Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky
Erscheinungsjahr:
2013
Medientyp:
Text
Schlagworte:
transcranial magnetic stimulation
short latency afferent inhibition
long-loop reflex
sensori-motor integration
cortical relay
610 Medizin, Gesundheit
44.90 Neurologie
ddc:610
Beschreibung:
Background: The transcranial magnetic stimulation (TMS) paradigm short-latency sensory afferent inhibition (SAI) investigates sensori-motor integration. Conventionally, one stimulation intensity is used for the conditioning pulse to the peripheral nerve,. Objective/hypothesis: To examine the variability, the dimension of stimulus intensity and recording site in SAI. Methods: In 17 healthy individuals three peripheral nerve stimulation intensities were used: Just above sensory threshold, just above motor threshold, and in between. Motor evoked potentials (MEPs) and long-loop reflexes were recorded from first dorsal interosseus (FDI) and abductor pollicis brevis (APB) before and after repetitive motor cortex TMS (1Hz, 1800 stimuli at 95% resting motor threshold). Results: Between-subjects variability of SAI was higher than variability between sessions. Median, or ulnar, nerve stimulation decreased MEP size in FDI and APB at inter-stimulus intervals of N20, N20+2 and N20+4. Only with median nerve stimulation MEP size increased in APB, but not FDI, at N20+8 to N20+16. These effects increased with increasing stimulation intensity. RTMS reduced MEP size but had no effect on SAI, or transcortical reflexes. Conclusions: Effects on MEP size in SAI depend on stimulus intensity and are not limited to anatomically homotopic muscles. Inhibitory rTMS modulates motor output but not the interaction of sensory inputs with the motor cortex.