Perceptual category learning in autism spectrum disorder: Truth and consequences

Transitive inference in a clinical childhood sample with a focus on autism spectrum disorder

Transitive inference (TI) has a long history in the study of human development. There have, however, few pediatric studies that report clinical diagnoses have tested trial-and-error TI learning, in which participants infer item relations, rather than evaluate them explicitly from verbal descriptions. Children aged 8-10 underwent a battery of clinical assessments and received a range of diagnoses, potentially including autism spectrum disorder (ASD), attention-deficit hyperactive disorder (ADHD), anxiety disorders (AD), specific learning disorders (SLD), and/or communication disorders (CD). Participants also performed a trial-and-error learning task that tested for TI. Response accuracy and reaction time were assessed using a statistical model that controlled for diagnostic comorbidity at the group level. Participants in all diagnostic categories showed evidence of TI. However, a model comparison analysis suggested that those diagnosed with ASD succeeded in a qualitatively different way, responding more slowly to each choice and improving faster across trials than their non-ASD counterparts. Additionally, TI performance was not associated with IQ. Overall, our data suggest that superficially similar performance levels between ASD and non-ASD participants may have resulted from a difference in the speed-accuracy tradeoff made by each group. Our work provides a preliminary profile of the impact of various clinical diagnoses on TI performance in young children. Of these, an ASD diagnosis resulted in the largest difference in task strategy.

Associations Between Autism Spectrum Quotient and Integration of Visual Stimuli in 9-year-old Children: Preliminary Evidence of Sex Differences

PURPOSE

The dorsal stream vulnerability hypothesis posits that the dorsal stream, responsible for visual motion and visuo-motor processing, may be particularly vulnerable during neurodevelopment. Consistent with this, autism spectrum disorder (ASD) has been associated with deficits in global motion integration, though deficits in ventral stream tasks, such as form identification, have also been reported. In the current study, we examined whether a similar pattern of results is found in a cohort of 381 children born with neurodevelopmental risk factors and exhibiting a wide spectrum of caregiver-reported autistic traits.

METHODS

We examined the associations between global motion perception, global form perception, fine motor function, visual-motor integration, and autistic traits (autism spectrum quotient, AQ) using linear regression, accounting for possible interactions with sex and other factors relevant to neurodevelopment.

RESULTS

All assessments of dorsal stream function were significantly associated with AQ such that worse performance predicted higher AQ scores. We also observed a significant sex interaction, with worse global form perception associated with higher AQ in boys (n = 202) but not girls (n = 179).

CONCLUSION

We found widespread associations between dorsal stream functions and autistic traits. These associations were observed in a large group of children with a range of AQ scores, demonstrating a range of visual function across the full spectrum of autistic traits. In addition, ventral function was associated with AQ in boys but not girls. Sex differences in the associations between visual processing and neurodevelopment should be considered in the designs of future studies.

Contributions of dysfunctional plasticity mechanisms to the development of atypical perceptual processing

Experimental studies of sensory plasticity during development in birds and mammals have highlighted the importance of sensory experiences for the construction and refinement of functional neural circuits. We discuss how dysregulation of experience-dependent brain plasticity can lead to abnormal perceptual representations that may contribute to heterogeneous deficits symptomatic of several neurodevelopmental disorders. We focus on alterations of somatosensory processing and the dynamic reorganization of cortical synaptic networks that occurs during early perceptual development. We also discuss the idea that the heterogeneity of strengths and weaknesses observed in children with neurodevelopmental disorders may be a direct consequence of altered plasticity mechanisms during early development. Treating the heterogeneity of perceptual developmental trajectories as a phenomenon worthy of study rather than as an experimental confound that should be overcome may be key to developing interventions that better account for the complex developmental trajectories experienced by modern humans.

