Forced-Attention Dichotic Listening With University Students With Dyslexia: Search for a Core Deficit.

Rapidly changing environments in day-to-day activities, enriched with stimuli competing for attention, require a cognitive control mechanism to select relevant stimuli, ignore irrelevant stimuli, and shift attention between alternative features of the environment. Such attentional orchestration is essential to the acquisition of reading skills. In the present forced attention dichotic listening study, adults with moderate and severe dyslexia and nondisabled adults were tested on their ability to switch attention between ears for immediate recall. Blocks of pairs of consonant-vowel syllables were counterbalanced into left-ear first or right-ear first ordered conditions. Significant order effects showed that only those with severe dyslexia were poorer in switching attention to the left ear, whereas both groups with dyslexia were poorer switching attention to the right ear. Shifting left appears to be a normative function of reading level, whereas inferior ability to disengage attending to the left ear to report from the right ear qualifies as a dysfunctional facet of dyslexia with etiological significance. No support was found for the traditional proposition that dyslexia may be associated with atypical left hemisphere lateralization. Combining these results with previous dichotic and neuroimaging research implicates a dysfunctional frontostriatal cognitive control network in dyslexia. With due caution, the results suggest that a neurobiological feature of dyslexia may be a lack of control in downwardly modulating excessive left inferior frontal cortex activations. The results are consistent with impoverished connectedness between left anterior and posterior language areas and, pending future confirmation of these findings, suggest the need for a reconceptualization of remedial programming.