About

The Andermann Lab at Harvard University and the Beth Israel Deaconess Medical Center researches how internal motivational states create bias in sensory processing.

Research topics

• Biology
• Neuroscience
• Endocrinology
• Medicine
• Psychology
• Zoology
• Optics
• Physics
• Internal medicine
• Physiology
• Cognitive psychology

Selected publications

• Brainstem sensing of multiple body signals during food consumption

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-04-29 · 3 citations

  preprintOpen accessSenior authorCorresponding

  Abstract Studies of body-to-brain communication often examine one stimulus or organ at a time, yet the brain must integrate many body signals during behavior. For example, food consumption generates diverse oral and post-oral chemical and mechanical signals transduced by well-characterized peripheral neuronal pathways. Far less is known about how these and other bodily signals are integrated and organized in the brainstem lateral parabrachial nucleus (LPBN), a key interoceptive sensory hub. We established methods to image the activity of 1000s of neurons throughout a large region of mouse LPBN. Food consumption drove a seconds-long wave of activity across LPBN, with dynamics mirroring the movement of food through the upper gastrointestinal tract observed using X-ray fluoroscopy. By imaging the same neurons across days, we found that spatially clustered subsets of neurons encoded oral signals, stomach filling, visceral malaise, arousal, and/or body movement. Moreover, only certain subsets were modulated by cortical input. Together, these experiments reveal a functional specialization in the LPBN that integrates contextual information from the body to guide behavior.

  PublisherOA PDFDOI

• Obesity dysregulates feeding-evoked response dynamics in hypothalamic satiety neurons

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-05-27

  preprintOpen accessSenior authorCorresponding

  Abstract Melanocortin-4 receptor-expressing neurons in the paraventricular nucleus of the hypothalamus (PVH MC4R ) integrate hunger-promoting and hunger-suppressing signals to regulate satiety. Food consumption-evoked responses in PVH MC4R neurons increase gradually during meal consumption to promote satiety, and disrupting this process drives massive obesity. These critical satiety neurons are strongly affected by a high-fat diet, yet the impact on their functional properties remains unknown. We used fiber photometry to track PVH MC4R neurons’ responses to the consumption of drops of milkshake in animals fed a chow diet or a high-fat diet (HFD), both after obesity was established and after its reversal. PVH MC4R neurons in HFD-fed animals showed greater consumption-evoked responses than chow-fed animals at the early stages of meal consumption, and these responses did not increase further during the meal. HFD-fed animals also showed reduced licking vigor and motivation to consume Ensure. Switching HFD-fed obese animals to a normal chow diet (NCD) re-engaged the motivation to consume Ensure, partially restoring early-meal neural responses to a lower level, but did not restore the increase in consumption-evoked response magnitude across the meal. These findings highlight functional alterations in hypothalamic satiety-promoting neurons in obesity and provide insight into the pathological neural consequences of an obesogenic environment.

  PublisherOA PDFDOI

• Slow-Timescale Regulation of Dopamine Release and Mating Drive Over Days

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-06-02

  preprintOpen access

  The rise and fall of motivational states may take place over timescales as long as many days. We used mouse mating behavior to model how the brain orchestrates slow-timescale changes in motivation. Male mice become sexually satiated after successful matings, and their motivation to mate gradually recovers over a week. Using deep-brain fluorescence-lifetime imaging in the medial preoptic area (MPOA), we found that tonic dopamine transmission-which regulates mating drive-also declined after mating and re-emerged over a week. Two mechanisms regulated dopamine transmission. First, successful mating transiently reduced tonic firing of hypothalamic dopamine-releasing neurons, thereby inhibiting dopamine release and mating behavior. Second, mating reduced the ability of these neurons to produce and release dopamine, and this ability gradually returned over the week-long recovery time course. Therefore, fast and slow mechanisms of neuronal plasticity cooperate to control the early and late phases of motivational dynamics, respectively.

  PublisherOA PDFDOI

• Local inhibitory circuits mediate cortical reactivations and memory consolidation

  Science Advances · 2025-05-30 · 4 citations

  articleOpen access

  Highly salient events activate neurons across various brain regions. During subsequent rest or sleep, the activity patterns of these neurons often correlate with those observed during the preceding experience. Growing evidence suggests that these reactivations play a crucial role in memory consolidation, the process by which experiences are solidified in cortical networks for long-term storage. Here, we use longitudinal two-photon Ca 2+ imaging alongside paired LFP recordings in the hippocampus and cortex, to show that targeted manipulation of PV + inhibitory neurons in the lateral visual cortex after daily training selectively attenuates cue-specific reactivations and learning, with only minute effects on spontaneous activity and no apparent effect on normal function such as visual cue–elicited responses during training. In control mice, reactivations were biased toward salient cues, persisted for hours after training had ended, and the prevalence of reactivations was aligned with the learning process. Overall, our results underscore a crucial role for cortical reactivations in memory consolidation.

