Auditory evoked response data reduction by PCA: Development of variables sensitive to reading disability

Long latency auditory evoked responses (AER) were formed on 232 healthy nor mal and learning impaired subjects to tone pairs of 50 msec inter-stimulus interval (TALAER) and also to the words "tight" and "tyke" (TTAER). Both ev oked potential (EP) types have been used to demonstrate differences between good readers (WIAT Basic Reading score > 115, N=42) and poor readers (Read ing score < 85, N=42). A largely automated, hands off approach was used to reduce artifact contamination, to develop canonical measures for discrimina ting good from poor readers, and to predict reading scores across the entir e population including intermediate (average) readers. Eye and muscle artif act were diminished by multiple regression. Substantial EP data reduction w as enabled by an unrestricted use of Principal Components Analysis (PCA). F or each EP type, 40 factors encompassed 70-80% of initial variance, a meani ngful data reduction of about 90:1. Factor interpretation was enhanced by m apping of the factor loadings. By discriminant analysis, resulting factors predicted reading group membership with over 80% jackknifed and also split -half replication accuracy. By multiple regression, they produced a canonic al variate correlating significantly (p <0.001) with the Basic Reading scor e (r=0.39). The TTAER factors were more useful than the TALAER factors. The relevance of rapid auditory processing and phonemic discrimination measure ments to dyslexia is discussed.