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Brain : a Journal of Neurology Oct 2022Epilepsy is well-recognized as a disorder of brain networks. There is a growing body of research to identify critical nodes within dynamic epileptic networks with the... (Review)
Review
Epilepsy is well-recognized as a disorder of brain networks. There is a growing body of research to identify critical nodes within dynamic epileptic networks with the aim to target therapies that halt the onset and propagation of seizures. In parallel, intracranial neuromodulation, including deep brain stimulation and responsive neurostimulation, are well-established and expanding as therapies to reduce seizures in adults with focal-onset epilepsy; and there is emerging evidence for their efficacy in children and generalized-onset seizure disorders. The convergence of these advancing fields is driving an era of 'network-guided neuromodulation' for epilepsy. In this review, we distil the current literature on network mechanisms underlying neurostimulation for epilepsy. We discuss the modulation of key 'propagation points' in the epileptogenic network, focusing primarily on thalamic nuclei targeted in current clinical practice. These include (i) the anterior nucleus of thalamus, now a clinically approved and targeted site for open loop stimulation, and increasingly targeted for responsive neurostimulation; and (ii) the centromedian nucleus of the thalamus, a target for both deep brain stimulation and responsive neurostimulation in generalized-onset epilepsies. We discuss briefly the networks associated with other emerging neuromodulation targets, such as the pulvinar of the thalamus, piriform cortex, septal area, subthalamic nucleus, cerebellum and others. We report synergistic findings garnered from multiple modalities of investigation that have revealed structural and functional networks associated with these propagation points - including scalp and invasive EEG, and diffusion and functional MRI. We also report on intracranial recordings from implanted devices which provide us data on the dynamic networks we are aiming to modulate. Finally, we review the continuing evolution of network-guided neuromodulation for epilepsy to accelerate progress towards two translational goals: (i) to use pre-surgical network analyses to determine patient candidacy for neurostimulation for epilepsy by providing network biomarkers that predict efficacy; and (ii) to deliver precise, personalized and effective antiepileptic stimulation to prevent and arrest seizure propagation through mapping and modulation of each patients' individual epileptogenic networks.
Topics: Adult; Child; Humans; Deep Brain Stimulation; Anticonvulsants; Epilepsy; Subthalamic Nucleus; Thalamus; Epilepsies, Partial
PubMed: 35771657
DOI: 10.1093/brain/awac234 -
Nature Jan 2023In humans, traumatic social experiences can contribute to psychiatric disorders. It is suggested that social trauma impairs brain reward function such that social...
In humans, traumatic social experiences can contribute to psychiatric disorders. It is suggested that social trauma impairs brain reward function such that social behaviour is no longer rewarding, leading to severe social avoidance. In rodents, the chronic social defeat stress (CSDS) model has been used to understand the neurobiology underlying stress susceptibility versus resilience following social trauma, yet little is known regarding its impact on social reward. Here we show that, following CSDS, a subset of male and female mice, termed susceptible (SUS), avoid social interaction with non-aggressive, same-sex juvenile C57BL/6J mice and do not develop context-dependent social reward following encounters with them. Non-social stressors have no effect on social reward in either sex. Next, using whole-brain Fos mapping, in vivo Ca imaging and whole-cell recordings, we identified a population of stress/threat-responsive lateral septum neurotensin (NT) neurons that are activated by juvenile social interactions only in SUS mice, but not in resilient or unstressed control mice. Optogenetic or chemogenetic manipulation of NT neurons and their downstream connections modulates social interaction and social reward. Together, these data suggest that previously rewarding social targets are possibly perceived as social threats in SUS mice, resulting from hyperactive NT neurons that occlude social reward processing.
