In Huntington's disease (HD), reduced neuronal glucose transport plays an important role. We investigated the effects of GLUT3 knock-down (KD) on the trajectory of the HD phenotype in zQ175 model mice. GLUT3 (G3) expression was reduced in heterozygous (HT) and homozygous mice. zQ175 mice when crossed with Emx1-G3KD HT mice, created conditional GLUT3-KD in cortical pyramidal neurons (CPNs), allowing examination of Q175WT/G3WT, Q175WT/G3KD, Q175HT/G3WT, and Q175HT/G3KD genotypes. Immunohistochemically, higher GLUT3 expression and number of GLUT3 positive CPNs were observed in Q175WT/G3WT compared to Q175WT/G3KD, Q175HT/G3WT, and Q175HT/G3KD, with no difference among these three groups, supporting a protective floor effect. Behaviorally, Q175HT/G3KD mice faced difficulty learning tasks and thereby performed worse than the other three groups. Electrophysiologically, the basic membrane properties of cortical pyramidal neurons (CPNs) were not affected. In contrast, in striatal medium-sized spiny neurons (MSNs) significant increases in cell membrane input resistance occurred in Q175HT/G3WT and Q175HT/G3KD compared to Q175WT/G3WT and Q175WT/G3KD, with no difference between Q175HT/G3WT and Q175HT/G3KD. Upon examination of spontaneous glutamatergic and GABAergic synaptic currents, the cumulative interevent intervals (IEI) revealed increased glutamatergic activity in GLUT3 KD, suggesting increased cortical excitability, with a concomitant compensatory increase in GABA synaptic activity. In striatal MSNs, a subtle but significant decrease in sEPSCs frequency occurred between Q175HT/G3WT and Q175HT/G3KD. The key change was an increase in frequency of sIPSCs in Q175HT/G3WT and Q175HT/G3KD compared to Q175WT/G3WT. These results underscore complex modifications of the HD phenotype among groups related to the interplay between GLUT3 KD, compensatory mechanisms, and floor effects.

3,4-dihydroxyphenethylamine, commonly known as dopamine (DA), is a neuromodulator that fine-tunes neuronal excitability, neurotransmitter release, and the effects of other neurotransmitters on postsynaptic neurons. DA, acting on D1 and D2 receptor families, is involved in myriad functions. In the striatum, it is mainly implicated in motor control, motivation, and reward mechanisms. In the cerebral cortex it participates in attention processes, working memory, long-term memory, etc. DA overproduction or deficits lead to neuronal circuit imbalance that underlies a number of neurological and psychiatric diseases, including Parkinson’s disease (PD), schizophrenia, Huntington’s disease (HD), and substance use disorders (SUDs), to name a few. DA regulates neuronal excitability by modulating ion channels, the release of excitatory (glutamate) and inhibitory (γ-aminobutyric acid, GABA) neurotransmitters, and postsynaptic interactions with glutamate and GABA receptors. Together, these pre- and postsynaptic actions of DA underlie a number of synergistic or antagonistic actions that have important implications for setting membrane potentials, improving the signal-to-noise ratio, and directing the sign of synaptic plasticity. In this review, I will first provide a historical overview of the many studies exploring DA actions in the brain, with particular focus on the striatum. Then, I will emphasize some of the contributions of our laboratory to the understanding of DA modulatory effects from an electrophysiological perspective. Finally, I will discuss the mechanistic and therapeutic implications of DA function and dysfunction.

Adaptive decision making requires agency, knowledge that actions produce particular outcomes. For well-practiced routines, agency is relinquished in favor of habit. Here, we asked how dorsomedial striatum D1+ and D2/A2A+ neurons contribute to agency and habit. We imaged calcium activity of these neurons as mice learned to lever press with agency and formed habits with overtraining. Whereas many D1+ neurons stably encoded actions throughout learning and developed encoding of reward outcomes, A2A+ neurons reorganized their encoding of actions from initial action-outcome learning to habit formation. Chemogenetic manipulations indicated that both D1+ and A2A+ neurons support action-outcome learning, but only D1+ neurons enable the use of such agency for adaptive, goal-directed decision making. These data reveal coordinated dorsomedial striatum D1+ and A2A+ function for the development of agency, cell-type specific stability and reorganization underlying agency and habit, and important insights into the neuronal circuits of how we learn and decide.

