The modality shift experiment in adults and children with high functioning autism

Slower Processing Speed in Autism Spectrum Disorder: A Meta-analytic Investigation of Time-Based Tasks

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition affecting information processing across domains. The current meta-analysis investigated whether slower processing speed is associated with the ASD neurocognitive profile and whether findings hold across different time-based tasks and stimuli (social vs. nonsocial; linguistic vs. nonlinguistic). Mean RTs of ASD and age-matched neurotypical comparison groups (N = 893 ASD, 1063 neurotypical; mean age ASD group = 17 years) were compared across simple RT, choice RT, and interference control tasks (44 studies, 106 effects) using robust variance estimation meta-analysis. Simple RT tasks required participants to respond to individual stimuli, whereas choice RT tasks required forced-choice responses to two or more stimuli. Interference control tasks required a decision in the context of a distractor or priming stimulus; in an effort to minimize inhibitory demands, we extracted RTs only from baseline and congruent conditions of such tasks. All tasks required nonverbal (motor) responses. The overall effect-size estimate indicated significantly longer mean RTs in ASD groups (g = .35, 95% CI = .16; .54) than comparison groups. Task type moderated effects, with larger estimates drawn from simple RT tasks than interference control tasks. However, across all three task types, ASD groups exhibited significantly longer mean RTs than comparison groups. Stimulus type and age did not moderate effects. Generalized slowing may be a domain-general characteristic of ASD with potential consequences for social, language, and motor development. Assessing processing speed may inform development of interventions to support autistic individuals and their diverse cognitive profiles.

Resolution of impaired multisensory processing in autism and the cost of switching sensory modality

Children with autism spectrum disorders (ASD) exhibit alterations in multisensory processing, which may contribute to the prevalence of social and communicative deficits in this population. Resolution of multisensory deficits has been observed in teenagers with ASD for complex, social speech stimuli; however, whether this resolution extends to more basic multisensory processing deficits remains unclear. Here, in a cohort of 364 participants we show using simple, non-social audiovisual stimuli that deficits in multisensory processing observed in high-functioning children and teenagers with ASD are not evident in adults with the disorder. Computational modelling indicated that multisensory processing transitions from a default state of competition to one of facilitation, and that this transition is delayed in ASD. Further analysis revealed group differences in how sensory channels are weighted, and how this is impacted by preceding cross-sensory inputs. Our findings indicate that there is a complex and dynamic interplay among the sensory systems that differs considerably in individuals with ASD.

Crosse et al. study a cohort of 364 participants with autism spectrum disorders (ASD) and matched controls, and show that deficits in multisensory processing observed in high-functioning children and teenagers with ASD are not evident in adults with the disorder. Using computational modelling they go on to demonstrate that there is a delayed transition of multisensory processing from a default state of competition to one of facilitation in ASD, as well as differences in sensory weighting and the ability to switch between sensory modalities, which sheds light on the interplay among sensory systems that differ in ASD individuals.

Shifting attention between modalities: Revisiting the modality-shift effect in autism

Selective attention to a sensory modality has been observed experimentally in studies of the modality-shift effect – a relative performance benefit for targets preceded by a target in the same modality, compared to a different modality. Differences in selective attention are commonly observed in autism and we investigated whether exogenous (automatic) shift costs between modalities are increased. Autistic adults and neurotypical controls made speeded discrimination responses to simple visual, tactile and auditory targets. Shift costs were observed for each target modality in participant response times and were largest for auditory targets, reflective of fast responses on auditory repeat trials. Critically, shift costs were similar between the groups. However, integrating speed and accuracy data using drift-diffusion modelling revealed that shift costs in drift rates (reflecting the quality of information extracted from the stimulus) were reduced for autistic participants compared with neurotypicals. It may be that, unlike neurotypicals, there is little difference between attention within and between sensory modalities for autistic people. This finding also highlights the benefit of combining reaction time and accuracy data using decision models to better characterise selective attention in autism.

