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. 2014 Feb 25;4:444-53.
doi: 10.1016/j.nicl.2014.02.008. eCollection 2014.

Increased Topographical Variability of Task-Related Activation in Perceptive and Motor Associative Regions in Adult Autistics

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Free PMC article

Increased Topographical Variability of Task-Related Activation in Perceptive and Motor Associative Regions in Adult Autistics

Marie-Pier Poulin-Lord et al. Neuroimage Clin. .
Free PMC article

Abstract

Background: An enhanced plasticity is suspected to play a role in various microstructural alterations, as well as in regional cortical reallocations observed in autism. Combined with multiple indications of enhanced perceptual functioning in autism, and indications of atypical motor functioning, enhanced plasticity predicts a superior variability in functional cortical allocation, predominant in perceptual and motor regions.

Method: To test this prediction, we scanned 23 autistics and 22 typical participants matched on age, FSIQ, Raven percentile scores and handedness during a visuo-motor imitation task. For each participant, the coordinates of the strongest task-related activation peak were extracted in the primary (Brodmann area 4) and supplementary (BA 6) motor cortex, the visuomotor superior parietal cortex (BA 7), and the primary (BA 17) and associative (BAs 18 + 19) visual areas. Mean signal changes for each ROI in both hemispheres, and the number of voxels composing the strongest activation cluster were individually extracted to compare intensity and size of the signal between groups. For each ROI, in each hemisphere, and for every participant, the distance from their respective group average was used as a variable of interest to determine group differences in localization variability using repeated measures ANOVAs. Between-group comparison of whole-brain activation was also performed.

Results: Both groups displayed a higher mean variability in the localization of activations in the associative areas compared to the primary visual or motor areas. However, despite this shared increased variability in associative cortices, a direct between-group comparison of the individual variability in localization of the activation revealed a significantly greater variability in the autistic group than in the typical group in the left visuo-motor superior parietal cortex (BA 7) and in the left associative visual areas (BAs 18 + 19).

Conclusion: Different and possibly unique strategies are used by each autistic individual. That enhanced variability in localization of activations in the autistic group is found in regions typically more variable in non-autistics raises the possibility that autism involves an enhancement and/or an alteration of typical plasticity mechanisms. The current study also highlights the necessity to verify, in fMRI studies involving autistic people, that hypoactivation at the group level does not result from each individual successfully completing a task using a unique brain allocation, even by comparison to his own group.

Keywords: Associative areas; Autism; Plasticity; Primary areas; fMRI.

Figures

Fig. 1
Fig. 1
Two different sample stimuli from the visuo-motor imitation task.
Fig. 2
Fig. 2
Mean distances in millimeters from the group mean activation peak in the motor and visual ROIs in autistic and typical groups during the visuo-motor imitation task. Differences between groups reaching significance (p < .05) are indicated by an asterisk (*).
Fig. 3
Fig. 3
Localization of all individual peaks of activation in the left visual ROIs. Each peak is represented as a 1 cm diameter sphere projected on the cortical surface using Freesurfer. The color scale represents the overlap of individual peaks, darker being 1 individual and brighter 5 and more. The primary area (BA 17) is in red and the associative area (BAs 18•19) is in blue. The autism and typical groups are displayed separately.
Fig. 4
Fig. 4
Localization of all individual peaks of activation in the left motor ROIs. Each peak is represented as a 1 cm diameter sphere projected on the cortical surface using Freesurfer. The color scale represents the overlap of individual peaks, darker being 1 individual and brighter 5 and more. The primary area (BAs 4•6) is in red and the associative area (BA 7) is in blue. The autistic and typical groups are displayed separately.
Fig. 5
Fig. 5
Mean signal change in motor and visual ROIs in autistic and typical groups during the visuo-motor imitation task. No difference between groups was observed.
Fig. 6
Fig. 6
Mean size of activation in motor and visual ROIs in autistic and typical groups during the visuo-motor imitation task. No difference between groups was observed.

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