RESUMEN
AIM: People with autism spectrum disorder (ASD) typically have deficits in the working memory (WM) system. WM is found to be an essential chain in successfully navigating in the social world. We hypothesize that brain networks for WM have an altered network integrity in ASD compared to controls. METHODS: Thirteen adolescents (one female) with autistic disorder (n = 1), Asperger's disorder (n = 7), or pervasive developmental disorder not otherwise specified (n = 5), and 13 typically developing healthy control adolescents (one female) participated in this study. Functional magnetic resonance imaging (MRI) was performed using an n-back task and in resting state. RESULTS: The analysis of the behavioral data revealed deficits in WM performance in ASD, but only when tested to the limit. Adolescents with ASD showed lower binary global efficiency in the WM network than the healthy control group with n-back and resting-state data. This correlated with diagnostic scores for total problems, reciprocity, and language. CONCLUSION: Adolescents with higher-functioning autism have difficulty with the WM system, which is typically compensated. Functional MRI markers of brain network organization in ASD are related to characteristics of autism as represented in diagnostic scores. Therefore, functional MRI provides neuronal correlates for memory difficulties in adolescents with ASD.
Asunto(s)
Trastorno del Espectro Autista/fisiopatología , Corteza Cerebral/fisiopatología , Neuroimagen Funcional/métodos , Memoria a Corto Plazo/fisiología , Red Nerviosa/fisiopatología , Adolescente , Síndrome de Asperger/diagnóstico por imagen , Síndrome de Asperger/fisiopatología , Trastorno del Espectro Autista/diagnóstico por imagen , Corteza Cerebral/diagnóstico por imagen , Niño , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Red Nerviosa/diagnóstico por imagenRESUMEN
Of the triad of symptoms found in autism spectrum disorder (ASD), that is, social impairments, communication difficulties and repetitive interests and behaviour, the social impairments are the most stable and common throughout the lifespan. They typically manifest themselves in abnormalities as reciprocal interactions and difficulties in the expression and recognition of emotions. Although peer interactions become especially important during adolescence, little is known about the mentalizing abilities of high-functioning adolescents with ASD. Here, we compared the mentalizing skills and emotion recognition abilities of 21 high-functioning adolescents with ASD and 21 matched controls. All adolescents had estimated above-average verbal intelligence levels. Spontaneous social abilities and task-related social abilities were measured using questionnaires, tasks and the Autism Diagnostic Observation Schedule. Results confirm social impairment in daily life situations in adolescents with ASD, but were not found on experimental tasks of social cognition. The use of more explicit cognitive or verbally mediating reasoning techniques and a lesser tendency of high-functioning adolescents with ASD to search for and use social information in natural environments are further discussed.
Asunto(s)
Trastorno del Espectro Autista/psicología , Cognición , Conducta Social , Adolescente , Manual Diagnóstico y Estadístico de los Trastornos Mentales , Emociones , Emoción Expresada , Femenino , Humanos , Inteligencia , Pruebas de Inteligencia , Masculino , Pruebas Neuropsicológicas , Reconocimiento en Psicología , Autoimagen , Percepción Social , Teoría de la MenteRESUMEN
Introduction: Autism spectrum disorder (ASD) is mainly characterized by functional and communication impairments as well as restrictive and repetitive behavior. The leading hypothesis for the neural basis of autism postulates globally abnormal brain connectivity, which can be assessed using functional magnetic resonance imaging (fMRI). Even in the absence of a task, the brain exhibits a high degree of functional connectivity, known as intrinsic, or resting-state, connectivity. Global default connectivity in individuals with autism versus controls is not well characterized, especially for a high-functioning young population. The aim of this study is to test whether high-functioning adolescents with ASD (HFA) have an abnormal resting-state functional connectivity. Materials and Methods: We performed spatial and temporal analyses on resting-state networks (RSNs) in 13 HFA adolescents and 13 IQ- and age-matched controls. For the spatial analysis, we used probabilistic independent component analysis (ICA) and a permutation statistical method to reveal the RSN differences between the groups. For the temporal analysis, we applied Granger causality to find differences in temporal neurodynamics. Results: Controls and HFA display very similar patterns and strengths of resting-state connectivity. We do not find any significant differences between HFA adolescents and controls in the spatial resting-state connectivity. However, in the temporal dynamics of this connectivity, we did find differences in the causal effect properties of RSNs originating in temporal and prefrontal cortices. Conclusion: The results show a difference between HFA and controls in the temporal neurodynamics from the ventral attention network to the salience-executive network: a pathway involving cognitive, executive, and emotion-related cortices. We hypothesized that this weaker dynamic pathway is due to a subtle trigger challenging the cognitive state prior to the resting state.
