Abstract
Comprehending high-imagery sentences like The number eight when rotated 90 degrees looks like a pair of eyeglasses involves the participation and integration of several cortical regions. The linguistic content must be processed to determine what is to be mentally imaged, and then the mental image must be evaluated and related to the sentence. A theory of cortical underconnectivity in autism predicts that the interregional collaboration required between linguistic and imaginal processing in this task would be underserved in autism. This functional MRI study examined brain activation in 12 participants with autism and 13 age- and IQ-matched control participants while they processed sentences with either high- or low-imagery content. The analysis of functional connectivity among cortical regions showed that the language and spatial centres in the participants with autism were not as well synchronized as in controls. In addition to the functional connectivity differences, there was also a group difference in activation. In the processing of low-imagery sentences (e.g. Addition, subtraction and multiplication are all math skills), the use of imagery is not essential to comprehension. Nevertheless, the autism group activated parietal and occipital brain regions associated with imagery for comprehending both the low and high-imagery sentences, suggesting that they were using mental imagery in both conditions. In contrast, the control group showed imagery-related activation primarily in the high-imagery condition. The findings provide further evidence of underintegration of language and imagery in autism (and hence expand the understanding of underconnectivity) but also show that people with autism are more reliant on visualization to support language comprehension.
Highlights
Language comprehension and visual imagery are two separable facets of cognition, but in everyday thinking, they are used concurrently rather often, when language makes reference to spatial or physical objects
A separate 2 (Group) · 4 (Network) · 2 (Condition) mixed ANOVA for the four intra-lobe connectivities revealed no interaction with group. This result indicates that local intra-lobe functional connectivity in this task was not reliably different in autism compared with controls, in contrast to the underconnectivity seen for frontal–parietal inter-lobe connections
Region labels apply to the entire extent of the cluster. t-Value scores and Montreal Neurological Institute (MNI) coordinates are for the peak activated voxel in each cluster only
Summary
Language comprehension and visual imagery are two separable facets of cognition, but in everyday thinking, they are used concurrently rather often, when language makes reference to spatial or physical objects. In the visual imagery comprehension task, the prediction was that the underconnectivity would be most apparent in synchronizations between the frontal and parietal regions that are required in the integration of language and spatial processing (Just et al, 2004b). Another prediction in this study concerned the way people with autism approach this task. The neural resources and neural connectivity of participants without autism are hypothesized to be more than adequate to meet the task demands
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