Parietal rTMS disrupts the initiation but not the execution of on-line adjustments to a perturbation of object size.
Previous studies have implicated the human parietal lobes in the on-line guidance of action. However, no study to date has examined at what stage in the on-line adjustment process do the parietal lobes play their most critical role. Repetitive transcranial magnetic stimulation (rTMS) was applied over the left intraparietal sulcus as participants reached to grasp a small or large illuminated cylinder. On some trials, the illumination could suddenly switch from the small to large cylinder, or vice-versa. Small-Large switches were associated with relatively early grip aperture adjustments, whereas Large-Small switches were associated with relatively late grip aperture adjustments. When rTMS was applied early in the movement, it disrupted on-line adjustments to Small-Large target switches, but not to Large-Small switches. Conversely, when rTMS was applied late in the movement, it disrupted adjustments to Large-Small target switches but not to Small-Large switches. The timing of the disruption by rTMS appeared linked to the initiation of the adjustment. It was concluded that the left parietal lobe plays a critical role in initiating an on-line adjustment to a change in target size, but not in executing that adjustment. The implications of these results for current views of on-line control are discussed.
Glover
Scott
S
University of Oxford. scott.glover@rhul.ac.uk
Miall
R Chris
RC
Rushworth
Matthew F S
MF
D000222:Adaptation, Physiological / Q000528:radiation effects*; D004558:Electric Stimulation / Q000379:methods; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008280:Magnetics; D008960:Models, Psychological; D010296:Parietal Lobe / Q000502:physiology / Q000528:radiation effects*; D011597:Psychomotor Performance / Q000528:radiation effects*; D011930:Reaction Time / Q000528:radiation effects; D012858:Size Perception / Q000502:physiology*; D013997:Time Factors