Biology subjects

Fleming, W.

Publications and source records attributed to Fleming, W..

12 recordsLinked to original sources

bioRxiv2026

A cholinergic eligibility trace facilitates amygdala plasticity in flavour avoidance learning

When an animal consumes a new food and consequently feels ill, it rapidly and robustly learns to avoid this food in the future, a form of learning termed conditioned flavour avoidance (CFA). Postingestive malaise often occurs long after novel food consumption, necessitating a neural mechanism that can facilitate plasticity between temporally distant events. Neuromodulators, acting through G-protein-coupled receptors (GPCRs) that can influence neuronal excitability on extended timescales, may facilitate this process. The projection of parabrachial (PB) Calca neurons to the central amygdala (CeA) is critical for formation of CFA. Here, we demonstrate that these neurons overlap with a PB population that releases acetylcholine (ACh) in the CeA. ACh is released in CeA during consumption of a novel solution and subsequent visceral malaise, consistent with a role in CFA acquisition. Two-photon calcium imaging in brain slices reveals that ACh widely activates CeA neurons and enhances glutamatergic responsivity on a timescale consistent with CFA learning. CRISPR-Cas9-mediated genetic knockdown and optogenetics demonstrate that ACh from PB facilitates CFA behavior. Large-scale neuronal recordings in the CeA along with our CRISPR approach reveal that loss of ACh signaling to CeA blocks key signatures of CFA-associated plasticity. Together, these data point to the cholinergic input from PB to central amygdala as a critical neuromodulatory signal that links activity over long timespans to facilitate associative learning in CFA.

neuroscience↗

bioRxiv2024

Opioid-driven disruption of the septal complex reveals a role for neurotensin- expressing neurons in withdrawal

Because opioid withdrawal is an intensely aversive experience, persons with opioid use disorder (OUD) often relapse to avoid it. The lateral septum (LS) is a forebrain structure that is important in aversion processing, and previous studies have linked the lateral septum (LS) to substance use disorders. It is unclear, however, which precise LS cell types might contribute to the maladaptive state of withdrawal. To address this, we used single-nucleus RNA-sequencing to interrogate cell type specific gene expression changes induced by chronic morphine and withdrawal. We discovered that morphine globally disrupted the transcriptional profile of LS cell types, but Neurotensin-expressing neurons (Nts; LS-Nts neurons) were selectively activated by naloxone. Using two-photon calcium imaging and ex vivo electrophysiology, we next demonstrate that LS-Nts neurons receive enhanced glutamatergic drive in morphine-dependent mice and remain hyperactivated during opioid withdrawal. Finally, we showed that activating and silencing LS-Nts neurons during opioid withdrawal regulates pain coping behaviors and sociability. Together, these results suggest that LS-Nts neurons are a key neural substrate involved in opioid withdrawal and establish the LS as a crucial regulator of adaptive behaviors, specifically pertaining to OUD.

neuroscience↗

bioRxiv2022

Independent inhibitory control mechanisms for aggressive motivation and action

Social behaviors, like other motivated behaviors, frequently consist of a flexible motivated-seeking or approach phase followed by social action. Dysregulated social behavior may arise from changes to motivation, wherein individuals fail to enter a motivated seeking state, or may be in the execution of the social action itself. However, it is unclear how the brain generates and gates this flexible motivation-to-action sequence, and whether aggressive motivation and action are controlled by separate circuit mechanisms. Here, we record populations of neurons in the ventromedial hypothalamus ventrolateral area (VMHvl) of male mice at cellular resolution during "free" aggression and also during an aggression operant task, where the behaviors that precede attack are stereotyped. We find that this population encodes the temporal sequence of aggressive motivation to action and that the temporal selectivity of neurons is invariant to differences in motivated behavior. To test whether motivation and action could be independently regulated, we focused on two key inhibitory inputs to the VMHvl: a source of local inhibition (VMHvl shell) and the primary source of long-range inhibition (the medial preoptic area, MPO). While we find that the VMHvl receives broad monosynaptic inhibitory input from both inputs, optogenetic perturbation of these inputs during recording reveals temporal selectivity during aggressive motivation and action, suggesting specificity of function. Encoding models applied to population calcium recordings of these inhibitory inputs during naturalistic social interactions and during the social operant task further reveal that these inputs have different temporal dynamics during aggression: VMHvl shellvgat+ activity peaks at the start of aggressive interactions, while MPO-VMHvlvgat+ activity peaks at behaviorally aligned endpoints of aggressive interactions. Finally, using closed-loop optogenetic stimulation timed to specific phases of the aggression-operant task, we find a double-dissociation of the effects on aggressive motivation and action: activation of MPO-VMHvlvgat+, even briefly and temporally distant from the initiation of aggression, produces long-lasting motivational deficits, delaying the initiation of aggression and generating behaviors consistent with an unmotivated state. In contrast, activation of VMHvl shellvgat+ produces acute action-related deficits, causing an exit from an attack state. Fitting a Hidden Markov Model (HMM) to behavior further corroborates these findings by showing that MPO-VMHvlvgat+ stimulation prolongs a low motivation state and VMHvl shellvgat+ promotes exit from an attack state. Together, these data demonstrate how separable inhibitory circuits in the hypothalamus can independently gate the motivational and action phases of aggression through a single locus of control.

