Application of Sensory Nerve Signals in Neural Prosthesis Devices

In this presentation, I will review our experience as to how signals recorded from cutaneous and muscle nerves can be applied to restore foot, hand, and bladder control in subjects with central nervous lesions. Electric stimulation of the peroneal nerve used for correction of gait is used to enhance dorsiflexion in the swing phase of walking in lower extremities of hemiplegic patients. Instead of an artificial external heel switch, we have tested the use of a nerve cuff electrode picking up information from the sural nerve and calcaneal nerve and feeding this into a one channel FES system (Haugland and Sinkjær, 1995; Upshaw and Sinkjær, 1998; Hansen et al., 1999) In natural hand control, cutaneous receptors from the fingers play an important role in controlling the muscle activation level. We have implemented an algorithm that makes an FES system able to adjust the stimulation based on the compound information from the mechanoreceptors as recorded by a nerve cuff electrode from a digital nerve (Haugland et al., 1999). For restoration of bladder function in SCI patients, the sacral root stimulator by Brindley is useful in controlling the emptying of the bladder. At present we are carrying out experiments on animals using cuff electrodes on sacral roots and the pelvic nerve to detect hyperreflexia and to give "warning signals" when the bladder gets full (Jezernik et al., 1999) This information can potentially be used to inhibit unwanted bladder contractions and to trigger the FES system and thereby bladder emptying.