Altered processing of corollary discharge in thalamic lesion patients
C. Bellebaum, K.-P. Hoffmann, B. Koch, M. Schwarz & I. Daum
Eur. J. Neurosci. 24:2375-2388, 2006
- Accumulating evidence suggests that thalamic nuclei relay corollary discharge information of saccadic eye movements,
enabling the visual system to update the representation of visual space. The present study aimed to explore the
effect of thalamic lesions in humans on updating-related cortical processing. Event-related potentials were recorded
while four patients with impairments in using corollary discharge information and 12 healthy control subjects performed
a saccadic double-step task. In the experimental condition, which required the use of corollary discharge information,
control subjects showed a pronounced positivity over the parietal cortex starting about 150 ms after first saccade
onset, reflecting the updating process. In the patients, parietal processing related to updating was altered. Three
patients showed evidence of reduced updating event-related potential effects, consistent with a unilateral deficit
in using corollary discharge information. In two patients, the event-related potential topography differed significantly
from the topography pattern observed in controls. Thalamic damage affects updating-related processing, presumably
due to insufficient transfer of saccade-related information to parietal areas. This study thus provides further
evidence for thalamic involvement in relaying corollary discharge information related to saccadic eye movements.
Our data suggest that integration of corollary discharge and motor information occurs directly before the second
saccade in a double-step task.
|
