Pseudo-random number generation in children with high-functioning autism and Asperger's disorder: further evidence for a dissociation in executive functioning?

Exploring randomness in autism

Introduction

The fast, intuitive and autonomous system 1 along with the slow, analytical and more logical system 2 constitute the dual system processing model of decision making. Whether acting independently or influencing each other both systems would, to an extent, rely on randomness in order to reach a decision. The role of randomness, however, would be more pronounced when arbitrary choices need to be made, typically engaging system 1. The present exploratory study aims to capture the expression of a possible innate randomness mechanism, as proposed by the authors, by trying to isolate system 1 and examine arbitrary decision making in autistic participants with high functioning Autism Spectrum Disorders (ASD).

Methods

Autistic participants withhigh functioning ASD and an age and gender matched comparison group performed the random number generation task. The task was modified to limit the contribution of working memory and allow any innate randomness mechanisms expressed through system 1, to emerge.

Results

Utilizing a standard analyses approach, the random number sequences produced by autistic individuals and the comparison group did not differ in their randomness characteristics. No significant differences were identified when the sequences were examined using a moving window approach. When machine learning was used, random sequences' features could discriminate the groups with relatively high accuracy.

Conclusions

Our findings indicate the possibility that individual patterns during random sequence production could be consistent enough between groups to allow for an accurate discrimination between the autistic and the comparison group. In order to draw firm conclusions around innate randomness and further validate our experiment, our findings need to be replicated in a bigger sample.

Counting on random number generation: Uncovering mild executive dysfunction in congenital heart disease

Congenital heart disease (CHD) is associated with various neurocognitive deficits, particularly targeting executive functions (EFs), of which random number generation (RNG) is one indicator. RNG has, however, never been investigated in CHD. We administered the Mental Dice Task (MDT) to 67 young adults with CHD and 55 healthy controls. This 1-minute-task requires the generation of numbers 1 to 6 in a random sequence. RNG performance was correlated with a global EF score. Participants underwent MRI to examine structural-volumetric correlates of RNG. Compared to controls, CHD patients showed increased backward counting, reflecting deficient inhibition of automatized behavior. They also lacked a small-number bias (higher frequency of small relative to large numbers). RNG performance was associated with global EF scores in both groups. In CHD patients, MRI revealed an inverse association of counting bias with most of the volumetric measurements and the amount of small numbers was positively associated with corpus callosum volume, suggesting callosal involvement in the "pseudoneglect in number space". In conclusion, we found an impaired RNG performance in CHD patients, which is associated with brain volumetric measures. RNG, reportedly resistant to learning effects, may be an ideal task for the longitudinal assessment of EFs in patients with CHD.

Increased scale-free dynamics in salience network in adult high-functioning autism

Autism spectrum disorder (ASD) is clinically characterized by extremely slow and inflexible behavior. The neuronal mechanisms of these symptoms remain unclear though. Using fMRI, we investigate the resting state's temporal structure in the frequency domain (scale-free activity as measured with Power-Law Exponent, PLE, and Spectral Entropy, SE) and temporal variance (neural variability) in high-functioning, adult ASD comparing them with schizophrenic and neurotypical subjects. We show that ASD is characterized by high PLE in salience network, especially in dorsal anterior cingulate. This increase in PLE was 1) specific for salience network; 2) independent of other measures such as neuronal variability/SD and functional connectivity, which did not show any significant difference; 3) detected in two independent samples of ASD but not in the schizophrenia sample. Among salience network subregions, dorsal anterior cingulate cortex exhibited PLE differences between ASD and neurotypicals in both samples, showing high robustness in ROC curves values. Salience network abnormal temporal structure was confirmed by SE, which was strongly anticorrelated with PLE and thus decreased in ASD. Taken together, our findings show abnormal temporal structure (but normal temporal variance) in resting state salience network in adult high-functioning ASD. The abnormally high PLE indicates a relative predominance of slower over faster frequencies, which may underlie the slow adaptation to unexpected changes and the inflexible behavior observed in autistic individuals. The specificity of abnormal PLE in salience network suggests its potential utility as biomarker in ASD.