Local Processing Bias Impacts Implicit and Explicit Memory in Autism

Autism spectrum disorder (ASD) is characterized by atypical perception, including processing that is biased toward local details rather than global configurations. This bias may impact on memory. The present study examined the effect of this perception on both implicit (Experiment 1) and explicit (Experiment 2) memory in conditions that promote either local or global processing. The first experiment consisted of an object identification priming task using two distinct encoding conditions: one favoring local processing (Local condition) and the other favoring global processing (Global condition) of drawings. The second experiment focused on episodic (explicit) memory with two different cartoon recognition tasks that favored either local (i.e., processing specific details) or a global processing (i.e., processing each cartoon as a whole). In addition, all the participants underwent a general clinical cognitive assessment aimed at documenting their cognitive profile and enabling correlational analyses with experimental memory tasks. Seventeen participants with ASD and 17 typically developing (TD) controls aged from 10 to 16 years participated to the first experiment and 13 ASD matched with 13 TD participants were included for the second experiment. Experiment 1 confirmed the preservation of priming effects in ASD but, unlike the Comparison group, the ASD group did not increase his performance as controls after a globally oriented processing. Experiment 2 revealed that local processing led to difficulties in discriminating lures from targets in a recognition task when both lures and targets shared common details. The correlation analysis revealed that these difficulties were associated with processing speed and inhibition. These preliminary results suggest that natural perceptual processes oriented toward local information in ASD may impact upon their implicit memory by preventing globally oriented processing in time-limited conditions and induce confusion between explicit memories that share common details.

Characteristic Executive Dysfunction for High-Functioning Autism Sustained to Adulthood

The comprehensiveness and severity of executive dysfunction in high-functioning autism (HFA) spectrum disorder have not reached a unified conclusion especially in patients in adulthood. Clarifying this issue is critical for guiding clinical diagnosis and targeted intervention. The primary objective of the present meta-analysis was to study the characteristics of executive function (EF) in adults with HFA compared to typically developing (TD) adults, by taking five key components into consideration, including inhibition, working memory, flexibility, planning, and fluency. The PubMed and Embase databases were searched to identify peer-reviewed studies that compared EF in adults with and without HFA from 1980 to November 2018. Hedges' g effect sizes were computed to measure the primary outcome. Moderators like age, sex, and diagnostic tools were controlled using meta-regressions. Forty-two studies satisfying the selection criteria were included, which resulted in a large sample size of 2419 participants. A moderate overall effect size for reduced EF across domains was found in adults with HFA, compared with TD (g = 0.57, 95% confidence interval 0.47-0.66). Subsequently, a broad executive dysfunction was found in adults with HFA in this study (flexibility [g = 0.69], planning [g = 0.64], inhibition [g = 0.61], working memory [g = 0.48], fluency [g = 0.42]), with the predominated impairment on flexibility and planning. Taken together, these results provide evidence for the executive dysfunction hypothesis and may assist in the clinical diagnosis and targeted intervention, suggesting the necessity of sustained intervention on EF for individuals with HFA from childhood to adulthood. LAY SUMMARY: The meta-analysis explored the characteristics of EF in adults with high-functioning autism (HFA) comparing to typically developing controls. Moderate effect sizes for reduced EF across domains were found in adults with HFA, with the flexibility and planning being the most predominately impaired. A comprehensive measurement of EF in adults with HFA has important clinical implications for the diagnosis, treatment, prognosis, and a fundamental understanding for developmental trajectory of these patients.

Within- and Cross-Modal Integration and Attention in the Autism Spectrum

Although impairment in sensory integration is suggested in the autism spectrum (AS), empirical evidences remain equivocal. We assessed the integration of low-level visual and tactile information within and across modalities in AS and typically developing (TD) individuals. TD individuals demonstrated increased redundancy gain for cross-modal relative to double tactile or visual stimulation, while AS individuals showed similar redundancy gain between cross-modal and double tactile conditions. We further observed that violation of the race model inequality for cross-modal conditions was observed over a wider proportion of the reaction times distribution in TD than AS individuals. Importantly, the reduced cross-modal integration in AS individuals was not related to atypical attentional shift between modalities. We conclude that AS individuals displays selective decrease of cross-modal integration of low-level information.

