Saccade planning is dissociated from pre-saccadic attentional facilitation after damage to the posterior parietal cortex

Abstract

Numerous studies have suggested that saccades to a location trigger an automatic attentional shift to the saccade goal, which enhances perceptual processing at that location. Here, we argue for a functional dissociation between pre-saccadic perceptual enhancement and saccade planning. A patient with a lesion in the right posterior parietal cortex participated in a dual saccade and letter discrimination task. The patient made saccades to the left or right visual field. During the saccade latency a letter was briefly presented at the saccade goal and the patient was asked to discriminate the letter after he completed the saccade. The patient was able to make the normal saccades to the left, impaired visual field that could not be distinguished from saccades to the right, healthy, visual field. However, he was unable to discriminate the letters presented at the saccade goal on his left visual field whereas his performance was excellent in his right visual field. By presenting letter changes at locations that were either closer to or further away from to the saccade goal location, we also tested whether this inability to discriminate a letter at the saccade goal in the impaired visual field was attributable to a distorted attentional shift. The patient performed at chance for all letters presented in the contralesional visual field. We conclude that the leftward saccades were made without an anticipating attentional shift, whereas the rightward saccades were accompanied by a normal attentional shift.