neuroscience↗

bioRxiv2022

The transcriptional and epigenetic reprogramming mediated by chronic IL1β exposure drives self-renewal ability and myeloid priming in TET2 deficient stem and progenitor cells.

Clonal hematopoiesis (CH) increases the risk for the development of hematological malignancy and cardiovascular disease. IL1{beta} is elevated in patients with CH and its inhibition mitigates cardiovascular risk in murine models with Tet2 loss-of-function. How IL1{beta} alters population dynamics of hematopoietic cells upon Tet2 deletion (Tet2-KO) is not well understood. We demonstrated IL1{beta} expands Tet2-KO monocytes/macrophages, and long-term hematopoietic stem cells. IL1{beta} promoted myeloid bias over other lineages of Tet2-KO HSPCs coinciding with the failure to demethylate lineage-associated enhancer and transcription factor binding sites. IL1{beta} enhanced the self-renewal ability of Tet2-KO HSPCs by upregulating genes associated with self-renewal and by resisting the demethylation of binding sites of transcription factors promoting terminal differentiation. The IL1{beta}-mediated premalignant phenotype is suppressed by the IL1{beta} antagonist or deletion of the IL1 receptor-1, in vivo in aged mice. Our results demonstrate that targeting IL1 signaling could be an efficient early intervention strategy in preleukemic disorders. STATEMENT OF SIGNIFICANCEIL1{beta} promoted myeloid expansion and self-renewal capacity of TET2-null pre-leukemic cells. Lineage bias occurred early within progenitors towards pro-inflammatory macrophages. Genes specific to aging and with roles in promoting self-renewal capacity, and myeloid bias were upregulated. Hypermethylation occurred within lymphoid and erythroid lineage-specific regulatory elements. Targeting IL1R1 reduced aberrant myeloid bias and premalignant phenotype.

cancer biology↗

bioRxiv2022

A neural substrate of sex-dependent modulation of motivation by value

While there is emerging evidence of sex differences in decision-making behavior, the neural substrates that underlie such differences remain largely unknown. Here, we demonstrate that in mice performing a value-based decision-making task, while choices are similar between the sexes, motivation to engage in the task is modulated by action value in females more strongly than in males. Inhibition of activity in anterior cingulate cortex (ACC) neurons that project to the dorsomedial striatum (DMS) disrupts this relationship between value and motivation preferentially in females, without affecting choice in either sex. In line with these effects, in females compared to males, ACC-DMS neurons have stronger representations of negative outcomes, and more neurons are active when the value of the chosen option is low. In contrast, the representation of each choice is similar between the sexes. Thus, we identify a neural substrate that contributes to sex-specific modulation of motivation by value.

neuroscience↗

bioRxiv2021

Spinal cord injury reprograms muscle fibro-adipogenic progenitors to formheterotopic bones within muscles

