ABSTRACT
Observational learning is a powerful survival tool allowing individuals to learn about threat-predictive stimuli without directly experiencing the pairing of the predictive cue and punishment. This ability has been linked to the anterior cingulate cortex (ACC) and the basolateral amygdala (BLA). To investigate how information is encoded and transmitted through this circuit, we performed electrophysiological recordings in mice observing a demonstrator mouse undergo associative fear conditioning and found that BLA-projecting ACC (ACCâBLA) neurons preferentially encode socially derived aversive cue information. Inhibition of ACCâBLA alters real-time amygdala representation of the aversive cue during observational conditioning. Selective inhibition of the ACCâBLA projection impaired acquisition, but not expression, of observational fear conditioning. We show that information derived from observation about the aversive value of the cue is transmitted from the ACC to the BLA and that this routing of information is critically instructive for observational fear conditioning. VIDEO ABSTRACT.
Subject(s)
Basolateral Nuclear Complex/physiology , Cerebral Cortex/physiology , Learning/physiology , Amygdala/physiology , Animals , Behavior, Animal , Conditioning, Classical , Electrophysiological Phenomena , Fear , Light , Male , Memory/physiology , Mice , Neural Pathways/physiology , Neurons/physiology , Optogenetics , Prefrontal Cortex/physiologyABSTRACT
The ability to associate temporally segregated information and assign positive or negative valence to environmental cues is paramount for survival. Studies have shown that different projections from the basolateral amygdala (BLA) are potentiated following reward or punishment learning1-7. However, we do not yet understand how valence-specific information is routed to the BLA neurons with the appropriate downstream projections, nor do we understand how to reconcile the sub-second timescales of synaptic plasticity8-11 with the longer timescales separating the predictive cues from their outcomes. Here we demonstrate that neurotensin (NT)-expressing neurons in the paraventricular nucleus of the thalamus (PVT) projecting to the BLA (PVT-BLA:NT) mediate valence assignment by exerting NT concentration-dependent modulation in BLA during associative learning. We found that optogenetic activation of the PVT-BLA:NT projection promotes reward learning, whereas PVT-BLA projection-specific knockout of the NT gene (Nts) augments punishment learning. Using genetically encoded calcium and NT sensors, we further revealed that both calcium dynamics within the PVT-BLA:NT projection and NT concentrations in the BLA are enhanced after reward learning and reduced after punishment learning. Finally, we showed that CRISPR-mediated knockout of the Nts gene in the PVT-BLA pathway blunts BLA neural dynamics and attenuates the preference for active behavioural strategies to reward and punishment predictive cues. In sum, we have identified NT as a neuropeptide that signals valence in the BLA, and showed that NT is a critical neuromodulator that orchestrates positive and negative valence assignment in amygdala neurons by extending valence-specific plasticity to behaviourally relevant timescales.
Subject(s)
Basolateral Nuclear Complex , Learning , Neural Pathways , Neurotensin , Punishment , Reward , Basolateral Nuclear Complex/cytology , Basolateral Nuclear Complex/physiology , Calcium/metabolism , Cues , Neuronal Plasticity , Neurotensin/metabolism , Optogenetics , Thalamic Nuclei/cytology , Thalamic Nuclei/physiologyABSTRACT
Dopamine modulates medial prefrontal cortex (mPFC) activity to mediate diverse behavioural functions1,2; however, the precise circuit computations remain unknown. One potentially unifying model by which dopamine may underlie a diversity of functions is by modulating the signal-to-noise ratio in subpopulations of mPFC neurons3-6, where neural activity conveying sensory information (signal) is amplified relative to spontaneous firing (noise). Here we demonstrate that dopamine increases the signal-to-noise ratio of responses to aversive stimuli in mPFC neurons projecting to the dorsal periaqueductal grey (dPAG). Using an electrochemical approach, we reveal the precise time course of pinch-evoked dopamine release in the mPFC, and show that mPFC dopamine biases behavioural responses to aversive stimuli. Activation of mPFC-dPAG neurons is sufficient to drive place avoidance and defensive behaviours. mPFC-dPAG neurons display robust shock-induced excitations, as visualized by single-cell, projection-defined microendoscopic calcium imaging. Finally, photostimulation of dopamine terminals in the mPFC reveals an increase in the signal-to-noise ratio in mPFC-dPAG responses to aversive stimuli. Together, these data highlight how dopamine in the mPFC can selectively route sensory information to specific downstream circuits, representing a potential circuit mechanism for valence processing.