  PublisherDOI

• Simultaneous, real-time tracking of many neuromodulatory signals with Multiplexed Optical Recording of Sensors on a micro-Endoscope

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-01-26 · 1 citations

  preprintOpen accessSenior authorCorresponding

  Abstract Dozens of extracellular molecules jointly impact a given neuron, yet we lack methods to simultaneously record many such signals in real time. We developed a probe to track ten or more neuropeptides and neuromodulators using spatial multiplexing of genetically encoded fluorescent sensors. Cultured cells expressing one sensor at a time are immobilized at the front of a gradient refractive index (GRIN) lens for 3D two-photon imaging in vitro and in vivo. The sensor identity and detection sensitivity of each cell are determined via robotic dipping of the probe into wells containing various ligands and concentrations. Using this probe, we detected stimulation-evoked release of multiple neuromodulators in acute brain slices. We also tracked endogenous and drug-evoked changes in cerebrospinal fluid composition in the awake mouse lateral ventricle, which triggered downstream activation of the choroid plexus epithelium. Our approach offers a first step towards quantitative, real-time, high-dimensional tracking of brain fluid composition.

  PublisherOA PDFDOI

• Obesity dysregulates feeding-evoked response dynamics in hypothalamic satiety neurons

  Scientific Reports · 2025-10-14 · 3 citations

  articleOpen accessSenior author

  Abstract Melanocortin-4 receptor-expressing neurons in the paraventricular nucleus of the hypothalamus (PVH MC4R ) integrate hunger-promoting and hunger-suppressing signals to regulate satiety. Food consumption-evoked responses in PVH MC4R neurons increase gradually during meal consumption to promote satiety, and disrupting this process drives massive obesity. These critical satiety neurons are strongly affected by a high-fat diet, yet the impact on their functional properties remains unknown. We used fiber photometry to track PVH MC4R neurons’ responses to the consumption of drops of milkshake in animals fed a chow diet or a high-fat diet (HFD), both after obesity was established and after its reversal. PVH MC4R neurons in HFD-fed animals showed greater consumption-evoked responses than chow-fed animals at the early stages of meal consumption, and these responses did not increase further during the meal. HFD-fed animals also showed reduced licking vigor and motivation to consume milkshake. Switching HFD-fed obese animals to a normal chow diet (NCD) re-engaged the motivation to consume milkshake, partially restored early-meal neural responses to a lower level, but did not restore the increase in consumption-evoked response magnitude across the meal. These findings highlight functional alterations in hypothalamic satiety-promoting neurons in obesity and provide insight into the pathological neural consequences of an obesogenic environment.

  PublisherOA PDFDOI

• Rapid fluorescence lifetime sensor development of LifeCamp enables transient and baseline absolute calcium measurements

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-12-25

  articleOpen access

  Abstract Genetically encoded calcium sensors (GECIs) have been instrumental for studying neuronal activity and intracellular signaling. GECIs are typically fluorescence-intensity sensors that change brightness upon calcium binding. Iterative improvements in GECIs have yielded indicators that report action potential-evoked calcium entry with high sensitivity and temporal resolution, enabling measurement of network activity across thousands of neurons. However, fluorescence intensity-based measurements generally cannot report baseline or absolute calcium levels and may confound neuromodulatory regulation of calcium handling with changes in action potential firing. Fluorescence lifetime sensors are insensitive to many artifacts that plague intensity-based measures and report absolute substrate levels, including those at rest. However, relatively few lifetime sensors for neuronal signals exist, and developing new sensors is typically difficult and low-yield. Here, we introduce a new rapid lifetime sensor development (RALISED) platform, which we use to build a new GCaMP8m-based high-speed lifetime calcium sensor, termed LifeCamp. We show that LifeCamp enables comparison of baseline calcium signals in cell culture, brain slices, and mice. In addition, we show that LifeCamp enables the detection of fast action potential-evoked calcium transients in single neurons from brain slices and in behaving mice. Using LifeCamp, we discovered calcium baseline changes associated with neuronal activity in brain slices and behaving mice, as well as slow average calcium changes in neuronal populations of freely moving mice. Altogether, this study highlights the utility of the RALISED method to rapidly develop new lifetime sensors and the application of the LifeCamp calcium lifetime sensor to study fast and slow calcium signaling. Significance statement: We developed a new high-speed, sensitive calcium lifetime sensor (LifeCamp) using a novel rapid lifetime sensor development (RALISED) platform. LifeCamp has high sensitivity and a large substrate-dependent lifetime change (<1ns), allowing for the capture of baseline calcium levels, transient calcium changes, and neuronal firing in vitro and behaving animals. LifeCamp lifetime measurement is insensitive to artifacts that plague conventional intensity imaging and enables absolute comparison of baseline and transient calcium changes across cells, brain regions, and experimental conditions. Hence, LifeCamp is a powerful tool that enables a more accurate and in-depth understanding of neuronal activity and calcium signaling.

