The influence of the shape of mechanical stimuli on muscle stretch reflexes and SEP.
Stretching of human thenar muscle was carried out using mechanical stimuli of different amplitudes and velocities in 50 normal subjects. Amplitudes of early M1 and late M2 reflex responses as well as cortical evoked potentials were recorded. M1 and M2 increased with a larger mechanical stimulus. Steeper mechanical stimuli generated larger M1 amplitudes, whereas M2 remained unaffected. Amplitudes of early cortical evoked potentials increased with increase of both rise-time and amplitude of muscle stretch. The shape of the mechanical stimulus is critical for the resulting reflex response. The different behaviours of M1 and M2 with increasing stimulus velocity are in favour of their different origins. Our results support a participation of slowly conducting muscle spindle afferents in the generation of the late M2 response in distal human hand muscles.
Spitzer
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Department of Neurology, University Erlangen-Nuremberg, Germany.
Claus
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D
D000328:Adult; D000368:Aged; D004569:Electroencephalography; D004576:Electromyography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D009132:Muscles / Q000502:physiology*; D010812:Physical Stimulation; D011930:Reaction Time / Q000502:physiology; D012026:Reflex, Stretch / Q000502:physiology*