Abstract
Left hemispatial neglect manifests itself in a rightward bias in perceptual tasks, yet the presence of this neglect-specific bias in visuomotor control remains a matter of debate. Here we investigated the ability of neglect patients (compared to patients without neglect and healthy controls) to rapidly adjust or interrupt (stop) their ongoing reach in response to a rightward or leftward target jump. Although neglect patients successfully corrected their reaches towards the left and right target shifts, these corrections were significantly slowed for leftward jumps. Interestingly though, in the stop condition neglect patients performed involuntary corrections towards the leftward target, similarly to those seen for the control groups. Furthermore, and unexpectedly, we found that neglect patients were impaired at stopping their movements in response to target jumps towards both sides of space. We argue that, in contrast to optic ataxic patients, who suffered from lesions in their dorsal visual stream, neglect patients show an ‘automatic pilot’ for reaching, yet that this ‘pilot’ is markedly slowed when the target jumps in a leftward direction. We also suggest that the inability to stop an ongoing reach might be related to non-lateralized deficits in response inhibition.
This work was supported by a grant (SFRH/BD/23230/2005) from the Foundation for Science and Technology (FCT, Portugal) to S. Rossit.