GAIT OF A DEAFFERENTED SUBJECT WITHOUT LARGE MYELINATED SENSORY FIBERS BELOW THE NECK

We evaluated the gait pattern of a deafferented subject who suffered a permanent loss of large sensory myelinated fibers below the neck foll owing an acute episode of purely sensory neuropathy 21 years ago. The subject has developed several strategies to achieve a secure gait, nam ely: (1) a reduction of the degrees of freedom by freezing the knee ar ticulations during the stance phase, (2) a preservation of body balanc e by enlarging his base of support, and (3) visual monitoring of his s tep by stabilizing the head-trunk linkage together with a characterist ic forward tilt. As a result, the gait of the deafferented subject lac ks the fluidity of normal gait. Compared with normal subjects, the gai t pattern of the deafferented subject is characterized by a shorter cy cle length, a longer cycle duration, a slower speed, and a lower caden ce. Using a dual-task paradigm, the attentional demands for walking we re particularly important (as indexed by longer probe reaction times) during the double-support phase, suggesting that the deafferented subj ect uses the double-support phase as a transitory stable phase to upda te cognitively the postural features necessary for generating his next step.