Auditory Deficits in Audiovisual Speech Perception in Adult Asperger's Syndrome: fMRI Study

Abstract

Audiovisual (AV) integration deficits have been proposed to underlie difficulties in speech perception in Asperger's syndrome (AS). It is not known, if the AV deficits are related to alterations in sensory processing at the level of unisensory processing or at levels of conjoint multisensory processing. Functional Magnetic-resonance images (MRI) was performed in 16 adult subjects with AS and 16 healthy controls (HC) matched for age, gender, and verbal IQ as they were exposed to disyllabic AV congruent and AV incongruent nouns. A simple semantic categorization task was used to ensure subjects' attention to the stimuli. The left auditory cortex (BA41) showed stronger activation in HC than in subjects with AS with no interaction regarding AV congruency. This suggests that alterations in auditory processing in unimodal low-level areas underlie AV speech perception deficits in AS. Whether this is signaling a difficulty in the deployment of attention remains to be demonstrated.

Keywords: Asperger’s syndrome; audiovisual; autism; fMRI; multisensory; speech.

FIGURE 1

Depicted are sagittal views on the left (L) and right hemisphere and the horizontal view on the averaged brain of the measured population at Talairach coordinates X = 46, –46 and Z = –2. Color coded are voxels that survived conservative significance level of p < 0.05 corrected for multiple comparisons (Bonferroni, Bonf) for the main factor AV congruency. The use of this very conservative significance level was necessary for isolation of separated clusters due to the fact of widespread activation clusters covering almost the whole brain resulting from strong congruency effect and spatial smoothing at the same significance level but corrected for multiple comparisons by means of the false discovery rate.

FIGURE 2

Depicted is horizontal view on the brain at the Talairach coordinate X = 12. On the left (L) hemisphere color coded cluster within the auditory cortex is shown. The identified cluster occupies Brodmann area 41 (BA41) and survived significance level of q < 0.05 corrected for multiple comparisons (false discovery rate, FDR) for the main factor Asperger’s syndrome. Healthy control subjects showed in this area stronger activation than Asperger’s subjects for both experimental conditions (audiovisual congruent and incongruent). Color coded is the F-value.