INDUCED MICROGYRIA AND AUDITORY TEMPORAL PROCESSING IN RATS - A MODELFOR LANGUAGE IMPAIRMENT

Studies have shown the existence of minor developmental cortical malfo rmations, including microgyria, in the brains of dyslexics, Concomitan t studies have shown that language-impaired individuals exhibit severe deficits in the discrimination of rapidly presented auditory stimuli, including phonological and nonverbal stimuli (i.e., sequential tones) . In an effort to relate these results, male rats with neonatally indu ced microgyria were tested in an operant paradigm for auditory discrim ination of stimuli consisting of two sequential tones. Subjects were s haped to perform a go/no-go target identification, using water reinfor cement. Stimuli were reduced in duration from 540 to 249 msec across 2 4 d of testing. Results showed that all subjects were able to discrimi nate at longer stimulus durations. However, bilaterally lesioned subje cts showed specific impairment at stimulus durations of 332 msec or le ss, and were significantly depressed in comparison to shams. Right- an d left-lesioned subjects were significantly depressed in comparison to shams at the shortest duration (249 msec). These results suggest a po ssible link between the neuropathologic anomalies and the auditory tem poral processing deficits reported for language-impaired individuals.