AUDITORY PROCESSING DEFICITS IN LEARNING DISABILITY (EVOKED POTENTIALS, BRAINSTEM RESPONSE, NEUROPSYCHOLOGY, ASSESSMENT)

The relationship of auditory-linguistic processing dysfunction to impaired reading and spelling ability was examined in eleven control and nine learning disabled children (LD) ages 12-15 using neuropsychological and electrophysiological measures. The groups were matched on age and WISC-R Performance IQ, but differed on Verbal IQ and WRAT Reading and Spelling achievement. All LDs, except two who were impaired only in spelling, scored poorly on decoding tests (Word Identification and Word Attack subtests of the Woodcock Reading Mastery test; Goldman Fristoe Woodcock (GFW) Reading and Spelling subtests). The majority of the LDs also scored poorly on the GFW Sound Analysis and Sound Blending subtests, but performed adequately on auditory discrimination and sound-symbol association tests.; No group differences were found for Wave V latency of the Auditory Brainstem Response at any rate or intensity indicating that transmission delay did not explain the behavioral deficits. Event-Related Potentials (ERPs) to monaural syllables and tones showed that auditory processing deficits were not limited to verbal stimuli. At Cz, no group latency or amplitude differences were found for components before 200 msec. N200 and P300 latencies were prolonged in LDs for syllables presented to the right ear. P300 amplitude at Pz showed the expected enhancement to target stimuli. For syllables, amplitude was enhanced for left-ear presentation in LDs and right-ear presentation in control subjects. Amplitude for target tones was enhanced in the LDs with left-ear presentation and both groups with right-ear presentation.; Group differences emerged for both stimulus types for P450 and Slow Wave (SW; average amplitude from 500-800 msec); amplitude at Pz was greater in the control subjects. The target/nontarget SW difference amplitude for syllables correlated positively with performance on word decoding and sound analysis tests, especially for right-ear presentation. SW difference amplitude for tones was not correlated with behavior, even though SW for right-ear presentation of syllables and tones was highly correlated. Thus, auditory processing deficits occurred for verbal and nonverbal stimuli in LD. A deficient temporal-sequential mechanism may underlie the deficits in linguistic processing observed on behavioral and ERP tasks.