Functional heterogeneity of left inferior frontal cortex as revealed by fMRI

Neuroreport. 1997 May 27;8(8):2011-7. doi: 10.1097/00001756-199705260-00042.


Using functional magnetic resonance imaging (fMRI), we mapped brain activity in six normal volunteers during two silent verbal fluency tasks, one with a phonemic (letter) cue and one with a semantic (category) cue. In comparison with resting state, both tasks activated the anterior triangular portion of the left inferior frontal gyrus (IFG or F3, for third frontal gyrus) and the left thalamus. There were also areas activated in one task but not in the other: the posterior opercular portion of the left IFG for phonemic fluency, and the left retrosplenial region for semantic fluency. Our findings concur with normal psychophysical data and neuropsychological observations to suggest the recruitment of two overlapping but dissociable systems for the two tasks, and demonstrate functional heterogeneity within the left IFG (Broca's area), where the opercular portion is responsible for obtaining access to words through a phonemic/articulatory route.

Publication types

  • Clinical Trial
  • Controlled Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Cerebrovascular Circulation / physiology
  • Frontal Lobe / anatomy & histology
  • Frontal Lobe / blood supply
  • Frontal Lobe / physiology*
  • Functional Laterality / physiology
  • Humans
  • Image Processing, Computer-Assisted
  • Magnetic Resonance Imaging
  • Male
  • Recruitment, Neurophysiological / physiology
  • Rest / physiology
  • Verbal Behavior / physiology