Autism Pathogenesis: The Superior Colliculus

Mesenchymal Stem Cell-Induced Neuroprotection in Pediatric Neurological Diseases: Recent Update of Underlying Mechanisms and Clinical Utility

Pediatric neurological diseases refer to a group of disorders that affect the nervous system in children. These conditions can have a significant impact on a child's development, cognitive function, motor skills, and overall quality of life. Stem cell therapy is a new and innovative approach to treat various neurological conditions by repairing damaged neurons and replacing those that have been lost. Mesenchymal stem cells (MSCs) have gained significant recognition in this regard due to their ability to differentiate into different cell types. MSCs are multipotent self-replicating stem cells known to render promising results in the treatment of stroke and spinal cord injury in adults. When delivered to the foci of damage in the central nervous system, stem cells begin to differentiate into neural cells under the stimulation of paracrine factors and secrete various neurotrophic factors (NTFs) like nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) that expedite the repair process in injured neurons. In the present review, we will focus on the therapeutic benefits of the MSC-based therapies in salient pediatric neurological disorders including cerebral palsy, stroke, and autism.

Multipotent progenitors instruct ontogeny of the superior colliculus

The superior colliculus (SC) in the mammalian midbrain is essential for multisensory integration and is composed of a rich diversity of excitatory and inhibitory neurons and glia. However, the developmental principles directing the generation of SC cell-type diversity are not understood. Here, we pursued systematic cell lineage tracing in silico and in vivo, preserving full spatial information, using genetic mosaic analysis with double markers (MADM)-based clonal analysis with single-cell sequencing (MADM-CloneSeq). The analysis of clonally related cell lineages revealed that radial glial progenitors (RGPs) in SC are exceptionally multipotent. Individual resident RGPs have the capacity to produce all excitatory and inhibitory SC neuron types, even at the stage of terminal division. While individual clonal units show no pre-defined cellular composition, the establishment of appropriate relative proportions of distinct neuronal types occurs in a PTEN-dependent manner. Collectively, our findings provide an inaugural framework at the single-RGP/-cell level of the mammalian SC ontogeny.

Involvement of the Superior Colliculus in SIDS Pathogenesis

The aim of this study was to investigate the involvement of the mesencephalic superior colliculus (SC) in the pathogenetic mechanism of SIDS, a syndrome frequently ascribed to arousal failure from sleep. We analyzed the brains of 44 infants who died suddenly within the first 7 months of life, among which were 26 infants with SIDS and 18 controls. In-depth neuropathological investigations of serial sections of the midbrain showed the SC layered cytoarchitectural organization already well known in animals, as made up of seven distinct layers, but so far never highlighted in humans, albeit with some differences. In 69% of SIDS cases but never in the controls, we observed alterations of the laminar arrangement of the SC deep layers (precisely, an increased number of polygonal cells invading the superficial layers and an increased presence of intensely stained myelinated fibers). Since it has been demonstrated in experimental studies that the deep layers of the SC exert motor control including that of the head, their developmental disorder could lead to the failure of newborns who are in a prone position to resume regular breathing by moving their heads in the sleep-arousal phase. The SC anomalies highlighted here represent a new step in understanding the pathogenetic process that leads to SIDS.

Simulating developmental diversity: Impact of neural stochasticity on atypical flexibility and hierarchy

Introduction

Investigating the pathological mechanisms of developmental disorders is a challenge because the symptoms are a result of complex and dynamic factors such as neural networks, cognitive behavior, environment, and developmental learning. Recently, computational methods have started to provide a unified framework for understanding developmental disorders, enabling us to describe the interactions among those multiple factors underlying symptoms. However, this approach is still limited because most studies to date have focused on cross-sectional task performance and lacked the perspectives of developmental learning. Here, we proposed a new research method for understanding the mechanisms of the acquisition and its failures in hierarchical Bayesian representations using a state-of-the-art computational model, referred to as in silico neurodevelopment framework for atypical representation learning.

Methods

Simple simulation experiments were conducted using the proposed framework to examine whether manipulating the neural stochasticity and noise levels in external environments during the learning process can lead to the altered acquisition of hierarchical Bayesian representation and reduced flexibility.

Results

Networks with normal neural stochasticity acquired hierarchical representations that reflected the underlying probabilistic structures in the environment, including higher-order representation, and exhibited good behavioral and cognitive flexibility. When the neural stochasticity was high during learning, top-down generation using higher-order representation became atypical, although the flexibility did not differ from that of the normal stochasticity settings. However, when the neural stochasticity was low in the learning process, the networks demonstrated reduced flexibility and altered hierarchical representation. Notably, this altered acquisition of higher-order representation and flexibility was ameliorated by increasing the level of noises in external stimuli.

