'Virtual lesion' in pain research; a study on magnetic stimulation of the primary motor cortex.
BACKGROUND
'Virtual lesion' ('VL') is a transient disruption of cortical activity during task performance. It can be induced by single pulses or short trains of transcranial magnetic stimulation (TMS) directed to functionally relevant brain areas. We applied 'VL' methodology of a short train of TMS given on top of experimental tonic pain, expecting to see changes in pain scores.


METHODS
Thirty young healthy subjects (15 women) were assessed with active ('VL') or 'sham' TMS in different sessions, randomly. In each session, 30 sec-long contact heat (47.5 °C, right forearm) was applied stand-alone ('baseline') and with 5 sec-long 10 Hz-TMS over left primary motor cortex (M1) starting at 17 sec of the heat stimulation.


RESULTS
Pain scores decreased after 'VL' or 'sham' (p < 0.001). Independently of the type of TMS, pain reduction was stronger in women (p = 0.012). A triple Sex x Stimulation type ('VL' or 'sham') x Condition ('baseline' heat pain vs. heat pain with TMS) interaction (p = 0.027) indicated stronger pain reduction by 'VL' in women (p = 0.008) and not in men (p = 0.78) as compared to 'baseline'. Pain catastrophizing and perceived stress ratings affected the model (p = 0.010 and p < 0.001, respectively), but without sex differences.


CONCLUSIONS
This study indicates that interactions between cortical excitability of the motor cortex and nociceptive processing may be gender-related.
Department of Neurology, Rambam Medical Center, Haifa, Israel.|Clinical Neurophysiology Laboratory, Technion Faculty of Medicine, Haifa, Israel.
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Y
Granovsky
Faculty of Medicine, University Utrecht, The Netherlands.
K S
KS
Liem
Faculty of Social Welfare and Health Sciences, University of Haifa, Haifa, Israel.
I
I
Weissman-Fogel
Department of Neurology, Rambam Medical Center, Haifa, Israel.|Clinical Neurophysiology Laboratory, Technion Faculty of Medicine, Haifa, Israel.
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D
Yarnitsky
Neurosurgery Laboratory, Rambam Medical Center, Haifa, Israel.
A
A
Chistyakov
Department of Neurology, Rambam Medical Center, Haifa, Israel.|Neurosurgery Laboratory, Rambam Medical Center, Haifa, Israel.
A
A
Sinai
D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000503:physiopathology*; D010146:Pain / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D055815:Young Adult