  PublisherDOI

• Noradrenergic Modulation of an Amygdalo-thalamic Circuit

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-10-14

  preprintOpen accessCorresponding

  ABSTRACT Emotional and cognitive processing rely on communication between the basolateral amygdala (BLA) and the medial prefrontal cortex (mPFC). The BLA regulates mPFC both directly and indirectly via the medial sub-division of the medial dorsal thalamus (MDm). Although the BLA projection to MDm has been established anatomically, less is known about the functional properties of this synapse. Here, using patch-clamp electrophysiology and optogenetics in ex vivo mouse brain slices, we found that BLA neurons make potent synaptic connections onto MDm neurons capable of evoking action potentials. The site of this BLA input overlaps with strong innervation from locus coeruleus norepinephrine (NE) axons. We found that NE acts via α₂-adrenergic receptors to strongly reduce excitatory postsynaptic currents from BLA to MDm. NE also decreases the release probability of BLA axon terminals through a presynaptic mechanism. Postsynaptically, NE depolarizes MDm neurons and increases their tonic firing rates. These findings show that NE, whose levels are elevated during arousal and stress, can suppress transmission of affective information from BLA into MDm, thereby blunting this potent indirect pathway from BLA to mPFC. SIGNIFICANCE STATEMENT Previous anatomical studies have suggested the importance of amygdala input to the limbic thalamus. Here, using ex vivo electrophysiology and optogenetics in adult mice, we characterize the excitatory input from basolateral amygdala to mediodorsal thalamus, revealing the potency and physiological characteristics of this input. Further, we show that the stress-related neuromodulator, norepinephrine, binds to the α₂-adrenergic receptor to significantly dampen transmission of affective information carried by this synapse. These findings improve our understanding of key circuits involved in emotional processing and provide insight on how stress-induced neuromodulation may change circuit function, which is relevant to stress-related neuropsychiatric disorders such as depression, anxiety, schizophrenia, and PTSD.

  PublisherOA PDFDOI

• Author Response: Sensitization of meningeal afferents to locomotion-related meningeal deformations in a migraine model

