Neural Circuits Research Articles

Synaptic pruning by microglia: Lessons from genetic studies in mice.

Neural circuits are subjected to refinement throughout life. The dynamic addition and loss of synapses (pruning) are necessary for maturation of neural circuits and synaptic plasticity. Due to their phagocytic nature, microglia have been considered as the primary mediators of synaptic pruning. Synaptic pruning can strengthen an active synapse by removing excess weaker synapses during development. Inappropriate synaptic pruning can often influence a disease outcome or an injury response. This review offers a focused discussion on microglial roles in synaptic pruning, based on the evidence gathered from genetic manipulations in mice. Genetically-labeled microglia and synapses often allow assessment of their interactions in real time. Further manipulations involving synaptically-localized molecules, neuronally- or glial-derived diffusible factors, and their respective cognate receptors in microglia, provide critical evidence in support of a direct role of microglia in synaptic pruning. We discuss microglial contact-dependent "eat-me", "don't-eat-me" and "find-me" signals, as well as recently identified non-contact pruning, under the contexts of neural circuit, brain region, developmental window, and an injury or a disease state.

Encoding innate ability through a genomic bottleneck

Animals are born with extensive innate behavioral capabilities, which arise from neural circuits encoded in the genome. However, the information capacity of the genome is orders of magnitude smaller than that needed to specify the connectivity of an arbitrary brain circuit, indicating that the rules encoding circuit formation must fit through a "genomic bottleneck" as they pass from one generation to the next. Here, we formulate the problem of innate behavioral capacity in the context of artificial neural networks in terms of lossy compression of the weight matrix. We find that several standard network architectures can be compressed by several orders of magnitude, yielding pretraining performance that can approach that of the fully trained network. Interestingly, for complex but not for simple test problems, the genomic bottleneck algorithm also captures essential features of the circuit, leading to enhanced transfer learning to novel tasks and datasets. Our results suggest that compressing a neural circuit through the genomic bottleneck serves as a regularizer, enabling evolution to select simple circuits that can be readily adapted to important real-world tasks. The genomic bottleneck also suggests how innate priors can complement conventional approaches to learning in designing algorithms for AI.

Time Series Forecasting for Energy Management: Neural Circuit Policies (NCPs) vs. Long Short-Term Memory (LSTM) Networks

This paper investigates the effectiveness of Neural Circuit Policies (NCPs) compared to Long Short-Term Memory (LSTM) networks in forecasting time series data for energy production and consumption in the context of predictive maintenance. Utilizing a dataset generated from the energy production and consumption data of a Tuscan company specialized in food refrigeration, we simulate a scenario where the company employs a 60 kWh storage system and calculate the battery charge and discharge policies to assess potential cost reductions and increased self-consumption of produced energy. Our findings demonstrate that NCPs outperform LSTM networks by leveraging underlying physical models, offering superior predictive maintenance solutions for energy consumption and production.

Serotonergic modulation of swallowing in a complete fly vagus nerve connectome

How the body interacts with the brain to perform vital life functions, such as feeding, is a fundamental issue in physiology and neuroscience. Here, we use a whole-animal scanning transmission electron microscopy volume of Drosophila to map the neuronal circuits that connect the entire enteric nervous system to the brain via the insect vagus nerve at synaptic resolution. We identify a gut-brain feedback loop in which Piezo-expressing mechanosensory neurons in the esophagus convey food passage information to a cluster of six serotonergic neurons in the brain. Together with information on food value, these central serotonergic neurons enhance the activity of serotonin receptor 7-expressing motor neurons that drive swallowing. This elemental circuit architecture includes an axo-axonic synaptic connection from the glutamatergic motor neurons innervating the esophageal muscles onto the mechanosensory neurons that signal to the serotonergic neurons. Our analysis elucidates a neuromodulatory sensory-motor system in which ongoing motor activity is strengthened through serotonin upon completion of a biologically meaningful action, and it may represent an ancient form of motor learning.

Synaptotagmin 4 supports spontaneous axon sprouting after spinal cord injury.