Discrimination sensitivity of visual shapes sharpens in autistic adults but only after explicit category learning

BACKGROUND

Categorization and its influence on perceptual discrimination are essential processes to organize information efficiently. Individuals with Autism Spectrum Condition (ASC) are suggested to display enhanced discrimination on the one hand, but also to experience difficulties with generalization and ignoring irrelevant differences on the other, which underlie categorization. Studies on categorization and discrimination in ASC have mainly focused on one process at a time, however, and typically only used either behavioral or neural measures in isolation. Here, we aim to investigate the interrelationships between these perceptual processes using novel stimuli sampled from a well-controlled artificial stimulus space. In addition, we complement standard behavioral psychophysical tasks with frequency-tagging EEG (FT-EEG) to obtain a direct, non-task related neural index of discrimination and categorization.

METHODS

The study was completed by 38 adults with ASC and 38 matched neurotypical (NT) individuals. First, we assessed baseline discrimination sensitivity by administering FT-EEG measures and a complementary behavioral task. Second, participants were trained to categorize the stimuli into two groups. Finally, participants again completed the neural and behavioral discrimination sensitivity measures.

RESULTS

Before training, NT participants immediately revealed a categorical tuning of discrimination, unlike ASC participants who showed largely similar discrimination sensitivity across the stimuli. During training, both autistic and non-autistic participants were able to categorize the stimuli into two groups. However, in the initial training phase, ASC participants were less accurate and showed more variability, as compared to their non-autistic peers. After training, ASC participants showed significantly enhanced neural and behavioral discrimination sensitivity across the category boundary. Behavioral indices of a reduced categorical processing and perception were related to the presence of more severe autistic traits. Bayesian analyses confirmed overall results.

LIMITATIONS

Data-collection occurred during the COVID-19 pandemic.

CONCLUSIONS

Our behavioral and neural findings indicate that adults with and without ASC are able to categorize highly similar stimuli. However, while categorical tuning of discrimination sensitivity was spontaneously present in the NT group, it only emerged in the autistic group after explicit categorization training. Additionally, during training, adults with autism were slower at category learning. Finally, this multi-level approach sheds light on the mechanisms underlying sensory and information processing issues in ASC.

Category learning in autistic individuals: A meta-analysis

Learning new categories is a fundamental human skill. In the present article, we report the first comprehensive meta-analysis of category learning in autism. Including studies comparing groups of autistic and nonautistic individuals, we investigated whether autistic individuals differ in category learning from nonautistic individuals. In addition, we examined moderator variables accounting for variability between studies. A multilevel meta-analysis of k = 50 studies examining n = 1,220 autistic and n = 1,445 nonautistic individuals based on 112 effect sizes in terms of the standardized mean difference revealed lower-level category learning skills for autistic compared with nonautistic individuals, g = -0.55, 95% CI = [-0.73, -0.38], p < .0001. According to moderator analyses, the significant amount of heterogeneity, Q(111) = 617.88, p < .0001, was explained by only one of the moderator variables under investigation-namely, study language. For the remaining variables-namely, age, year of publication, risk of bias, type of control group, IQ of autistic group, percentage of male autistic participants, type of category, type of task, and type of dependent measure-there were no significant effects. Although hat values and Cook's distance statistics confirmed the robustness of findings, results of Egger's test and a funnel plot suggested the presence of publication bias reflecting an overrepresentation of disadvantageous findings for autistic groups. Objectives for future work include identifying additional moderator variables, examining downstream effects of suboptimal category learning skills, and developing interventions.

Are sleep disturbances a cause or consequence of autism spectrum disorder?

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by core symptoms such as atypical social communication, stereotyped behaviors, and restricted interests. One of the comorbid symptoms of individuals with ASD is sleep disturbance. There are two major hypotheses regarding the neural mechanism underlying ASD, i.e., the excitation/inhibition (E/I) imbalance and the altered neuroplasticity hypotheses. However, the pathology of ASD remains unclear due to inconsistent research results. This paper argues that sleep is a confounding factor, thus, must be considered when examining the pathology of ASD because sleep plays an important role in modulating the E/I balance and neuroplasticity in the human brain. Investigation of the E/I balance and neuroplasticity during sleep might enhance our understanding of the neural mechanisms of ASD. It may also lead to the development of neurobiologically informed interventions to supplement existing psychosocial therapies.