Discussion

These results demonstrated that the proposed method assists in modeling developmental disorders by bridging between multiple factors, such as the inherent characteristics of neural dynamics, acquisitions of hierarchical representation, flexible behavior, and external environment.

Modulation of cholinergic, GABA-ergic and glutamatergic components of superior colliculus affect REM sleep in rats

The superior colliculus (SC) is associated with visual attention, spatial navigation, decision making, escape and approach responses, some of which are important for defence and survival in rodents. SC helps in initiating and controlling saccadic eye movements and gaze during wakefulness. It is also activated during rapid eye movement (REM) sleep associated rapid eye movements (REMs). To investigate the contribution of SC in sleep-wake behaviour, we have demonstrated that manipulation of SC with scopolamine, carbachol, muscimol, picrotoxin and MK-801 decreased the amount of REM sleep. We observed that scopolamine and picrotoxin as well as muscimol decreased REM sleep frequency. MK-801 decreased percent amount of REM sleep, however, neither the frequency nor the duration/episode was affected. The cholinergic and GABA-ergic modulation of SC affecting REM sleep may be involved in REM sleep associated visuo-spatial learning and memory consolidation, which however, need to be confirmed. Furthermore, the results suggest involvement of efferent from SC in modulation of sleep-waking via the brainstem sleep regulating areas.

Valproic acid affects neurogenesis during early optic tectum development in zebrafish

The mammalian superior colliculus and its non-mammalian homolog, the optic tectum (OT), are midbrain structures that integrate multimodal sensory inputs and guide non-voluntary movements in response to prevalent stimuli. Recent studies have implicated this structure as a possible site affected in autism spectrum disorder (ASD). Interestingly, fetal exposure to valproic acid (VPA) has also been associated with an increased risk of ASD in humans and animal models. Therefore, we took the approach of determining the effects of VPA treatment on zebrafish OT development as a first step in identifying the mechanisms that allow its formation. We describe normal OT development during the first 5 days of development and show that in VPA-treated embryos, neuronal specification and neuropil formation was delayed. VPA treatment was most detrimental during the first 3 days of development and did not appear to be linked to oxidative stress. In conclusion, our work provides a foundation for research into mechanisms driving OT development, as well as the relationship between the OT, VPA, and ASD. This article has an associated First Person interview with one of the co-first authors of the paper.

Exploring the Social Environment with the Eyes: A Review of the Impact of Facial Stimuli on Saccadic Trajectories

Eye movement parameters can be highly informative regarding how people explore the social environment around them. This theoretical review examines how human faces and their features (e.g., eye-gaze direction, emotional expressions) can modulate saccadic trajectories. In the first part, studies in which facial stimuli were presented in a central location, such as during a face-to-face social interaction, are illustrated. The second part focuses on studies in which facial stimuli were placed in the periphery. Together, these works confirm the presence of an intriguing link between eye movements and facial processing, and invite consideration of saccadic trajectories as a useful (and still underused) opportunity to track ongoing mechanisms that support the social vision. Some directions for future research are also discussed.

The “Primitive Brain Dysfunction” Theory of Autism: The Superior Colliculus Role

A better understanding of the pathogenesis of autism will help clarify our conception of the complexity of normal brain development. The crucial deficit may lie in the postnatal changes that vision produces in the brainstem nuclei during early life. The superior colliculus is the primary brainstem visual center. Although difficult to examine in humans with present techniques, it is known to support behaviors essential for every vertebrate to survive, such as the ability to pay attention to relevant stimuli and to produce automatic motor responses based on sensory input. From birth to death, it acts as a brain sentinel that influences basic aspects of our behavior. It is the main brainstem hub that lies between the environment and the rest of the higher neural system, making continuous, implicit decisions about where to direct our attention. The conserved cortex-like organization of the superior colliculus in all vertebrates allows the early appearance of primitive emotionally-related behaviors essential for survival. It contains first-line specialized neurons enabling the detection and tracking of faces and movements from birth. During development, it also sends the appropriate impulses to help shape brain areas necessary for social-communicative abilities. These abilities require the analysis of numerous variables, such as the simultaneous evaluation of incoming information sustained by separate brain networks (visual, auditory and sensory-motor, social, emotional, etc.), and predictive capabilities which compare present events to previous experiences and possible responses. These critical aspects of decision-making allow us to evaluate the impact that our response or behavior may provoke in others. The purpose of this review is to show that several enigmas about the complexity of autism might be explained by disruptions of collicular and brainstem functions. The results of two separate lines of investigation: 1. the cognitive, etiologic, and pathogenic aspects of autism on one hand, and two. the functional anatomy of the colliculus on the other, are considered in order to bridge the gap between basic brain science and clinical studies and to promote future research in this unexplored area.

