Parkinsonian rigidity.

Rigidity is one of the major signs of P a r k i n s o n ’s disease (PD). However, its pathophysiology has rarely been studied. This appears a little surprising since data obtained from animal physiology, which offers a scheme of neuronal circuits that might be hyperor hypoactive, could be useful in the study of muscle tone problems, a classical area in neurological semiology. Experimental models of PD have not yet been analysed using neurophysiological techniques. Thus, the information currently available derives from clinical data and clinical neurophysiology.