The medial prefrontal cortex (MPF) regulates emotions, stress responses, and goal-directed behaviors like attention and decision-making. However, the precise mechanisms underlying MPF function remain poorly understood, largely due to an incomplete characterization of its neural circuitry. Leveraging neuroanatomical, neurophysiological, and behavioral techniques, we present a detailed wiring diagram of the MPF, with a particular focus on the dorsal peduncular area (DP), an underexplored MPF area implicated in psychological stress, fear conditioning, anxiety, depression, and opioid addiction. Our analysis identifies the deep (DPd) and superficial (DPs) layers of the DP, together with the infralimbic area (ILA), as key components of the primary visceromotor cortex, that generate monosynaptic projections to regulate neuroendocrine, sympathetic, and parasympathetic functions in distinct, yet coordinated ways. Further, we demonstrate that the DP serves as a unique network hub for unidirectional cortical information flow, that integrates diverse cortical inputs and modulates social behavior. Based on the mesoscale connectome of entire MPF, we propose a unified MPF network model that regulates different aspects of motor actions associated with goal-directed behavior. This study provides novel insights into the complex role of the MPF in orchestrating physiological and behavioral responses to environmental stimuli in mammals.

The medial prefrontal cortex (MPF) regulates autonomic and neuroendocrine responses to stress1,2 and coordinates goal-directed behaviours such as attention, decision-making and social interactions3-8. However, the underlying mechanisms remain unclear due to incomplete circuit-level MPF characterization7. Here, using integrated neuroanatomical, physiological and behavioural approaches, we construct a comprehensive wiring diagram of the MPF, focused on the dorsal peduncular area (DP)-a poorly understood prefrontal area. We identify its deep (DPd) and superficial (DPs) layers, along with the infralimbic area, as major components of the visceromotor cortex that directly project to hypothalamic and brainstem structures to govern neuroendocrine, sympathetic and parasympathetic output. Notably, the DP functions as a network hub integrating diverse cortical inputs and modulating goal-directed behaviour through a largely unidirectional cortical information flow. On the basis of the mesoscale MPF connectome, we propose a unified network model in which distinct MPF areas orchestrate physiological and behavioural responses to internal and external stimuli.

Once believed to be the culprits of epileptogenic activity, the functional properties of balloon/giant cells (BC/GC), commonly found in some malformations of cortical development including focal cortical dysplasia type IIb (FCDIIb) and tuberous sclerosis complex (TSC), are beginning to be unraveled. These abnormal cells emerge during early brain development as a result of a hyperactive mTOR pathway and may express both neuronal and glial markers. A paradigm shift occurred when our group demonstrated that BC/GC in pediatric cases of FCDIIb and TSC are unable to generate action potentials and lack synaptic inputs. Hence, their role in epileptogenesis remained obscure. In this review, we provide a detailed characterization of abnormal non-neuronal cells including BC/GC, intermediate cells, and dysmorphic/reactive astrocytes found in FCDIIb and TSC cases, with special emphasis on electrophysiological and morphological assessments. Regardless of pathology, the electrophysiological properties of abnormal cells appear more glial-like, while others appear more neuronal-like. Their morphology also differs in terms of somatic size, shape, and dendritic elaboration. A common feature of these types of non-neuronal cells is their inability to generate action potentials. Thus, despite their distinct properties and etiologies, they share a common functional feature. We hypothesize that, although the exact role of abnormal non-neuronal cells in FCDIIb and TSC remains mysterious, it can be suggested that cells displaying more glial-like properties function in a similar way as astrocytes do, i.e., to buffer K+ ions and neurotransmitters, while those with more neuronal properties, may represent a metabolic burden due to high energy demands but inability to receive or transmit electric signals. In addition, due to the heterogeneity of these cells, a new classification scheme based on morphological, electrophysiological, and gene/protein expression in FCDIIb and TSC cases seems warranted.

