Affiliations: Brain Research and Rehabilitation Center Neuron,
Kuopio, Finland | Department of Psychiatry, University of Sao Paulo
Medical School, Sao Paulo, Brazil
Note: [] Corresponding author: Ina M. Tarkka, Ph.D., Brain Research and
Rehabilitation Center Neuron, Kortejoki, FIN-71130 Kuopio, Finland. Tel.: +358
17 460281; Fax: +358 17 460200.
Abstract: This study was an attempt to replicate recent
magnetoencephalographic (MEG) findings on human task-specific CNV sources
(Basile et al., Electroencephalography and Clinical Neurophysiology 90, 1994, 157-165) by means of a spatio-temporal electric source
localization method (Scherg and von Cramon, Electroencephalography and
Clinical Neurophysiology 62, 1985, 32-44; Scherg and von Cramon, Electroencephalography and Clinical Neurophysiology 65, 1986,
344-360; Scherg and Berg, Brain Electric Source Analysis Handbook,
Version 2). The previous MEG results showed CNV sources in the prefrontal
cortex of the two hemispheres for two tasks used, namely visual pattern
recognition and visual spatial recognition tasks. In the right hemisphere, the
sources were more anterior and inferior for the spatial recognition task than
for the pattern recognition task. In the present study we obtained CNVs in five
subjects during two tasks identical to the MEG study. The elicited electric
potentials were modeled with four spatio-temporal dipoles for each task, three
of which accounted for the visual evoked response and one that accounted for
the CNV. For all subjects the dipole explaining the CNV was always localized
in the frontal region of the head, however, the dipole obtained during the
visual spatial recognition task was more anterior than the one obtained during
the pattern recognition task. Thus, task-specific CNV sources were again
observed, although the stable model consisted of only one dipole located close
to the midline instead of one dipole in each hemisphere. This was a major
difference in the CNV sources between the previous MEG and the present electric
source analysis results. We discuss the possible basis for the difference
between the two methods used to study slow brain activity that is believed to
originate from extended cortical patches.
