Modulation of visual perception by eye gaze direction in patients with spatial neglect and extinction

Parietal neurons have retinotopic receptive fields whose response is modulated by eye gaze signals. We examined the role of eye position and eye movement direction on visual extinction in three patients with parietal damage and left neglect, characterized by impaired perception of contralesional field stimuli despite intact visual cortex. Patients tracked a horizontally moving fixation point, while discriminating fine changes at the fixated point and detecting more salient targets flashed on either side of fixation. Eye position modulated extinction, with worse detection of left field targets during eccentric fixation towards the left. Direction of eye movement also modulated extinction, with worse detection of left targets during rightward scanning. These results demonstrate that extinction in contralesional field is influenced by extra-retinal factors related to eye position and eye movements, consistent with a convergence of these signals in parietal cortex.