The neurocognitive basis of autism

Dental Conscious Sedation for the Treatment of Children With Autism Spectrum Disorder: A Narrative Review

Conscious sedation has been shown to be a reliable behavior management tool that can be used during dental treatments in children who are less cooperative with dental treatment. The purpose of this study is to review the currently available research on the use of conscious sedation during dental procedures for children diagnosed with autism spectrum disorder (ASD). A web-based search for published articles was conducted. Different electronic databases were searched, including PubMed, Google Scholar, Online Review, and the Cochrane Library database, for papers published until February 2023. Studies providing descriptive protocols for dental conscious sedation for children with ASD were included. The search strategy found two studies that met the included criteria. The use of nitrous oxide in conjunction with oral benzodiazepines was found to be effective in sedating children with ASD. This review highlights the lack of research on sedation techniques for children with ASD. Future studies are needed to determine the specific types of sedative medications, their combinations and dosages, and the best methods for conscious sedation during dental procedures for autistic children.

Cerebellar Coordination of Neuronal Communication in Cerebral Cortex

Cognitive processes involve precisely coordinated neuronal communications between multiple cerebral cortical structures in a task specific manner. Rich new evidence now implicates the cerebellum in cognitive functions. There is general agreement that cerebellar cognitive function involves interactions between the cerebellum and cerebral cortical association areas. Traditional views assume reciprocal interactions between one cerebellar and one cerebral cortical site, via closed-loop connections. We offer evidence supporting a new perspective that assigns the cerebellum the role of a coordinator of communication. We propose that the cerebellum participates in cognitive function by modulating the coherence of neuronal oscillations to optimize communications between multiple cortical structures in a task specific manner.

Implementation of a six-around-one optical probe based on diffuse light spectroscopy for study of cerebral properties in a murine mouse model of autism spectrum disorder

Light reflectance spectroscopy (LRS) is a multispectral technique, sensitive to the absorption and scattering properties of biological molecules in tissues. It is used as a noninvasive tool to extract quantitative physiological information from human tissues and organs. A near-infrared LRS based on a single optical probe was used to monitor changes in optical and hemodynamic parameters in a mouse model of autism. A murine model of autism induced by developmental exposure to valproic acid (VPA) was used. Since autism could be attributed to neuroanatomical changes, we hypothesize that these changes can be detected using the LRS because spectral properties depend on both molecular composition and structural changes. The fiber-optic probe in the setup consisted of seven small optical fibers: six fibers for illumination placed in a circular manner around a central single collection fiber. Overall, measurements demonstrate changes in diffused reflectance spectra, cerebral optical tissue properties (absorption and scattering), and chromophore levels. Furthermore, we were able to identify differences between male and female groups. Finally, the effectiveness of S-Adenosylmethionine as a drug therapy was studied and found to improve the hemodynamic outcome. For the first time, to the best of our knowledge, the LRS is utilized to study variations in brain parameters in the VPA autism model mice through an intact scalp.

Neural responses to heartbeats distinguish self from other during imagination

Imagination is an internally-generated process, where one can make oneself or other people appear as protagonists of a scene. How does the brain tag the protagonist of an imagined scene as being oneself or someone else? Crucially, during imagination, neither external stimuli nor motor feedback are available to disentangle imagining oneself from imagining someone else. Here, we test the hypothesis that an internal mechanism based on the neural monitoring of heartbeats could distinguish between self and other. 23 participants imagined themselves (from a first-person perspective) or a friend (from a third-person perspective) in various scenarios, while their brain activity was recorded with magnetoencephalography and their cardiac activity was simultaneously monitored. We measured heartbeat-evoked responses, i.e. transients of neural activity occurring in response to each heartbeat, during imagination. The amplitude of heartbeat-evoked responses differed between imagining oneself and imagining a friend, in the precuneus and posterior cingulate regions bilaterally. Effect size was modulated by the daydreaming frequency scores of participants but not by their interoceptive abilities. These results could not be accounted for by other characteristics of imagination (e.g., the ability to adopt the perspective, valence or arousal), nor by cardiac parameters (e.g., heart rate) or arousal levels (e.g. arousal ratings, pupil diameter). Heartbeat-evoked responses thus appear as a neural marker distinguishing self from other during imagination.

