Modulation of the long-latency reflex to stretch by the supplementary motor area in humans.
Surface-recorded, electromyographic responses to 200-ms ramp stretches were studied in the wrist flexor muscles from both arms of a patient with clinical and radiographic evidence of infarction in the right supplementary motor area (SMA). They were compared with those from 8 age-matched control subjects. The latencies of the spinal component of the stretch reflex were slightly longer than normal in both arms of the patient (normal subjects: 28.5 +/- 2.6 ms; patient: 35 ms, right arm and 32 ms left arm). However, the amplitude and duration of the short-latency response were identical in both arms. The onset of the long-latency response to stretch was symmetrical in both the patient's arms and was slightly later than normal (normal subjects 55.5 +/- 4.0 ms, patient: 72 ms right arm and 70 ms left arm); however, its duration was considerably prolonged in the arm contralateral to the SMA lesion (normal subjects: 44.8 +/- 6.0 ms; patient: 48 ms right arm. 105 ms left arm). These results are consistent with the hypothesis that the long-latency stretch reflex is mediated via a transcortical loop.
D000328:Adult; D000368:Aged; D001931:Brain Mapping; D002544:Cerebral Infarction / Q000473:pathology / Q000503:physiopathology; D004576:Electromyography; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000473:pathology / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012026:Reflex, Stretch; D014057:Tomography, X-Ray Computed