title: Inactivation of the Dorsal Premotor Area Disrupts Internally Generated, But Not Visually Guided, Sequential Movements.
abstract: As skill on a sequence of movements is acquired through practice, each movement in the sequence becomes seamlessly associated with another. To study the neural basis of acquired skills, we trained two monkeys (Cebus apella) to perform two sequential reaching tasks. In one task, sequential movements were instructed by visual cues, whereas in the other task, movements were generated from memory after extended practice. Then, we examined neural activity in the dorsal premotor area (PMd) and the effects of its local inactivation during performance of each task. Comparable numbers of neurons in the PMd were active during the two tasks. However, inactivation of the PMd had a marked effect only on the performance of sequential movements that were guided by memory. These results emphasize the importance of the PMd in the internal generation of sequential movements, perhaps through maintaining arbitrary motor-motor associations.
  
  
  CONCLUSIONS
  The dorsal premotor cortex (PMd) has long been thought to be a critical node in the cortical networks responsible for visually guided reaching. Here we show that PMd neurons are active during both visually guided and internally generated sequential movements. In addition, we found that local inactivation of the PMd has a marked effect only on the performance of sequential movements that were internally generated. These observations suggest that, although the PMd may participate in the generation of visually guided sequences, it is more important for the generation of internally guided sequences.
authors: Center for the Neural Basis of Cognition, Systems Neuroscience Institute, University of Pittsburgh Brain Institute, and Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261.
authors: Machiko
authors: http://orcid.org/0000-0003-2563-9049
authors: M
authors: Ohbayashi
authors: Center for the Neural Basis of Cognition, Systems Neuroscience Institute, University of Pittsburgh Brain Institute, and Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261.
authors: Nathalie
authors: N
authors: Picard
authors: Center for the Neural Basis of Cognition, Systems Neuroscience Institute, University of Pittsburgh Brain Institute, and Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 strickp@pitt.edu.
authors: Peter L
authors: PL
authors: Strick
mesh_terms: D000818:Animals; D002428:Cebus; D003463:Cues; D004558:Electric Stimulation; D005260:Female; D018755:GABA Agonists / Q000494:pharmacology; D008297:Male; D008568:Memory / Q000502:physiology; D009044:Motor Cortex / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009048:Motor Skills / Q000187:drug effects / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D009118:Muscimol / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000187:drug effects / Q000502:physiology*
chemical_list: D018755:GABA Agonists; D009118:Muscimol