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Heartbeat-evoked responses differentiate self from other during imagination.

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These effects were located in the precuneus and posterior cingulate.

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The neural monitoring of the heart could be a mechanism for self/other distinction.

Do patients with high-functioning autism have similar social cognitive deficits as patients with a chronic cause of schizophrenia?

OBJECTIVE

There is substantial evidence that both patients with schizophrenia and patients with autism spectrum disorders (ASD) have impaired social cognition including theory of mind (ToM) deficits. However, it remains unclear if both verbal (explicit) and non-verbal (implicit) ToM as well as social perception are similarly affected in both disorders.

METHODS

Twenty-one patients diagnosed with schizophrenia and 11 patients diagnosed with ASD were matched one-to-one to healthy controls based on gender, age, and educational level. Social functioning was measured by Personal and Social Performance (PSP) scale. Neurocognition was measured using Brief Assessment of Cognition in Schizophrenia (BACS-DK), and four subtests from Wechsler Adult Intelligence (WAIS-IV) scale were applied to estimate IQ. The Animated Triangles Task was used to measure implicit ToM, while explicit ToM and social perception were measured by The Awareness and Social Inference Test (TASIT).

RESULTS

Patients with schizophrenia had deficits in implicit ToM and complex social perception compared to their matched controls, but no problems with explicit ToM. Surprisingly, patients with ASD solely had deficits with regard to complex social perception compared to their matched controls. The two patient groups were similar regarding estimated IQ, social functioning and years of education, but differed in age and neurocognition. When adjusting the p-values for age and neurocognitive deficits, both patients groups had similar social cognitive deficits.

CONCLUSIONS

Results imply that we compared schizophrenia patients with substantial neurocognitive deficits to a group of high-functioning patients with ASD. However, these two subgroups may have the same level of social cognitive deficits.

Optically derived metabolic and hemodynamic parameters predict hippocampal neurogenesis in the BTBR mouse model of autism

In this study, we made use of dual-wavelength laser speckle imaging (DW-LSI) to assess cerebral blood flow (CBF) in the BTBR-genetic mouse model of autism spectrum disorder, as well as control (C57Bl/6J) mice. Since the deficits in social behavior demonstrated by BTBR mice are attributed to changes in neural tissue structure and function, we postulated that these changes can be detected optically using DW-LSI. BTBR mice demonstrated reductions in both CBF and cerebral oxygen metabolism (CMRO₂ ), as suggested by studies using conventional neuroimaging technologies to reflect impaired neuronal activation and cognitive function. To validate the monitoring of CBF by DW-LSI, measurements with laser Doppler flowmetry (LDF) were also performed which confirmed the lowered CBF in the autistic-like group. Furthermore, we found in vivo cortical CBF measurements to predict the rate of hippocampal neurogenesis, measured ex vivo by the number of neurons expressing doublecortin or the cellular proliferation marker Ki-67 in the dentate gyrus, with a strong positive correlation between CBF and neurogenesis markers (Pearson, r = 0.78; 0.9, respectively). These novel findings identifying cortical CBF as a predictive parameter of hippocampal neurogenesis highlight the power and flexibility of the DW-LSI and LDF setups for studying neurogenesis trends under normal and pathological conditions.

Computational Tracking of Mental Health in Youth: Latin American Contributions to a Low-Cost and Effective Solution for Early Psychiatric Diagnosis

The early onset of mental disorders can lead to serious cognitive damage, and timely interventions are needed in order to prevent them. In patients of low socioeconomic status, as is common in Latin America, it can be hard to identify children at risk. Here, we briefly introduce the problem by reviewing the scarce epidemiological data from Latin America regarding the onset of mental disorders, and discussing the difficulties associated with early diagnosis. Then we present computational psychiatry, a new field to which we and other Latin American researchers have contributed methods particularly relevant for the quantitative investigation of psychopathologies manifested during childhood. We focus on new technologies that help to identify mental disease and provide prodromal evaluation, so as to promote early differential diagnosis and intervention. To conclude, we discuss the application of these methods to clinical and educational practice. A comprehensive and quantitative characterization of verbal behavior in children, from hospitals and laboratories to homes and schools, may lead to more effective pedagogical and medical intervention.

