An empirical evaluation of executive function in Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) is a neurodevelopmental condition characterised by social impairment and restricted/repetitive behaviours. It is associated with significant disability and poor life outcomes with increasing interest in the factors that contribute to this disability. A significant body of research has focused on investigating the role of executive function (EF) in ASD. This thesis presents a series of studies that aim to advance the knowledge of EF in ASD. The studies considered factors that may moderate EF and investigated the role of EF in diagnosis and predicting disability. The research cohort comprised of youth and adults with ASD. Comparisons were made with clinical groups diagnosed with Social Anxiety Disorder and Early Psychosis. The first empirical study presented a meta-analysis of the extant literature on EF in ASD across the lifespan. Empirical studies 2 and 3, explored the role of moderators on EF including sex differences and affective states. Empirical study 4, examined the role of EF in differential diagnosis and in predicting disability. The final study utilised a machine learning paradigm and examined whether EF discriminated the ASD cohort from the comparison groups. The research results point to broad executive dysfunction in ASD not influenced by moderator variables or sex differences. Affective states moderated EF across all comparison groups, suggesting a transdiagnostic influence. EF differentiated the ASD cohort from comparison groups and was a unique predictor of disability for the ASD group only. The studies presented in this thesis highlight the importance of a multifaceted evaluation of EF in ASD. This will allow evaluation of unique and shared factors influencing disability outcomes, acknowledge the contribution of mental health factors to EF and facilitate targeted intervention and remediation programmes. Importantly, the cross diagnostic relevance of these factors could facilitate resource allocation and social inclusion

Investigating profiles of attention and arousal in Autism Spectrum Condition (ASC)

The present doctoral project aimed to investigate profiles of arousal and attention in autistic individuals and identify how atypicalities in these relate with specific clinical symptoms of autism. I recruited children and young people between the ages of 7 and 15 years who were either neurotypical (n= 31) or had autism (n= 18). I included a clinical control group of children and young people with ADHD (n= 24) as well as those who had comorbid autism and ADHD (n= 33). I collected indices of arousal and attention by measuring heart rate, brain activity (using electrophysiology) and eye movements in response to experimental tasks requiring involuntary orienting of attention to auditory and visual stimuli, and also systematically manipulated characteristics of the stimuli used. I found that there were no group-level differences in arousal profiles related to autism; but rather, that participants with ADHD (with or without autism) exhibited profiles of sympathetic underarousal. Given the heterogeneity in arousal profiles due to presence of ADHD in autistic participants, and due to heterogeneity apparent in the arousal literature in autism, I investigated the presence of subgroups with different arousal profiles in the autistic sample. This revealed that autistic participants could be stratified into distinct subgroups who showed tonic hyper- and hypo-arousal. These subgroups presented with different clinical profiles, such that the hyper-aroused subgroup showed worse autism symptom severity and higher rates of anxiety and sensory avoidance behaviours; while the hypo-aroused subgroup showed higher rates of hyperactive and impulsive behaviours as well as more sensory-seeking behaviours. I also found that autistic participants demonstrated intact abilities to orient to and habituate to simple auditory and visual stimuli. However, autistic participants (without ADHD) showed atypicalities in their profile of orienting to stimuli with higher complexity. These atypicalities in attention were related with social interaction symptoms of autism. Further, these atypicalities appeared to relate with presence of tonic hyperarousal. I verified the atypicalities observed in orienting to more complex visual stimuli in an independent sample of neurotypical children (n= 64) and found that neurotypical children with higher levels of subclinical autistic traits showed similar atypicalities in orienting attention to more complex stimuli. The implications of these findings within the context of the literature on arousal and attention and recommendations for future research are discussed

Investigating the effect of graphic advance organizers on the reading comprehension of secondary-age students with autism spectrum disorder

Reading comprehension interventions that target students with autism spectrum disorder (ASD) have traditionally included explicit instruction in the delivery of the intervention in order to compensate for the well-documented executive function difficulties experienced by many individuals within this population. A handful of single- case studies (n=9) within this literature have used supplementary graphic organizers (GOs), as one component of a larger treatment package, to successfully help students with ASD comprehend text more readily. The independent effect of a GO on the reading comprehension of individuals with ASD therefore remains untested. In this dissertation study, which employed single-case research methodology, five secondary students with ASD completed a reading comprehension intervention that featured graphic advance organizers (GAOs) with limited pre-training or instructional support provided by the implementer. Results indicated that some participants may be able to effectively use GAOs independently to increase their comprehension of expository texts. Findings, limitations, and implications are presented.Special Educatio

