Studies of fluid reasoning have characterized the involvement of regions in both frontal and parietal cortex (Jung & Haier, 2007; Perfetti et al., 2008). Increasing reasoning complexity is associated with increasing activity in this network, particularly in prefrontal cortical areas (Kroger et al., 2002; Wendelken et al., 2007). In addition, autistics tend to have higher scores when assessed with Raven’s Standard Progressive Matrices (RSPM) compared to Wechsler IQ tests, and to exhibit more occipital and less frontal activity than non-autistics while solving RSPM problems (Soulieres et al., 2010). These findings suggest that inter-regional functional coupling may be atypical in autism during matrix reasoning.
Our goal was to determine how reasoning complexity modulates inter-regional coupling in autistics compared to non-autistics.
15 autistics (2F, 13M) and 18 non-autistics (3F, 15M) solved RSPM problems during one self-paced fMRI scanning session (3mm cubic voxels, TR 2.7 s). The RSPM includes 60 fluid reasoning problems of progressively increasing difficulty. Each RSPM problem was presented as a 3x3 matrix with the final entry missing. Participants were instructed to take as much time as needed to select the correct answer from the eight choices provided. Problems were divided into figural, analytical, and complex analytical categories based on reasoning complexity. Psychophysiological interaction analysis was used to examine the effects of problem complexity on inter-regional coupling for three seed regions located in left superior parietal lobule, right inferior frontal gyrus, and left inferior occipital gyrus. Seeds were determined by identifying local maxima in occipital, parietal and frontal lobes using conjunctions of problem solving task-related activity in a combined autistic and non-autistic group.
While both autistics and non-autistics showed similar problem solving accuracy (p= 0.54), the autistics were responding faster (5350ms, p= 0.01). Non-autistics showed stronger coupling with respect to task complexity among: (1) all three seeds and the basal ganglia and (2) occipital and parietal seeds and the cingulate gyrus. Conversely, autistics showed stronger coupling than non-autistics for increasing complexity between the left inferior occipital gyrus and the left superior frontal gyrus.
As reported in previous studies, non-autistic participants showed stronger basal ganglia coupling with the three seeds as task complexity increased, suggesting that autistics rely less on the basal ganglia than non-autistics for decision-making. Also, as task complexity increased, coupling between occipital and frontal cortex increased more strongly in autistics. This result may reflect an increased reliance by autistics on perceptual processes when engaged in matrix reasoning, consistent with a more prominent role for perceptual processing in multiple high level tasks for autistics (Mottron et al., 2012).
See more of: Brain Imaging
See more of: Brain Structure & Function