Conditioning effect on the long latency potentials in the lower limb to transcranial magnetic stimulation.
OBJECTIVE
We used an electrical conditioning stimulation followed by transcranial magnetic stimulation (TMS) to facilitate the occurrence of long latency potentials (LLPs) in order to study the relationship between primary motor evoked potentials (MEPs) and LLPs in the lower limbs.


METHODS
The study group included 6 healthy subjects, 1 patient with right thalamic infarction, and 3 patients with spinal cord injuries. The subjects were subjected to electrical conditioning (C) stimulation delivered to the left big toe at 250 Hz in a train of pulses of 20 ms duration prior to TMS (T) from 0 to 150 ms at an increment of 10 ms. The surface electromyographic signals were recorded at the tibialis anterior and gastrocnemius medialis for 400 ms.


RESULTS
The C-T test facilitated both primary MEPs and LLPs with a pattern similar to the primary MEPs of its antagonist. There was no facilitation of the primary MEPs or LLPs in the affected limb of patients with thalamic or spinal cord lesions.


CONCLUSIONS
At appropriate C-T interval, LLPs could be consistently provoked by TMS. The LLPs were absent in the patients with thalamic infarction and spinal cord injuries. It suggests that LLPs might be provoked through a supraspinal control.
Chen
J T
JT
Neurology, The Neurological Institute, Veterans General Hospital-Taipei, Taiwan.
Chen
C C
CC
Kao
K P
KP
Wu
Z A
ZA
Liao
K K
KK
D000328:Adult; D000368:Aged; D002544:Cerebral Infarction / Q000503:physiopathology; D003213:Conditioning, Psychological / Q000502:physiology*; D004574:Electromagnetic Fields; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D007866:Leg / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology; D011930:Reaction Time / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology; D013119:Spinal Cord Injuries / Q000503:physiopathology; D013788:Thalamus / Q000098:blood supply / Q000502:physiology; D004561:Transcutaneous Electric Nerve Stimulation