Parietal rTMS disrupts the initiation but not the execution of on-line adjustments to a perturbation of object size

J Cogn Neurosci. 2005 Jan;17(1):124-36. doi: 10.1162/0898929052880066.


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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Physiological / radiation effects*
  • Electric Stimulation / methods
  • Hand Strength / physiology*
  • Humans
  • Magnetics*
  • Models, Psychological
  • Parietal Lobe / physiology
  • Parietal Lobe / radiation effects*
  • Psychomotor Performance / radiation effects*
  • Reaction Time / radiation effects
  • Size Perception / physiology*
  • Time Factors