  2024-02-08

  peer-reviewOpen access

  Full text Figures and data Side by side Abstract eLife assessment Introduction Results Discussion Materials and methods Data availability References Peer review Author response Article and author information Abstract Migraine headache is hypothesized to involve the activation and sensitization of trigeminal sensory afferents that innervate the cranial meninges. To better understand migraine pathophysiology and improve clinical translation, we used two-photon calcium imaging via a closed cranial window in awake mice to investigate changes in the responses of meningeal afferent fibers using a preclinical model of migraine involving cortical spreading depolarization (CSD). A single CSD episode caused a seconds-long wave of calcium activation that propagated across afferents and along the length of individual afferents. Surprisingly, unlike previous studies in anesthetized animals with exposed meninges, only a very small afferent population was persistently activated in our awake mouse preparation, questioning the relevance of this neuronal response to the onset of migraine pain. In contrast, we identified a larger subset of meningeal afferents that developed augmented responses to acute three-dimensional meningeal deformations that occur in response to locomotion bouts. We observed increased responsiveness in a subset of afferents that were already somewhat sensitive to meningeal deformation before CSD. Furthermore, another subset of previously insensitive afferents also became sensitive to meningeal deformation following CSD. Our data provides new insights into the mechanisms underlying migraine, including the emergence of enhanced meningeal afferent responses to movement-related meningeal deformations as a potential neural substrate underlying the worsening of migraine headache during physical activity. eLife assessment This fundamental study explored the impact of migraine-related cortical spreading depression (CSD) on the firing of nerves innervating the coverings of the brain that are considered the putative source of migraine-related pain. Using convincing approaches they show that these responses are altered in response to mechanical deformation of the brain coverings. Given that migraine is characterized by worsening head pain in response to movement, the findings offer a potential mechanism that may explain this clinical phenomenon. https://doi.org/10.7554/eLife.91871.3.sa0 About eLife assessments Introduction A large body of evidence supports the notion that migraine headache involves the trigeminal meningeal sensory system (Ashina et al., 2019; Levy and Moskowitz, 2023). Persistent discharge of meningeal afferents is thought to mediate the ongoing headache, while their augmented mechanosensitivity has been suggested to underlie migraine headache exacerbation during normally innocuous physical activities that cause transient intracranial hypertension, such as coughing and other types of straining (Blau and Dexter, 1981). Current understanding of migraine-related responses of meningeal afferents is largely based on animal models. For example, triggering an episode of cortical spreading depolarization (CSD), a self-propagating wave of neuronal and glial depolarizations thought to mediate migraine aura, causes persistent activation and mechanical sensitization of meningeal afferents (Zhang et al., 2010; Zhao and Levy, 2015; Zhao and Levy, 2016). Despite the preclinical evidence implicating enhanced responsiveness of meningeal afferents as a driver of migraine headache (Levy and Moskowitz, 2023), these studies have almost all used acute invasive experiments involving electrophysiological recordings in anesthetized animals with surgically exposed and mildly inflamed meninges (Levy et al., 2007). Moreover, studies documenting the mechanical sensitization of meningeal afferents were based on findings of increased responsiveness to artificial compressive forces applied to the meninges of a depressurized brain. Hence, there is a significant gap in our understanding of whether and how meningeal afferents respond to migraine-related events under more naturalistic conditions in behaving animals with an intact and pressurized intracranial space. To better understand migraine pathophysiology and improve clinical translation, we leveraged a newly developed approach for two-photon calcium imaging of meningeal afferent responses within the closed intracranial space of an awake-behaving mouse (Blaeser et al., 2022d) in the CSD model of migraine. We studied changes in afferent ongoing activity and afferent responses to three-dimensional (3D) meningeal deformation associated with locomotion Blaeser et al., 2022d following the triggering of a single CSD episode. Our data provides new insights into the mechanisms underlying migraine pathophysiology, including acute calcium signaling in meningeal afferent fibers as a potentially critical nociceptive factor contributing to migraine pain and the emergence of enhanced meningeal afferent responses to movement-related meningeal deformations as the neural substrate underlying the worsening of migraine headache during physical activity. Results Propagating calcium activity across afferent fibers during CSD To investigate meningeal afferent responses to CSD, we performed two-photon calcium imaging of GCaMP6s-expressing trigeminal afferent fibers innervating the meninges above the visual cortex (n=325 fibers from 9 fields of view [FOVs] from 7 mice, Figure 1A). We triggered a single CSD episode in the frontal cortex with a cortical pinprick. In every experiment (9 CSDs in 7 mice), we detected a slow, CSD-like wave of calcium activity in numerous meningeal afferent fibers within 1 min following the pinprick (Figure 1B, Figure 1—video 1) as well as in background regions (likely reflecting signal from small, out-of-focus afferent branches). These calcium waves proceeded from the pinprick site in an anterior-to-posterior direction across the FOV (Figure 1C). We also observed progressive activation of portions of individual afferent fibers aligned to the wave’s movement direction. To characterize this phenomenon, we focused on sets of regions of interest (ROIs) belonging to the same long afferent fiber oriented along the direction of the calcium wave (Figure 1D, Figure 1—video 1). Compared to baseline afferent calcium signals observed during periods of locomotion, during which all ROIs belonging to an afferent were activated near-simultaneously, as previously reported (Blaeser et al., 2022d), the sequential recruitment of ROIs along an afferent fiber during the CSD-like wave was much slower (Figure 1E–G). The proportion of afferents activated during this period exceeded the proportion activated during locomotion bouts (Figure 1I). The magnitude of activation was also larger (Figure 1J). Figure 1 with 3 supplements see all Download asset Open asset Cortical spreading depolarization (CSD) drives wave-like calcium activity in meningeal afferents. (A) Mice received a trigeminal