Gyrification changes are related to cognitive strengths in autism.

Background: Behavioral, cognitive and functional particularities in autism differ according to autism subgroups and might be associated with domain-specific cognitive strengths. It is unknown whether structural changes support this specialization. We investigated the link between cortical folding, its maturation and cognitive strengths in autism subgroups presenting verbal or visuo-spatial peaks of abilities. Methods: We measured gyrification, a structural index related to function, in 55 autistic participants with (AS-SOD, N = 27) or without (AS-NoSOD, N = 28) a speech onset delay (SOD) with similar symptom severity but respectively perceptual and verbal cognitive strengths, and 37 typical adolescents and young adults matched for intelligence and age. We calculated the local Gyrification Index (lGI) throughout an occipito-temporal region of interest and independently modeled age and peak of ability effects for each group. Results: Unique gyrification features in both autistic groups were detected in localized clusters. When comparing the three groups, gyrification was found lower in AS-SOD in a fusiform visual area, whereas it was higher in AS-NoSOD in a temporal language-related region. These particular areas presented age-related gyrification differences reflecting contrasting local maturation pathways in AS. As expected, peaks of ability were found in a verbal subtest for the AS-NoSOD group and in the Block Design IQ subtest for the AS-SOD group. Conclusions: Irrespective of their direction, regional gyrification differences in visual and language processing areas respectively reflect AS-SOD perceptual and AS-NoSOD language-oriented peaks. Unique regional maturation trajectories in the autistic brain may underline specific cognitive strengths, which are key variables for understanding heterogeneity in autism.

Enhanced mental image mapping in autism.

The formation and manipulation of mental images represents a key ability for successfully solving visuospatial tasks like Wechsler's Block Design or visual reasoning problems, tasks where autistics perform at higher levels than predicted by their Wechsler IQ. Visual imagery can be used to compare two mental images, allowing judgment of their relative properties. To examine higher visual processes in autism, and their possible role in explaining autistic visuospatial peaks, we carried out two mental imagery experiments in 23 autistic and 14 age and IQ matched, non-autistic adolescents and adults. Among autistics, 11 had significantly higher Block Design scores than predicted by their IQ. Experiment 1 involved imagining a letter inside a circle, followed by a decision concerning which of two highlighted portions of the circle would contain the greater proportion of the letter. Experiment 2 involved four classic mental rotation tasks utilizing two- and three-dimensional geometric figures, hands and letters. Autistics were more accurate in the formation and comparison of mental images than non-autistics. Autistics with a Block Design peak outperformed other participants in both speed and accuracy of mental rotation. Also, Performance IQ and Block Design scores were better predictors of mental rotation accuracy in autistic compared to non-autistic participants. The ability to form, access and manipulate visual mental representations may be more developed in autistics. We propose two complementary mechanisms to explain these processing advantages: (1) a global advantage in perceptual processing, discussed in the framework of the enhanced perceptual functioning model, and (2) particular strengths in veridical mapping, the ability to efficiently detect isomorphisms among entities and then to use these mappings to process stimulus characteristics, thereby facilitating judgments about their differences.

What some effects might not be: the time to verify membership in "well-defined" categories.

Armstrong, Gleitman, and Gleitman (1983) reported shorter categorization times for members of well-defined categories judged more typical. They concluded that these effects could not originate in a graded, similarity-based category representation and consequently that the typicality effects obtained with natural categories might not be indicative of such a structure either. In this article, we re-examine this conclusion, focusing first on the performance obtained with well-defined categories of different sizes. Only the larger categories used showed variations in typicality ratings and produced typicality effects on categorization times. However, multiple regression analyses showed the effects on categorization times to be better explained by a measure of associative strength, called category dominance. The range of various predictor variables was equated in a follow-up experiment involving large, natural, and well-defined categories. Results obtained with well-defined categories showed pronounced dominance effects when typicality was controlled, but no reliable typicality effect when category dominance and instance familiarity were controlled. Results were opposite for natural categories. By showing that well-defined categories fail to produce unbiased typicality effects, our results bring added support to the hypothesis that the effects obtained with natural categories originate in a graded, similarity-based category structure.