Processing Speed is Impaired in Adults with Autism Spectrum Disorder, and Relates to Social Communication Abilities

Autism spectrum disorder (ASD) is characterized by a variety of social and non-social behavioral deficits. One potential mechanism that could unify this diverse profile of behaviors is slower processing speed. Seventy-six high-functioning adults with ASD were compared to 64 matched controls on standardized measures of processing speed. Participants with ASD were significantly slower on all measures, and on the composite score from the three tests (d's > .65). ASD participants with slower processing speeds scored higher on the ADOS Communication and Reciprocal Social Interaction scale (r = .34). These findings provide evidence of slower processing speeds in adults with ASD, and that this may be contributing to impairments in social communication skills. Interventions that improve processing speed might improve social communication abilities in ASD.

Effects of Methylphenidate on Reaction Time in Children with Attention Deficit / Hyperactivity Disorder

INTRODUCTION

Attention-deficit/hyperactivity disorder (ADHD) is associated with a broad range of neuropsychological impairments that are attenuated with methylphenidate (MPH) treatment. The aim of this study was to determine how MPH effects attentional functioning in terms of reaction time (RT) in ADHD.

METHODS

Eighteen pre-medicated ADHD children (7 to 12 years old) and eighteen gender matched normal controls (7 to 12 years old) were included in the study. Participants performed an auditory attention task and the RT of participants to each target response was calculated automatically. The same test was repeated 3 months after OROS-MPH administration for ADHD group. RT, RT standard deviation (RTSD), and response errors (omission and commission errors) were compared between control and pre-MPH ADHD groups, and between Pre-MPH and post-MPH ADHD groups.

RESULTS

Relative to control subjects, significantly longer RTs, higher RTSD and more errors of omission were observed in unmedicated ADHD children during auditory attention task. Analyses revealed significant effects of medication across all measures except commission errors. After treatment RTs were faster, RTSD values were lower, and errors of omission were attenuated compared to pre-medication condition in ADHD group. There were no significant differences in terms of commission errors between groups.

CONCLUSION

In this study it was observed that MPH reduced RTs to stimuli, attenuated omission errors during the task in ADHD group and after 3 months of treatment ADHD children showed similar patterns in RT as compared to controls. Results suggest that when treating ADHD, it might help clinicians to evaluate objective and non-invasive cognitive outcomes such as RT, RTSD and response errors to evaluate the effects of treatment.

Aberrant Intrinsic Brain Activity in Patients with Autism Spectrum Disorder: Insights from EEG Microstates

Autism spectrum disorder (ASD) involves aberrant organization and functioning of large-scale brain networks. The aim of this study was to examine whether the resting-state EEG microstate analysis could provide novel insights into the abnormal temporal and spatial properties of intrinsic brain activities in patients with ASD. To achieve this goal, EEG microstate analysis was conducted on the resting-state EEG datasets of 15 patients with ASD and 18 healthy controls from the Healthy Brain Network. The parameters (i.e., duration, occurrence rate, time coverage and topographical configuration) of four classical microstate classes (i.e., class A, B, C and D) were statistically tested between two groups. The results showed that: (1) the occurrence rate and time coverage of microstate class B in ASD group were significantly larger than those in control group; (2) the duration of microstate class A, the duration and time coverage of microstate class C were significantly smaller than those in control group; (3) the map configuration and occurrence rate differed significantly between two groups for microstate class D. These results suggested that EEG microstate analysis could be used to detect the deviant functions of large-scale cortical activities in ASD, and may provide indices that could be used in clinical researches of ASD.

No difference in cross-modal attention or sensory discrimination thresholds in autism and matched controls

Autism has been associated with abnormalities in sensory and attentional processing. Here, we assessed these processes independently in the visual and auditory domains using a visual contrast-discrimination task and an auditory modulation-depth discrimination task. To evaluate changes in sensory function by attention, we measured behavioral performance (discrimination accuracy) when subjects were cued to attend and respond to the same stimulus (frequent valid cue) or cued to attend to one stimulus and respond to the non-cued stimulus (infrequent invalid cue). The stimuli were presented at threshold to ensure equal difficulty across participants and groups. Results from fifteen high-functioning adult individuals with autism and fifteen matched controls revealed no significant differences in visual or auditory discrimination thresholds across groups. Furthermore, attention robustly modulated performance accuracy (performance was better for valid than invalid cues) in both sensory modalities and to an equivalent extent in both groups. In conclusion, when using this well-controlled method, we found no evidence of atypical sensory function or atypical attentional modulation in a group of high functioning individuals with clear autism symptomatology.

