Upper limb H reflexes and somatosensory evoked potentials modulated by movement

In the human lower limb, the magnitudes of both Hoffmann (H) reflexes and p rimary somatosensory evoked potentials (SEPs) from scalp electrodes, are re duced by active and/or passive movement. We surmised that similar effects o ccur for the upper limb and specifically hypothesised that amplitudes of me dian nerve induced flexor carpii radialis H reflexes and cortical SEPs are reduced with passive movement about the wrist or elbow. The results showed (P<0.05) that either movement significantly attenuated mean magnitudes of S EPs elicited from stimulation at elbow or wrist and that reflex magnitudes attenuated with wrist movement. Thus, the upper limb shows similar movement -induced modulation to the lower limb. These attenuations of fast conductin g sensory paths consequent to movement per se, may be a basic level of moto r control, initiated from muscle mechanoreceptor discharge. Upon this basic level, more complex modulations then may be laid as appropriate for the pa rticular characteristics of active motor tasks. (C) 2000 Elsevier Science L td. All rights reserved.