Asunto(s)
Trastorno del Espectro Autista , Cognición/fisiología , Emociones/fisiología , Corteza Prefrontal , Lóbulo Temporal , Adolescente , Trastorno del Espectro Autista/fisiopatología , Trastorno del Espectro Autista/psicología , Mapeo Encefálico/métodos , Conectoma/métodos , Femenino , Humanos , Imagen por Resonancia Magnética/métodos , Masculino , Red Nerviosa/diagnóstico por imagen , Red Nerviosa/fisiopatología , Corteza Prefrontal/diagnóstico por imagen , Corteza Prefrontal/fisiopatología , Análisis Espacio-Temporal , Lóbulo Temporal/diagnóstico por imagen , Lóbulo Temporal/fisiopatologíaRESUMEN
Previous studies have suggested that alterations in excitatory/inhibitory neurotransmitters might play a crucial role in autism spectrum disorder (ASD). Proton magnetic resonance spectroscopy (1H-MRS) can provide valuable information about abnormal brain metabolism and neurotransmitter concentrations. However, few 1H-MRS studies have been published on the imbalance of the two most abundant neurotransmitters in ASD: glutamate (Glu) and gamma-aminobutyric acid (GABA). Moreover, to our knowledge none of these published studies is performed with a study population consisting purely of high-functioning autism (HFA) adolescents. Selecting only individuals with HFA eliminates factors possibly related to intellectual impairment instead of ASD. This study aims to assess Glu and GABA neurotransmitter concentrations in HFA. Occipital concentrations of Glu and GABA plus macromolecules (GABA+) were obtained using 1H-MRS relative to creatine (Cr) in adolescents with HFA (n=15 and n=13 respectively) and a healthy control group (n=17). Multiple linear regression revealed significantly higher Glu/Cr and lower GABA+/Glu concentrations in the HFA group compared to the controls. These results imply that imbalanced neurotransmitter levels of excitation and inhibition are associated with HFA in adolescents.
Asunto(s)
Trastorno del Espectro Autista/metabolismo , Ácido Glutámico/metabolismo , Ácido gamma-Aminobutírico/metabolismo , Adolescente , Creatina/metabolismo , Femenino , Humanos , Espectroscopía de Resonancia Magnética/métodos , Masculino , Espectroscopía de Protones por Resonancia MagnéticaRESUMEN
Working memory is a temporary storage system under attentional control. It is believed to play a central role in online processing of complex cognitive information and may also play a role in social cognition and interpersonal interactions. Adolescents with a disorder on the autism spectrum display problems in precisely these domains. Social impairments, communication difficulties, and repetitive interests and activities are core domains of autism spectrum disorders (ASD), and executive function problems are often seen throughout the spectrum. As the main cognitive theories of ASD, including the theory of mind deficit hypotheses, weak central coherence account, and the executive dysfunction theory, still fail to explain the broad spectrum of symptoms, a new perspective on the etiology of ASD is needed. Deficits in working memory are central to many theories of psychopathology, and are generally linked to frontal-lobe dysfunction. This article will review neuropsychological and (functional) brain imaging studies on working memory in adolescents with ASD. Although still disputed, it is concluded that within the working memory system specific problems of spatial working memory are often seen in adolescents with ASD. These problems increase when information is more complex and greater demands on working memory are made. Neuroimaging studies indicate a more global working memory processing or connectivity deficiency, rather than a focused deficit in the prefrontal cortex. More research is needed to relate these working memory difficulties and neuroimaging results in ASD to the behavioral difficulties as seen in individuals with a disorder on the autism spectrum.