Topics: Animals; Female; Male; Mice; Brain; Calcium; Mice, Inbred C57BL; Neural Pathways; Neurons; Neurotensin; Optogenetics; Psychological Trauma; Reward; Septal Nuclei; Social Behavior; Stress, Psychological
PubMed: 36450985
DOI: 10.1038/s41586-022-05484-5 -
Nature Nov 2021Social memory-the ability to recognize and remember familiar conspecifics-is critical for the survival of an animal in its social group. The dorsal CA2 (dCA2) and...
Social memory-the ability to recognize and remember familiar conspecifics-is critical for the survival of an animal in its social group. The dorsal CA2 (dCA2) and ventral CA1 (vCA1) subregions of the hippocampus, and their projection targets, have important roles in social memory. However, the relevant extrahippocampal input regions remain poorly defined. Here we identify the medial septum (MS) as a dCA2 input region that is critical for social memory and reveal that modulation of the MS by serotonin (5-HT) bidirectionally controls social memory formation, thereby affecting memory stability. Novel social interactions increase activity in dCA2-projecting MS neurons and induce plasticity at glutamatergic synapses from MS neurons onto dCA2 pyramidal neurons. The activity of dCA2-projecting MS cells is enhanced by the neuromodulator 5-HT acting on 5-HT receptors. Moreover, optogenetic manipulation of median raphe 5-HT terminals in the MS bidirectionally regulates social memory stability. This work expands our understanding of the neural mechanisms by which social interactions lead to social memory and provides evidence that 5-HT has a critical role in promoting not only prosocial behaviours, but also social memory, by influencing distinct target structures.
Topics: Animals; CA2 Region, Hippocampal; Female; Glutamic Acid; Male; Memory; Mice; Neural Pathways; Neuronal Plasticity; Optogenetics; Pyramidal Cells; Receptor, Serotonin, 5-HT1B; Septal Nuclei; Serotonin; Social Behavior; Synapses
PubMed: 34616037
DOI: 10.1038/s41586-021-03956-8 -
Neuron Jun 2020Calorie-rich diets induce hyperphagia and promote obesity, although the underlying mechanisms remain poorly defined. We find that short-term high-fat-diet (HFD) feeding...
Calorie-rich diets induce hyperphagia and promote obesity, although the underlying mechanisms remain poorly defined. We find that short-term high-fat-diet (HFD) feeding of mice activates prepronociceptin (PNOC)-expressing neurons in the arcuate nucleus of the hypothalamus (ARC). PNOC neurons represent a previously unrecognized GABAergic population of ARC neurons distinct from well-defined feeding regulatory AgRP or POMC neurons. PNOC neurons arborize densely in the ARC and provide inhibitory synaptic input to nearby anorexigenic POMC neurons. Optogenetic activation of PNOC neurons in the ARC and their projections to the bed nucleus of the stria terminalis promotes feeding. Selective ablation of these cells promotes the activation of POMC neurons upon HFD exposure, reduces feeding, and protects from obesity, but it does not affect food intake or body weight under normal chow consumption. We characterize PNOC neurons as a novel ARC neuron population activated upon palatable food consumption to promote hyperphagia.
Topics: Animals; Arcuate Nucleus of Hypothalamus; Diet, High-Fat; Feeding Behavior; GABAergic Neurons; Hyperphagia; Mice; Neural Inhibition; Neurons; Obesity; Optogenetics; Pro-Opiomelanocortin; Protein Precursors; Receptors, Opioid; Septal Nuclei; Weight Gain
PubMed: 32302532
DOI: 10.1016/j.neuron.2020.03.022 -
Nature Aug 2023Fasting initiates a multitude of adaptations to allow survival. Activation of the hypothalamic-pituitary-adrenal (HPA) axis and subsequent release of glucocorticoid...