Single-Cell RNA Sequencing Characterizes the Molecular Heterogeneity of the Larval Zebrafish Optic Tectum

The optic tectum (OT) is a multilaminated midbrain structure that acts as the primary retinorecipient in the zebrafish brain. Homologous to the mammalian superior colliculus, the OT is responsible for the reception and integration of stimuli, followed by elicitation of salient behavioral responses. While the OT has been the focus of functional experiments for decades, less is known concerning specific cell types, microcircuitry, and their individual functions within the OT. Recent efforts have contributed substantially to the knowledge of tectal cell types; however, a comprehensive cell catalog is incomplete. Here we contribute to this growing effort by applying single-cell RNA Sequencing (scRNA-seq) to characterize the transcriptomic profiles of tectal cells labeled by the transgenic enhancer trap line y304Et(cfos:Gal4;UAS:Kaede). We sequenced 13,320 cells, a 4X cellular coverage, and identified 25 putative OT cell populations. Within those cells, we identified several mature and developing neuronal populations, as well as non-neuronal cell types including oligodendrocytes and microglia. Although most mature neurons demonstrate GABAergic activity, several glutamatergic populations are present, as well as one glycinergic population. We also conducted Gene Ontology analysis to identify enriched biological processes, and computed RNA velocity to infer current and future transcriptional cell states. Finally, we conducted in situ hybridization to validate our bioinformatic analyses and spatially map select clusters. In conclusion, the larval zebrafish OT is a complex structure containing at least 25 transcriptionally distinct cell populations. To our knowledge, this is the first time scRNA-seq has been applied to explore the OT alone and in depth.

Superior Colliculus to VTA pathway controls orienting response and influences social interaction in mice

Social behaviours characterize cooperative, mutualistic, aggressive or parental interactions that occur among conspecifics. Although the Ventral Tegmental Area (VTA) has been identified as a key substrate for social behaviours, the input and output pathways dedicated to specific aspects of conspecific interaction remain understudied. Here, in male mice, we investigated the activity and function of two distinct VTA inputs from superior colliculus (SC-VTA) and medial prefrontal cortex (mPFC-VTA). We observed that SC-VTA neurons display social interaction anticipatory calcium activity, which correlates with orienting responses towards an unfamiliar conspecific. In contrast, mPFC-VTA neuron population activity increases after initiation of the social contact. While protracted phasic stimulation of SC-VTA pathway promotes head/body movements and decreases social interaction, inhibition of this pathway increases social interaction. Here, we found that SC afferents mainly target a subpopulation of dorsolateral striatum (DLS)-projecting VTA dopamine (DA) neurons (VTA^DA-DLS). While, VTA^DA-DLS pathway stimulation decreases social interaction, VTA^DA-Nucleus Accumbens stimulation promotes it. Altogether, these data support a model by which at least two largely anatomically distinct VTA sub-circuits oppositely control distinct aspects of social behaviour.

Solié, Contestabile et al. show that the superior colliculus to ventral tegmental area (VTA) pathway encodes orienting behavior toward conspecifics, and modulates VTA dopamine neurons projecting onto dorsolateral striatum perturbing social interaction.

The Brainstem-Informed Autism Framework: Early Life Neurobehavioral Markers

Autism spectrum disorders (ASD) have long-term implications on functioning at multiple levels. In this perspective, we offer a brainstem-informed autism framework (BIAF) that traces the protracted neurobehavioral manifestations of ASD to early life brainstem dysfunctions. Early life brainstem-mediated markers involving functions of autonomic/arousal regulation, sleep-wake homeostasis, and sensorimotor integration are delineated. Their possible contributions to the early identification of susceptible infants are discussed. We suggest that the BIAF expands our multidimensional understanding of ASD by focusing on the early involvement of brainstem systems. Importantly, we propose an integrated BIAF screener that brings about the prospect of a sensitive and reliable early life diagnostic scheme for weighing the risk for ASD. The BIAF screener could provide clinicians substantial gains in the future and may carve customized interventions long before the current DSM ASD phenotype is manifested using dyadic co-regulation of brainstem-informed autism markers.

Chronic nutritional restriction of omega-3 fatty acids induces a pro-inflammatory profile during the development of the rat visual system

Modern western diets have been associated with a reduced proportion of dietary omega-3 fatty acids leading to decreased levels of DHA (docosahexaenoic acid) in the brain. Low DHA content has been associated with altered development of visual acuity in infants and also with an altered time course of synapse elimination and plasticity in subcortical visual nuclei in rodents. Microglia has an active role in normal developmental processes such as circuitry refinement and plasticity, and its activation status can be modulated by omega-3 (ω3) and omega-6 (ω6) essential fatty acids. In the present study, we investigated the impact of dietary restriction of DHA (ω3^-), through the chronic administration of a coconut-based diet as the only fat source. This dietary protocol resulted in a reduction in DHA content in the retina and superior colliculus (SC) and in a neuroinflammatory outcome during the development of the rodent visual system. The ω3^- group showed changes in microglial morphology in the retina and SC and a corresponding altered pattern of pro-inflammatory cytokine expression. Early and late fish oil protocols supplementation were able to restore DHA levels. The early supplementation also decreased neuroinflammatory markers in the visual system. The present study indicates that a chronic dietary restriction of omega-3 fatty acids and the resulting deficits in DHA content, commonly observed in Western diets, interferes with the microglial profile leading to an inflamed microenvironment which may underlie a disruption of synapse elimination, altered topographical organization, abnormal plasticity, and duration of critical periods during brain development.