Investigating profiles of attention and arousal in Autism Spectrum Condition (ASC)

The present doctoral project aimed to investigate profiles of arousal and attention in autistic individuals and identify how atypicalities in these relate with specific clinical symptoms of autism. I recruited children and young people between the ages of 7 and 15 years who were either neurotypical (n= 31) or had autism (n= 18). I included a clinical control group of children and young people with ADHD (n= 24) as well as those who had comorbid autism and ADHD (n= 33). I collected indices of arousal and attention by measuring heart rate, brain activity (using electrophysiology) and eye movements in response to experimental tasks requiring involuntary orienting of attention to auditory and visual stimuli, and also systematically manipulated characteristics of the stimuli used. I found that there were no group-level differences in arousal profiles related to autism; but rather, that participants with ADHD (with or without autism) exhibited profiles of sympathetic underarousal. Given the heterogeneity in arousal profiles due to presence of ADHD in autistic participants, and due to heterogeneity apparent in the arousal literature in autism, I investigated the presence of subgroups with different arousal profiles in the autistic sample. This revealed that autistic participants could be stratified into distinct subgroups who showed tonic hyper- and hypo-arousal. These subgroups presented with different clinical profiles, such that the hyper-aroused subgroup showed worse autism symptom severity and higher rates of anxiety and sensory avoidance behaviours; while the hypo-aroused subgroup showed higher rates of hyperactive and impulsive behaviours as well as more sensory-seeking behaviours. I also found that autistic participants demonstrated intact abilities to orient to and habituate to simple auditory and visual stimuli. However, autistic participants (without ADHD) showed atypicalities in their profile of orienting to stimuli with higher complexity. These atypicalities in attention were related with social interaction symptoms of autism. Further, these atypicalities appeared to relate with presence of tonic hyperarousal. I verified the atypicalities observed in orienting to more complex visual stimuli in an independent sample of neurotypical children (n= 64) and found that neurotypical children with higher levels of subclinical autistic traits showed similar atypicalities in orienting attention to more complex stimuli. The implications of these findings within the context of the literature on arousal and attention and recommendations for future research are discussed

Fine Motor, Social, and Adaptive Function in Autism Spectrum Disorder

This study researched kernel-based methods and max-margin learning for largescale datasets. It advanced several theoretical and practical aspects of kernel-based and max-margin methods at the intersection with Bayesian modelling. New learning methods were proposed to avoid the curse of kernelisation while simultaneously yielding superior accuracy compared with state-of-the-art baselines

An Investigation of Gait and Language Function in Children With Autism Spectrum Disorder

This study examined gait and language function in children with ASD. Results suggested that in comparison to TD peers, children with ASD demonstrated shorter, slower steps with increased swaying. These gait disturbances also appeared to be more pronounced in children with poorer language abilities and greater ASD symptom severity

Time Distortions in Mind

Time Distortions in Mind brings together current research on temporal processing in clinical populations to elucidate the interdependence between perturbations in timing and disturbances in the mind and brain. For the student, the scientist, and the stepping-stone for further research

Time Distortions in Mind

Time Distortions in Mind brings together current research on temporal processing in clinical populations to elucidate the interdependence between perturbations in timing and disturbances in the mind and brain. For the student, the scientist, and the stepping-stone for further research. Readership: An excellent reference for the student and the scientist interested in aspects of temporal processing and abnormal psychology