Subject(s)
Avoidance Learning/physiology , Dopamine/metabolism , Periaqueductal Gray/cytology , Periaqueductal Gray/physiology , Prefrontal Cortex/cytology , Prefrontal Cortex/physiology , Animals , Calcium Signaling , Female , Male , Mice , Mice, Inbred C57BL , Neural Pathways , Rats , Rats, Long-Evans , Signal-To-Noise Ratio , Single-Cell Analysis , TailABSTRACT
The ability to differentiate stimuli predicting positive or negative outcomes is critical for survival, and perturbations of emotional processing underlie many psychiatric disease states. Synaptic plasticity in the basolateral amygdala complex (BLA) mediates the acquisition of associative memories, both positive and negative. Different populations of BLA neurons may encode fearful or rewarding associations, but the identifying features of these populations and the synaptic mechanisms of differentiating positive and negative emotional valence have remained unknown. Here we show that BLA neurons projecting to the nucleus accumbens (NAc projectors) or the centromedial amygdala (CeM projectors) undergo opposing synaptic changes following fear or reward conditioning. We find that photostimulation of NAc projectors supports positive reinforcement while photostimulation of CeM projectors mediates negative reinforcement. Photoinhibition of CeM projectors impairs fear conditioning and enhances reward conditioning. We characterize these functionally distinct neuronal populations by comparing their electrophysiological, morphological and genetic features. Overall, we provide a mechanistic explanation for the representation of positive and negative associations within the amygdala.
Subject(s)
Amygdala/cytology , Amygdala/physiology , Fear/physiology , Neural Pathways , Neurons/physiology , Reward , Animals , Conditioning, Classical , Fear/psychology , Gene Expression Profiling , Long-Term Potentiation , Male , Mice , Mice, Inbred C57BL , Motivation , Nucleus Accumbens/cytology , Nucleus Accumbens/physiology , Nucleus Accumbens/radiation effects , Reinforcement, Psychology , Transcription, GeneticABSTRACT
Single administration of low-dose ketamine has both acute and sustained anti-depressant effects. Sustained effect is associated with restoration of glutamatergic synapses in medial prefrontal cortic (mFPC) neurons. Ketamine induced profound changes in a number of molecular pathways in a mouse model for chronic stress. Cell-cell communication analyses predicted that planar-cell-polarity (PCP) signaling was decreased after chronic administration of corticosterone but increased following ketamine administration in most of the excitatory neurons. Similar decrease of PCP signaling in excitatory neurons was predicted in dorsolateral prefrontal cortical (dl-PFC) neurons of patients with major depressive disorder (MDD). We showed that the basolateral amygdala (BLA)-projecting infralimbic prefrontal cortex (IL PFC) neurons regulate immobility time in the tail suspension test and food consumption. Conditionally knocking out Celsr2 and Celsr3 or Prickle2 in the BLA-projecting IL PFC neurons abolished ketamine-induced synapse restoration and behavioral remission. Therefore, PCP proteins in IL PFC-BLA neurons mediate synapse restoration induced by of low-dose ketamine.
