Impaired anti-pointing and anti-saccade performance in patients with hemispatial neglect

Hemispatial neglect is generally defined as the inability to spontaneously report, respond or orient towards events on the contralesional side of space. Milner and Goodale (2006) have claimed that the disorder results from a breakdown in a system that puts together visual information received via the ventral stream but that such patients are relatively unimpaired when programming goal-directed movements. We asked 6 neglect patients and right hemisphere lesioned patients without neglect as well as healthy elderly control subjects to perform both pro-and anti-pointing movements (anti-pointing movements require an explicit representation of the target location and are thus thought rely more on ventral stream structures). We found no specific impairments in the pro-pointing condition, but neglect patients were selectively impaired in the anti-pointing in terms of final accuracy as well as in terms of directional errors in that they failed to inhibit a pro-pointing movement. We then investigated how these same patients would perform on an antisaccade task. Neglect patients showed relatively good prosaccade performance but clear impairments in the anti-saccade task in that they oftenly failed to suppress incorrect pro-saccades. These data confirm that on-line visuomotor processing is relatively normal in neglect patients but that they fail to acquire and/or transform the explicit spatial representation of targets for off-line remapping actions. Our data also further indicate that neglect patients suffer deficits in response inhibition. Milner and Goodale (2006) The visual brain in action. OUP