Biology subjects

Storace, D. A.

Publications and source records attributed to Storace, D. A..

6 recordsLinked to original sources

bioRxiv2025

Heterogeneous monotonic and non-monotonic responses to odor in mitral/tufted glomeruli of the mouse olfactory bulb

Animals can recognize and discriminate between different odors and the same odor over a range of concentrations. Processing within the mouse olfactory bulb (OB) may be involved, yet the underlying mechanisms remain unclear. Each olfactory receptor neuron (ORN) type maps to the OB in olfactory receptor specific channels called glomeruli where they connect with the dendrites of mitral/tufted cells (MTCs), which project their axons to the rest of the brain. Differences between input and output define the functions carried out by a brain region. Using in vivo dual-color 2-photon Ca2+ imaging from the ORNs and MTCs innervating the same glomeruli in the mouse OB, we identified a novel MTC response type with a non-monotonic concentration-response relationship. We used mathematical modeling to demonstrate that non-monotonic response types are consistent with a form of interglomerular processing, which we propose is a mechanism to facilitate odor discrimination and the ability to achieve concentration-invariant odor perception. Graphical AbstractThe olfactory bulb input-output transformation was imaged using dual-color 2-photon imaging. (Top) Cartoon and histological examples of labeling the olfactory bulb input and output using spectrally distinct optical sensors. (Middle) Modeling and experimental work reveal that input neurons that respond with primarily monotonic concentration-response relationships are transformed into a mix of monotonic and non-monotonic responses. (Bottom) Olfactory bulb output state space for a population of 3 glomeruli with exclusively monotonic responses (black), and with both monotonic and non-monotonic responses (red). Each trajectory represents a cloud of points that reflects variations in the fluctuations of molecular components present in natural odor stimuli. Monotonic responses alone cluster together, while multiple response types broaden coverage of MTC state space. Greater coverage of state space makes it easier to discriminate one odor from another, even though the dimension of olfactory bulb state space is larger than 3. Key PointsO_LIAlthough the olfactory bulb is the first stage of olfactory sensory processing, its role in transforming sensory information remains poorly understood. C_LIO_LIDifferent olfactory receptor neuron types map to the olfactory bulb in olfactory receptor specific channels called glomeruli, where they interact with the dendrites of mitral/tufted cells, which project to the rest of the brain. C_LIO_LIWe used dual-color 2-photon Ca2+ imaging to image the input-output transformation olfactory receptor neuron (ORN) and mitral/tufted (MTC) glomeruli across a wide concentration range. C_LIO_LIThe ORN input to all tested glomeruli responded to increasing concentration changes with monotonic increases, while the corresponding MTCs outputs of each glomerulus responded with monotonic and non-monotonic changes. C_LIO_LIThe results were consistent with a mathematical model of the olfactory bulb incorporating feed-forward and lateral inhibition. C_LI

neuroscience↗

bioRxiv2025

Glutamatergic heterogeneity in the neuropeptide projections from the lateral hypothalamus to the mouse olfactory bulb

The direct pathway from the lateral hypothalamus to the mouse olfactory bulb (OB) includes neurons that express the neuropeptide orexin-A, and others that do not. The OB-projecting neurons that do not express orexin-A are present in an area of the lateral hypothalamus known to contain neurons that express the neuropeptide melanin-concentrating hormone (MCH). We used virally mediated anterograde tract tracing and immunohistochemistry for orexin-A and MCH to demonstrate that the OB is broadly innervated by axon projections from both populations of neurons. Orexin-A and MCH were expressed in each OB layer across its anterior to posterior axis. Both orexin-A and MCH neurons are genetically heterogeneous, with subsets that co-express an isoform of vesicular glutamate transporter (VGLUT). We used high-resolution confocal imaging to test whether the projections from orexin-A and MCH neurons to the OB reflect this glutamatergic heterogeneity. The majority ([~]57%) of putative orexin-A axon terminals overlapped with VGLUT2, with smaller proportions that co-expressed VGLUT1, or that did not overlap with either VGLUT1 or VGLUT2. In contrast, only [~]26% of putative MCH axon terminals overlapped with VGLUT2, with the majority not overlapping with either VGLUT. Therefore, the projections from the lateral hypothalamus to the OB are genetically heterogeneous and include neurons that can release two different neuropeptides. The projections from both populations are themselves genetically heterogeneous with distinct ratios of glutamatergic and non-glutamatergic axon terminals. Three Key PointsO_LIA direct anterograde projection from orexin-A-expressing neurons in the hypothalamus to the mouse olfactory bulb (OB) was confirmed using virally mediated tract tracing. C_LIO_LIOrexin-A and melanin-concentrating hormone (MCH), two neuropeptides primarily produced in the lateral hypothalamus are broadly expressed throughout the mouse OB. C_LIO_LIApproximately 64% of putative orexin-A axon terminals overlapped with vesicular glutamate transporter type 1 (VGLUT1) or type 2 (VGLUT2). In contrast, only 25% of putative MCH axon terminals overlapped with VGLUT2. C_LI

neuroscience↗

bioRxiv2024

Recent odor experience selectively modulates olfactory sensitivity across the glomerular output in the mouse olfactory bulb