Reduced Efficiency and Capacity of Cognitive Control in Autism Spectrum Disorder

Cognitive control constrains mental operations to prioritize information that reaches conscious awareness and is essential to flexible, adaptive behavior under conditions of uncertainty. Cognitive control can be compromised by neurodevelopmental disorders such as autism spectrum disorder (ASD), which is characterized by the presence of social and communicative deficits, and restricted interests/repetitive behaviors. Although prior investigations have attempted to elucidate the nature of cognitive control in ASD, whether there is an underlying information processing deficit associated with cognitive control remains unclear. This study challenged cognitive control in 15 high-functioning adults with ASD and 15 typically developing (TD) controls using three novel tasks designed to systematically manipulate uncertainty. We aimed to investigate the efficiency of cognitive control in sequential information processing, cognitive control of nonsequential information processing across a range of cognitive loads and cognitive control capacity under time constraint. Results demonstrated that the ASD group performed less efficiently on sequential and nonsequential information processing, and had reduced cognitive control capacity under time constraint relative to the TD group. These findings suggest that inefficient cognitive control of information processing may be a fundamental deficit in ASD.

Further understanding of complex information processing in verbal adolescents and adults with autism spectrum disorders

More than 20 years ago, Minshew and colleagues proposed the Complex Information Processing model of autism in which the impairment is characterized as a generalized deficit involving multiple modalities and cognitive domains that depend on distributed cortical systems responsible for higher order abilities. Subsequent behavioral work revealed a related dissociation between concept formation and concept identification in autism suggesting the lack of an underlying organizational structure to manage increases in processing loads. The results of a recent study supported the impact of this relative weakness in conceptual reasoning on adaptive functioning in children and adults with autism. In this study, we provide further evidence of the difficulty relatively able older adolescents and adults with autism have with conceptual reasoning and provide evidence that this characterizes their difference from age- and ability-matched controls with typical development better than their differences in language. For verbal adults with autism, language may serve as a bootstrap or compensatory mechanism for learning but cannot overcome an inherent weakness in concept formation that makes information processing challenging as task demands increase.

Binding in working memory and frontal lobe in normal aging: is there any similarity with autism?

Some studies highlight similarities between Autism Spectrum Disorder (ASD) and healthy aging. Indeed, the decline in older individuals’ ability to create a unified representation of the individual features of an event is thought to arise from a disruption of binding within the episodic buffer of working memory (WM) as the same way as observed in ASD. In both cases, this deficit may result from an abnormal engagement of a frontohippocampal network. The objective of the present study is to identify both cognitive processes and neural substrates associated with the deficit of binding in WM in healthy aging. We studied the capacity of binding and the cognitive processes that might subtend its decline in 72 healthy participants aged 18–84 years. We examined the behavioral data in relation to the changes in brain metabolism associated with the age-related decline in a subgroup of 34 healthy participants aged 20–77 years using the resting-state [¹⁸F] fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET). Forward stepwise regression analyses showed that the age-related decline in binding was partially explained by a decline in inhibition and processing speed. PET correlation analyses indicated that metabolism of the frontal regions, anterior and middle cingulate cortices is implicated in this phenomenon. These data suggest that executive functions and processing speed may play a crucial role in the capacity to integrate unified representations in memory in aging. Possible implications are discussed in ASD.

No evidence of reaction time slowing in autism spectrum disorder

A total of 32 studies comprising 238 simple reaction time and choice reaction time conditions were examined in individuals with autism spectrum disorder (n = 964) and controls (n = 1032). A Brinley plot/multiple regression analysis was performed on mean reaction times, regressing autism spectrum disorder performance onto the control performance as a way to examine any generalized simple reaction time/choice reaction time slowing exhibited by the autism spectrum disorder group. The resulting regression equation was Y (autism spectrum disorder) = 0.99 × (control) + 87.93, which accounted for 92.3% of the variance. These results suggest that there are little if any simple reaction time/choice reaction time slowing in this sample of individual with autism spectrum disorder, in comparison with controls. While many cognitive and information processing domains are compromised in autism spectrum disorder, it appears that simple reaction time/choice reaction time remain relatively unaffected in autism spectrum disorder.