Auditory perceptual learning in autistic adults

The automatic retuning of phoneme categories to better adapt to the speech of a novel talker has been extensively documented across various (neurotypical) populations, including both adults and children. However, no studies have examined auditory perceptual learning effects in populations atypical in perceptual, social, and language processing for communication, such as populations with autism. Employing a classic lexically-guided perceptual learning paradigm, the present study investigated perceptual learning effects in Australian English autistic and non-autistic adults. The findings revealed that automatic attunement to existing phoneme categories was not activated in the autistic group in the same manner as for non-autistic control subjects. Specifically, autistic adults were able to both successfully discern lexical items and to categorize speech sounds; however, they did not show effects of perceptual retuning to talkers. These findings may have implications for the application of current sensory theories (e.g., Bayesian decision theory) to speech and language processing by autistic individuals. LAY SUMMARY: Lexically guided perceptual learning assists in the disambiguation of speech from a novel talker. The present study established that while Australian English autistic adult listeners were able to successfully discern lexical items and categorize speech sounds in their native language, perceptual flexibility in updating speaker-specific phonemic knowledge when exposed to a novel talker was not available. Implications for speech and language processing by autistic individuals as well as current sensory theories are discussed.

Object label and category knowledge among toddlers at risk for autism spectrum disorder: An application of the visual array task

Individuals diagnosed with autism spectrum disorder (ASD) demonstrate atypical development of receptive language and object category knowledge. Yet, little is known about the emerging relation between these two competencies in this population. The present study utilized a gaze-based paradigm, the visual array task (VAT), to examine the relation between object label and object category knowledge in a sample of toddlers at heightened genetic risk for developing ASD. Eighty-eight toddlers with at least one typically developing older sibling (low-risk; LR) or one older sibling diagnosed with ASD (high-risk; HR) completed the VAT at 17 (LR n = 20; HR n = 27) and/or 25 months of age (LR n = 42; HR n = 22). Results indicated that the VAT was both a sensitive measure of receptive vocabulary as well as capable of reflecting gains in category knowledge for toddlers at genetic risk of developing ASD. Notably, an early emerging difference in the relation between target label knowledge and category knowledge for the groups was observed at 17 months of age but dissipated by 25 months of age. This suggests that while the link between receptive vocabulary and category knowledge may develop earlier in LR groups, HR groups may potentially catch up by the second year of life. Therefore, it is likely meaningful to consider differences in category knowledge when conceptualizing the receptive language deficits associated with HR populations. During language learning, typically developing children are sensitive to the common features of category members and use this information to generalize known object labels to newly encountered exemplars. The inability to identify similarities between category members and/or utilize this information when learning new object referents at 17 months of age may be a potential mechanism underlying the delays observed in HR populations.

Prototype-based category learning in autism: A review

Similarity-based categorization, as an important cognitive skill, can be performed by abstracting a categories' central tendency, the so-called prototype, or by memorizing individual exemplars of a category. The flexible selection of an appropriate strategy is crucial for effective cognitive functioning. The detail-focused cognitive style in individuals with autism spectrum disorders (ASD) has been hypothesized to specifically impair prototype-based categorization but to leave exemplar-based categorization unimpaired. We first give an overview of approaches to investigate prototype-based abstraction in the prototype-distortion task, with an emphasis on model-based approaches suitable to discern the two strategies on the individual level. The second part summarizes literature speaking to prototype-based categorization in ASD using that task. Despite considerable inconsistencies, most studies appear to confirm that autistic individuals have more difficulties to perform prototype-distortion tasks than non-autistic individuals. We highlight how inconsistencies in literature can be resolved by taking the differences in task designs into account. The current review illustrates the need for sensitive computational approaches, suitable to detect hidden individual differences and potential compensatory strategies.