Accumulating morphological and electrophysiological evidence demonstrates that abnormal brain development is a key element in the progression of Huntington's disease (HD). Mutant huntingtin affects corticogenesis, cell migration, and differentiation. Cortical changes are reminiscent of focal cortical dysplasia, a malformation of cortical development that leads to hyperexcitability and epilepsy. Striatal development also is affected by the mutation. In animal models, recent studies provide additional evidence that neuronal morphology and intrinsic and electrophysiological properties deviate from normal development. Some changes indicate delayed development of cortical pyramidal neurons, while a subtype of striatal projection neuron displays a transient accelerated maturation. However, the brain is able to compensate for early abnormalities and, during a variable latent period, brain function appears normal. Eventually, homeostatic mechanisms begin to fail, resulting in the emergence of HD symptoms. The realization that neurodevelopment in HD is abnormal offers new insights and opens new avenues for early treatment. In this review, we present a brief summary of imaging and morphological studies from human carriers of the HD mutation followed by a more in-depth examination of recent findings in genetic animal models.

Abnormalities in the mammalian target of the rapamycin (mTOR) pathway have been implicated in numerous developmental brain disorders. While the molecular and histological abnormalities have been described, less is known about alterations in membrane and synaptic excitability with chronic changes in the mTOR pathway. In the present study, we used a conditional mouse model with a deletion of the phosphatase and tensin homologue (Pten-/-, a negative regulator of mTOR) from cortical pyramidal neurons (CPNs). Whole-cell patch clamp recordings in ex vivo slices examined the intrinsic and synaptic membrane properties of layer II/III CPNs in normal mice treated with rapamycin for four weeks, and Pten-/- mice with and without chronic treatment with rapamycin. Compared with control mice, CPNs from Pten-/- mice demonstrated increased membrane capacitance and time constant in association with increased neuronal somatic size, reduced neuronal firing, and decreased frequency of spontaneous and miniature inhibitory postsynaptic currents, consistent with decreased pre-synaptic GABA release. Rapamycin treatment for four weeks prevented these changes in Pten-/- mice. CPNs from normal mice chronically treated with rapamycin, compared with CPNs from naïve mice, showed reduced capacitance and time constant, increased input resistance, and changes in inhibitory synaptic inputs, consistent with increased pre-synaptic GABA release. These results support the concept that Pten deletion results in significant changes in inhibitory inputs onto CPNs, and these alterations can be prevented with chronic rapamycin treatment. In addition, normal mice treated with rapamycin also display altered membrane and synaptic properties. These findings have potential implications for the treatment of neurological disorders associated with mTOR pathway dysfunction, such as epilepsy and autism.

Autism Spectrum Disorder (ASD) is a highly heritable condition with diverse clinical presentations. Approximately 20% of ASD's genetic susceptibility is imparted by de novo mutations of major effect, most of which cause haploinsufficiency. We mapped enhancers of two high confidence autism genes - CHD8 and SCN2A and used CRISPR-based gene activation (CRISPR-A) in hPSC-derived excitatory neurons and cerebral forebrain organoids to correct the effects of haploinsufficiency, taking advantage of the presence of a wildtype allele of each gene and endogenous gene regulation. We found that CRISPR-A induced a sustained increase in CHD8 and SCN2A expression in treated neurons and organoids, with rescue of gene expression levels and mutation-associated phenotypes, including gene expression and physiology. These data support gene activation via targeting enhancers of haploinsufficient genes, as a therapeutic intervention in ASD and other neurodevelopmental disorders.