Age-related differences in inhibitory control and memory updating in boys with Asperger syndrome

Deficits in specific executive domains are highly prevalent in autism spectrum disorder; however, age-related improvements in executive functions (reflecting prefrontal maturational changes) have been reported even in individuals diagnosed with autism. The current study examined two components of cognitive flexibility (inhibition of prepotent responses and memory monitoring/updating) by using a random-motor-generation task (MPT) in a group of 23 boys with Asperger syndrome (AS) and 23 matched healthy controls. We found poorer inhibition and more repetitive responses in younger AS children solely, but comparable memory monitoring/updating skills across groups. Overall, our findings correspond well with previous studies and reveal that even in AS specific EFs may improve with age and, thus, call for a more differentiated view of executive (dys) function profiles in children diagnosed with AS. Tests such as the random-motor-generation task may help to disentangle more specific processes of executive deficits in autism spectrum disorder as compared to the more classical tests.

Reversal learning in C58 mice: Modeling higher order repetitive behavior

Restricted, repetitive behaviors are diagnostic for autism and prevalent in other neurodevelopmental disorders. These behaviors cluster as repetitive sensory-motor behaviors and behaviors reflecting resistance to change. The C58 mouse strain is a promising model for these behaviors as it emits high rates of aberrant repetitive sensory-motor behaviors. The purpose of the present study was to extend characterization of the C58 model to resistance to change. This was done by comparing C58 to C57BL/6 mice on a reversal learning task under either a 100% or 80%/20% probabilistic reinforcement schedule. In addition, the effect of environmental enrichment on performance of this task was assessed as this rearing condition markedly reduces repetitive sensory-motor behavior in C58 mice. Little difference was observed between C58 and control mice under a 100% schedule of reinforcement. The 80%/20% probabilistic schedule of reinforcement generated substantial strain differences, however. Importantly, no strain difference was observed in acquisition, but C58 mice were markedly impaired in their ability to reverse their pattern of responding from the previously high density reinforcement side. Environmental enrichment did not impact acquisition under the probabilistic reinforcement schedule, but enriched C58 mice performed significantly better than standard housed C58 mice in reversal learning. Thus, C58 mice exhibit behaviors that reflect both repetitive sensory motor behaviors as well as behavior that reflects resistance to change. Moreover, both clusters of repetitive behavior were attenuated by environmental enrichment. Such findings, along with the reported social deficits in C58 mice, increase the translational value of this mouse model to autism.

Human behavioral complexity peaks at age 25

Random Item Generation tasks (RIG) are commonly used to assess high cognitive abilities such as inhibition or sustained attention. They also draw upon our approximate sense of complexity. A detrimental effect of aging on pseudo-random productions has been demonstrated for some tasks, but little is as yet known about the developmental curve of cognitive complexity over the lifespan. We investigate the complexity trajectory across the lifespan of human responses to five common RIG tasks, using a large sample (n = 3429). Our main finding is that the developmental curve of the estimated algorithmic complexity of responses is similar to what may be expected of a measure of higher cognitive abilities, with a performance peak around 25 and a decline starting around 60, suggesting that RIG tasks yield good estimates of such cognitive abilities. Our study illustrates that very short strings of, i.e., 10 items, are sufficient to have their complexity reliably estimated and to allow the documentation of an age-dependent decline in the approximate sense of complexity.

It has been unclear how this ability evolves over a person’s lifetime and it had not been possible to be assessed with previous classical tools for statistical randomness. To better understand how age impacts behavior, we have assessed more than 3,400 people aged 4 to 91 years old. Each participant performed a series of online tasks that assessed their ability to behave randomly. The five tasks included listing the hypothetical results of a series of 12 coin flips so that they would “look random to somebody else,” guessing which card would appear when selected from a randomly shuffled deck, and listing the hypothetical results of 10 rolls of a die. We analyzed the participants’ choices according to their algorithmic randomness, which is based on the idea that patterns that are more random are harder to encode in a short computer program. After controlling for characteristics such as gender, language, and education. We have found that age was the only factor that affected the ability to behave randomly. This ability peaked at age 25, on average, and declined from then on. We also demonstrate that a relatively short list of choices, say 10 hypothetical coin flips, can be used to reliably gauge randomness of human behavior. A similar approach could be then used to study potential connections between the ability to behave randomly, cognitive decline, neurodegenerative diseases and abilities such as human creativity.

