Abstract
Objective: Most evidences from animal models and human subjects with auditory deprivation report that the children rehabilitated later than 5-6 years of age show abnormal CAEPs (absence of N1) even after a long period of cochlear implant usage and attributed to cortical decoupling. The current study aims to explore the auditory cortical activation in congenitally deaf adults who never received any rehabilitation.
Design: Aided CAEPs were elicited using 1000 Hz pure tone at 30 dB SL from 11 congenitally deaf adults and age/gender matched controls aged between 17 and 45 years. The latencies and amplitudes of the P1-N1-P2 obligatory responses were measured and compared using topographic ANOVA (TANOVA).
Results: The morphology of CAEP responses from the deaf group was similar to that of the normal hearing group except the presence of a broader P2. The amplitude measures between the groups did not reveal statistical significance; however, P2 latency revealed a significant difference between the groups. TANOVA revealed that the topographic maps between the groups did not significantly differ.
Conclusions: The matured cortical response for acoustic stimulus, especially the presence of N1, clearly signifies the activation of auditory cortex. The presence of matured CAEPs might be due to the abnormal synaptogenesis of auditory neurons transforming into multisensory neurons and continues the normal course of maturation. These matured CAEP responses will be an indication of closure of critical period and limited benefit with rehabilitation.