Task-specific magnetic fields from the left human frontal cortex
- 16 Downloads
In this study we attempted to extend our previous results on regional specialization of frontal cortical function in humans, by means of magnetoencephalography (MEG). We used a verbal task and predicted that some part of the left frontal lobe would be active during engagement in that task, since the left hemisphere is known to be implicated in language. We did not require a motor response because in previous experiments we observed bilateral frontal magnetic activity, and we suspected that it was due to the addition of movement-related fields to our recordings. Six right handed subjects (three males and three females) participated in the study. The task consisted in silently counting the number of word pairs that matched with respect to semantic category. Experimental runs were composed by series of 120 trials or word pairs. All six subjects presented dipolar magnetic field distributions on the left fronto-temporal area of the scalp, but not on the right, during different portions of the trial duration. These fields were successfully modeled as equivalent current dipoles (ECDs). The spatial ECD coordinates were translated onto magnetic resonance image (MRI) coordinates for each subject. The dipole positions were typically near the cortical surface corresponding to areas 6 and 44 of Brodmann. No dipole-like sources were observed in the right frontal lobe.
Key wordsMagnetoencephalography Frontal cortex Verbal task Hemispheric asymmetry
Unable to display preview. Download preview PDF.
- Basile, L.F.H., Brunder, D.G. and Papanicolaou, A.C. Magnetic fields from human prefrontal cortex differ during two recognition tasks. Int. J. Psychophysiol., (in press 1996).Google Scholar
- Eckenstein, F. and Baughman, R.W. Cholinergic innervation in cerebral cortex. In: Cerebral Cortex. Vol 6: Chap 3. Jones, E.G. and Peters, A. (Eds). Plenum Press. New York, 1987.Google Scholar
- Fallon, J.H. and Loughlin, S.E. Monoamine innervation of cerebral cortex and a theory of the role of monoamines in cerebral cortex and basal ganglia. In: Cerebral Cortex. Vol 6: Chap 2. Jones, E.G. and Peters, A. (Eds). Plenum Press. New York, 1987.Google Scholar
- Fuster, J.M. The Prefrontal Cortex (2nd ed). Raven Press. New York, 1989.Google Scholar
- Hämäläinen, M., Hari, R., Ilmoniemi, R.J., Knuutila, J. and Lounasmaa, O.V. Magnetoencephalography — theory, instrumentation, and applications to noninvasive studies of the working human brain. Reviews of Modern Physics, 1993, 65:413–497.Google Scholar
- Kaufman, L., Schwartz, B., Salustri, C. and Williamson, S.J. Modulation of spontaneous brain activity during mental imagery. J. of Cogn. Neurosci., 1990, 2:124–132.Google Scholar
- Lewine, J.D. Neuromagnetic techniques for the noninvasive analysis of brain function. In: Noninvasive Techniques in Biology and Medicine. Chap 3. Freeman, S.E.; Fukushima, E. and Greene, E.R. (Eds). San Francisco Press, San Francisco, 1990.Google Scholar
- Williamson, S.J. and Kaufman, L. Analysis of neuromagnetic signals. In: Handbook of Electroencephalography and Clinical Neurophysiology. Human Event-Related Potentials (revised series vol.1) Gevins, A.S. and Remond, A. (Eds.). Elsevier Science Publishers, 1987, 405–448.Google Scholar
- Wilson, F.A.W., Scalaidhe, S.P.O. and Goldman-Rakic, P.S. Dissociations of object and spatial processing domains in primate prefrontal cortex. Science, 1993, 260:1995–1958.Google Scholar