Random Item Generation Is Affected by Age

PURPOSE

Random item generation (RIG) involves central executive functioning. Measuring aspects of random sequences can therefore provide a simple method to complement other tools for cognitive assessment. We examine the extent to which RIG relates to specific measures of cognitive function, and whether those measures can be estimated using RIG only.

METHOD

Twelve healthy older adults (age: M = 70.3 years, SD = 4.9; 8 women and 4 men) and 20 healthy young adults (age: M = 24 years, SD = 4.0; 12 women and 8 men) participated in this pilot study. Each completed a RIG task, along with the color Stroop test, the Repeatable Battery for the Assessment of Neuropsychological Status, and the Peabody Picture Vocabulary Test-Fourth Edition (Dunn & Dunn, 2007). Several statistical features extracted from RIG sequences, including recurrence quantification, were found to be related to the other measures through correlation, regression, and a neural-network model.

RESULTS

The authors found significant effects of age in RIG and demonstrate that nonlinear machine learning can use measures of RIG to accurately predict outcomes from other tools.

CONCLUSIONS

These results suggest that RIG can be used as a relatively simple predictor for other tools and in particular seems promising as a potential screening tool for selective attention in healthy aging.

Repetitive Behavior in Neurodevelopmental Disorders: Clinical and Translational Findings

Repetitive behavior refers to a highly heterogeneous set of responses associated with a wide range of conditions, including normative development. Treatment studies for aberrant repetitive behavior are limited although one promising approach involves conceptualizing such behavior as a generalized inflexibility or lack of variability in responding. Relatively little is known about the neurobiological mechanisms that mediate the development and expression of repetitive behavior, information critical to the design of effective pharmacotherapies, early interventions, and prevention strategies. We will review clinical findings in repetitive behavior as well as findings from animal models highlighting environmental factors and the role of cortical-basal ganglia circuitry in mediating the development and expression of these behaviors. Findings from animal models have included identification of a specific neural pathway important in mediating repetitive behavior. Moreover, pharmacological studies that support the importance of this pathway have led to the identification of novel potential therapeutic targets. Expanding the evidence base for environmental enrichment-derived interventions and focusing on generalized variability in responding will aid in addressing the broader problem of rigidity or inflexibility.

Asperger's disorder will be back

This review focuses on identifying up-to-date number of publications that compared DSM-IV/ICD-10 Asperger's disorder (AspD) to Autistic Disorder/High-functioning Autism (AD/HFA). One hundred and twenty-eight publications were identified through an extensive search of major electronic databases and journals. Based on more than 90 clinical variables been investigated, 94 publications concluded that there were statistically significant or near significant level of quantitative and/or qualitative differences between AspD and AD/HFA groups; 4 publications found both similarities and differences between the two groups; 30 publications concluded with no differences between the two groups. Although DSM-5 ASD will eliminate Asperger's disorder. However, it is plausible to predict that the field of ASD would run full circle during the next decade or two and that AspD will be back in the next edition of DSM.

Algorithmic complexity for short binary strings applied to psychology: a primer

As human randomness production has come to be more closely studied and used to assess executive functions (especially inhibition), many normative measures for assessing the degree to which a sequence is randomlike have been suggested. However, each of these measures focuses on one feature of randomness, leading researchers to have to use multiple measures. Although algorithmic complexity has been suggested as a means for overcoming this inconvenience, it has never been used, because standard Kolmogorov complexity is inapplicable to short strings (e.g., of length l ≤ 50), due to both computational and theoretical limitations. Here, we describe a novel technique (the coding theorem method) based on the calculation of a universal distribution, which yields an objective and universal measure of algorithmic complexity for short strings that approximates Kolmogorov-Chaitin complexity.

