Use of an Early Life Exposure Assessment Tool (ELEAT) for autism in Portugal
Recent theoretical accounts have proposed excitation and inhibition (E/I) imbalance as a possible mechanistic, network-level hypothesis underlying neural and behavioral dysfunction across neurodevelopmental disorders, particularly autism spectrum disorder (ASD) and schizophrenia (SCZ). These two disorders share some overlap in their clinical presentation as well as convergence in their underlying genes and neurobiology. However, there are also clear points of dissociation in terms of phenotypes and putatively affected neural circuitry. We highlight emerging work from the clinical neuroscience literature examining neural correlates of E/I imbalance across children and adults with ASD and adults with both chronic and early-course SCZ. We discuss findings from diverse neuroimaging studies across distinct modalities, conducted with electroencephalography, magnetoencephalography, proton magnetic resonance spectroscopy, and functional magnetic resonance imaging, including effects observed both during task and at rest. Throughout this review, we discuss points of convergence and divergence in the ASD and SCZ literature, with a focus on disruptions in neural E/I balance. We also consider these findings in relation to predictions generated by theoretical neuroscience, particularly computational models predicting E/I imbalance across disorders. Finally, we discuss how human noninvasive neuroimaging can benefit from pharmacological challenge studies to reveal mechanisms in ASD and SCZ. Collectively, we attempt to shed light on shared and divergent neuroimaging effects across disorders with the goal of informing future research examining the mechanisms underlying the E/I imbalance hypothesis across neurodevelopmental disorders. We posit that such translational efforts are vital to facilitate development of neurobiologically informed treatment strategies across neuropsychiatric conditions.
Keywords: Autism; Computational modeling; E/I balance; Mechanism; Neuroimaging; Review; Schizophrenia.
The human amygdala is a key structure for processing emotional facial expressions, but it remains unclear what aspects of emotion are processed. We investigated this question with three different approaches: behavioural analysis of 3 amygdala lesion patients, neuroimaging of 19 healthy adults, and single-neuron recordings in 9 neurosurgical patients. The lesion patients showed a shift in behavioural sensitivity to fear, and amygdala BOLD responses were modulated by both fear and emotion ambiguity (the uncertainty that a facial expression is categorized as fearful or happy). We found two populations of neurons, one whose response correlated with increasing degree of fear, or happiness, and a second whose response primarily decreased as a linear function of emotion ambiguity. Together, our results indicate that the human amygdala processes both the degree of emotion in facial expressions and the categorical ambiguity of the emotion shown and that these two aspects of amygdala processing can be most clearly distinguished at the level of single neurons.
There is a conflicting literature on facial emotion processing in autism spectrum disorder (ASD): both typical and atypical performance have been reported, and inconsistencies in the literature may stem from different processes examined (emotion judgment, face perception, fixations) as well as differences in participant populations. Here we conducted a detailed investigation of the ability to discriminate graded emotions shown in morphs of fear-happy faces, in a well-characterized high-functioning sample of participants with ASD and matched controls. Signal detection approaches were used in the analyses, and concurrent high-resolution eye-tracking was collected. Although people with ASD had typical thresholds for categorical fear and confidence judgments, their psychometric specificity to detect emotions across the entire range of intensities was reduced. However, fixation patterns onto the stimuli were typical and could not account for the reduced specificity of emotion judgment. Together, our results argue for a subtle and specific deficit in emotion perception in ASD that, from a signal detection perspective, is best understood as a reduced specificity due to increased noise in central processing of the face stimuli.
Keywords: Ambiguity; Autism spectrum disorder; Confidence; Emotion; Eye tracking; Face morph.
Background: Phelan-McDermid syndrome (PMS) occurs as a result of a chromosomal abnormality, most frequently
deletion, in the long arm of chromosome 22, involving the SHANK3 gene. Our goal was to prospectively assess the
neurological phenotype in this syndrome.
METHODS: Twenty-nine participants were recruited from ongoing studies in PMS at the Seaver Autism Center. They
had a structured, uniform neurological examination performed by a pediatric neurologist (Y.F.). Abnormal findings
were graded as mild, moderate or severe. In addition, reports of seizures, magnetic resonance imaging (MRI) and
electroencephalograms (EEG) were reviewed. We calculated the frequency and severity of neurological
abnormalities, as well as correlations between items on the neurological examination and items on the Mullen Scales
of Early Learning and on the Vineland Adaptive Behavioral Scales (VABS).
RESULTS: Hypotonia, abnormal gait, fine motor coordination deficits, and expressive and receptive language delays
were present in all participants. Attention deficits were present in 96% (severe in 62%), and abnormal visual tracking
was present in 86%. A history of seizures was obtained in 44.8% of participants but 46.1% of these were febrile only.
Of the 13 EEG reports available for review – 69.2% were abnormal- with epileptic features present in 53.8%.
Abnormalities were present in 62.5% of MRI reports. Correlations were found between neurological abnormalities
and scores on the Mullen and Vineland Scales.
CONCLUSIONS: Neurological abnormalities are very common in PMS and are correlated with measures of cognitive
and adaptive functioning. The neurological examination may be used for clinical diagnosis, identification of PMS
phenotypes, and, in the future, for evaluation of therapy.
The cognitive phenotype of autism has been correlated with an altered balance of excitation to inhibition in the cerebral cortex, which could result from a change in the number, function, or morphology of GABA-expressing interneurons. The number of GABAergic interneuron subtypes has not been quantified in the autistic cerebral cortex. We classified interneurons into 3 subpopulations based on expression of the calcium-binding proteins parvalbumin, calbindin, or calretinin. We quantified the number of each interneuron subtype in postmortem neocortical tissue from 11 autistic cases and 10 control cases. Prefrontal Brodmann Areas (BA) BA46, BA47, and BA9 in autism and age-matched controls were analyzed by blinded researchers. We show that the number of parvalbumin+ interneurons in these 3 cortical areas-BA46, BA47, and BA9-is significantly reduced in autism compared with controls. The number of calbindin+ and calretinin+ interneurons did not differ in the cortical areas examined. Parvalbumin+ interneurons are fast-spiking cells that synchronize the activity of pyramidal cells through perisomatic and axo-axonic inhibition. The reduced number of parvalbumin+ interneurons could disrupt the balance of excitation/inhibition and alter gamma wave oscillations in the cerebral cortex of autistic subjects. These data will allow development of novel treatments specifically targeting parvalbumin interneurons.
Keywords: autism; basket cells; chandelier cells; interneurons; parvalbumin; prefrontal cortex.