The cells-of-origin of neurogenic heterotopic ossifications (NHO), which develop frequently in the periarticular muscles following spinal cord injuries (SCI) and traumatic brain injuries, remain unclear because the skeletal muscle harbors two progenitor cell populations: satellite cells (SCs) which are myogenic, and fibro-adipogenic progenitors (FAPs) which are mesenchymal. Lineage-tracing experiments using the Cre recombinase /LoxP system were performed in two mouse strains with the fluorescent protein ZsGreen specifically expressed in either SCs or FAPs in the skeletal muscles under the control of the Pax7 or Prrx1 gene promotors respectively. These experiments demonstrate that following a muscle injury, SCI causes the upregulation of PDGFR on FAPs but not SCs and the failure of SCs to regenerate myofibers in the injured muscle, with instead reduced apoptosis and continued proliferation of muscle resident FAPs enabling their osteogenic differentiation into NHO. No cells expressing ZsGreen under the Prrx1 promoter were detected in the blood after injury suggesting that the cells-of-origin of NHO are locally derived from the injured muscle. We validated these findings in the human pathology using human NHO biopsies. PDGFR+ mesenchymal cells isolated from the muscle surrounding NHO biopsies could develop ectopic human bones when transplanted into immunocompromised mice whereas CD56+ myogenic cells had a much lower potential. Therefore, NHO is a pathology of the injured muscle in which SCI reprograms FAPs to uncontrolled proliferation and differentiation into osteoblasts.

pathology↗

bioRxiv2021

Interleukin-1 is overexpressed in injured muscles following spinal cord injury and promotes neurogenic heterotopic ossification

Neurogenic heterotopic ossifications (NHOs) form in periarticular muscles following severe spinal cord (SCI) and traumatic brain injuries. The pathogenesis of NHO is poorly understood with no effective preventive treatment. The only curative treatment remains surgical resection of pathological NHOs. In a mouse model of SCI-induced NHO that involves a transection of the spinal cord combined with a muscle injury, a differential gene expression analysis revealed that genes involved in inflammation such as interleukin-1{beta} (IL-1{beta}) were overexpressed in muscles developing NHO. Using mice knocked-out for the gene encoding IL-1 receptor (IL1R1) and neutralizing antibodies for IL-1 and IL-1{beta}, we show that IL-1 signaling contributes to NHO development following SCI in mice. Interestingly, other proteins involved in inflammation that were also overexpressed in muscles developing NHO, such as colony-stimulating factor-1, tumor necrosis factor or C-C chemokine ligand-2 did not promote NHO development. Finally using NHO biopsies from SCI and TBI patients, we show that IL-1{beta} is expressed by CD68+ macrophages. IL-1 and IL-1{beta} produced by activated human monocytes promote calcium mineralization of fibro-adipogenic progenitors isolated from muscles surrounding NHOs. Altogether these data suggest that interleukin-1 promotes NHO development in both humans and mice.

physiology↗

bioRxiv2021

Cholinergic interneurons mediate cocaine extinction through similar plasticity across medium spiny neuron subtypes

Cholinergic interneurons (ChINs) in the nucleus accumbens (NAc) have been implicated in the acquisition and extinction of drug associations, as well as related plasticity in medium spiny neurons (MSNs). However, since most previous work has relied on artificial manipulations, if and how endogenous patterns of cholinergic signaling relate to drug associations is unknown. Moreover, despite great interest in the opposing effects of dopamine on MSN subtypes, whether ChIN-mediated effects are similar or different across MSN subtypes is also unknown. Here, we find that endogenous acetylcholine event frequency during extinction negatively correlates with the strength and persistence of cocaine-context associations across individuals, consistent with effects of artificial manipulation of ChIN activity during extinction. Moreover, ChIN activation during extinction produces a reduction in excitatory synaptic strength on both MSN subtypes, similar to the effect of multiple extinction sessions in the absence of ChIN manipulations. Together, our findings indicate that natural variation in NAc acetylcholine may contribute to individual differences in drug-context extinction by modulating glutamatergic presynaptic strength similarly at both D1R and D2R MSN subtypes. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=146 SRC="FIGDIR/small/458113v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@14b4cc1org.highwire.dtl.DTLVardef@9c5224org.highwire.dtl.DTLVardef@d4bff3org.highwire.dtl.DTLVardef@1862150_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2020

