Abstract

The purpose of this study was to examine the extent to which reorganization of the central auditory system (CAS) occurs in the presence of modality specific sensory deprivation. The P1 cortical auditory evoked potential (CAEP) is a useful biomarker for examining maturation of the CAS. Recording the P1 CAEP in children with cochlear implants poses a unique problem in that large electrical artifacts are present on the scalp. In Experiment 1, independent component analysis (ICA) was successfully used to identify the artifacts, and systematically remove them from the CAEP. In Experiment 2, the P1 was recorded from 64 locations on the scalp in a group of normal hearing children (NH), children implanted early in childhood, and children implanted late in childhood. Current source reconstructions revealed dominant activity in the right inferior temporal gyrus in NH and early implanted children, and in the right parietotemporal cortex in late implanted children. Dipoles were located at the superior temporal sulcus in NH and early implanted children, and in parietotemporal cortex in late implanted children. The parietotemporal activity in late implanted children likely reflects cross-modal reorganization of visual pathways that may have occurred during auditory deprivaton. In Experiment 3, psychophysical responses to auditory (A), visual (V), and combined auditory-visual (AV) stimuli were assessed in these children. Cumulative probabilities for reaction time to the AV stimuli were compared to the joint predicted probabilities from A and V stimuli to determine the nature of multisensory processing. NH and early implanted children revealed evidence of coactivation for multisensory processing, while late implanted children revealed evidence for separate parallel processing streams. Taken together, these results suggest that cochlear implants can provide the stimulation necessary for typical development of the CAS. However, the extent to which typical CAS development can occur after hearing is restarted with a cochlear implant may be limited by the reorganization and/or deterioration of auditory pathways during early periods of auditory deprivation.