Auditory and visual cortical activity during selective attention in fragile X syndrome: a cascade of processing deficiencies.

OBJECTIVE

This study examined whether attention deficits in fragile X syndrome (FXS) can be traced back to abnormalities in basic information processing.

METHOD: Sixteen males with FXS and 22 age-matched control participants (mean age 29 years) performed a standard oddball task to examine selective attention in both auditory and visual modalities. Five FXS males were excluded from analysis because they performed below chance level on the auditory task. ERPs were recorded to investigate the N1, P2, N2b, and P3b components.

RESULTS

N1 and N2b components were significantly enhanced in FXS males to both auditory and visual stimuli. Interestingly, in FXS males, the P3b to auditory stimuli was significantly reduced relative to visual stimuli. These modality differences in information processing corresponded to behavioral results, showing more errors on the auditory than on the visual task.

CONCLUSIONS

The current findings suggest that attentional impairments in FXS at the behavioral level can be traced back to abnormalities in event-related cortical activity. These information processing abnormalities in FXS may hinder the allocation of attentional resources needed for optimal processing at higher-levels.

SIGNIFICANCE: These findings demonstrate that auditory information processing in FXS males is critically impaired relative to visual information processing.