[Autism spectrum symptoms in children with congenital blindness]

Autism spectrum symptoms in children with congenital blindness Abstract. Objective: Previous studies reported increased rates of autistic symptoms in children with impaired visual abilities (IV). However, the application of existing screening questionnaires for autism spectrum disorders (ASD) proved problematic, as intact visual abilities are typically required. The current study examines the general applicability of three autism-screening questionnaires in children with congenital blindness. Methods: Autistic symptoms were assessed in 15 children with congenital blindness, 15 children with ASD (without IV), and 20 typically developing controls (aged from 8 to 14 years), using the Social Communication Questionnaire, the Marburg Rating Scale for Asperger's Syndrome, and the Social Responsiveness Scale. Results: Items assessing motor, mimic/gesture-related, or joint attention deficits were identified as highly prevalent in children with congenital blindness. These children scored, in general, higher on ASD-screening questionnaires than typically developing controls but lower than sighted children with ASD. Depending on the screening questionnaire used, between 23 % and 67 % of the sample with congenital blindness reached clinical cutoff scores for ASD. SRS total score was negatively correlated to cognitive empathy and verbal IQ in those children. Conclusions: Mothers of children with congenital blindness reported increased autistic symptoms in ASD-screening questionnaires. ASD and IV might share a broad range of symptoms. Future development and validation of screening instruments specifically adapted to the needs of persons with impaired visual abilities seem necessary.

The influence of subcortical shortcuts on disordered sensory and cognitive processing

The very earliest stages of sensory processing have the potential to alter how we perceive and respond to our environment. These initial processing circuits can incorporate subcortical regions, such as the thalamus and brainstem nuclei, which mediate complex interactions with the brain's cortical processing hierarchy. These subcortical pathways, many of which we share with other animals, are not merely vestigial but appear to function as 'shortcuts' that ensure processing efficiency and preservation of vital life-preserving functions, such as harm avoidance, adaptive social interactions and efficient decision-making. Here, we propose that functional interactions between these higher-order and lower-order brain areas contribute to atypical sensory and cognitive processing that characterizes numerous neuropsychiatric disorders.

An innate brainstem self-other system involving orienting, affective responding, and polyvalent relational seeking: Some clinical implications for a "Deep Brain Reorienting" trauma psychotherapy approach

Underlying any complex relational intersubjectivity there is an inherent urge to connect, to have proximity, to engage in an experience of interpersonal contact. The hypothesis set out here is that this most basic urge to connect is dependent on circuits based in three main components: the midbrain superior colliculi (SC), the midbrain periaqueductal gray (PAG), and the mesolimbic and mesocortical dopamine systems originating in the midbrain ventral tegmental area. Firstly, there is orienting towards or away from interpersonal contact, dependent on approach and/or defensive/withdrawal areas of the SC. Secondly, there is an affective response to the contact, mediated by the PAG. Thirdly, there is an associated, affectively-loaded, seeking drive based in the mesolimbic and mesocortical dopamine systems. The neurochemical milieu of these dopaminergic systems is responsive to environmental factors, creating the possibility of multiple states of functioning with different affective valences, a polyvalent range of subjectively positive and negative experiences. The recognition of subtle tension changes in skeletal muscles when orienting to an affectively significant experience or event has clinical implications for processing of traumatic memories, including those of a relational/interpersonal nature. Sequences established at the brainstem level can underlie patterns of attachment responding that repeat over many years in different contexts. The interaction of the innate system for connection with that for alarm, through circuits based in the locus coeruleus, and that for defence, based in circuits through the PAG, can lay down deep patterns of emotional and energetic responses to relational stimuli. There may be simultaneous sequences for attachment approach and defensive aggression underlying relational styles that are so deep as to be seen as personality characteristics, for example, of borderline type. A clinical approach derived from these hypotheses, Deep Brain Reorienting, is briefly outlined as it provides a way to address the somatic residues of adverse interpersonal interactions underlying relational patterns and also the residual shock and horror of traumatic experiences. We suggest that the innate alarm system involving the SC and the locus coeruleus can generate a pre-affective shock while an affective shock can arise from excessive stimulation of the PAG. Clinically significant residues can be accessed through careful, mindful, attention to orienting-tension-affect-seeking sequences when the therapist and the client collaborate on eliciting and describing them.