Subject(s)
Disease Models, Animal , Ketamine , Neurons , Prefrontal Cortex , Synapses , Animals , Ketamine/pharmacology , Prefrontal Cortex/metabolism , Prefrontal Cortex/drug effects , Synapses/drug effects , Synapses/metabolism , Neurons/metabolism , Neurons/drug effects , Mice , Male , Humans , Cell Polarity/drug effects , Depressive Disorder, Major/metabolism , Depressive Disorder, Major/drug therapy , Mice, Knockout , Stress, Psychological , Corticosterone , Basolateral Nuclear Complex/metabolism , Basolateral Nuclear Complex/drug effects , Mice, Inbred C57BL , LIM Domain Proteins/metabolism , LIM Domain Proteins/genetics , Glutamic Acid/metabolism , Antidepressive Agents/pharmacologyABSTRACT
The insular cortex, or insula, is a large brain region involved in the detection of thirst and the regulation of water intake. However, our understanding of the topographical, circuit, and molecular mechanisms for controlling water intake within the insula remains parcellated. We found that type-1 cannabinoid (CB1) receptors in the insular cortex cells participate in the regulation of water intake and deconstructed the circuit mechanisms of this control. Topographically, we revealed that the activity of excitatory neurons in both the anterior insula (aIC) and posterior insula (pIC) increases in response to water intake, yet only the specific removal of CB1 receptors in the pIC decreases water intake. Interestingly, we found that CB1 receptors are highly expressed in insula projections to the basolateral amygdala (BLA), while undetectable in the neighboring central part of the amygdala. Thus, we recorded the neurons of the aIC or pIC targeting the BLA (aIC-BLA and pIC-BLA) and found that they decreased their activity upon water drinking. Additionally, chemogenetic activation of pIC-BLA projection neurons decreased water intake. Finally, we uncovered CB1-dependent short-term synaptic plasticity (depolarization-induced suppression of excitation [DSE]) selectively in pIC-BLA, compared with aIC-BLA synapses. Altogether, our results support a model where CB1 receptor signaling promotes water intake by inhibiting the pIC-BLA pathway, thereby contributing to the fine top-down control of thirst responses.
Subject(s)
Drinking , Insular Cortex , Receptor, Cannabinoid, CB1 , Animals , Receptor, Cannabinoid, CB1/metabolism , Male , Mice , Drinking/physiology , Insular Cortex/physiology , Cannabinoids/metabolism , Cannabinoids/pharmacology , Neurons/physiology , Neurons/metabolism , Mice, Inbred C57BL , Neuronal Plasticity/physiology , Basolateral Nuclear Complex/physiology , Basolateral Nuclear Complex/metabolismABSTRACT
RATIONALE: The basolateral amygdala (BLA) and medial geniculate nucleus of the thalamus (MGN) have both been shown to be necessary for the formation of associative learning. While the role that the BLA plays in this process has long been emphasized, the MGN has been less well-studied and surrounded by debate regarding whether the relay of sensory information is active or passive. OBJECTIVES: We seek to understand the role the MGN has within the thalamoamgydala circuit in the formation of associative learning. METHODS: Here, we use optogenetics and in vivo electrophysiological recordings to dissect the MGN-BLA circuit and explore the specific subpopulations for evidence of learning and synthesis of information that could impact downstream BLA encoding. We employ various machine learning techniques to investigate function within neural subpopulations. We introduce a novel method to investigate tonic changes across trial-by-trial structure, which offers an alternative approach to traditional trial-averaging techniques. RESULTS: We find that the MGN appears to encode arousal but not valence, unlike the BLA which encodes for both. We find that the MGN and the BLA appear to react differently to expected and unexpected outcomes; the BLA biased responses toward reward prediction error and the MGN focused on anticipated punishment. We uncover evidence of tonic changes by visualizing changes across trials during inter-trial intervals (baseline epochs) for a subset of cells. CONCLUSION: We conclude that the MGN-BLA projector population acts as both filter and transferer of information by relaying information about the salience of cues to the amygdala, but these signals are not valence-specified.