Injuries to the central nervous system (CNS) can cause severe neurological deficits. Axonal regrowth is a fundamental process for the reconstruction of compensatory neuronal networks after injury; however, it is extremely limited in the adult mammalian CNS. In this study, we conducted a loss-of-function genetic screen in cortical neurons, combined with a web-resource-based phenotypic screen, and identified synaptotagmin 4 (Syt4) as a novel regulator of axon elongation. Silencing Syt4 in primary cultured cortical neurons inhibits neurite elongation, with changes in gene expression involved in signaling pathways related to neuronal development. In a spinal cord injury model, inhibition of Syt4 expression in cortical neurons prevented axonal sprouting of the corticospinal tract, as well as neurological recovery after injury. These results provide a novel therapeutic approach to CNS injury by modulating Syt4 function.Significance Statement Promoting axonal regrowth has been considered a promising therapeutic target for functional recovery after central nervous system injury. In the present study, we used a web-resource-based phenotypic screening followed by loss-of-functional screening for neurite elongation. We identified a novel role of synaptotagmin 4 (Syt4), a well-characterized regulator of synaptic function, in neurite elongation. In addition, Syt4 knockdown in corticospinal tract inhibited axonal regrowth and functional recovery after spinal cord injury. In this way, we provide a new screening method, which allows us to efficiently find new targets regulating CNS therapeutics.

Resting-state EEG correlates of sustained attention in healthy ageing: Cross-sectional findings from the LEISURE study

While structural and biochemical brain changes are well-documented in ageing, functional neuronal network differences, as indicated by electrophysiological markers, are less clear. Moreover, age-related changes in sustained attention and their associated electrophysiological correlates are still poorly understood. To address this, we analysed cross-sectional baseline electroencephalography (EEG) and cognitive data from the Lifestyle Intervention Study for Dementia Risk Reduction (LEISURE). Participants were 96 healthy older adults, aged 50–84. We examined resting-state EEG periodic (individual alpha frequency [IAF], aperiodic-adjusted individual alpha power [aIAP]) and aperiodic (exponent and offset) activity, and their associations with age and sustained attention. Results showed associations between older age and slower IAF, but not aIAP or global aperiodic exponent and offset. Additionally, hierarchical linear regression revealed that after controlling for demographic variables, faster IAF was associated with better Sustained Attention to Response Task performance, and mediation analysis confirmed IAF as a mediator between age and sustained attention performance. These findings indicate that IAF may be an important marker of ageing, and a slower IAF may signal diminished cognitive processing capacity for sustained attention in older adults.

Connectome-constrained networks predict neural activity across the fly visual system.

We can now measure the connectivity of every neuron in a neural circuit1-9, but we cannot measure other biological details, including the dynamical characteristics of each neuron. The degree to which measurements of connectivity alone can inform the understanding of neural computation is an open question10. Here we show that with experimental measurements of only the connectivity of a biological neural network, we can predict the neural activity underlying a specified neural computation. We constructed a model neural network with the experimentally determined connectivity for 64 cell types in the motion pathways of the fruit fly optic lobe1-5 but with unknown parameters for the single-neuron and single-synapse properties. We then optimized the values of these unknown parameters using techniques from deep learning11, to allow the model network to detect visual motion12. Our mechanistic model makes detailed, experimentally testable predictions for each neuron in the connectome. We found that model predictions agreed with experimental measurements of neural activity across 26 studies. Our work demonstrates a strategy for generating detailed hypotheses about the mechanisms of neural circuit function from connectivity measurements. We show that this strategy is more likely to be successful when neurons are sparsely connected-a universally observed feature of biological neural networks across species and brain regions.

Projections from the ventral tegmental area to zona incerta regulate fear generalization in a mouse model of PTSD

Generalized fear is a maladaptive behavior in which non-threatening stimuli elicit a fearful response. The ventral tegmental area (VTA) has been demonstrated to play important roles in fear response and fear memory generalization, but the precious neural circuit mechanism is still unclear. Here, we demonstrated that VTA-zona incerta (ZI) glutamatergic projection is involved in regulating high-intensity threatening training induced generalization and anxiety. Combining calcium signal recording and chemogentics, our work reveals that VTA glutamatergic neurons respond to closed arm entering in the model of PTSD. Inhibition of VTA glutamatergic neurons or the glutamatergic projection to ZI could both relieve fear generalization and anxiety. Together, our study proves the VTA - ZI glutamatergic circuit is involved in mediating fear generalization and anxiety, and provides a potential target for treating post-traumatic stress disorder.

