Abstract
We examined if a neglect patient (with a lesion to the right temporal lobe and insula) could either adapt his pointing trajectory or interrupt his movement in response to a rightward or leftward target shift. Spatial and temporal analysis of the movement trajectories indicated that the patient was as accurate as the control group when performing on-line corrections to target shifts, even when the shift occurred in the leftward direction. However, when asked to stop his movement “in flight” in response to a left or right target jump, his performance was considerably impaired, both in terms of timing and number of correct stop responses. Fast, on-line corrections to target jumps are thought to be the mediated by the visual dorsal stream, while stop responses require an intentional reprogramming which is thought to be dependent upon the conscious perception mediated by the ventral stream. Our findings indicate that the deficits present in hemispatial neglect are more closely related to damaged ventral areas of visual processing and further agree with previous neuropsychological evidence regarding the dissociability of these pathways for fast automatic movements versus slow, intentional motor control.
This work was supported by the Fundação para a Ciência e a Tecnologia (SFRH/BD/23230/2005), Royal Society of Edinburgh and Wellcome Trust. We would like to thank Satu Baylan for helping with data collection.