Correlates of Social Functioning in Autism Spectrum Disorder: The Role of Social Cognition

BACKGROUND

Individuals with autism spectrum disorder (ASD) experience marked challenges with social function by definition, but few modifiable predictors of social functioning in ASD have been identified in extant research. This study hypothesized that deficits in social cognition and motor function may help to explain poor social functioning in individuals with ASD.

METHOD

Cross-sectional data from 108 individuals with ASD and without intellectual disability ages 9 through 27.5 were used to assess the relationship between social cognition and motor function, and social functioning.

RESULTS

Results of hierarchical multiple regression analyses revealed that greater social cognition, but not motor function, was significantly associated with better social functioning when controlling for sex, age, and intelligence quotient. Post-hoc analyses revealed that, better performance on second-order false belief tasks was associated with higher levels of socially adaptive behavior and lower levels of social problems.

CONCLUSIONS

Our findings support the development and testing of interventions that target social cognition in order to improve social functioning in individuals with ASD. Interventions that teach generalizable skills to help people with ASD better understand social situations and develop competency in advanced perspective taking have the potential to create more durable change because their effects can be applied to a wide and varied set of situations and not simply a prescribed set of rehearsed situations.

Differentiating between self and others: an ALE meta-analysis of fMRI studies of self-recognition and theory of mind

The perception of self and others is a key aspect of social cognition. In order to investigate the neurobiological basis of this distinction we reviewed two classes of task that study self-awareness and awareness of others (theory of mind, ToM). A reliable task to measure self-awareness is the recognition of one's own face in contrast to the recognition of others' faces. False-belief tasks are widely used to identify neural correlates of ToM as a measure of awareness of others. We performed an activation likelihood estimation meta-analysis, using the fMRI literature on self-face recognition and false-belief tasks. The brain areas involved in performing false-belief tasks were the medial prefrontal cortex (MPFC), bilateral temporo-parietal junction, precuneus, and the bilateral middle temporal gyrus. Distinct self-face recognition regions were the right superior temporal gyrus, the right parahippocampal gyrus, the right inferior frontal gyrus/anterior cingulate cortex, and the left inferior parietal lobe. Overlapping brain areas were the superior temporal gyrus, and the more ventral parts of the MPFC. We confirmed that self-recognition in contrast to recognition of others' faces, and awareness of others involves a network that consists of separate, distinct neural pathways, but also includes overlapping regions of higher order prefrontal cortex where these processes may be combined. Insights derived from the neurobiology of disorders such as autism and schizophrenia are consistent with this notion.

Neurocognitive functioning in adolescents with autism spectrum disorder

There is a paucity of research studying comprehensive neurocognitive profiles of adolescents with higher functioning autism spectrum disorders (ASD). This study compared the neurocognitive profiles of higher functioning adolescents with ASD (n = 30, mean age 13.5) with that of typically developing adolescents (n = 30; mean age 13.7). Adolescents with ASD demonstrated a significantly higher mean Verbal Intelligence Quotient compared to the standardized mean. However, the ASD group had significantly lower scores than the control group on the subtests Auditory Attention and Response Set, Memory for Faces, Visuomotor Precision, and Design Copying. Thus, particular strengths were seen in verbal reasoning, while weaknesses were observed in auditory attention, facial recognition memory, and visuomotor functions in adolescents with ASD.

What makes the dorsomedial frontal cortex active during reading the mental states of others?

The dorsomedial frontal part of the cerebral cortex is consistently activated when people read the mental states of others, such as their beliefs, desires, and intentions, the ability known as having a theory of mind (ToM) or mentalizing. This ubiquitous finding has led many researchers to conclude that the dorsomedial frontal cortex (DMFC) constitutes a core component in mentalizing networks. Despite this, it remains unclear why the DMFC becomes active during ToM tasks. We argue that key psychological and behavioral aspects in mentalizing are closely associated with DMFC functions. These include executive inhibition, distinction between self and others, prediction under uncertainty, and perception of intentions, all of which are important for predicting others' intention and behavior. We review the literature supporting this claim, ranging in fields from developmental psychology to human neuroimaging and macaque electrophysiology. Because perceiving intentions in others' actions initiates mentalizing and forms the basis of virtually all types of social interaction, the fundamental issue in social neuroscience is to determine the aspects of physical entities that make an observer perceive that they are intentional beings and to clarify the neurobiological underpinnings of the perception of intentionality in others' actions.