Orexin improves chronic restraint stress induced depressive-like behavior via modulating the lateral septum in mice

The orexin system participates in the regulation of depression; however, its effects show significant heterogeneity, indicating the involvement of complex downstream neural circuit mechanisms. The lateral septum (LS), located downstream of the orexin system, contributes to depression. However, the effects and mechanisms underlying the orexin-mediated modulation of the LS in patients with depression remain unclear. Herein, we applied fiber photometry, chemogenetics, neuropharmacology, and in vitro electrophysiology to show that LS orexinergic afferents are sensitive to acute restraint and that chronic restraint stress (CRS) inhibits LS-projecting orexin neurons. Chemogenetic activation of LS orexinergic afferents or injection of orexin-A into the LS improved CRS-induced depression-like behavior. In vitro perfusion of orexin-A increased the action potential of somatostatin neurons in the LS. Overall, this study provides evidence that orexin improves depressive-like behavior by modulating the LS, and that this effect is probably mediated by the upregulation of LS somatostatin neurons.

Pesticides and pollinator brain: How do neonicotinoids affect the central nervous system of bees?

Neonicotinoids represent over a quarter of the global pesticide market. Research on their environmental impact has revealed their adverse effect on the cognitive functions of pollinators, in particular of bees. Cognitive impairments, mostly revealed by behavioural studies, are the phenotypic expression of an alteration in the underlying neural circuits, a matter deserving greater attention. Here, we reviewed studies on the impact of field-relevant doses of neonicotinoids on the neurophysiology and neurodevelopment of bees. In particular, we focus on their olfactory system as much knowledge has been gained on the different brain areas that participate in odour processing. Recent studies have revealed the detrimental effects of neonicotinoids at multiple levels of the olfactory system, including modulation of odorant-induced activity in olfactory sensory neurons, diminished neural responses in the antennal lobe (the first olfactory processing centre) and abnormal development of the neural connectivity within the mushroom bodies (central neuropils involved in multisensory integration, learning and memory storage, among others). Given the importance of olfactory perception for multiple aspects of bee biology, the reported disruption of the olfactory circuit, which can occur even upon exposure to sublethal doses of neonicotinoids, has severe consequences at both individual and colony levels. Moreover, the effects reported for a multimodal structure such as the mushroom bodies indicate that neonicotinoids' impact translates to other sensory domains. Assessing the impact of field-relevant doses of pesticides on bee neurophysiology is crucial for understanding how neonicotinoids influence their behaviour in ecological contexts and for defining effective and sustainable agricultural practices.

Neuroelectrophysiology-compatible electrolytic lesioning.

Lesion studies have historically been instrumental for establishing causal connections between brain and behavior. They stand to provide additional insight if integrated with multielectrode techniques common in systems neuroscience. Here, we present and test a platform for creating electrolytic lesions through chronically implanted, intracortical multielectrode probes without compromising the ability to acquire neuroelectrophysiology. A custom-built current source provides stable current and allows for controlled, repeatable lesions in awake-behaving animals. Performance of this novel lesioning technique was validated using histology from ex vivo and in vivo testing, current and voltage traces from the device, and measurements of spiking activity before and after lesioning. This electrolytic lesioning method avoids disruptive procedures, provides millimeter precision over the extent and submillimeter precision over the location of the injury, and permits electrophysiological recording of single-unit activity from the remaining neuronal population after lesioning. This technique can be used in many areas of cortex, in several species, and theoretically with any multielectrode probe. The low-cost, external lesioning device can also easily be adopted into an existing electrophysiology recording setup. This technique is expected to enable future causal investigations of the recorded neuronal population's role in neuronal circuit function, while simultaneously providing new insight into local reorganization after neuron loss.

Novel Two-Terminal Synapse/Neuron Based on an Antiferroelectric Hafnium Zirconium Oxide Device for Neuromorphic Computing.