ganglion injection of an AAV to express GCaMP6s in trigeminal meningeal afferents. After 8–10 weeks, following the implantation of a headpost and a cranial window, mice were habituated to head restraint and subjected to two-photon calcium imaging while head-fixed on a running wheel to study the effect of pinprick-triggered CSD on the activity of meningeal afferents. (B) Example of a CSD-associated meningeal calcium wave that spreads across the field of view (FOV), with local segments of long afferent fibers becoming sequentially activated as the wave progresses (arrowheads). M: medial, L: lateral, A: anterior, P: posterior. (C) Summary of speed and direction of CSD-associated meningeal calcium waves, typically from anterior (‘Ant.’) (closer to where CSD was triggered anterior to the cranial window) to more posterior locations (‘Post.’). Speed estimates were obtained using the analysis method described in Figure 1—figure supplement 1. On average, the wave progressed at 3.8±0.2 mm/min. (D) Map of 18 regions of interest (ROIs) belonging to a single meningeal afferent fiber visible in B. (E) Activity heatmap of the afferent ROIs indicated in D illustrating progressive activation in response to CSD. (F) In contrast, the same afferent ROIs became activated simultaneously during a locomotion bout. Top trace depicts locomotion speed. (G) The pace of the CSD-associated afferent calcium wave was much slower than the spread of activity along the same afferent fibers during locomotion-evoked activity pre-CSD (****p<0.0001, paired, two-tailed t-test). (H) Example heatmaps of afferent activity observed during CSD showing different time course and magnitudes when compared to the activity observed during a locomotion bout. Bottom trace depicts locomotion speed. (I) Comparisons across all FOVs indicate a higher proportion of afferents exhibiting acute activation during the CSD vs. during locomotion (****p<0.0001, iterated bootstrap). (J) A higher proportion of afferents also displayed increased magnitudes of activation (*p<0.05, paired, two-tailed t-test). See also Figure 1—video 1. Acute afferent activation is not related to CSD-evoked meningeal deformation CSD gives rise to acute neuronal and glial swelling and shrinkage of the cortical extracellular space (Mazel et al., 2002; Takano et al., 2007; Rosic et al., 2019). Such cortical mechanical perturbations could lead to acute meningeal deformation, which we have shown previously can activate mechanosensitive meningeal afferents (Blaeser et al., 2022d). We postulated that if CSD leads to meningeal deformations, these deformations could drive the acute afferent response during the CSD wave. Assessment of meningeal deformation parameters (see Materials and methods) revealed severe meningeal scaling and shearing during the CSD-evoked afferent calcium wave (6 CSDs in 6 mice, Figure 1—figure supplement 2A–D). In some experiments, the temporal pattern of meningeal shearing (Figure 1—figure supplement 2C) somewhat resembled that of the acute afferent response. However, the pattern of meningeal scaling (Figure 1—figure supplement 2B) was incongruent with the acute afferent response. Surprisingly, the direction of Z-shifts in the meninges during this epoch was inconsistent across mice, resulting in no significant Z-shift on average relative to the pre-CSD epoch (Figure 1—figure supplement 2D). To estimate the relative contribution of the CSD-driven meningeal deformation to the acute afferent responses we observed, we used a general linear model (GLM; see Blaeser et al., 2022d, and Materials and methods). We focused on afferents whose pre-CSD (baseline) activity could be predicted by the GLM based on deformation predictors (n=145 afferents from 6 mice). We then plugged the peri-CSD deformation data into these GLMs to generate predictions of peri-CSD afferent activity and compared them to the observed activity. Overall, we observed a poor match between the real peri-CSD calcium signals and those predicted by the GLMs trained using pre-CSD deformation data (see example in Figure 1—figure supplement 2E and summary GLM fits in Figure 1—figure supplement 2F), suggesting that the model poorly predicted the magnitude of the activity and/or its temporal pattern in response to CSD. Because ~95% of the afferents were acutely activated by CSD (Figure 1I), we propose that this response is mostly driven by other non-mechanical factors, such as the local depolarizing effects of diffusible excitatory molecules. A minority of afferents exhibit prolonged activation or suppression after CSD In anesthetized rats with exposed meninges, CSD drives sustained increases in ongoing activity lasting tens of minutes in ~50% of meningeal afferents (Zhao and Levy, 2015). To directly assess CSD-related changes in afferent ongoing activity in awake mice with intact meninges, we focused on afferent responses during epochs of immobility between locomotion bouts (8 CSDs in 7 mice). We observed low levels of ongoing activity at baseline before CSD (fluorescent events occurring 6.9 ± 0.3% of the time), consistent with our previous study in naïve mice (Blaeser et al., 2022d). Unexpectedly, most afferents (~70%, 201/288) did not display any change in ongoing activity during the 2 hr following CSD (termed ‘post-CSD’). However, we identified sustained increases in ongoing activity in ~10% (30/288) of the afferents during this period. Surprisingly, we also observed a larger afferent population (~20%; 57/288) whose activity was suppressed (Figure 2A–C). Afferents with sustained activation showed increased ongoing activity that emerged at an ~25 min delay on average (Figure 2D). In contrast, afferents with sustained suppression showed decreases in ongoing activity beginning shortly after the passage of the acute calcium wave (Figure 2D). The durations of the afferent activation or suppression were similar, lasting ~25 min on average (Figure 2E). Figure 2 Download asset Open asset Cortical spreading depolarization (CSD)-related persistent changes in the ongoing activity of meningeal afferents. (A) Example heatmap of normalized ongoing activity (fraction of time afferents exhibited calcium events when the mouse is not locomoting) for all afferent fibers from a single field of view (FOV) during baseline and up to 120 min following CSD (termed ‘“post-CSD’). Data shows concatenated 1-min bins of activity. Afferents were either activated, suppressed, or unaffected by CSD. Note the delayed activation and immediate suppression in two small subsets of fibers. (B) Mean activity time course of the activated and suppressed afferents from the same population depicted in A. (C) Pie chart depicting the breakdown of the afferent subpopulations based on their change in ongoing activity following CSD. Most afferents were not affected (orange), while two smaller populations either exhibited prolonged activation (maroon) or suppression (blue) of ongoing activity following CSD (8 CSDs in 7 mice). (D) Afferents exhibiting prolonged activation had a longer onset latency