Oral motor deficits in speech-impaired children with autism

Absence of communicative speech in autism has been presumed to reflect a fundamental deficit in the use of language, but at least in a subpopulation may instead stem from motor and oral motor issues. Clinical reports of disparity between receptive vs. expressive speech/language abilities reinforce this hypothesis. Our early-intervention clinic develops skills prerequisite to learning and communication, including sitting, attending, and pointing or reference, in children below 6 years of age. In a cohort of 31 children, gross and fine motor skills and activities of daily living as well as receptive and expressive speech were assessed at intake and after 6 and 10 months of intervention. Oral motor skills were evaluated separately within the first 5 months of the child's enrolment in the intervention programme and again at 10 months of intervention. Assessment used a clinician-rated structured report, normed against samples of 360 (for motor and speech skills) and 90 (for oral motor skills) typically developing children matched for age, cultural environment and socio-economic status. In the full sample, oral and other motor skills correlated with receptive and expressive language both in terms of pre-intervention measures and in terms of learning rates during the intervention. A motor-impaired group comprising a third of the sample was discriminated by an uneven profile of skills with oral motor and expressive language deficits out of proportion to the receptive language deficit. This group learnt language more slowly, and ended intervention lagging in oral motor skills. In individuals incapable of the degree of motor sequencing and timing necessary for speech movements, receptive language may outstrip expressive speech. Our data suggest that autistic motor difficulties could range from more basic skills such as pointing to more refined skills such as articulation, and need to be assessed and addressed across this entire range in each individual.

Brain mechanisms of plasticity in response to treatments for core deficits in autism

Autism spectrum disorders (ASD) are neurodevelopmental disorders characterized by social communication impairments and repetitive behaviors. Although the prevalence of ASD is estimated at 1 in 88, understanding of the neural mechanisms underlying the disorder is still emerging. Regions including the amygdala, superior temporal sulcus, orbitofrontal cortex, fusiform gyrus, medial prefrontal cortex, and insula have been implicated in social processing. Neuroimaging studies have demonstrated both anatomical and functional differences in these areas of the brain in individuals with ASD when compared to controls; however, research on the neural basis for response to treatment in ASD is limited. Results of the three studies that have examined the neural mechanisms underlying treatment response are promising; following treatment, the brains of individuals with ASD seem to "normalize," responding more similarly to those of typically developing individuals. The research in this area is in its early stages, and thus a focused effort examining the neural basis of treatment response in ASD is crucial.

Digit ratio and faculty membership: implications for the relationship between prenatal testosterone and academia

Digit ratio (length of index finger divided by length of ring finger) is an index of exposure to prenatal testosterone. Prenatal testosterone slows the growth rate of the left side of the brain while enhancing growth of the right side. Right hemisphere processing is associated with better visual-spatial and mathematical abilities, as is digit ratio. Thus, traditional sex differences in visual-spatial and mathematical abilities can be attributed to differences in exposure to prenatal testosterone, indexed by a sex dimorphic pattern in digit ratio (female=1.00, male=0.98 for UK samples). Additionally, the digit ratio is a marker for within-sex variance in visual-spatial ability. This study examines the digit ratio of an academic sample. No sex differences are found and there is a significant difference between the Science Faculty and Social Science Faculty. Social Scientists of both sexes have a ratio consistent with the male norm (0.98) whilst Scientists have a digit ratio consistent with the female norm (1.00). These results are discussed in terms of the lower normal range of male testosterone being associated with highest visual spatial abilities. Relationships with fertility and Dyslexia are also identified.

Disordered connectivity in the autistic brain: challenges for the "new psychophysiology"

