Cognition and the Brain
Annual technical rept. 15 Feb 1990-14 Feb 1991,
NEW YORK UNIV NY NEUROMAGNETISM LAB
Pagination or Media Count:
Using an array of 14 superconducting magnetic field sensors we succeeded in establishing the locations of neuronal activity that produce the dominant alpha rhythm recorded in the electroencephalogram and magnetoencephalogram. Of particular interest is our observation that spontaneous alpha activity is suppressed over the visual area when a person is engaged in mental imagery, and over other functional areas when appropriate cognitive tasks are performed. Computer simulations of the changes in patterns of alpha field power reveal how the power map is related to the underlying cortical topography when suppression occurs. In studies of sensory evoked cortical activity, an analysis of published current source density measurements on animals provides information from which we obtain the first realistic measure for the spatial extent of cortical activity in human cortex when responding to sensory stimuli. Measurements with a 5-sensor system for chrominance and luminance stimuli shows that the sites of response in visual cortex coincide. The separation of color information processing apparently takes place at a later stage, if at all. Responses in human auditory cortex to appropriate sound stimuli reveal activity not previously identified, which has characteristics that suggest it is related to sensory memory functions.
- Anatomy and Physiology