Functionally diverse devices with artificial neuron and synapse properties are critical for neuromorphic systems. We present a two-terminal artificial leaky-integrate-fire (LIF) neuron based on 6 nm Hf0.1Zr0.9O2 (HZO) antiferroelectric (AFE) thin films and develop a synaptic device through work function (WF) engineering. LIF neuron characteristics, including integration, firing, and leakage, are achieved in W/HZO/W devices due to the accumulated polarization and spontaneous depolarization of AFE HZO films. By engineering the top electrode with asymmetric WFs, we found that Au/Ti/HZO/W devices exhibit synaptic weight plasticity, such as paired-pulse facilitation and long-term potentiation/depression, achieving >90% accuracy in digit recognition within constructed artificial neural network systems. These findings suggest that AFE HZO capacitor-based neurons and WF-engineered artificial synapses hold promise for constructing efficient spiking neuron networks and artificial neural networks, thereby advancing neuromorphic computing applications based on emerging AFE HZO devices.

Whole Nervous System Expression of Glutamate Receptors Reveals Distinct Receptor Roles in Sensorimotor Circuits.

The goal of connectomics is to reveal the links between neural circuits and behavior. Larvae of the primitive chordate Ciona are well-suited to make contributions in this area. In addition to having a described connectome, Ciona larvae have a range of readily quantified behaviors. Moreover, the small number of neurons in the larval CNS (∼180) holds the promise of a comprehensive characterization of individual neurons. We present single-neuron predictions for glutamate receptor (GlutR) expression based on in situ hybridization. Included are both ionotropic receptors (AMPA, NMDA, and kainate) and metabotropic receptors. The predicted glutamate receptor expression dataset is discussed in the context of known circuits driving behaviors such as phototaxis, mechanosensation, and looming shadow response. The predicted expression of AMPA and NMDA receptors may help resolve issues regarding the co-production of GABA and glutamate by a subset of photoreceptors. The targets of these photoreceptors in the midbrain appear to express NMDA receptors, but not AMPA receptors. This is in agreement with previous results indicating that GABA is the primary neurotransmitter from the photoreceptors evoking a swimming response through a disinhibition mechanism and that glutamate may, therefore, have only a modulatory action in this circuit. Other findings reported here are more unexpected. For example, many of the targets of glutamatergic epidermal sensory neurons (ESNs) do not express any of the ionotropic receptors, yet the ESNs themselves express metabotropic receptors. Thus, we speculate that their production of glutamate may be for communication with neighboring ESNs, rather than to their interneuron targets.

Unique Pathology in the Locus Coeruleus of Individuals with Down Syndrome.

Down syndrome (DS) is one of the most commonly occurring chromosomal conditions. Most individuals with DS develop Alzheimer's disease (AD) by 50 years of age. Recent evidence suggests that AD pathology in the locus coeruleus (LC) is an early event in sporadic AD. It is likely that the widespread axonal network of LC neurons contributes to the spread of tau pathology in the AD brain, although this has not been investigated in DS-AD. The main purpose of this study was to profile AD pathology and neuroinflammation in the LC, comparing AD and DS-AD in postmortem human tissues. We utilized immunofluorescence and semi-quantitative analyses of pTau (4 different forms), amyloid-β (Aβ), glial, and neuronal markers in the LC across 36 cases (control, DS-AD, and AD) to compare the different pathological profiles. Oligomeric tau was highly elevated in DS-AD cases compared to LOAD or EOAD cases. The distribution of staining for pT231 was elevated in DS-AD and EOAD compared to the LOAD group. The DS-AD group exhibited increased Aβ immunostaining compared to AD cases. The number of tau-bearing neurons was also significantly different between the EOAD and DS-AD cases compared to the LOAD cases. While inflammation, pTau, and Aβ are all involved in AD pathology, their contribution to disease progression may differ depending on the diagnosis. Our results suggest that DS-AD and EOAD may be more similar in pathology than LOAD. Our study highlights unique avenues to further our understanding of the mechanisms governing AD neuropathology.

Exploring the Link between Premature Ovarian Insufficiency, Insomnia and Circadian Pathways.

