Resistance of peripheral and sub-cortical somatosensory pathway to electrical noise

The somatosensory system is vulnerable to large amounts of noise distortion. But how does the central nervous system distinguish the peripheral inputs which carry information to the brain from that which does not possess information? To address this question we studied the effect of electrical stimulation of the median nerve on tactile spatial frequency perception in healthy subjects and Parkinson's disease (PD) patients. Subjects were categorized in two groups (healthy and PD patients) and were asked to report if a test tactile frequency pattern (TFP) was the same as the reference TFP given to the other hand. In each case stimulation was either present or absent on the median nerve of the hand holding the test pattern. We observed no impairment of tactile performance in the presence of electrical stimulation of the median nerve. This result together with previous work on direct stimulation of the somatosensory relay nucleus of the thalamus (Abbassian et al., Stereotact Funct Neurosurg 76: 19-28, 2001) in which the same result of no impairment of the tactile discrimination task was observed suggest a high degree of noise tolerance exists in the somatosensory pathway.