Subject(s)
Amygdala , Basolateral Nuclear Complex , Amygdala/physiology , Thalamus , Basolateral Nuclear Complex/physiology , Conditioning, Classical/physiology , ArousalABSTRACT
The hypothesis that reversed, excitatory GABA may be involved in various brain pathologies, including epileptogenesis, is appealing but controversial because of the technical difficulty of probing endogenous GABAergic synaptic function in vivo. We overcome this challenge by non-invasive extracellular recording of neuronal firing responses to optogenetically evoked and spontaneously occurring inhibitory perisomatic GABAergic field potentials, generated by individual parvalbumin interneurons on their target pyramidal cells. Our direct probing of GABAergic transmission suggests a rather anecdotal participation of excitatory GABA in two specific models of epileptogenesis in the mouse CA3 circuit in vivo, even though this does not preclude its expression in other brain areas or pathological conditions. Our approach allows the detection of distinct alterations of inhibition during spontaneous activity in vivo, with high sensitivity. It represents a promising tool for the investigation of excitatory GABA in different pathological conditions that may affect the hippocampal circuit.
Subject(s)
CA3 Region, Hippocampal/physiology , GABAergic Neurons/physiology , Synaptic Transmission/physiology , Action Potentials/physiology , Acute Disease , Animals , Disease Models, Animal , Gene Silencing , Inhibitory Postsynaptic Potentials/physiology , Interneurons/physiology , Kainic Acid , Male , Mice , Optogenetics , Parvalbumins/metabolism , Pyramidal Cells/physiology , Seizures/physiopathology , Time FactorsABSTRACT
The serotonergic system of the central nervous system (CNS) has been implicated in a broad range of physiological functions and behaviors, such as cognition, mood, social interaction, sexual behavior, feeding behavior, sleep-wake cycle and thermoregulation. Serotonin (5-hydroxytryptamine, 5-HT) establishes a plethora of interactions with neurochemical systems in the CNS via its numerous 5-HT receptors and autoreceptors. The facets of this control are multiple if we consider the molecular actors playing a role in the autoregulation of 5-HT neuron activity including the 5-HT1A, 5-HT1B, 5-HT1D, 5-HT2B, 5-HT7 receptors as well as the serotonin transporter. Moreover, extrinsic loops involving other neurotransmitters giving the other 5-HT receptors the possibility to impact 5-HT neuron activity. Grasping the complexity of these interactions is essential for the development of a variety of therapeutic strategies for cognitive defects and mood disorders. Presently we can illustrate the plurality of the mechanisms and only conceive that these 5-HT controls are likely not uniform in terms of regional and neuronal distribution. Our understanding of the specific expression patterns of these receptors on specific circuits and neuronal populations are progressing and will expand our comprehension of the function and interaction of these receptors with other chemical systems. Thus, the development of new approaches profiling the expression of 5-HT receptors and autoreceptors should reveal additional facets of the 5-HT controls of neurochemical systems in the CNS.
Subject(s)
Serotonin/metabolism , Autoreceptors , Humans , Neurotransmitter Agents , Receptors, SerotoninABSTRACT
Intracellular calcium signaling underlies the astroglial control of synaptic transmission and plasticity. Mitochondria-endoplasmic reticulum contacts (MERCs) are key determinants of calcium dynamics, but their functional impact on astroglial regulation of brain information processing is unexplored. We found that the activation of astrocyte mitochondrial-associated type-1 cannabinoid (mtCB1) receptors determines MERC-dependent intracellular calcium signaling and synaptic integration. The stimulation of mtCB1 receptors promotes calcium transfer from the endoplasmic reticulum to mitochondria through a specific molecular cascade, involving the mitochondrial calcium uniporter (MCU). Physiologically, mtCB1-dependent mitochondrial calcium uptake determines the dynamics of cytosolic calcium events in astrocytes upon endocannabinoid mobilization. Accordingly, electrophysiological recordings in hippocampal slices showed that conditional genetic exclusion of mtCB1 receptors or dominant-negative MCU expression in astrocytes blocks lateral synaptic potentiation, through which astrocytes integrate the activity of distant synapses. Altogether, these data reveal an endocannabinoid link between astroglial MERCs and the regulation of brain network functions.
