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Motor responses to transcranial magnetic stimulation in schizophrenia

Published online by Cambridge University Press:  02 January 2018

N. J. Davey
Affiliation:
Division of Neuroscience & Psychological Medicine, Imperial College School of Medicine, Charing Cross Hospital, Fulham Palace Road, London W6 8RF
B. K. Puri
Affiliation:
MRI Unit, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital, London W12 0HS
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Abstract

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Copyright © 2000 The Royal College of Psychiatrists 

We read with interest the paper by Boroojerdi et al (Reference Boroojerdi, Topper and Foltys1999). Our group found a shorter latency for motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) in unmedicated people with schizophrenia of, on average, 2 ms compared with age- and gender-matched normal subjects (Reference Puri, Davey and EllawayPuri et al, 1996). In contrast, Boroojerdi et al (Reference Boroojerdi, Topper and Foltys1999) reported no such latency difference (in their group of medicated patients) and speculated that the presence of antipsychotic medication may have confounded their results. Indeed, our group has previously reported the effects of such medication on the latency and form of the inhibitory silent periods to TMS (Reference Davey, Puri and LewisDavey et al, 1997), which is known to occur as a result of activating superficial intracortical inhibitory interneurons, possibly GABAergic (Reference Davey, Romaiguère and MaskillDavey et al, 1994). Boroojerdi et al (Reference Boroojerdi, Topper and Foltys1999) found a longer latency of transcallosal inhibition to TMS in a group of medicated patients with schizophrenia but did not include a group of drug-naïve patients. It is clearly important to be able to differentiate between pathophysiological mechanisms resulting from schizophrenia and the actions of antipsychotic medication on the corticospinal system.

References

Boroojerdi, B., Topper, R., Foltys, H., et al (1999) Transcallosal inhibition and motor conduction studies in patients with schizophrenia using transcranial magnetic stimulation. British Journal of Psychiatry, 175, 375379.Google Scholar
Davey, N. J., Romaiguère, P., Maskill, D. W., et al (1994) Suppression of voluntary motor activity revealed using transcranial magnetic stimulation of the motor cortex in man. Journal of Physiology, 477, 223235.Google Scholar
Davey, N. J., Puri, B. K., Lewis, H. S., et al (1997) The effects of antipsychotic medication on electromyographic responses to transcranial magnetic stimulation of the motor cortex in schizophrenia. Journal of Neurology Neurosurgery and Psychiatry, 63, 468473.Google Scholar
Puri, B. K., Davey, N. J., Ellaway, P. H., et al (1996) An investigation of motor function in schizophrenia using transcranial magnetic stimulation of the motor cortex. British Journal of Psychiatry, 169, 690695.Google Scholar
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