Neurocognitive deficits, craving, and abstinence among alcohol-dependent individuals following detoxification

Alcohol dependence, a chronic relapsing disorder, is characterized by an impaired ability to regulate compulsive urges to consume alcohol. Very few empirical studies have examined the presence of these executive deficits, how they relate to craving, and the enduring nature of these deficits during abstinence. As such, the current study aimed to characterize these cognitive deficits within a sample of 24 alcohol-dependent participants post-detoxification and 23 non-alcohol-dependent participants. Participants were administered the Sustained Attention to Response Task to measure response inhibition and sustained attention and the Random Number Generation Task to examine executive deficits. Correlations between cognitive performance and clinical measures of alcohol dependence were examined. As predicted, the alcohol-dependent group exhibited poorer performance across the domains of response inhibition, executive function, and attentional control. Cognitive performance was related to clinical measures of craving and years of alcohol consumption, whereas the duration of abstinence was not associated with improved cognitive performance. These findings highlight the need for therapeutic strategies to target these enduring neurocognitive deficits in improving the treatment of alcohol dependence.

Atypical visuospatial processing in autism: insights from functional connectivity analysis

Atypical visuospatial processing is commonly described in autism spectrum disorders (ASDs); however the specific neurobiological underpinnings of this phenomenon are poorly understood. Given the extensive evidence suggesting ASDs are characterized by abnormal neural connectivity, this study aimed to investigate network connectivity during visuospatial processing in ASD. Twenty-two males with ASD without intellectual disability and 22 individually matched controls performed a mental rotation task during functional magnetic resonance imaging (MRI) in which two rotated stimuli were judged to be same ("Same Trials") or mirror-imaged ("Mirror Trials"). Behavioral results revealed a relative advantage of mental rotation in the ASD group-controls were slower responding to the more difficult Mirror Trials than Same Trials whereas the ASD group completed Mirror Trials and Same-trials at similar speeds. In the ASD group, brain activity was reduced in frontal, temporal, occipital, striatal, and cerebellar regions and, consistent with previous literature, functional connectivity between a number of brain regions was reduced. However, some connections appeared to be conserved and were recruited in a qualitatively different way by the two groups. As task difficulty increased (on Mirror Trials), controls tended to increase connections between certain brain regions, whereas the ASD group appeared to suppress connections between these regions. There was an interesting exception to this pattern in the visual cortex, a finding that may suggest an advantage in early visual perceptual processing in ASD. Overall, this study has identified a relative advantage in mental rotation in ASD that is associated with aberrant neural connectivity and that may stem from enhanced visual perceptual processing.

On the relationship between autistic traits and executive functioning in a non-clinical Dutch student population

We examined the association between autistic traits and different aspects of executive functioning (EF), using non-clinical Social Science and Science students as participants. Autistic traits, and associated personality traits, were measured using the Autism Quotient (AQ) and the Temperament and Character Inventory (TCI), respectively. EF was examined by means of a random number generation test and a phonemic fluency test. Using appropriate dependent measures, the following EF components were examined: 1) inhibition of prepotent responding, 2) simple output inhibition, 3) working memory monitoring and updating, and 4) switching. No significant relationship was found between the AQ and each of the four components of EF. However, two TCI subscales were reliably correlated with either the working memory or the shifting component. These results were discussed in view of the concept of an autism spectrum with respect to executive abilities.

Can Asperger syndrome be distinguished from autism? An anatomic likelihood meta-analysis of MRI studies

BACKGROUND

The question of whether Asperger syndrome can be distinguished from autism has attracted much debate and may even incur delay in diagnosis and intervention. Accordingly, there has been a proposal for Asperger syndrome to be subsumed under autism in the forthcoming Diagnostic and Statistical Manual of Mental Disorders, fifth edition, in 2013. One approach to resolve this question has been to adopt the criterion of absence of clinically significant language or cognitive delay--essentially, the "absence of language delay." To our knowledge, this is the first meta-analysis of magnetic resonance imaging (MRI) studies of people with autism to compare absence with presence of language delay. It capitalizes on the voxel-based morphometry (VBM) approach to systematically explore the whole brain for anatomic correlates of delay and no delay in language acquisition in people with autism spectrum disorders.

METHODS

We conducted a systematic search for VBM MRI studies of grey matter volume in people with autism. Studies with a majority (at least 70%) of participants with autism diagnoses and a history of language delay were assigned to the autism group (n = 151, control n = 190). Those with a majority (at least 70%) of individuals with autism diagnoses and no language delay were assigned to the Asperger syndrome group (n = 149, control n = 214). We entered study coordinates into anatomic likelihood estimation meta-analysis software with sampling size weighting to compare grey matter summary maps driven by Asperger syndrome or autism.