Fasting initiates a multitude of adaptations to allow survival. Activation of the hypothalamic-pituitary-adrenal (HPA) axis and subsequent release of glucocorticoid hormones is a key response that mobilizes fuel stores to meet energy demands. Despite the importance of the HPA axis response, the neural mechanisms that drive its activation during energy deficit are unknown. Here, we show that fasting-activated hypothalamic agouti-related peptide (AgRP)-expressing neurons trigger and are essential for fasting-induced HPA axis activation. AgRP neurons do so through projections to the paraventricular hypothalamus (PVH), where, in a mechanism not previously described for AgRP neurons, they presynaptically inhibit the terminals of tonically active GABAergic afferents from the bed nucleus of the stria terminalis (BNST) that otherwise restrain activity of corticotrophin-releasing hormone (CRH)-expressing neurons. This disinhibition of PVH neurons requires γ-aminobutyric acid (GABA)/GABA-B receptor signalling and potently activates the HPA axis. Notably, stimulation of the HPA axis by AgRP neurons is independent of their induction of hunger, showing that these canonical 'hunger neurons' drive many distinctly different adaptations to the fasted state. Together, our findings identify the neural basis for fasting-induced HPA axis activation and uncover a unique means by which AgRP neurons activate downstream neurons: through presynaptic inhibition of GABAergic afferents. Given the potency of this disinhibition of tonically active BNST afferents, other activators of the HPA axis, such as psychological stress, may also work by reducing BNST inhibitory tone onto PVH neurons.
Topics: Agouti-Related Protein; Corticotropin-Releasing Hormone; Fasting; GABAergic Neurons; gamma-Aminobutyric Acid; Hypothalamo-Hypophyseal System; Neurons; Paraventricular Hypothalamic Nucleus; Pituitary-Adrenal System; Presynaptic Terminals; Septal Nuclei
PubMed: 37495689
DOI: 10.1038/s41586-023-06358-0 -
Neuron Jun 2020The lateral parabrachial nucleus (lPBN) is a major target of spinal projection neurons conveying nociceptive input into supraspinal structures. However, the functional...
The lateral parabrachial nucleus (lPBN) is a major target of spinal projection neurons conveying nociceptive input into supraspinal structures. However, the functional role of distinct lPBN efferents in diverse nocifensive responses have remained largely uncharacterized. Here we show that that the lPBN is required for escape behaviors and aversive learning to noxious stimulation. In addition, we find that two populations of efferent neurons from different regions of the lPBN collateralize to distinct targets. Activation of efferent projections to the ventromedial hypothalamus (VMH) or lateral periaqueductal gray (lPAG) drives escape behaviors, whereas activation of lPBN efferents to the bed nucleus stria terminalis (BNST) or central amygdala (CEA) generates an aversive memory. Finally, we provide evidence that dynorphin-expressing neurons, which span cytoarchitecturally distinct domains of the lPBN, are required for aversive learning.
Topics: Animals; Avoidance Learning; Central Amygdaloid Nucleus; Escape Reaction; Mice; Neural Pathways; Neurons, Efferent; Nociception; Optogenetics; Pain; Parabrachial Nucleus; Periaqueductal Gray; Septal Nuclei; Ventromedial Hypothalamic Nucleus
PubMed: 32289251
DOI: 10.1016/j.neuron.2020.03.014 -
Science Advances Apr 2022The comorbidity of chronic pain and mental dysfunctions such as depression and anxiety disorders has long been recognized, but the underlying mechanisms remain poorly...
The comorbidity of chronic pain and mental dysfunctions such as depression and anxiety disorders has long been recognized, but the underlying mechanisms remain poorly understood. Here, using a mouse model of neuropathic pain, we demonstrated neuronal plasticity in the bed nucleus of the stria terminalis (BNST), which plays a critical role in chronic pain-induced maladaptive anxiety. Electrophysiology demonstrated that chronic pain increased inhibitory inputs to lateral hypothalamus (LH)-projecting BNST neurons. Chemogenetic manipulation revealed that sustained suppression of LH-projecting BNST neurons played a crucial role in chronic pain-induced anxiety. Furthermore, using a molecular genetic approach, we demonstrated that chronic pain elevated the excitability of a specific subpopulation of BNST neurons, which express cocaine- and amphetamine-regulated transcript (CART). The elevated excitability of CART-positive neurons caused the increased inhibitory inputs to LH-projecting BNST neurons, thereby inducing anxiety-like behavior. These findings shed light on how chronic pain induces psychiatric disorders, characterized by maladaptive anxiety.
