Functional and Anatomical Cortical Underconnectivity in Autism: Evidence from an fMRI Study of an Executive Function Task and Corpus Callosum Morphometry

Abstract

The brain activation of a group of high-functioning autistic participants was measured using functional magnetic resonance imaging during the performance of a Tower of London task, in comparison with a control group matched with respect to intelligent quotient, age, and gender. The 2 groups generally activated the same cortical areas to similar degrees. However, there were 3 indications of underconnectivity in the group with autism. First, the degree of synchronization (i.e., the functional connectivity or the correlation of the time series of the activation) between the frontal and parietal areas of activation was lower for the autistic than the control participants. Second, relevant parts of the corpus callosum, through which many of the bilaterally activated cortical areas communicate, were smaller in cross-sectional area in the autistic participants. Third, within the autism group but not within the control group, the size of the genu of the corpus callosum was correlated with frontal-parietal functional connectivity. These findings suggest that the neural basis of altered cognition in autism entails a lower degree of integration of information across certain cortical areas resulting from reduced intracortical connectivity. The results add support to a new theory of cortical underconnectivity in autism, which posits a deficit in integration of information at the neural and cognitive levels.

Sensory Sensitivities and Performance on Sensory Perceptual Tasks in High-functioning Individuals with Autism

“…The elementary sensory-higher cortical sensory dichotomy is also consistent with the pattern of dichotomous deficits reported in the motor, memory, language, and abstraction domains in studies of the profile of neuropsychologic functioning in high functioning individuals with autism (Minshew, Goldstein, & Siegel, 1997;Williams, Goldstein & Minshew, 2006) and of the impairments in integration of information causing postural instability (Minshew, Sung, Jones, & Furman, 2004). Functional imaging studies using social, language, and reasoning tasks have provided evidence of a generalized pattern of underdevelopment of the higher-order circuitry necessary for these tasks Just et al, 2004;Just et al, 2007;Kana et al, 2006Kana et al, , 2007Koshino et al, 2007;Minshew, Sweeney, & Luna, 2002). The presence of the same pattern of elementary ability-higher ability dissociation in the sensory and motor domains as in the memory, language and abstraction domains suggests that the sensory and motor impairments are involved by the same neurobiological process as the triad of signs and symptoms on which the diagnosis is based.…”

Differences in brain morphology and working memory capacity across childhood

“…To summarize briefly: it has been hypothesized that interhemispheric connections of the corpus callosum provide inhibition between functionally homologous areas in the left and right hemisphere (Gazzaniga, 2000). Differences in corpus callosum anatomy such as reduced volume or reduced microstructural integrity are related to lower lateralization of function in typical participants and patient groups (Hinkley et al., 2016; Just, Cherkassky, Keller, Kana, & Minshew, 2007; Persson et al., 2006). In turn, lower lateralization is associated with lower performance on cognitive tasks, including executive function tasks (Hinkley et al., 2012; Just et al., 2007; Nagel, Herting, Maxwell, Bruno, & Fair, 2013).…”

“…Differences in corpus callosum anatomy such as reduced volume or reduced microstructural integrity are related to lower lateralization of function in typical participants and patient groups (Hinkley et al., 2016; Just, Cherkassky, Keller, Kana, & Minshew, 2007; Persson et al., 2006). In turn, lower lateralization is associated with lower performance on cognitive tasks, including executive function tasks (Hinkley et al., 2012; Just et al., 2007; Nagel, Herting, Maxwell, Bruno, & Fair, 2013). Similarly, posterior temporal white matter may provide connections for integration between specialized regions of temporal lobe for verbal and visuospatial working memory with the posterior parietal executive attention network.…”

Theory of Mind disruption and recruitment of the right hemisphere during narrative comprehension in autism

“…This prediction arises because functional underconnectivity between the frontal lobe and other regions has been found in autism in language comprehension (Just et al, 2004;Kana et al, 2006) and Theory of Mind (Castelli et al, 2002) tasks. In addition, the functional connectivity between the frontal and parietal has repeatedly been found to be abnormally low Just, Cherkassky, Keller, Kana, & Minshew, 2007). This particular interregional underconnectivity is relevant here because the Theory of Mind network includes frontal and parietal areas.…”

“…It is important to consider the structural properties of the brain when describing the functional connectivity and to relate the structural properties to the functional properties revealed by brain activation measures. Previous research has found a correlation between the size of regions of the corpus callosum and the functional connectivity between the cortical regions connected through these regions (Just et al, 2007;Kana et al, 2006). To examine this structure-function correlation in discourse processing, the size of the various segments of the corpus callosum of each participant in the current discourse processing study was measured.…”