Subject(s)
Astrocytes/metabolism , Calcium/metabolism , Cannabinoids/metabolism , Endoplasmic Reticulum/metabolism , Mitochondria/metabolism , Receptors, Cannabinoid/physiology , Synapses/physiology , Animals , Astrocytes/cytology , Calcium Channels/physiology , Calcium Signaling , Cells, Cultured , Hippocampus/metabolism , Homeostasis , Mice , Mice, Inbred C57BL , Neuronal Plasticity , Synaptic TransmissionABSTRACT
The serotonin (5-HT) system is the target of multiple anxiolytics, including Buspirone, which is a partial agonist of the serotonin 1A receptor (5-HT1A). Similarly, ligands of the serotonin 2A receptor (5-HT2A) were shown to alter anxiety level. The 5-HT1A and 2A receptors are widely expressed across the brain, but the target region(s) underlying the influence of those receptors on anxiety remain unknown. Interestingly, recent studies in human and non-human primates have shown that the 5-HT1A and 5-HT2A binding potentials within the insular cortex (insula) are correlated to anxiety. As an initial step to define the function of 5-HT transmission in the insula, we quantified the proportion of specific neuronal populations of the insula expressing 5-HT1A or 5-HT2A. We analyzed seven neural populations, including three defined by a molecular marker (putative glutamate, GABA or parvalbumin), and four defined by their projections to different downstream targets. First, we found that more than 70% of putative glutamatergic neurons, and only 30% of GABAergic neurons express the 5-HT1A. Second, within insular projection neurons, 5-HT1A is highly expressed (75-80%) in the populations targeting one sub-nuclei of the amygdala (central or basolateral), or targeting the rostral or caudal sections of the lateral hypothalamus (LH). Similarly, 70% of putative glutamatergic neurons and only 30% of insular GABAergic neurons contain 5-HT2A. Finally, the 5-HT2A is present in a majority of insula-amygdala and insula-LH projection neurons (73-82%). These observations suggest that most glutamatergic neurons can respond to 5-HT through 5-HT1A or 5-HT2A in the insula, and that 5-HT directly affects a limited number of GABAergic neurons. This study defines a molecular and neuroanatomical map of the 5-HT system within the insular cortex, providing ground knowledge to identify the potential role of serotonergic modulation of selective insular populations in anxiety.
Subject(s)
Cerebral Cortex/metabolism , Neurons/metabolism , Receptor, Serotonin, 5-HT1A/metabolism , Receptor, Serotonin, 5-HT2A/metabolism , Amygdala/metabolism , Animals , Anxiety/metabolism , Female , Glutamic Acid/metabolism , Hypothalamus/metabolism , Male , Mice, Inbred C57BL , Serotonin/metabolism , Synapses/metabolism , gamma-Aminobutyric Acid/metabolismABSTRACT
Water intake is crucial for maintaining body fluid homeostasis and animals' survival [1-4]. In the brain, complex processes trigger thirst and drinking behavior [1-5]. The anterior wall of the third ventricle formed by the subfornical organ (SFO), the median preoptic nucleus, and the organum vasculosum of the lamina terminalis (OVLT) constitute the primary structures sensing thirst signals and modulating water intake [6-10]. These subcortical regions are connected with the neocortex [11]. In particular, insular and anterior cingulate cortices (IC and ACC, respectively) have been shown to receive indirect innervations from the SFO and OVLT in rats [11] and to be involved in the control of water intake [12-15]. Type-1 cannabinoid receptors (CB1) modulate consummatory behaviors, such as feeding [16-26]. However, the role of CB1 receptors in the control of water intake is still a matter of debate [27-31]. Here, we show that endogenous activation of CB1 in cortical glutamatergic neurons of the ACC promotes water intake. Notably, presynaptic CB1 receptors of ACC glutamatergic neurons are abundantly located in the basolateral amygdala (BLA), a key area in the regulation of water intake. The selective expression of CB1 receptors in the ACC-to-BLA-projecting neurons is sufficient to stimulate drinking behavior. Moreover, chemogenetic stimulation of these projecting neurons suppresses drinking behavior, further supporting the role of this neuronal population in the control of water intake. Altogether, these data reveal a novel cortico-amygdalar mechanism involved in the regulation of drinking behavior.
