This has been examined in our laboratories in a number of fields, including:

Motor cortical functions, measurement of corticospinal conduction time using the appropriate orientation of the magnetic coil, mapping muscle and motor unit representation using focal magnetic stimulation, and using focal magnetic mapping to demonstrate reorganization of the motor cortex after spinal cord lesions (Miami project). Spared muscles were shown to have a greatly expanded area of representation.

Mapping the speech expressive frontal cortex. Four separate areas were defined. Magnetic stimulation of the supplementary motor area: interference with sequential movements.

Eliciting sensory effects including: magnetic stimulation of the visual cortex. It was shown to elicit perceptual suppression of flashed visual stimuli and phosphenes. The recovery time from suppression yielded the exit time of the visual information. Unmasking was demonstrated when two visual stimuli were presented and the masking (second) response was magnetically suppressed. Single magnetic stimuli to the frontal (but not parietal) lobe elicited a projected sense of movement, and in some normals, paresthesias. (These findings led to the hypothesis that the heavy frontal lobe projections to the thalamic intralaminar N. opens a gate for cortical output which leads to conscious perception.

Tracking information flow by: recording frontal lobe evoked potentials to stimulation of the opposite hemisphere, or the cerebellum, measuring the delays from output of visual cortex to vocalization, and subsequently fractionating the delays, thus yielding an estimate of the delay for conscious perception.

Magnetic stimulation of temporo-parieto-occipital cortex in some individuals shows lateralization of immune responses during vocalization reaction time tasks. In these individuals, CD4, CD8, and CD16 (NK) cells increase within 6 hrs. with left-sided stimulation alone, and decrease 24 hrs. later with right-sided stimulation alone. A rat model of cortical lateralization of immune cell function has been developed by Mr. Moshel.

Magnetic stimulation of the monkey brain has been combined with electrophysiological recording to test and amplify hypotheses developed from the human experiments.

Selected Publications

Amassian, V. E., Cracco, R. Q., Maccabee, P. J., Cracco, J. B., and Henry, K. (1995). Some positive effects of transcranial magnetic stimulation. In: Neurology 67, Negative Motor Phenomena (Fahn, S., Hallett, M., Luders, H. O., and Marsden, C.D., eds.), New York, Raven Press, pp. 79-106.

Amassian, V. E., Cracco, R. Q., Vergara, M., Maccabee, P. J., Somasundaram, M., and Cracco, J. B. (1998). Magnetic transcranial stimulation studies in humans on the roles of frontal and occipital lobes in perception, on estimating perceptual delay, and on temporary pain relief with parietal stimulation. In: Pain Mechanisms and Management (Ayrapetyan, S. N., and Apkarian, A.V., eds.), IOS Press, Washington, pp. 260-282.

Amassian, V. E., Cracco, R. Q., Maccabee, P. J., Cracco, J. B., Rudell, A. P., and Eberle, L. (1998). Transcranial magnetic stimulation in the study of the visual pathway. J. Clin. Neurophysiol. 15:288-304.

Amassian, V. E., and Deletis, V. (1999). Relationships between animal and human corticospinal responses. In: Electroenceph. Clin. Neurophysiol.; Suppl. 51. Transcranial Magnetic Stimulation (Paulus, W., Hallett, P. M., Rossini, J. C., Amassian, V. E., and Deletis, V., eds.), Elsevier, New York, pp. 79-92.

Maccabee, P. J., Amassian, V. E., Ziemann, U., Wassermann, E., and Deletis, V. (2000). Emerging applications in neuromagnetic stimulation. In: Comprehensive Clinical Neurophysiology (Levin, K. H., and Luders, H. O., eds.), W. W. Saunders, Philadelphia.

Personnel

Larry Eberle, B.A., University Instructional Specialist
Yaron Moshel, M.D. Ph.D. Student

Service Functions

Ad Hoc reviewer for various scientific journals