To establish an interaction network for genes related to premature ovarian insufficiency (POI) and insomnia, and to identify biological processes that connect POI to the physiological clock. Previously reported lists of genes associated to POI and insomnia were contrasted and their intersection was used as input on protein-protein interaction analyses. POI-associated genes were contrasted with gene expression markers for neural circadian control and enriched pathways among their shared content were dissected. The functional network generated from the intersection between POI and insomnia gene lists pointed to the central nervous system as the most relevant cellular context for this connection. After identifying POI-associated genes that play a role in neural circadian patterns, we observed the disruption of pathways related to the hypothalamic-pituitary-gonadal axis as the major genetic link between ovarian function and circadian neural circuits. These findings highlight neurological mechanisms that support the POI-insomnia interplay.

GluN3A and excitatory glycine receptors in the adult hippocampus.

The GluN3A subunit of N-methyl-D-aspartate receptors (NMDARs) plays an established role in synapse development, but its contribution to neural circuits in the adult brain is less clear. Recent work has demonstrated that in select cell populations, GluN3A assembles with GluN1 to form GluN1/GluN3A receptors that are insensitive to glutamate and instead serve as functional excitatory glycine receptors (eGlyRs). Our understanding of these eGlyRs, and how they contribute to intrinsic excitability and synaptic communication within relevant networks of the developing and the mature brain, is only beginning to be uncovered. Here, using male and female mice, we demonstrate that GluN3A subunits are enriched in the adult ventral hippocampus (VH), where they localize to synaptic and extrasynaptic sites and can assemble as functional eGlyRs on CA1 pyramidal cells. GluN3A expression was barely detectable in the adult dorsal hippocampus (DH). We also observed a high GluN2B content in the adult VH, characterized by slow NMDAR current decay kinetics and a high sensitivity to the GluN2B-containing NMDAR antagonist ifenprodil. Interestingly, the GluN2B enrichment in the adult VH was dependent on GluN3A as GluN3A deletion accelerated NMDAR decay and reduced ifenprodil sensitivity in the VH, suggesting that GluN3A expression can regulate the balance of conventional NMDAR subunit composition at synaptic sites. Lastly, we found that GluN3A knockout also enhanced both NMDAR-dependent calcium influx and NMDAR-dependent long-term potentiation in the VH. Together, these data reveal a novel role for GluN3A and eGlyRs in the control of ventral hippocampal circuits in the mature brain.Significance statement Glutamate is the brain's most abundant excitatory neurotransmitter. One of its most common receptors is the NMDA receptor (NMDAR), composed of a variety of subunits. Here, we show that an atypical NMDAR subunit, GluN3A, is enriched in the ventral hippocampus, where it forms a receptor that is no longer sensitive to glutamate. Instead, it acts as an excitatory receptor for glycine, normally an inhibitory transmitter. We show that GluN3A plays essential roles in the adult ventral hippocampus, modulating transmitter release probability, conventional NMDAR subunit composition, calcium entry, and synaptic plasticity. These findings are important as they shed light on the role of GluN3A and these newly discovered excitatory glycine receptors in the mature brain.

Sequential activation of lateral hypothalamic neuronal populations during feeding and their assembly by gamma oscillations.

Neural circuits supporting innate behaviors, such as feeding, exploration, and social interaction, intermingle in the lateral hypothalamus (LH). Although previous studies have shown that individual LH neurons change their firing relative to the baseline during one or more behaviors, the firing rate dynamics of LH populations within behavioral episodes as well as the coordination of behavior-related LH populations remain largely unknown. Here, using unsupervised graph-based clustering of LH neurons firing rate dynamics in freely behaving male mice, we identified distinct populations of cells whose activity corresponds to feeding, specific times during feeding bouts or to other innate behaviors - social interaction and novel object exploration. Feeding-related cells fired together with a higher probability during slow and fast gamma oscillations (30-60 and 60-90 Hz) than during non-rhythmic epochs. In contrast, the co-firing of neurons signaling other behaviors than feeding was overall similar between slow gamma and non-rhythmic epochs but increased during fast gamma oscillations. These results reveal a neural organization of ethological hierarchies in the LH and point to behavior-specific motivational systems, dysfunction of which may contribute to mental disorders.Significance Statement The LH is pivotal for the regulation of innate behaviors yet the organization of LH neuronal populations at fine temporal resolution within behavioral episodes remains unknown. Such knowledge would be crucial for understanding the contribution of the LH to different innate behaviors. Here, we identified distinct groups of LH cells active at specific times within feeding bouts, and additionally, populations more continuously active during feeding, exploration or social interaction. Cells from feeding-related populations coalesce during LH slow gamma oscillations, while fast gamma also promotes assembly across multiple behavioral populations. Our findings suggest that appetitive behaviors and phases of consummatory acts are supported by distinct LH populations. Dysfunction of their interaction and plasticity during network oscillations may contribute to eating disorders.