than those exhibiting suppression (****p<0.0001, Mann-Whitney U-test. Error bars: SEM). (E) The duration of increases in ongoing activity and suppressions in activity were similar (p=0.97, two-tailed t-test. Error bars: SEM). CSD augments afferent responsiveness associated with meningeal deformations Meningeal deformation associated with locomotion bouts can lead to the activation of mechanosensitive meningeal afferents (Blaeser et al., 2022d). We wondered whether, following CSD, afferent responses to a given level of mechanical deformation would be enhanced (i.e. mechanical sensitization). If so, this could explain the exacerbation of migraine headaches during physical activity. CSD suppresses cortical activity, leading to decreased motor function (Houben et al., 2017), including reduced locomotion in head-fixed mice (Enger et al., 2017). CSD-related vascular changes and reduced extracellular space (Mazel et al., 2002; Takano et al., 2007) could also affect meningeal deformations and the associated afferent response. Hence, we first analyzed the effect of CSD on wheel running activity and the associated meningeal deformation. In most sessions, mice stopped locomoting following the CSD (8/9 CSDs in 7 mice) but resumed sporadic wheel running activity ~6 min later on average (range 0.5–16.5 min). However, the mice ran less during the 2 hr following CSD than during the baseline period (Figure 3B). Locomotion bout analysis also revealed an overall reduction in bout rate during the post-CSD period (Figure 3C). Remarkably, despite the reduction in locomotion following CSD, we observed similar bout characteristics at baseline and post-CSD, including bout duration (Figure 3D) and peak velocity (Figure 3E). Given that CSD had minimal effect on locomotion bout characteristics, we next examined its effect on meningeal deformations. Surprisingly, CSD did not affect bout-related meningeal deformations: we observed similar scaling, shearing, and Z-shift values during the 2 hr post-CSD (Figure 3F–H). Figure 3 Download asset Open asset Locomotion and related meningeal deformations pre- and post-cortical spreading depolarization (CSD). (A) In head-fixed mice, wheel running is associated with meningeal scaling, shearing, and positive Z-shift (i.e. meningeal movement toward the skull). (B) When compared to the baseline period, there was an overall reduction in the time mice spent running during the 2 hr post-CSD observation period (**p<0.01, paired t-test, 9 CSDs in 7 mice). (C) CSD also decreased locomotion bout rate (*p<0.05, Wilcoxon, signed rank test). (D, E) However, CSD did not affect bout duration (p=0.50, paired t-test) or bout peak velocity (p=0.18, paired t-test). (F, G, H) CSD also did not affect subsequent locomotion-evoked meningeal scaling, shearing, or Z-shift (p=0.56; p=0.55, p=0.18, paired t-tests, respectively, 9 CSDs, in 7 mice for scale and shear, 7 CSDs in 7 mice for Z-shift). Bars depict the mean. Having shown that locomotion bout charactersitics and the related meningeal deformations are not altered during the 2 hrs following CSD, we next compared afferent responses during locomotion bouts before and after CSD. Initial observations of afferent activation during locomotion indicated enhanced responsiveness following CSD (Figure 4A). To systematically investigate this augmented afferent response, we used GLMs (see Materials and methods and Blaeser et al., 2022d) to assess whether meningeal afferent activity becomes sensitized to the state of locomotion and/or to various aspects of meningeal deformation following CSD. We modeled each afferent’s activity based on variables that describe (1) the binary state of locomotion, (2) mouse velocity, or (3) aspects of meningeal deformation, including scaling, shearing, and Z-shift. Figure 4 Download asset Open asset Cortical spreading depolarization (CSD) leads to sensitization of meningeal afferents to local deformation signals. (A) Example of meningeal afferent sensitization following CSD. Locomotion and its related Z-shift (bottom traces) are comparable before (left) and after (right) CSD, but afferent fibers exhibit greater responses associated with the Z-shift after CSD (heatmaps, top panels). (B) Example general linear model (GLM) fit of afferent activity in response to Z-shifts before CSD. A raw calcium activity trace recorded pre-CSD (gray traces, Z-scored; σ: 1 standard deviation) is plotted along with the model fit (purple). The deviance explained (‘dev exp’) is a metric of GLM fit quality and is above the threshold (0.05) for classifying an afferent’s activity as reasonably well fit by the GLM. The activity of this example afferent could not be predicted by other deformation or locomotion variables (not shown), suggesting unique sensitivity to Z-shift. (C) GLM β coefficients used as a metric of the coupling between the Z-shift and the activity of the example afferent shown in b across different delays. A maximal coefficient at zero delay indicates the alignment of activity with Z-shifts. Note the greater afferent activation per unit Z-shift after CSD relative to baseline, indicative of an augmented or sensitized response. (D) Pie chart indicating the numbers and distribution of all afferents well fit by deformation and/or locomotion signals either before and/or after CSD. Afferents were categorized as sensitized if they (i) had significant GLM fits both pre- and post-CSD and higher coefficients for a given deformation and/or locomotion predictor post-CSD (purple) or (ii) were well fit only post-CSD (magenta). Two small subsets of afferents categorized as desensitized had worse GLM fits post-CSD (mustard) or were no longer well fit post-CSD (orange). The incidence of afferent sensitization exceeded that of desensitization (p<0.001, Χ2 test). (E, F) Comparisons of pre- and post-CSD GLM coefficients for the deformation and locomotion predictors. Data are shown for sensitized afferents with well-fit models pre- and post-CSD (corresponding to the purple population in d) and for afferents with well-fit models only post-CSD (i.e. silent pre-CSD, corresponding to the magenta population in d). Mouse velocity coefficients were close to 0 in all cases (not shown). In the two sensitized afferent populations, only coefficients related to deformation predictors increased post-CSD (**p<0.01, ***p<0.001, ****p<0.0001, Wilcoxon sign rank test with correction for multiple analyses). (G, H) The response bias of sensitized afferents to meningeal deformation was further observed when comparing these GLMs to restricted GLMs that included only the group of deformation predictors or the group of locomotion predictors. The deviance explained by the deformation response component (estimated as the difference between the full GLM and the GLM lacking deformation variables) was significantly greater than for the locomotion response component in sensitized afferents that were well fit pre- and post-CSD and for those that were well fit only post-CSD (***p<0.001 and ****p<0.0001, Wilcoxon test for g and