The neurophysiological basis of reciprocal inhibition in man

Abstract

The current paper reviews the current evidence on the neurophysiological basis of reciprocal inhibition, and in particular the role of Ia inhibitory interneurones, both as a basis for normal motor development and in providing a better understanding of the clinical presentation of a number of neurological conditions (e.g. stroke and cerebral palsy). The Ia inhibitory interneurones which mediate reciprocal inhibition have been studied extensively in animals and in man. Stimulation of low threshold Group Ia afferent fibres leads to excitation of the homonymous muscle and inhibition of its antagonist via this disynaptic pathway. It has been demonstrated that α-motoneurones are inhibited not only by strict antagonists but also from other muscles connected to them in Ia synergism. On the basis of convergence from supraspinal and spinal pathways it has been proposed that they act as integrative centres. Moreover, their extensive distribution to α-motoneurones within upper and lower limbs supports their role as pattern registers. Reciprocal inhibition thus contributes to the patterning of movement required for different motor synergies. However, in normal development in man, it is not clear whether this pathway plays a role in the fundamental shaping of spinal cord circuitry, as it does in animals by suppressing inappropriate heteronymous excitatory projections in the spinal cord.

Keywords:

• ANIMAL
• DEVELOPMENT
• MAN
• MOTOR CONTROL
• RECIPROCAL INHIBITION
• SPASTICITY