Criticality and universality in neuronal cultures during "up" and "down" states.

The brain can be seen as a self-organized dynamical system that optimizes information processing and storage capabilities. This is supported by studies across scales, from small neuronal assemblies to the whole brain, where neuronal activity exhibits features typically associated with phase transitions in statistical physics. Such a critical state is characterized by the emergence of scale-free statistics as captured, for example, by the sizes and durations of activity avalanches corresponding to a cascading process of information flow. Another phenomenon observed during sleep, under anesthesia, and in in vitro cultures, is that cortical and hippocampal neuronal networks alternate between "up" and "down" states characterized by very distinct firing rates. Previous theoretical work has been able to relate these two concepts and proposed that only up states are critical whereas down states are subcritical, also indicating that the brain spontaneously transitions between the two. Using high-speed high-resolution calcium imaging recordings of neuronal cultures, we test this hypothesis here by analyzing the neuronal avalanche statistics in populations of thousands of neurons during "up" and "down" states separately. We find that both "up" and "down" states can exhibit scale-free behavior when taking into account their intrinsic time scales. In particular, the statistical signature of "down" states is indistinguishable from those observed previously in cultures without "up" states. We show that such behavior can not be explained by network models of non-conservative leaky integrate-and-fire neurons with short-term synaptic depression, even when realistic noise levels, spatial network embeddings, and heterogeneous populations are taken into account, which instead exhibits behavior consistent with previous theoretical models. Similar differences were also observed when taking into consideration finite-size scaling effects, suggesting that the intrinsic dynamics and self-organization mechanisms of these cultures might be more complex than previously thought. In particular, our findings point to the existence of different mechanisms of neuronal communication, with different time scales, acting during either high-activity or low-activity states, potentially requiring different plasticity mechanisms.

Genetics and Epigenetic in Mental Health

Genetics and epigenetics play critical roles in mental health, offering insights into the complex interplay between biological predisposition and environmental influences in the development and progression of mental disorders. Genetic studies have identified numerous risk loci associated with conditions such as schizophrenia, bipolar disorder, and depression, highlighting the polygenic nature of these illnesses. However, the presence of genetic risk factors alone does not fully account for the variability in disease onset, severity, or response to treatment. This gap is increasingly understood through the lens of epigenetics, which involves heritable changes in gene expression that do not alter the DNA sequence itself but are influenced by environmental factors, such as stress, diet, and exposure to toxins. Epigenetic mechanisms, including DNA methylation, histone modification, and non-coding RNAs, can modulate gene activity in response to external stimuli, leading to long-lasting effects on brain function and behavior. These processes are particularly important during critical periods of brain development, where epigenetic modifications can shape neural circuits involved in emotion regulation, cognition, and stress response. Emerging research suggests that the interaction between genetic predisposition and epigenetic changes contributes to the heterogeneity observed in mental health disorders, explaining why individuals with similar genetic risks can have different outcomes. Understanding these intricate genetic and epigenetic networks is essential for developing personalized therapeutic strategies, which could revolutionize the prevention, diagnosis, and treatment of mental health conditions. Advances in this field hold the promise of identifying biomarkers for early intervention and creating targeted interventions that consider an individual’s unique genetic and epigenetic profile, ultimately improving mental health outcomes on a global scale.

