abnormal search functions relative to normal control participants when a singleton distractor irrelevant to the target-defining feature was presented. YW showed longer RTs when a target was presented in the contralesional visual field and a singleton distractor was in the ipsilesional visual field (Experiment 1), or when both were presented in the contralesional visual field (Experiment 2). These results suggest that YW's difficulty is due to a failure of selectivity for targets based on top-down control of target-defining features. Experiment 3 compared singleton detection tasks and feature detection tasks. YW showed no deficits on the singleton detection tasks, where no knowledge of target-defining features was required. However, on the feature detection tasks, YW showed long RTs when targets were presented in the contralesional visual field where knowledge of target-defining features was required. We concluded that YW's difficulty in visual search with singleton distractors was due to deficits in feature-based control. We discuss the role of fronto-temporal regions in feature-based control of attention.