In 2002, we published a paper [Brock, J., Brown, C., Boucher, J., Rippon, G., 2002. The temporal binding deficit hypothesis of autism. Development and Psychopathology 142, 209-224] highlighting the parallels between the psychological model of 'central coherence' in information processing [Frith, U., 1989. Autism: Explaining the Enigma. Blackwell, Oxford] and the neuroscience model of neural integration or 'temporal binding'. We proposed that autism is associated with abnormalities of information integration that is caused by a reduction in the connectivity between specialised local neural networks in the brain and possible overconnectivity within the isolated individual neural assemblies. The current paper updates this model, providing a summary of theoretical and empirical advances in research implicating disordered connectivity in autism. This is in the context of changes in the approach to the core psychological deficits in autism, of greater emphasis on 'interactive specialisation' and the resultant stress on early and/or low-level deficits and their cascading effects on the developing brain [Johnson, M.H., Halit, H., Grice, S.J., Karmiloff-Smith, A., 2002. Neuroimaging of typical and atypical development: a perspective from multiple levels of analysis. Development and Psychopathology 14, 521-536]. We also highlight recent developments in the measurement and modelling of connectivity, particularly in the emerging ability to track the temporal dynamics of the brain using electroencephalography (EEG) and magnetoencephalography (MEG) and to investigate the signal characteristics of this activity. This advance could be particularly pertinent in testing an emerging model of effective connectivity based on the balance between excitatory and inhibitory cortical activity [Rubenstein, J.L., Merzenich M.M., 2003. Model of autism: increased ratio of excitation/inhibition in key neural systems. Genes, Brain and Behavior 2, 255-267; Brown, C., Gruber, T., Rippon, G., Brock, J., Boucher, J., 2005. Gamma abnormalities during perception of illusory figures in autism. Cortex 41, 364-376]. Finally, we note that the consequence of this convergence of research developments not only enables a greater understanding of autism but also has implications for prevention and remediation.

Abnormal Selective Attention Normalizes P3 Amplitudes in PDD

This paper studied whether abnormal P3 amplitudes in PDD are a corollary of abnormalities in ERP components related to selective attention in visual and auditory tasks. Furthermore, this study sought to clarify possible age differences in such abnormalities. Children with PDD showed smaller P3 amplitudes than controls, but no abnormalities in selective attention. Adolescents with PDD showed abnormal selective attention, as reflected by larger auditory Processing Negativity (PN) and visual N2b, but no P3 abnormalities. Dipole localizations revealed that the locations of PN generators in subjects with PDD differed from controls. It was concluded that the abnormalities in selective attention in adolescents with PDD have a normalizing effect on P3, and possibly act as a compensatory process.

Gestalt processing in autism: failure to process perceptual relationships and the implications for contextual understanding

BACKGROUND

Deficits in autism have been characterised as a bias towards local over global processing. This paper examines whether there is a deficit in gestalt grouping in autism.

METHOD

Twenty-five low-functioning children with autism and 25 controls who were matched for chronological age and verbal mental age took part in the study.

RESULTS

The autism group utilised gestalt grouping principles (proximity, similarity, closure) significantly less than the controls. Calculating an overall index of gestalt grouping, the autism group performed at chance level. There was also a deficit in identifying certain impossible figures. This pattern was not reflected in a drawing task, in which the autism sample conformed more to gestalt grouping principles than controls (non-significantly).

CONCLUSIONS

The results are discussed in terms of a failure in autism to process inter-element relationships that would allow for the appreciation of larger perceptually coherent units that comprise of multiple elements and, consequently, context. The processes are argued to be preattentive.

Development of theory of mind and executive control

Several recent studies have demonstrated a developmental link, in the age range of 3-5 years, between the acquisition of a 'theory of mind' and self control. In this review, we consider the existence of such a link in assessing five competing theoretical hypotheses that might help us to understand the nature of this developmental advance: (1) executive control depends on theory of mind; (2) theory of mind development depends on executive control; (3) the relevant theory of mind tasks require executive control; (4) both kinds of task require the same kind of embedded conditional reasoning; (5) theory of mind and executive control involve the same brain region. We briefly describe these theoretical accounts and evaluate them in the light of existing empirical evidence. At present, only account (3) can be ruled out with some confidence.

Atypical memory performance in an autistic savant

This study explored the mechanisms underlying the hypermnesia of an autistic savant (NM) through three experiments. The first two served to assess whether absence of interference was responsible for NM's exceptional list memory. The third investigated the type of cues used in recall. Results indicated absence of retroactive interference but presence of slight proactive interference in list recall of proper names. Normal interference effects were found, however, in list recall of common nouns. Exceptional performance was also demonstrated in a missing-name task involving spatial and verbal recall cues. The findings suggest that the outstanding episodic memory presented by some savant persons with autism might be related to an abnormally high resistance to interference.