h, respectively). Bars depict mean; error bars indicate SEM. (I) Among the sensitized afferents with enhanced sensitivity to deformation variables, we observed a similar sensitization to scale, shear, and Z-shift variables. Bars depict mean; error bars indicate SEM. (J) There was no difference in the incidence of sensitized afferents among afferents that showed prolonged activation, prolonged suppression, or no change in ongoing activity post-CSD (p=0.9, Χ2 test; Figure 2). We first focused on afferents whose activity could be predicted by the same variables both at baseline and following CSD (i.e. afferents that exhibited sensitivities to locomotion and/or deformation signals both before and after CSD, n=67/325 afferents, 9 CSDs in 7 mice). Higher GLM coefficients for a given variable post-CSD indicate greater afferent response during an equal expression level of that variable. Thus, we defined an afferent as sensitized by CSD if its GLM coefficients post-CSD were larger than at baseline (i.e. stronger activation of afferents per unit deformation or locomotion; for example, see Figure 4C). Using these criteria, we identified elevated locomotion and/or deformation-related activity (i.e. sensitization) post-CSD in ~51% of afferents (34/67; Figure 4D). In contrast, only 12% of afferents (8/67) showed reduced locomotion- and deformation-related activity (i.e. desensitization) post-CSD. Sensitivity was unchanged in the remaining 37% of afferents (25/67). Meningeal afferent sensitization following CSD may reflect increased sensitivity to mechanical deformation and/or to other physiological processes that occur in response to locomotion (Blaeser et al., 2022d). Because locomotion and meningeal deformations are partially correlated (Blaeser et al., 2022d), we next estimated their relative contributions to the augmented afferent responsiveness post-CSD by comparing, for each sensitized afferent, the GLM coefficients for baseline epochs and for post-CSD Surprisingly, we that only the deformation coefficients were increased post-CSD (Figure suggesting that meningeal afferent sensitization following CSD an increased sensitivity to local mechanical deformations. We next considered the that sensitization is also in the of responsiveness to locomotion and/or meningeal deformation in previously silent (i.e. meningeal afferents (Levy and 2002; Levy and Moskowitz, 2023). among the afferents that were not well fit before CSD (i.e. we detected a population that developed a sensitivity to locomotion and deformation variables following CSD afferents whose activity could be well predicted by locomotion and deformation variables following contrast, their sensitivity to these variables after CSD (i.e. afferents that were well fit before but not after Overall, the above findings show that more afferents displayed increased sensitivity than decreased sensitivity following CSD This sensitized afferent population also displayed post-CSD increases in GLM coefficients related to deformation but not to locomotion (Figure To further the of the locomotion and deformation variables to the afferent we estimated their relative contributions to the overall of the models to the afferent activity pre- vs. post-CSD. To this we the difference in model fit using the full model with all variables or models lacking either the of deformation variables or locomotion variables. We that the impact of deformation variables on the model fit was greater post-CSD than pre-CSD, while the impact of locomotion variables was similar pre- and post-CSD. This was for afferents with models that were well fit both at baseline and following CSD (Figure purple subset in Figure and for those with models that were well fit only post-CSD (Figure magenta subset in Figure 4D). analysis revealed that scale, shear, and Z-shift deformations on average, in the activity of sensitized afferents (Figure these data that the afferent sensitization following CSD involves increased afferent responsiveness to a of meningeal deformation variables than to other studies in anesthetized rats suggested that the mechanisms underlying meningeal afferent mechanical sensitization are of those for increased ongoing discharge in migraine including CSD (Levy and 2002; et al., et al., Zhao and Levy, Zhao et al., using the CSD model in awake mice, we also no between sensitization and sustained changes in ongoing activity, as similar of sensitized and afferents were activated, suppressed, or did not display any change in their ongoing activity following CSD (Figure Discussion studies suggested that CSD drives meningeal that can lead to the headache in migraine with These which mostly invasive experiments in anesthetized rats with surgically exposed meninges, showed prolonged activation and mechanical sensitization of meningeal afferents and Levy, To better understand migraine pathophysiology and improve clinical translation, we used two-photon calcium imaging to for the first CSD-related changes in the responsiveness of individual meningeal sensory afferents at the level of their fibers in the closed of a behaving We show that a single CSD episode drives a wave of calcium activity across most afferents while a more prolonged change in ongoing activity in only a small We then afferent calcium imaging with of locomotion and estimates of local meningeal deformations. This approach revealed that CSD causes prolonged of afferent responsiveness to meningeal deformations associated with locomotion in previously sensitive afferents and mechanical responses in previously silent afferents. These data the notion that enhanced responsiveness of meningeal afferents to local meningeal deformation is the neural substrate for headache pain associated with physical activity following migraine The study the first of a CSD-associated calcium wave across meningeal afferent fibers and along the length of individual fibers. A rise in calcium detected by the normally indicates an calcium et al., In contrast, the seconds-long wave of calcium along individual afferent fibers we observed is incongruent with the of may be related to depolarizations et al., and the of calcium et al., Our data the notion that meningeal afferents can generate and calcium during CSD. In increased calcium could drive the of sensory such as that can a local response to migraine pain et al., et al., Levy and Moskowitz, 2023). The mechanisms underlying the acute CSD-related afferent calcium wave We observed meningeal deformation in response to CSD, to the swelling of cortical and decreased extracellular space. However, this deformation was not associated with the acute afferent response, to be its A mechanism involving local depolarizing effects of diffusible excitatory such as whose cortical levels show a wave of with the of the CSD wave et al., is more to a we also observed in calcium activity across of individual afferent fibers oriented to the calcium we the that some afferents also signal via during the passage of the CSD wave. recordings in anesthetized rats previously prolonged in