Impact of Social Connectedness on Neuroinflammation and Brain Architecture in Non-Human Primates

Social connectedness plays a critical role in the mental and physical health of primates, including humans.1-3 Social isolation and loneliness have been linked to a variety of negative health outcomes, such as increased risk of neurological disorders like Alzheimer’s, anxiety, and depression.2 Despite extensive research on the effects of early isolation, there is limited understanding of the neurobiological consequences of social deprivation during adulthood. This project aims to fill this gap by exploring how changes in social connectedness influence neuroinflammation and brain architecture in non-human primates (NHPs). The study utilized a longitudinal design involving 19 adult cynomolgus macaques to examine the effects of social living conditions on neuroinflammation and brain structure. The NHPs were first housed in group living conditions, transitioned to single-living conditions, and finally returned to group living. Multimodal neuroimaging was conducted to evaluate changes in cortical thickness, myelination, and brain connectivity across these phases. Blood and cerebrospinal fluid samples were collected at multiple time points to assess levels of pro-inflammatory cytokines (TNF-a, IL-1β, IL-6) and a biomarker for neuroplasticity (BDNF).4-6 Advanced biomarker detection technology, such as SIMOA, ELISA, and Luminex, could be leveraged to achieve highly sensitive measurements of these markers.7,8 Preliminary findings indicate that social deprivation leads to decreases in cortical thickness and myelination in key brain regions associated with social cognition; however, these changes may be reversible upon reintroduction to group living.9-12 This study hypothesizes that the observed structural changes correlate with increases in neuroinflammatory markers. If confirmed, these results could highlight the critical role of social connectedness in maintaining brain health and suggest potential biomarkers for loneliness and related neuropsychiatric conditions. This research could inform interventions aimed at mitigating the negative health impacts of social isolation and improve welfare standards in NHP research, enhancing the translational relevance of such models to human health. References Holt-Lunstad J, Steptoe A. Social Isolation: An underappreciated determinant of physical health. Current Opinion in Psychology. 2022;43:232-237. doi:10.1016/j.copsyc.2021.07.012 Bzdok D, Dunbar RIM. The neurobiology of social distance. Trends in Cognitive Sciences. 2020;24(9):717-733. doi:10.1016/j.tics.2020.05.016 Cacioppo JT, Cacioppo S. The growing problem of loneliness. The Lancet. 2018;391(10119):426. doi:10.1016/s0140-6736(18)30142-9 Magalhães DM, Mampay M, Sebastião AM, Sheridan GK, Valente CA. Age-related impact of social isolation in mice: Young vs middle-aged. Neurochemistry International. 2024;174:105678. doi:10.1016/j.neuint.2024.105678 Van Bogart K, Engeland CG, Sliwinski MJ, et al. The association between loneliness and inflammation: Findings from an older adult sample. Frontiers in Behavioral Neuroscience. 2022;15. doi:10.3389/fnbeh.2021.801746 Bathina S, Das UN. Brain-derived neurotrophic factor and its clinical implications. Archives of Medical Science. 2015;6:1164-1178. doi:10.5114/aoms.2015.56342 Lasseter HC, Provost AC, Chaby LE, Daskalakis NP, Haas M, Jeromin A. Cross-platform comparison of highly sensitive immunoassay technologies for cytokine markers: Platform performance in post-traumatic stress disorder and parkinson’s disease. Cytokine: X. 2020;2(2):100027. doi:10.1016/j.cytox.2020.100027 Platchek M, Lu Q, Tran H, Xie W. Comparative analysis of multiple immunoassays for cytokine profiling in drug discovery. SLAS Discovery. 2020;25(10):1197-1213. doi:10.1177/2472555220954389 Miller JG, López V, Buthmann JL, Garcia JM, Gotlib IH. A social gradient of cortical thickness in adolescence: Relationships with neighborhood socioeconomic disadvantage, family socioeconomic status, and depressive symptoms. Biological Psychiatry Global Open Science. 2022;2(3):253-262. doi:10.1016/j.bpsgos.2022.03.005 Yang Y, Cheng Z, Tang H, et al. Neonatal maternal separation impairs prefrontal cortical myelination and cognitive functions in rats through activation of Wnt Cerebral Cortex. Published online May 13, 2016. doi:10.1093/cercor/bhw121 Sallet J, Mars RB, Noonan MP, et al. Social network size affects neural circuits in macaques. Science. 2011;334(6056):697-700. doi:10.1126/science.1210027 Makinodan M, Rosen KM, Ito S, Corfas A critical period for social experience–dependent oligodendrocyte maturation and myelination. Science. 2012;337(6100):1357-1360. doi:10.1126/science.1220845