Delay of movement caused by disruption of cortical preparatory activity

J Neurophysiol. 2007 Jan;97(1):348-59. doi: 10.1152/jn.00808.2006. Epub 2006 Sep 27.


We tested the hypothesis that delay-period activity in premotor cortex is essential to movement preparation. During a delayed-reach task, we used subthreshold intracortical microstimulation to disrupt putative "preparatory" activity. Microstimulation led to a highly specific increase in reach reaction time. Effects were largest when activity was disrupted around the time of the go cue. Earlier disruptions, which presumably allowed movement preparation time to recover, had only a weak impact. Furthermore, saccadic reaction time showed little or no increase. Finally, microstimulation of nearby primary motor cortex, even when slightly suprathreshold, had little effect on reach reaction time. These findings provide the first evidence, of a causal and temporally specific nature, that activity in premotor cortex is fundamental to movement preparation. Furthermore, although reaction times were increased, the movements themselves were essentially unperturbed. This supports the suggestion that movement preparation is an active and actively monitored process and that movement can be delayed until inaccuracies are repaired. These results are readily interpreted in the context of the recently developed optimal-subspace hypothesis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Action Potentials / physiology
  • Animals
  • Conditioning, Psychological / physiology
  • Decision Making / physiology
  • Electric Stimulation
  • Macaca mulatta
  • Male
  • Motor Cortex / anatomy & histology
  • Motor Cortex / physiology*
  • Movement / physiology*
  • Nerve Net / anatomy & histology
  • Nerve Net / physiology*
  • Neural Pathways / anatomy & histology
  • Neural Pathways / physiology*
  • Neurons / physiology*
  • Neuropsychological Tests
  • Psychomotor Performance / physiology
  • Reaction Time / physiology
  • Time Factors