title: Exploring the temporal nature of hemodynamic responses of cortical motor areas using functional MRI.
abstract: OBJECTIVE
  To use functional MRI (fMRI) to study grouped patterns of cerebral activation and the course of hemodynamic responses during performance of two activation tasks (paradigms) using a hand-held joystick to perform movements in a repetitively fixed direction and movements in freely selected random directions.
  
  
  BACKGROUND
  Evidence from lesion, electrophysiologic, and functional imaging studies implicates prefrontal and mesial frontal cortex in motor preparation and primary motor cortex in motor execution. fMRI can be used to study cerebral activation and has practical advantages over other methods of functional neuroimaging.
  
  
  METHODS
  We acquired 100 multislice T2*-weighted data sets from five healthy volunteers during performance of each paradigm using conventional fMRI. For each paradigm, rest and movement epochs were alternated every 30 seconds. After coregistration and spatial normalization, we combined the data for group studies. We used statistical parametric mapping to compare the early (first 15 seconds) components of the movement epochs with rest as well as the late (last 15 seconds) components of the movement epochs with rest.
  
  
  RESULTS
  During the early phase of both paradigms, significant activation was present in rostral and caudal mesial premotor cortex. Right prefrontal cortex was significantly activated during the early component of freely selected joystick movements. Activation of rostral supplementary motor area was maintained during the late component of freely selected movements but decreased during repetitively fixed movements. In contrast, significant activation in contralateral sensorimotor cortex was maintained during both early and late components of both paradigms.
  
  
  CONCLUSIONS
  fMRI can detect cortical activation. The temporal resolution of fMRI also allows adaptation of blood oxygenation level-dependent (BOLD) contrast signal to be detected in association cortex. However, the level of BOLD contrast signal in primary motor cortex remained significantly elevated throughout task performance.
authors.affiliation: MRC Cyclotron Unit, Hammersmith Hospital, London, UK.
authors.forename: M
authors.initials: M
authors.lastname: Samuel
authors.forename: S C
authors.initials: SC
authors.lastname: Williams
authors.forename: P N
authors.initials: PN
authors.lastname: Leigh
authors.forename: A
authors.initials: A
authors.lastname: Simmons
authors.forename: S
authors.initials: S
authors.lastname: Chakraborti
authors.forename: C M
authors.initials: CM
authors.lastname: Andrew
authors.forename: K J
authors.initials: KJ
authors.lastname: Friston
authors.forename: L H
authors.initials: LH
authors.lastname: Goldstein
authors.forename: D J
authors.initials: DJ
authors.lastname: Brooks
mesh_terms: D000328:Adult; D001479:Basal Ganglia / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology; D006225:Hand / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000098:blood supply*; D017397:Prefrontal Cortex / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology; D013788:Thalamus / Q000502:physiology; D013997:Time Factors