Mammalian cells have evolved to function under Earth’s gravity, but how they respond to microgravity remains largely unknown. Neural stem cells (NSCs) are essential for the maintenance of central nervous system (CNS) functions during development and the regeneration of all CNS cell populations. Here, we examined the behavior of space (SPC)-flown NSCs as they readapted to Earth’s gravity. We found that most of these cells survived the space flight and self-renewed. Yet, some showed enhanced stress responses as well as autophagy-like behavior. To ascertain if the secretome from SPC-flown NSCs contained molecules inducing these responses, we incubated naïve, non-starved NSCs in a medium containing SPC-NSC secretome. We found a four-fold increase in stress responses. Proteomic analysis of the secretome revealed that the protein of the highest content produced by SPC-NSCs was secreted protein acidic and rich in cysteine (SPARC), which induces endoplasmic reticulum (ER) stress, resulting in the cell’s demise. These results offer novel knowledge on the response of neural cells, particularly NSCs, subjected to space microgravity. Moreover, some secreted proteins have been identified as microgravity sensing, paving a new venue for future research aiming at targeting the SPARC metabolism. Although we did not establish a direct relationship between microgravity-induced stress and SPARC as a potential marker, these results represent the first step in the identification of gravity sensing molecules as targets to be modulated and to design effective countermeasures to mitigate intracranial hypertension in astronauts using structure-based protein design.

Glucose is the primary energy source for most mammalian cells and its transport is affected by a family of facilitative glucose transporters (GLUTs) encoded by the SLC2 gene. GLUT1 and GLUT3, highly expressed isoforms in the blood–brain barrier and neuronal membranes, respectively, are associated with multiple neurodevelopmental disorders including epilepsy, dyslexia, ADHD, and autism spectrum disorder (ASD). Dietary therapies, such as the ketogenic diet, are widely accepted treatments for patients with the GLUT1 deficiency syndrome, while ameliorating certain symptoms associated with GLUT3 deficiency in animal models. A ketogenic diet, high-fat diet, and calorie/energy restriction during prenatal and postnatal stages can also alter the placental and brain GLUTs expression with long-term consequences on neurobehavior. This review focuses primarily on the role of diet/energy perturbations upon GLUT isoform-mediated emergence of neurodevelopmental and neurodegenerative disorders.

Maternal inflammatory response (MIR) during early gestation in mice induces a cascade of physiological and behavioral changes that have been associated with autism spectrum disorder (ASD). In a prior study and the current one, we find that mild MIR results in chronic systemic and neuro-inflammation, mTOR pathway activation, mild brain overgrowth followed by regionally specific volumetric changes, sensory processing dysregulation, and social and repetitive behavior abnormalities. Prior studies of rapamycin treatment in autism models have focused on chronic treatments that might be expected to alter or prevent physical brain changes. Here, we have focused on the acute effects of rapamycin to uncover novel mechanisms of dysfunction and related to mTOR pathway signaling. We find that within 2 hours, rapamycin treatment could rapidly rescue neuronal hyper-excitability, seizure susceptibility, functional network connectivity and brain community structure, and repetitive behaviors and sensory over-responsivity in adult offspring with persistent brain overgrowth. These CNS-mediated effects are also associated with alteration of the expression of several ASD-,ion channel-, and epilepsy-associated genes, in the same time frame. Our findings suggest that mTOR dysregulation in MIR offspring is a key contributor to various levels of brain dysfunction, including neuronal excitability, altered gene expression in multiple cell types, sensory functional network connectivity, and modulation of information flow. However, we demonstrate that the adult MIR brain is also amenable to rapid normalization of these functional changes which results in the rescue of both core and comorbid ASD behaviors in adult animals without requiring long-term physical alterations to the brain. Thus, restoring excitatory/inhibitory imbalance and sensory functional network modularity may be important targets for therapeutically addressing both primary sensory and social behavior phenotypes, and compensatory repetitive behavior phenotypes.