Subject(s)
Basolateral Nuclear Complex/physiology , Drinking/physiology , Gyrus Cinguli/physiology , Receptor, Cannabinoid, CB1/metabolism , Animals , Basolateral Nuclear Complex/cytology , Genes, Reporter , Gyrus Cinguli/cytology , Male , Mice , Mice, Transgenic , Models, Animal , Neural Pathways/physiology , Neurons/metabolism , Thirst/physiologyABSTRACT
The neural mechanisms underlying emotional valence are at the interface between perception and action, integrating inputs from the external environment with past experiences to guide the behavior of an organism. Depending on the positive or negative valence assigned to an environmental stimulus, the organism will approach or avoid the source of the stimulus. Multiple convergent studies have demonstrated that the amygdala complex is a critical node of the circuits assigning valence. Here we examine the current progress in identifying valence coding properties of neural populations in different nuclei of the amygdala, based on their activity, connectivity, and gene expression profile.
ABSTRACT
Stress and anxiety have intertwined behavioral and neural underpinnings. These commonalities are critical for understanding each state, as well as their mutual interactions. Grasping the mechanisms underlying this bidirectional relationship will have major clinical implications for managing a wide range of psychopathologies. After briefly defining key concepts for the study of stress and anxiety in pre-clinical models, we present circuit, as well as cellular and molecular mechanisms involved in either or both stress and anxiety. First, we review studies on divergent circuits of the basolateral amygdala (BLA) underlying emotional valence processing and anxiety-like behaviors, and how norepinephrine inputs from the locus coeruleus (LC) to the BLA are responsible for acute-stress induced anxiety. We then describe recent studies revealing a new role for mitochondrial function within the nucleus accumbens (NAc), defining individual trait anxiety in rodents, and participating in the link between stress and anxiety. Next, we report findings on the impact of anxiety on reward encoding through alteration of circuit dynamic synchronicity. Finally, we present work unravelling a new role for hypothalamic corticotropin-releasing hormone (CRH) neurons in controlling anxiety-like and stress-induce behaviors. Altogether, the research reviewed here reveals circuits sharing subcortical nodes and underlying the processing of both stress and anxiety. Understanding the neural overlap between these two psychobiological states, might provide alternative strategies to manage disorders such as post-traumatic stress disorder (PTSD).
ABSTRACT
The basolateral amygdala (BLA) mediates associative learning for both fear and reward. Accumulating evidence supports the notion that different BLA projections distinctly alter motivated behavior, including projections to the nucleus accumbens (NAc), medial aspect of the central amygdala (CeM), and ventral hippocampus (vHPC). Although there is consensus regarding the existence of distinct subsets of BLA neurons encoding positive or negative valence, controversy remains regarding the anatomical arrangement of these populations. First, we map the location of more than 1,000 neurons distributed across the BLA and recorded during a Pavlovian discrimination task. Next, we determine the location of projection-defined neurons labeled with retrograde tracers and use CLARITY to reveal the axonal path in 3-dimensional space. Finally, we examine the local influence of each projection-defined populations within the BLA. Understanding the functional and topographical organization of circuits underlying valence assignment could reveal fundamental principles about emotional processing.
Subject(s)
Amygdala/growth & development , Basolateral Nuclear Complex/growth & development , Neurons/metabolism , Animals , Male , MiceABSTRACT
Recombinant rabies viral vectors have proven useful for applications including retrograde targeting of projection neurons and monosynaptic tracing, but their cytotoxicity has limited their use to short-term experiments. Here we introduce a new class of double-deletion-mutant rabies viral vectors that left transduced cells alive and healthy indefinitely. Deletion of the viral polymerase gene abolished cytotoxicity and reduced transgene expression to trace levels but left vectors still able to retrogradely infect projection neurons and express recombinases, allowing downstream expression of other transgene products such as fluorophores and calcium indicators. The morphology of retrogradely targeted cells appeared unperturbed at 1 year postinjection. Whole-cell patch-clamp recordings showed no physiological abnormalities at 8 weeks. Longitudinal two-photon structural and functional imaging in vivo, tracking thousands of individual neurons for up to 4 months, showed that transduced neurons did not die but retained stable visual response properties even at the longest time points imaged.