Optical imaging in galagos reveals parietal-frontal circuits underlying motor behavior

Iwona Stepniewska, Robert M. Friedman, Omar A. Gharbawie, Christina M. Cerkevich, Anna W. Roe, Jon H. Kaas

Research output: Contribution to journalArticlepeer-review

44 Scopus citations


The posterior parietal cortex (PPC) of monkeys and prosimian galagos contains a number of subregions where complex, behaviorally meaningful movements, such as reaching, grasping, and body defense, can be evoked by electrical stimulation with long trains of electrical pulses through microelectrodes. Shorter trains of pulses evoke no or simple movements. One possibility for the difference in effectiveness of intracortical microstimulation is that long trains activate much larger regions of the brain. Here, we show that long-train stimulation of PPC does not activate wide-spread regions of frontal motor and premotor cortex but instead, produces focal, somatotopically appropriate activations of frontal motor and premotor cortex. Shorter stimulation trains activate the same frontal foci but less strongly, showing that longer stimulus trains do not produce less specification. Because the activated sites in frontal cortex correspond to the locations of direct parietal-frontal anatomical connections from the stimulated PPC subregions, the results show the usefulness of optical imaging in conjunction with electrical stimulation in showing functional pathways between nodes in behavior-specific cortical networks. Thus, long-train stimulation is effective in evoking ethologically relevant sequences of movements by activating nodes in a cortical network for a behaviorally relevant period rather than spreading activation in a nonspecific manner.

Original languageEnglish (US)
Pages (from-to)E725-E732
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number37
StatePublished - Sep 13 2011
Externally publishedYes


  • Complex movements
  • Neocortex
  • Nonhuman primate

ASJC Scopus subject areas

  • General


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