Event-related brain potentials during orienting to auditory and visual stimulation in spinal cord injured humans

In intact humans, deprivation of somatosensory and kinesthetic sensations result in significant alterations in perception and information processing. There have been very few studies to discover if the loss of sensation with spinal cord injury (SCI) in humans affects perceptual operations. We hypothesized that the SCI participant would either exhibit arousal, perceptual, and information processing alterations similar to experimentally sensory deprived subjects (who provide the closest human analogue), or that the somatosensory cortex would show reorganization for the processing of other modalities of stimulation. The subjects consisted of 16 paraplegic, 13 quadriplegic, and 22 non SCI controls. Subjects received an auditory orienting task consisting of a 500 Hz tone presented 20 times each at 66, 75, 88, and 101 db and a visual orienting task incorporating light flashes of 115, 123, 131, and 140 lux presented 20 times each. EEG information processing data were recorded from C3 and C4 for 100 msec prior to and 500 msec post stimulation. Information processing variables, analyzed as event-related potentials, indicated that the somatosensory cortex of SCI groups had a flattened response to auditory stimulation. The control group had a significantly larger P2 component. We concluded that these data signified that the somatosensory cortex did not reorganize function in response to chronic deafferentation nor was the SCI subject hyperresponsive to stimulation.