Topics: Anxiety; Anxiety Disorders; Chronic Pain; Humans; Neuronal Plasticity; Septal Nuclei
PubMed: 35476439
DOI: 10.1126/sciadv.abj5586 -
Nature Sep 2021The hippocampus has previously been implicated in both cognitive and endocrine functions. We simultaneously measured electrophysiological activity from the hippocampus...
The hippocampus has previously been implicated in both cognitive and endocrine functions. We simultaneously measured electrophysiological activity from the hippocampus and interstitial glucose concentrations in the body of freely behaving rats to identify an activity pattern that may link these disparate functions of the hippocampus. Here we report that clusters of sharp wave-ripples recorded from the hippocampus reliably predicted a decrease in peripheral glucose concentrations within about 10 min. This correlation was not dependent on circadian, ultradian or meal-triggered fluctuations, could be mimicked with optogenetically induced ripples in the hippocampus (but not in the parietal cortex) and was attenuated to chance levels by pharmacogenetically suppressing activity of the lateral septum, which is the major conduit between the hippocampus and the hypothalamus. Our findings demonstrate that a function of the sharp wave-ripple is to modulate peripheral glucose homeostasis, and offer a mechanism for the link between sleep disruption and blood glucose dysregulation in type 2 diabetes.
Topics: Animals; Diabetes Mellitus, Type 2; Glucose; Hippocampus; Homeostasis; Hypothalamus; Optogenetics; Pharmacogenetics; Rats; Rats, Long-Evans; Septal Nuclei; Sleep; Time Factors
PubMed: 34381214
DOI: 10.1038/s41586-021-03811-w -
Neuropharmacology Oct 2021Our understanding of the role of the parabrachial nucleus (PBN) has evolved as technology has advanced, in part due to cell-specific studies and complex behavioral... (Review)
Review
Our understanding of the role of the parabrachial nucleus (PBN) has evolved as technology has advanced, in part due to cell-specific studies and complex behavioral assays. This is reflected in the heterogeneous neuronal populations within the PBN to the extended amygdala (EA) circuits which encompass the bed nucleus of the stria terminalis (BNST) and central amygdala (CeA) circuitry, as they differentially modulate aspects of behavior in response to diverse threat-like contexts necessary for survival. Here we review how the PBN→CeA and PBN→BNST pathways differentially modulate fear-like behavior, innate and conditioned, through unique changes in neurotransmission in response to stress-inducing contexts. Furthermore, we hypothesize how in specific instances the PBN→CeA and PBN→BNST circuits are redundant and in part intertwined with their respective reciprocal projections. By deconstructing the interoceptive and exteroceptive components of affect- and stress related behavioral paradigms, evidence suggests that the PBN→CeA circuit modulates innate response to physical stimuli and fear conditioning. Conversely, the PBN→BNST circuit modulates distress-like stress in unpredictable contexts. Thereby, the PBN provides a pathway for alarming interoceptive and exteroceptive stimuli to be processed and relayed to the EA to induce stress-relevant affect. Additionally, we provide a framework for future studies to detail the cell-type specific intricacies of PBN→EA circuits in mediating behavioral responses to threats, and the relevance of the PBN in drug-use as it relates to threat and negative reinforcement. This article is part of the special Issue on 'Neurocircuitry Modulating Drug and Alcohol Abuse'.
Topics: Affect; Amygdala; Animals; Fear; Humans; Parabrachial Nucleus; Septal Nuclei; Stress, Psychological
PubMed: 34461068
DOI: 10.1016/j.neuropharm.2021.108757