Objectives: The objective of this study was to compare regional brain activity between individuals with an ASC and typically developing (TD) controls during a visual language task.
Methods: Functional magnetic resonance imaging (fMRI) was performed on a 3-Tesla Siemens Trio MR scanner of individuals engaging in a visual language task. Participants in the study were 22 high-functioning ASC males (aged 12-42 years, mean age of 23 years, 1 left-handed) and 29 TD males (aged 8-39 years, mean age of 21 years, 1 left-handed). The visual language task consisted of alternating blocks of fixation on a crosshair and sentence reading, with each block lasting for 20 seconds, for a total task time of 4 minutes. The sentences in each sentence reading block were presented individually, where each sentence contained a blank that represented a missing word at the end. Participants were instructed to read each sentence presented on the screen via LCD projector and to think, not speak, the word they thought best completed each sentence. Data processing and analysis was performed using SPM 8 in Matlab.
Results: When comparing brain activity during sentence reading to that during fixation/rest across all participants, similar patterns of activity were observed between the two groups, with activation in brain regions typically associated with reading, such as Broca’s (left inferior frontal gyrus) area, Wernicke’s (left laterosuperior temporal) area, supplementary motor area, lateral premotor cortex, and the cerebellum, based on family-wise error (FWE) corrected p-values less than or equal to 0.05. Both groups were strongly left-lateralized in Broca's area, Wernicke's area, and lateral premotor cortex. No regions showed significantly higher activity for control than for ASC participants, but significantly increased brain activity was found in ASC relative to control participants in bilateral area MT (V5), bilateral frontal eye field, and left intraparietal sulcus (IPS). The left IPS cluster was significantly different after FWE correction for p<0.05 and all clusters showed differences with uncorrected p<0.001.
Conclusions: Because increased brain activity was found in brain regions associated with the attention network in the ASC group, one possible conclusion is that ASC individuals use more attentional resources or concentration while reading than do TD individuals. This increase might be a compensatory mechanism for the language deficits commonly found in ASCs or might indicate a failure of ASC individuals to disengage attention to external stimuli while reading [1-3].
1. Anderson JS, et al. Decreased left posterior insular activity during auditory language in autism. AJNR, 2010. 31(1):131-9.
2. Kleinhans NM, et al. Atypical functional lateralization of language in autism spectrum disorders. Brain Res, 2008. 1221:115-25.
3. Kennedy DP, Redcay E, Courchesne E. Failing to deactivate: resting functional abnormalities in autism. Proc Natl Acad Sci U S A, 2006. 103(21):8275-80.