Task-Specific Magnetic Fields from the Left Human Prefrontal Cortex

Abstract

Recent studies have provided evidence for task-specific activity in distinct areas of the frontal cortex [1,2,3]. In a previous study, we used magnetoencephalography (MEG) to test the hypothesis of functional specialization of the frontal cortex [1] by asking subjects to perform two visual recognition tasks. A spatial recognition task was associated with sources of magnetic fields in the right frontal lobe, which were localized more anteriorly and inferiorly, than the sources of activity obtained during a visual pattern recognition task. Both tasks involved presentation of common visual stimuli and required common motor responses. These results were analogous to the findings from a multi-unit recording study in the monkey [3]. That study showed concentrations of neurons in dorsolateral and inferior convexity prefrontal areas, that responded preferentially during the performance of a visuo-spatial and a visual-pattern delayed response task, respectively. Another experiment from our laboratory (unpublished data) provided evidence for different sources of activity in the right frontal lobe, when a familiar-person recognition task was compared to a visual pattern recognition task. Sources in more medial areas of the right prefrontal cortex were obtained when subjects performed the familiar-person recognition task. A study by Petrides et al. [2], using positron emission tomography in humans, also reported regional prefrontal cortical activity corresponding to the performance of two different tasks.