How auditory temporal processing deficits relate to dyslexia.

Studies have shown that dyslexic children present a deficiency in the temporal processing of auditory stimuli applied in rapid succession. However, discussion continues concerning the way this deficiency can be influenced by temporal variables of auditory processing tests. Therefore, the purpose of the present study was to analyze by auditory temporal processing tests the effect of temporal variables such as interstimulus intervals, stimulus duration and type of task on dyslexic children compared to a control group. Of the 60 children evaluated, 33 were dyslexic (mean age = 10.5 years) and 27 were normal controls (mean age = 10.8 years). Auditory processing tests assess the abilities of discrimination and ordering of stimuli in relation to their duration and frequency. Results showed a significant difference in the average accuracy of control and dyslexic groups considering each variable (interstimulus intervals: 47.9 +/- 5.5 vs 37.18 +/- 6.0; stimulus duration: 61.4 +/- 7.6 vs 50.9 +/- 9.0; type of task: 59.9 +/- 7.9 vs 46.5 +/- 9.0) and the dyslexic group demonstrated significantly lower performance in all situations. Moreover, there was an interactive effect between the group and the duration of stimulus variables for the frequency-pattern tests, with the dyslexic group demonstrating significantly lower results for short durations (53.4 +/- 8.2 vs 48.4 +/- 11.1), as opposed to no difference in performance for the control group (62.2 +/- 7.1 vs 60.6 +/- 7.9). These results support the hypothesis that associates dyslexia with auditory temporal processing, identifying the stimulus-duration variable as the only one that unequally influenced the performance of the two groups.