Interaural cross correlation of event-related potentials and diffusion tensor imaging in the evaluation of auditory processing disorder: a case study.

In a previous publication (Jerger et al, 2002), we presented event-related potential (ERP) data on a pair of 10-year-old twin girls (Twins C and E), one of whom (Twin E) showed strong evidence of auditory processing disorder. For the present paper, we analyzed cross-correlation functions of ERP waveforms generated in response to the presentation of target stimuli to either the right or left ears in a dichotic paradigm. There were four conditions; three involved the processing of real words for either phonemic, semantic, or spectral targets; one involved the processing of a nonword acoustic signal. Marked differences in the cross-correlation functions were observed. In the case of Twin C, cross-correlation functions were uniformly normal across both hemispheres. The functions for Twin E, however, suggest poorly correlated neural activity over the left parietal region during the three word processing conditions, and over the right parietal area in the nonword acoustic condition. Differences between the twins' brains were evaluated using diffusion tensor magnetic resonance imaging (DTI). For Twin E, results showed reduced anisotropy over the length of the midline corpus callosum and adjacent lateral structures, implying reduced myelin integrity. Taken together, these findings suggest that failure to achieve appropriate temporally correlated bihemispheric brain activity in response to auditory stimulation, perhaps as a result of faulty interhemispheric communication via corpus callosum, may be a factor in at least some children with auditory processing disorder.