  PublisherDOI

• Reviewer #1 (Public Review): Sensitization of meningeal afferents to locomotion-related meningeal deformations in a migraine model

  2024-01-29

  peer-reviewOpen access

  Migraine headache is hypothesized to involve the activation and sensitization of trigeminal sensory afferents that innervate the cranial meninges. To better understand migraine pathophysiology and improve clinical translation, we used two-photon calcium imaging via a closed cranial window in awake mice to investigate changes in the responses of meningeal afferent fibers using a preclinical model of migraine involving cortical spreading depolarization (CSD). A single CSD episode caused a seconds-long wave of calcium activation that propagated across afferents and along the length of individual afferents. Surprisingly, unlike previous studies in anesthetized animals with exposed meninges, only a very small afferent population was persistently activated in our awake mouse preparation, questioning the relevance of this neuronal response to the onset of migraine pain. In contrast, we identified a larger subset of meningeal afferents that developed augmented responses to acute three-dimensional meningeal deformations that occur in response to locomotion bouts. We observed increased responsiveness in a subset of afferents that were already somewhat sensitive to meningeal deformation before CSD. Furthermore, another subset of previously insensitive afferents also became sensitive to meningeal deformation following CSD. Our data provides new insights into the mechanisms underlying migraine, including the emergence of enhanced meningeal afferent responses to movement-related meningeal deformations as a potential neural substrate underlying the worsening of migraine headache during physical activity.

  PublisherDOI

Recent grants

• Chronic two-photon calcium imaging of intracranial meningeal afferents in awake behaving mice

  NIH · $476k · 2017–2020

• Behavior-dependent neuromodulation of retinogeniculate axonal boutons

  NIH · $503k · 2019–2021

• Neural Pathway Linking Nutritional State To Food-Cue Responses In Insular Cortex

  NIH · $2.2M · 2016–2022

• Multiphoton Imaging of Thoughts of Food During Natural and Induced Hunger States

  NIH · $2.5M · 2014–2019

• Look inward: brainstem and cortical circuits for boosting interoceptive attention

  NIH · $6.6M · 2019–2025

Frequent coauthors

• Andrew Lutas

  National Institute of Diabetes and Digestive and Kidney Diseases

  81 shared

• Bradford B. Lowell

  Harvard University

  50 shared

• Arthur U. Sugden

  Harvard University

  49 shared

• Christopher I. Moore

  Providence College

  38 shared

• Rohan N. Ramesh

  Beth Israel Deaconess Medical Center

  38 shared

• Christian R. Burgess

  University of Michigan–Ann Arbor

  38 shared

• Joseph C. Madara

  Harvard University

  37 shared

• Maria K. Lehtinen

  Boston Children's Hospital

  30 shared