Effect of Exercise on Motor Evoked Potentials Elicited by Transcranial Magnetic Stimulation in Psychiatric Patients

Abstract

Under normal conditions, motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation increase in amplitude if the subject exercises the examined muscle immediately before recording. The authors examined the effect of nonfatiguing exercise on the amplitude of MEPs on 42 psychiatric, medicated inpatients (14 with depression, 14 with schizophrenia, and 14 with mania) compared with 14 healthy control subjects. For each subject, a total of 50 baseline and 50 postexercise MEPs were recorded. The mean (+/- standard deviation) postexercise MEP facilitation, expressed as a percentage of mean baseline values, was significantly lower (p </= 0.02) in all three patient groups (148 +/- 91% in the depressed, 107 +/- 43% in the schizophrenic, and 143 +/- 63% in the manic patients) compared with the control subjects (268 +/- 223%). There was no clear evidence that psychotropic medication could be fully responsible for the modified MEP response to exercise, but the degree to which they were responsible is impossible to assess. These findings indicate that the reduced postexercise MEP facilitation is not related to any particular psychiatric illness, but rather that it represents a suppressed reaction of cortical excitability shared by patients with either depression, mania, or schizophrenia. The authors propose that, despite the lack of specificity, the study of postexercise MEP alterations could be useful in the neurophysiologic evaluation of motor cortex excitability in some psychiatric illnesses, except in those patients who may have diminished somatosensory input associated with voluntary muscle contraction resulting in decreased cortical excitability.

Persistent Suppression of Postexercise Facilitation of Motor Evoked Potentials During Alternate Phases of Bipolar Disorder

“…It has been repeatedly shown that the increase of MEP amplitude immediately after nonfatiguing exercise expected in healthy subjects, seemed to be reduced in depressed patients (Samii et al, 1996;Shajahan et al, 1999a). In a previous study conducted by our group (Chroni et al, 2002) it was found that a similar reduced MEP reaction to exercise was evident both in schizophrenic and manic patients. This finding implies a uniform abnormal MEP facilitation in psychiatric patients.…”

“…However, these authors recognized the limitation of considerable intersubject MEP amplitude variability. Moreover, the view that reduced postexercise facilitation is a neurophysiologic marker characteristic of the depressed state is weakened by findings suggesting that schizophrenic patients too, have similarly impaired facilitation (Chroni et al, 2002;Reid et al, 2002).…”

“…Neither of the patients had a concomitant systematic or neurologic disease. The results were compared with mean values of a healthy control group (14 subjects, mean age 44 years), which were used in a similar previous study conducted by us (Chroni et al, 2002).…”

Effects of carotid endarterectomy on motor evoked potentials elicited by transcranial magnetic stimulation

“…In respect of the issue of the controls used, we recognise that a tempting option would be a group of age-matched healthy subjects that would possibly strengthen the abnormalities in the stroke patients. However, we chose to compare the operated side to the non-operated side of the same subjects since there are great diversions of MEPs parameters among individuals and the influence of the measurements by various factors such as drugs, mental concentration, attention or stress, is considerable [4].…”

Using Transcranial Magnetic Stimulation (TMS) to Compare Cortical Excitability Among Depressed Patients, Sleep-Deprived Controls, and Rested Controls

“…In one study, 11 patients with schizophrenia and 10 patients with major depression demonstrated decreased post-exercise facilitation in comparison with a group of 13 healthy control patients (7). Another study involving 14 patients with mania, 14 with major depression, 14 with schizophrenia, and 14 healthy controls were studied and in each non-control group, subjects showed significantly reduced post-exercise facilitation (8).…”