Dose-dependent reduction of cerebral blood-flow during rapid-rate transcranial magnetic stimulation of the human sensorimotor cortex.
Tom s Paus, Robert Jech, Christopher J. Thompson, Roch Comeau,Terry Peters,
Alan C. Evans
Montreal Neurological Institute, McGill University, Montreal, Quebec, H3A
2B4, Canada; and Department of Neurology, 1st Medical Faculty, Charles
University, Prague, Czech Republic.
APStracts 4:302N, 1997.
ABSTRACT
1. Rapid-rate transcranial magnetic stimulation (rTMS) was used to stimulate
the primary sensorimotor cortex in six healthy volunteers while regional
changes in cerebral blood-flow (CBF) were simultaneously measured by means of
positron emission tomography (PET). 2. A figure-eight TMS coil (Cadwell
Corticoil) was positioned, using frameless stereotaxy, over the probabilistic
location of the left primary sensorimotor cortex, and a series of brief 10-Hz
trains of TMS was delivered at subthreshold intensity during each of six 60-
sec scans. The scans differed in the number of trains delivered, namely 5, 10,
15, 20, 25 and 30 trains/scan, respectively. 3. In the left primary
sensorimotor cortex, CBF covaried significantly and negatively with the number
of stimulus trains. These CBF decreases may reflect TMS-induced activation of
local inhibitory mechanisms known to play a role in TMS-related phenomena,
such as the electro-myographic silent period.
Received 14 July 1997; accepted in final form 29 October 1997.
APS Manuscript Number J580-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 14 November 1997