Understanding intentions in animacy displays derived from human motion

As humans we live in a world where we are constantly interacting with those around us. To achieve this we must be able to successfully anticipate the intentions of others by correctly interpreting their movements. In studying how humans interpret intention from motion, we make use of simplified scenarios known as animacy displays where it has been shown that observers will attribute human-like qualities to the motion of geometric shapes (Heider and Simmel, 1944). This thesis advances the research into the attribution of social intentions by re-addressing the methods for the creation of animacy displays, leading to previously unexplored avenues of research. Where animacy displays are normally made via clever animations or mathematical algorithms, we introduce a method for creating these displays directly from video recordings of human motion, there by producing the first examples of animacy displays that are truly representative of human motion. Initially, explorative steps were taken to establish this technique as successful in creating displays that will be perceived as animate, using video recordings of simple and complex human interactions as a basis. Using a combination of tasks, including free response tasks and 10 point Likert scales, the use of this technique for stimulus production was validated. Furthermore, results showed that the viewpoint from which animacy displays are to be perceived from, comparing a side view and an overhead view, has effects on the ability to judge intentions in the displays, with a clear preference to the elevated viewpoint. Following this, the intentions of Chasing, Fighting, Flirting, Following, Guarding and Playing, thought to be generic to animacy displays, were used to create displays via this new method of stimulus production. Using a six Alternative Forced Choice (AFC) task it was shown that participants are successful at recognising these intentions, however, that the addition of ordinal depth cues, as well as cues to identity and boundaries, has little impact on increasing the ability to perceive intentions in animacy displays. Next, an experiment on the ability to judge intentions in animacy displays of brief durations was performed. Using the same 6 intentions as before, displays were created lasting 1, 5, and 10 seconds. Results of a 6 AFC task showed that observers are accurate at all durations, and furthermore, results indicate that participants are as accurate at recognising the intention in a display after 5 seconds, as after viewing longer durations of approximately 30 seconds. We then perform a comprehensive analysis of the animacy displays used, looking at the motion patterns and the kinematic properties such as speed, acceleration and distance of the agents. This analysis shows clear differences in the displays across viewpoints, and across intentions, that are indicative of the cues that participants may use to differentiate between intentions. We also perform a stepwise regression analysis to find the motion and positional predictors that best explain the variance in the behavioural data of previous experiments in this thesis. It is found that speed and acceleration cues are important for the classification of intentions in animacy displays. Finally, a study is presented that attempts to advance research into the perception of social intentions by people with Autistic Spectrum Disorders (ASDs), using video recordings of human motions and the resultant animacy displays. The intentions of Chasing, Fighting, Flirting, Following, Guarding and Playing, were again used in conjunction with a 6 AFC task. Comparing people with ASDs to an age-matched control population, results indicate that people with ASDs are poorer at judging intentions in animacy displays. In addition, results reveal an unknown deficit, not seen in the control population, in judging intentions from an elevated position in video displays. This work may be considered of interest to various groups of people with a wide range of research interests, including the perception and cognition of human motion, the attribution of social intent and “Theory of Mind”, and the surveillance of people via video techniques

Experience-based specialisation: underpinnings of communication in typical and atypical development

Autism Spectrum Disorder (ASD) is an umbrella term encompassing several neurodevelopmental conditions with complex, heterogeneous symptomatology. One way in which I addressed this complexity is by looking at a specific aspect of the phenotype to understand the contributing mechanisms. Communication difficulties are prevalent in ASD, and it has been suggested that this is a downstream effect of atypical functional specialisation in processing of both social and non-social auditory input in the brain. This thesis aimed to identify robust markers of specialisation across several methodologies and assess the links with the behavioural phenotype. First, a series of eye tracking studies was carried out with typically developing infants to identify age and language experience effects on speech perception and whether these can be linked to brain-based markers of specialisation. Then, three auditory EEG paradigms were used to measure differences in auditory perception in infants with increased familial likelihood of ASD and/or ADHD, as well as in a unique population of infants with NF1, who experience elevated rates of ASD and other neurodevelopmental conditions as part of the clinical symptomology. Through inclusion of several different participant groups, it was possible to examine whether atypical auditory processing was a specific marker of familial and/or monogenic likelihood of ASD or a general predictor of atypical development. Chapter 2 outlined the main techniques used to measure experience-dependent specialisation, including eye tracking, EEG and behavioural assessments. Chapter 3 investigated specialisation towards native speech perception though several novel paradigms in a longitudinal sample of neurotypical infants at 5, 10 and 14 months of age, as well as associations with parent and observer-rated language abilities. Chapter 4 examined the relationship between eye tracking, neural indices of vowel perception and communication skills in neurotypical infants and how these EEG-based indices may differ in a group of infants with NF1 at 5 and 10 months. Chapter 5 investigated differences in neural habituation and change detection responses across time and time-frequency analyses in 8-month-old infants with low and high familial likelihood of ASD and how these relate to language and ASD symptomology at three years. Lastly, Chapter 6 examined steady-state responses in the gamma frequency range in 14-month-old infants and whether this auditory marker can be used to differentiate between neurotypical infants and those with familial likelihood of ASD or ADHD or an NF1 diagnosis and to predict individual differences in communication skills. Taken together, the present work explored early markers of functional specialisation of auditory processing in typical and atypical development in association with parent/observer ratings of early language ability. Additionally, findings are reported from the first study of early brain development in infants with NF1. This is integral to the current understanding of pathways to ASD, with a further aim of informing clinical and research practices in rare genetic disorders