Considering the evolving and unpredictable job market, adaptability is an important skill for young adults. Such adaptability implies that schools need to teach key social competences, like communication, collaboration, or problem-solving. In this area, a gender gap has consistently been found, showing that boys display social competences less than girls. A large-scale nationwide multilab longitudinal experiment-the ProFAN project-was conducted in France among more than 10,000 vocational high-school students. Its primary goal was to develop and test an intervention promoting a range of psychological and psychosocial variables in vocational high schools, including social competences. This 2-year long, three-wave field experiment compared the effects of a cooperative learning method-the jigsaw classroom, that entails positive goal and resource interdependence-to two control conditions: one that involves cooperation with resource independence, and the other that remains business-as-usual. This article focuses on the differential development of perceived social competences of adolescent boys and girls over time, comparing the three pedagogical methods. Results of longitudinal multilevel modeling replicate the gender gap in perceived social competences and show that this gap widens with time. However, and most importantly, the analyses revealed that such widening of the gender gap was greater in the two control conditions than in the jigsaw condition, in which the evolution of boys' and girls' perceptions of social competences remained similar over time. Contributions to the understanding of the development and teaching of social competences in education settings are discussed. Social competences, like communication and collaboration, are key to adapting in today's ever-changing job market, and boys are usually found to be less skilled with social competences than girls. In a nationwide longitudinal intervention, we explored how schools can promote essential social competences in a way that compensates for this gap. In our study involving over 10,000 vocational high school students, we found that boys lag behind girls in reporting and valuing social competences and that this gap widens over time. However, implementing a jigsaw classroom-a cooperative learning method with positive goal and resource interdependence-was effective in refraining this gap from increasing. These findings emphasize that the jigsaw classroom allows all students to practice social competences and reduces the gender gap in social competences.

There is a growing consensus that brain development in Huntington's disease (HD) is abnormal, leading to the idea that HD is not only a neurodegenerative but also a neurodevelopmental disorder. Indeed, structural and functional abnormalities have been observed during brain development in both humans and animal models of HD. However, a concurrent study of cortical and striatal development in a genetic model of HD is still lacking. Here we report significant alterations of corticostriatal development in the R6/2 mouse model of juvenile HD. We examined wildtype (WT) and R6/2 mice at postnatal (P) days 7, 14, and 21. Morphological examination demonstrated early structural and cellular alterations reminiscent of malformations of cortical development, and ex vivo electrophysiological recordings of cortical pyramidal neurons (CPNs) demonstrated significant age- and genotype-dependent changes of intrinsic membrane and synaptic properties. In general, R6/2 CPNs had reduced cell membrane capacitance and increased input resistance (P7 and P14), along with reduced frequency of spontaneous excitatory and inhibitory synaptic events during early development (P7), suggesting delayed cortical maturation. This was confirmed by increased occurrence of GABA A receptor-mediated giant depolarizing potentials at P7. At P14, the rheobase of CPNs was significantly reduced, along with increased excitability. Altered membrane and synaptic properties of R6/2 CPNs recovered progressively, and by P21 they were similar to WT CPNs. In striatal medium-sized spiny neurons (MSNs), a different picture emerged. Intrinsic membrane properties were relatively normal throughout development, except for a transient increase in membrane capacitance at P14. The first alterations in MSNs synaptic activity were observed at P14 and consisted of significant deficits in GABAergic inputs, however, these also were normalized by P21. In contrast, excitatory inputs began to decrease at this age. We conclude that the developing HD brain is capable of compensating for early developmental abnormalities and that cortical alterations precede and are a main contributor of striatal changes. Addressing cortical maldevelopment could help prevent or delay disease manifestations.

Although much has been written about the beneficial effects of the Jigsaw method, little is known about how it affects students' motivation and self-regulation processes. In this study, we tested its effects on students' trajectories of autonomous mathematics motivation and academic self-regulation. We also examined whether these effects could be moderated by the students’ cooperative attitudes and initial mathematics achievement level. 4,698 students from French vocational high schools participated in the study over two years. They were divided into three groups: 1,641 were assigned to a cooperative learning condition with the Jigsaw method, 1,602 to a weakly structured cooperative learning condition, and 1,455 to a business-as-usual learning condition. Self-reported mathematics motivation, academic self-regulation, and cooperative attitudes were collected three times during the study. Overall, the multilevel growth model results indicate a general decline in students’ motivation and self-regulation, and student-reported cooperative attitudes did not moderate these effects. However, the trajectories of motivation and self-regulation differed by condition for low-achieving students. While these trajectories decreased over time amongst low-achieving students in the Jigsaw method condition and in the weakly structured cooperation condition, they were stable in the business-as-usual learning condition. These results provide a new perspective since they seem to question the implementation conditions of the Jigsaw method for low-achieving students.

The authors wish to make the following corrections to Figure 10 of this paper [...]