title: Encoding of speed and direction of movement in the human supplementary motor area.
abstract: OBJECTIVE
  The supplementary motor area (SMA) plays an important role in planning, initiation, and execution of motor acts. Patients with SMA lesions are impaired in various kinematic parameters, such as velocity and duration of movement. However, the relationships between neuronal activity and these parameters in the human brain have not been fully characterized. This is a study of single-neuron activity during a continuous volitional motor task, with the goal of clarifying these relationships for SMA neurons and other frontal lobe regions in humans.
  
  
  METHODS
  The participants were 7 patients undergoing evaluation for epilepsy surgery requiring implantation of intracranial depth electrodes. Single-unit recordings were conducted while the patients played a computer game involving movement of a cursor in a simple maze.
  
  
  RESULTS
  In the SMA proper, most of the recorded units exhibited a monotonic relationship between the unit firing rate and hand motion speed. The vast majority of SMA proper units with this property showed an inverse relation, that is, firing rate decrease with speed increase. In addition, most of the SMA proper units were selective to the direction of hand motion. These relationships were far less frequent in the pre-SMA, anterior cingulate gyrus, and orbitofrontal cortex.
  
  
  CONCLUSIONS
  The findings suggest that the SMA proper takes part in the control of kinematic parameters of endeffector motion, and thus lend support to the idea of connecting neuroprosthetic devices to the human SMA.
authors.affiliation: Department of Neurosurgery, University of California, Los Angeles, California, USA.
authors.forename: Ariel
authors.initials: A
authors.lastname: Tankus
authors.forename: Yehezkel
authors.initials: Y
authors.lastname: Yeshurun
authors.forename: Tamar
authors.initials: T
authors.lastname: Flash
authors.forename: Itzhak
authors.initials: I
authors.lastname: Fried
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D015331:Cohort Studies; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004827:Epilepsy / Q000503:physiopathology* / Q000523:psychology / Q000601:surgery; D005260:Female; D006225:Hand; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009044:Motor Cortex / Q000503:physiopathology*; D013647:Task Performance and Analysis; D055815:Young Adult