Short-latency afferent inhibition determined by the sensory afferent volley

Short-latency afferent inhibition (SAI) is characterized by the suppression of the Transcranial magnetic stimulation (TMS) motor evoked potential (MEP) by the cortical arrival of a somatosensory afferent volley. It remains unknown whether the magnitude of SAI reflects changes in the sensory afferent volley, similar to that observed for somatosensory evoked potentials (SEPs). The present study investigated stimulus-response relationships between sensory nerve action potentials (SNAPs), SAI and SEPs, and their interrelatedness. Experiment 1 (n=23, aged 23 ± 1.5) investigated the stimulus-response profile for SEPs and SAI in the flexor carpi radialis (FCR) muscle following stimulation of the mixed, median nerve at the wrist using ~25%, 50%, 75% and 100% of the maximum SNAP and at 1.2x and 2.4x motor threshold (the latter equated to 100% of the maximum SNAP). Experiment 2 (n=20, aged 23.1 ± 2) probed SEPs and SAI stimulus-response relationships following stimulation of the cutaneous digital nerve at ~25%, 50%, 75% and 100% of the maximum SNAP recorded at the elbow. Results indicate that, for both nerve types, SAI magnitude is dependent on the volume of the sensory afferent volley and ceases to increase once all afferent fibers within the nerve are recruited. Further, for both nerve types, the magnitude of SAI and SEPs are related such that an increase in excitation within somatosensory cortex is associated with an increase in the magnitude of afferent-induced MEP inhibition.

from Physiology via xlomafota13 on Inoreader http://ift.tt/22pT6Tx


from #Med Blogs by Alexandros G.Sfakianakis via Alexandros G.Sfakianakis on Inoreader http://ift.tt/1VjgFN0
via IFTTT