RESULTS

The summary autism grey matter map showed lower volumes in the cerebellum, right uncus, dorsal hippocampus and middle temporal gyrus compared with controls; grey matter volumes were greater in the bilateral caudate, prefrontal lobe and ventral temporal lobe. The summary Asperger syndrome map indicated lower grey matter volumes in the bilateral amygdala/hippocampal gyrus and prefrontal lobe, left occipital gyrus, right cerebellum, putamen and precuneus compared with controls; grey matter volumes were greater in more limited regions, including the bilateral inferior parietal lobule and the left fusiform gyrus. Both Asperger syndrome and autism studies reported volume increase in clusters in the ventral temporal lobe of the left hemisphere.

LIMITATIONS

We assigned studies to autism and Asperger syndrome groups for separate analyses of the data and did not carry out a direct statistical group comparison. In addition, studies available for analysis did not capture the entire spectrum, therefore we cannot be certain that our findings apply to a wider population than that sampled.

CONCLUSION

Whereas grey matter differences in people with Asperger syndrome compared with controls are sparser than those reported in studies of people with autism, the distribution and direction of differences in each category are distinctive.

Confusion and inconsistency in diagnosis of Asperger syndrome: a review of studies from 1981 to 2010

This paper presents a review of past and current research on the diagnosis of Asperger syndrome (AS) in children. It is suggested that the widely used criteria for diagnosing AS in the Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV are insufficient and invalid for a reliable diagnosis of AS. In addition, when these diagnostic criteria are applied, there is the potential bias of receiving a diagnosis towards the high-functioning end of the autism spectrum. Through a critical review of 69 research studies carried out between 1981 and 2010, this paper shows that six possible criteria for diagnosing AS (specifically, the age at which signs and symptoms related to autism become apparent, language and social communication abilities, intellectual abilities, motor or movement skills, repetitive patterns of behaviour and the nature of social interaction) overlap with the criteria for diagnosing autism. However, there is a possibility that some finer differences exist in the nature of social interaction, motor skills and speech patterns between groups with a diagnosis of AS and autism. These findings are proposed to be of relevance for designing intervention studies aimed at the treatment of specific symptoms in people with an autism spectrum disorder.

Lexical processing in individuals with high-functioning autism and Asperger's disorder

The presence or absence of clinically delayed language development prior to 3 years of age is a key, but contentious, clinical feature distinguishing autism from Asperger's disorder. The aim of this study was to examine language processing in children with high-functioning autism (HFA) and Asperger's disorder (AD) using a task which taps lexical processing, a core language ability. Eleven individuals with HFA, 11 with AD and 11 typically developing (TD) individuals completed a masked priming task, a psycholinguistic paradigm that directly examines lexical processes. Within-group analyses revealed the AD and TD groups had intact lexical processing systems and orthographic processing of the written word. The outcomes for the HFA group were ambiguous, suggesting that their lexical processing system is either delayed or is structurally different. This suggests that fundamental differences in lexical processing exist between HFA and AD and remain evident later in development.

Neurological soft signs in juvenile patients with Asperger syndrome, early-onset psychosis, and healthy controls

AIM

The study of neurological soft signs (NSS) in patients with Asperger syndrome may help us to elucidate the neurological basis of this disorder and to clarify its relationship with other neurodevelopmental disorders. The goal of this study was to compare the prevalence of NSS in a sample of patients with Asperger syndrome, early-onset psychosis and healthy controls.

METHOD

NSS were assessed by means of the Neurological Evaluation Scale in a sample of 29 patients with Asperger syndrome (mean age = 12.86 ± 2.58 years), 30 patients with first-episode early-onset psychoses (mean age 14.17 ± 1.02 years) and 30 healthy controls (mean age 12.33 ± 2.69 years).

RESULTS

Significant group differences were found between Asperger syndrome patients and healthy controls both in all the Neurological Evaluation Scale subscales and in the Neurological Evaluation Scale total score. There were no significant differences between both groups of patients in any of the Neurological Evaluation Scale scores.

CONCLUSIONS

NSS are more prevalent in Asperger syndrome than in healthy controls. The NSS profile was not disorder-specific in our samples of patients with Asperger syndrome and early-onset psychoses.