Inferring spikes from calcium imaging in dopamine neurons

Calcium imaging has led to discoveries about neural correlates of behavior in subcortical neurons, including dopamine (DA) neurons. However, spike inference methods have not been tested in most populations of subcortical neurons. To address this gap, we simultaneously performed calcium imaging and electrophysiology in DA neurons in brain slices, and applied a recently developed spike inference algorithm to the GCaMP fluorescence. This revealed that individual spikes can be inferred accurately in this population. Next, we inferred spikes in vivo from calcium imaging from these neurons during Pavlovian conditioning, as well as during navigation in virtual reality. In both cases, we quantitatively recapitulated previous in vivo electrophysiological observations. Our work provides a validated approach to infer spikes from calcium imaging in DA neurons, and implies that aspects of both tonic and phasic spike patterns can be recovered.

neuroscience↗

bioRxiv2020

A comparison of dopaminergic and cholinergic populations reveals unique contributions of VTA dopamine neurons to short-term memory

We systematically compared the contribution of two dopaminergic and two cholinergic ascending populations to a spatial short-term memory task in rats. In ventral tegmental area dopamine (VTA-DA) and nucleus basalis cholinergic (NB-ChAT) populations, trial-by-trial fluctuations in activity during the delay period related to performance with an inverted-U, despite the fact that both populations had low activity during that time. Transient manipulations revealed that only VTA-DA neurons, and not the other three populations we examined, contributed causally and selectively to short-term memory. This contribution was most significant during the delay period, when both increases or decreases in VTA-DA activity impaired short-term memory. Our results reveal a surprising dissociation between when VTA-DA neurons are most active and when they have the biggest causal contribution to short-term memory, while also providing new types of support for classic ideas about an inverted-U relationship between neuromodulation and cognition.

neuroscience↗

bioRxiv2020

Distinct signals in medial and lateral VTA dopamine neurons modulate fear extinction at different times

Dopamine (DA) neurons are known to encode reward prediction error (RPE), in addition to other signals, such as salience. While RPE is known to support learning, the role of salience in supporting learning remains less clear. To address this, we recorded and manipulated VTA DA neurons in mice during fear extinction, a behavior we observed to generate spatially segregated RPE and salience signals. We applied deep learning to classify mouse freezing behavior, eliminating the need for human scoring. Our fiber photometry recordings showed that DA neurons in medial and lateral VTA have distinct activity profiles during fear extinction: medial VTA activity more closely reflected RPE, while lateral VTA activity more closely reflected a salience-like signal. Optogenetic inhibition of DA neurons in either region slowed fear extinction, with the relevant time period for inhibition differing across regions. Our results indicate that salience-like signals can have similar downstream consequences to RPE-like signals, although with different temporal dependencies.

neuroscience↗

bioRxiv2018

Specialized and spatially organized coding of sensory, motor, and cognitive variables in midbrain dopamine neurons

There is increased appreciation that dopamine (DA) neurons in the midbrain respond not only to reward 1,2 and reward-predicting cues 1,3,4, but also to other variables such as distance to reward 5, movements 6-11 and behavioral choices 12-15. Based on these findings, a major open question is how the responses to these diverse variables are organized across the population of DA neurons. In other words, do individual DA neurons multiplex multiple variables, or are subsets of neurons specialized in encoding specific behavioral variables? The reason that this fundamental question has been difficult to resolve is that recordings from large populations of individual DA neurons have not been performed in a behavioral task with sufficient complexity to examine these diverse variables simultaneously. To address this gap, we used 2-photon calcium imaging through an implanted lens to record activity of >300 midbrain DA neurons in the VTA during a complex decision-making task. As mice navigated in a virtual reality (VR) environment, DA neurons encoded an array of sensory, motor, and cognitive variables. These responses were functionally clustered, such that subpopulations of neurons transmitted information about a subset of behavioral variables, in addition to encoding reward. These functional clusters were spatially organized, such that neighboring neurons were more likely to be part of the same cluster. Taken together with the topography between DA neurons and their projections, this specialization and anatomical organization may aid downstream circuits in correctly interpreting the wide range of signals transmitted by DA neurons.

neuroscience↗