Although animals can reliably locate and recognize odorants embedded in complex environments, the neural circuits for accomplishing these tasks remain incompletely understood. Adaptation is likely to be important as it could allow neurons in a brain area to adjust to the broader sensory environment. Adaptive processes must be flexible enough to allow the brain to make dynamic adjustments, while maintaining sufficient stability so that organisms do not forget important olfactory associations. Processing within the mouse olfactory bulb is likely involved in generating adaptation, although there are conflicting models of how it transforms the glomerular output of the mouse olfactory bulb. Here we performed 2-photon Ca2+ imaging from mitral/tufted glomeruli in awake mice to determine the time course of recovery from adaptation, and whether it acts broadly or selectively across the glomerular population. Individual glomerular responses, as well as the overall population odor representation was similar across imaging sessions. However, odor-concentration pairings presented with interstimulus intervals upwards of 30-s evoked heterogeneous adaptation that was concentration-dependent. We demonstrate that this form of adaptation is unrelated to variations in respiration, and olfactory receptor neuron glomerular measurements indicate that it is unlikely to be inherited from the periphery. Our results indicate that the olfactory bulb output can reliably transmit stable odor representations, but recent odor experiences can selectively shape neural responsiveness for upwards of 30 seconds. We propose that neural circuits that allow for non-uniform adaptation across mitral/tufted glomerular could be important for making dynamic adjustments in complex odor environments.

neuroscience↗

bioRxiv2022

Precise temporal control of GEVI conformations enables the visualization of charge migration in a fluorescent protein resulting in an improved optical response

Rapid and reproducible optical transitions of a fluorescent protein (FP) can be achieved with a Genetically Encoded Voltage Indicator (GEVI) via manipulation of the membrane potential. These transitions revealed novel effects of internal mutations near the chromophore that would not be detected under steady state conditions. Mutating an internal threonine (T203) affected the speed of the voltage-dependent fluorescence transition suggesting a conformational change inside the protein. These optical transitions also demonstrated interplay between internal and externally oriented sidechains of the {beta}-can structure. Replacing the steric hindrance of a phenylalanine near the chromophore with threonine (F165T) did not alter the resting fluorescence but resulted in a more complex fluorescent transition providing evidence for a flexible chromophore undergoing conformational changes. F165T orientation was influenced by the flanking external amino acids at positions 164 and 166 with 164F/165T/166T exacerbating the complexity of the voltage-dependent transition while 164T/165T/166F reduced the flexibility of the chromophore resembling the transition pattern of the original F165 version. Alphafold predictions reveal a threonine switch with different orientations of the F165T internal side chain depending on the direction of the offset in polarity at external positions 164 and 166. The crystal structures of the pH-sensitive FP, Super Ecliptic pHluorin and two derivatives solved in varying pH conditions also indicate interactions between the external protein surface and the internal environment providing another example of a threonine switch near the chromophore at T203. This ability to orient internal sidechains has led to the development of a novel GEVI that gets brighter upon depolarization of the plasma membrane, works at low light levels, is less susceptible to physiological pH, and provides in vivo signals. These observations affecting fluorescent transitions should also prove valuable to the development of any FP-based biosensor.

neuroscience↗

bioRxiv2020

Voltage imaging using transgenic mouse lines expressing the GEVI ArcLight in two olfactory cell types

Genetically encoded voltage indicators (GEVIs) allow for cell-specific optical recordings of membrane potential changes in defined cell populations. One tool that would further their use in the in vivo mammalian brain is transgenic reporter animals that facilitate precise and repeatable targeting with high expression levels. The present literature on the development and use of transgenic mouse lines as vehicles for GEVI expression is limited. Here we report the first in vivo experiments using a transgenic reporter mouse for the GEVI ArcLight (Ai86(TITL-ArcLight)), which utilizes a Cre/tTA dependent expression system (TIGRE 1.0). Following pairing to appropriate Cre- and tTA transgenic mice, we report two mouse lines with ArcLight expression restricted to olfactory sensory neurons (OMP-ArcLight), and a subpopulation of interneurons that include periglomerular and granule cells (Emx1-ArcLight) in the olfactory bulb (OB). The ArcLight expression in these lines was sufficient for in vivo imaging of odorant responses in single trials. Odor responses were measured in the OB using epifluorescence and 2-photon imaging. The voltage responses were odor-specific and concentration-dependent, and confirmed earlier conclusions from calcium measurements. This study shows that the ArcLight Ai86(TITL-ArcLight) transgenic line is a flexible genetic tool that can be used to record neuronal electrical activity of a variety of cell types with a signal-to-noise ratio that is comparable to previous reports using viral transduction.

neuroscience↗

bioRxiv2019

The olfactory bulb contributes to the adaptation of odor responses: the input-output transformation

While humans and other animals exhibit adaptation to odorants, the neural mechanisms involved in this process are incompletely understood. One possibility is that it primarily occurs as a result of the interactions between odorants and odorant receptors expressed on the olfactory sensory neurons in the olfactory epithelium. In this scenario, adaptation would arise as a peripheral phenomenon transmitted into the brain. An alternative possibility is that adaptation occurs as a result of processing in the brain. Here we asked whether the olfactory bulb, the first stage of olfactory information processing in the brain, is involved in perceptual adaptation. Multicolor imaging was used to simultaneously measure the olfactory receptor nerve terminals (input) and mitral/tufted cell apical dendrites (output) that innervate the olfactory bulb glomerular layer. Repeated odor stimulation of the same concentration resulted in a decline in the output maps, while the input remained relatively stable. The results indicate that the mammalian olfactory bulb participates in olfactory adaptation.

neuroscience↗