Risk factors for autism and Asperger syndrome

Using the Swedish Medical Birth Registry (MBR), obstetrical and demographic information was retrieved for 250 children with autism or Asperger syndrome who were born in Malmoe, Sweden, and enrolled at the local Child and Youth Habilitation Center. The reference group consisted of all children born in Malmoe during 1980—2005. Obstetric sub-optimality (prematurity, low Apgar scores, growth restriction, or macrosomia) was positively associated with autism but not with Asperger syndrome. Maternal birth outside the Nordic countries was positively associated with autism (adjusted OR: 2.2; 95%CI: 1.6—3.1) and negatively associated with Asperger syndrome (OR: 0.6; 95%CI: 0.3—0.97). The highest risk estimate for autism was found among children to women who were born in sub-Saharan Africa (OR: 7.3), or in East Asia (OR: 3.4).

Attentional blink in young people with high-functioning autism and Asperger's disorder

The aim of the study was to examine the temporal characteristics of information processing in individuals with high-functioning autism and Asperger's disorder using a rapid serial visual presentation paradigm. The results clearly showed that such people demonstrate an attentional blink of similar magnitude to comparison groups. This supports the proposition that the social processing difficulties experienced by these individuals are not underpinned by a basic temporal-cognitive processing deficit, which is consistent with Minshew's complex information processing theory. This is the second study to show that automatic inhibitory processes are intact in both autism and Asperger's disorder, which appears to distinguish these disorders from some other frontostriatal disorders. The finding that individuals with autism were generally poorer than the comparison group at detecting black Xs, while being as good in responding to white letters, was accounted for in the context of a potential dual-task processing difficulty or visual search superiority.

Distinct patterns of grey matter abnormality in high-functioning autism and Asperger's syndrome

BACKGROUND

Autism exists across a wide spectrum and there is considerable debate as to whether children with Asperger's syndrome, who have normal language milestones, should be considered to comprise a subgroup distinct other from high-functioning children with autism (HFA), who have a history of delayed language development. Magnetic resonance imaging (MRI) studies of autism are in disagreement. One possible reason is that the diagnosis of autism takes precedence over Asperger's syndrome and a distinction in language acquisition is rarely made. We therefore planned to examine a whole brain hypothesis that the patterns of grey matter differences in Asperger's syndrome and HFA can be distinguished.

METHODS

We used voxel-based computational morphometry to map grey matter volume differences in 33 children with either Asperger's syndrome or high-functioning autism compared to 55 typical developing control children balanced for age, IQ, gender, maternal language and ethnicity.

RESULTS

Children with HFA had significantly smaller grey matter volumes in subcortical, posterior cingulate and precuneus regions than the Asperger's group. Compared to controls, children with HFA had smaller grey matter volumes in predominantly fronto-pallidal regions, while children with Asperger's had less grey matter in mainly bilateral caudate and left thalamus. In addition we found a significant negative correlation between the size of a grey matter cluster around BA44 language area and the age of acquisition of phrase speech in the children with HFA. When the groups were combined we confirmed a mixed picture of smaller grey matter volumes in frontal, basal ganglia, temporal and parietal regions.

CONCLUSIONS

Our study suggests that the underlying neurobiology in HFA and Asperger's syndrome is at least partly discrete. Future studies should therefore consider the history of language acquisition as a valuable tool to refine investigation of aetiological factors and management options in pervasive developmental disorders.

Brief report: Inhibition of return in young people with autism and Asperger's disorder

The aim of this study was to investigate whether the superior search abilities observed in autism/Asperger's disorder may in part be a consequence of a more pronounced inhibition of return (IOR). Contrary to our prediction, IOR in individuals with autism was comparable to the matched comparison group. However, the autism group committed more false alarm responses than the matched comparison group; this may reflect a possible inhibitory deficit, or suggest that individuals with autism rely more on probabilities to determine their behavioural responses. There was a borderline-significant trend ( p = 0.052) to indicate that IOR may be more pronounced in individuals with Asperger's disorder. In contrast to the autism group, the Asperger's disorder group had a pattern of false alarm responses similar to that of the comparison group. The findings further inform Minshew's complex information processing theory which seeks to establish which areas of neuropsychological functioning are preserved and deficit in autism.