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Smear, M. C.

Publications and source records attributed to Smear, M. C..

7 recordsLinked to original sources

Visualizing and sonifying neurodata (ViSoND) for enhanced observation

Neuroscience needs observation. Observation lets us evaluate data quality, judge whether models are biologically realistic, and generate new hypotheses. However, high-dimensional behavioral and neural data are too complex to be easily displayed and eye-tested. Computational methods can reduce the dimensionality of data and reveal statistically robust dynamical structure but often yield results that are difficult to relate back to the underlying biology. In addition, the choice of what parameters to quantify may not capture unexpectedly relevant aspects of the data. To supplement quantification with enhanced qualitative observation, we developed Visualization and Sonification of NeuroData (ViSoND), an open-source approach for displaying multiple data streams using video and sonification. Sonification is nothing new to neuroscience. Scientists have sonified their physiological preparations since Lord Adrians earliest recordings. We extend this tradition by mapping multiple physiological datastreams to musical notes using MIDI. Synchronizing MIDI to video provides an opportunity to watch an animals movement while listening to physiological signals such as action potentials. Here we provide two demonstrations of this approach. First, we used ViSoND to interpret behavioral structure revealed by a computational model trained on the breathing rhythms of freely behaving mice. Second, ViSoND revealed patterns of neural activity in mouse visual cortex corresponding to eye blinks, events that were previously filtered out of analysis. These use cases show that ViSoND can supplement quantitative rigor with observational interpretability. Additionally, ViSoND provides an accessible way to display data which may broaden the audience for communication of neuroscientific findings.

neuroscience↗

The impact of a psychedelic drug on olfactory search behavior by mice

Animals use their sense of smell for survival and well-being. Any disruption to olfactory perception, such as in the case of olfactory hallucinations, can lead to devastating consequences and decreased quality of life. Psychedelics interrupt and distort accurate perception, yet little is known about the impact of psychedelics on olfactory behaviors. Using an olfactory search task, we investigated the impact of the psychedelic 2,5-dimethoxy-4-iodoamphetamine (DOI) on olfactory search behavior of mice. We found that DOI decreases search accuracy, alters movement, and increases sniff rate. These findings suggest that the olfactory behaviors are altered by DOI, elucidating psychedelic-induced changes to olfactory processes.

neuroscience↗

Olfactory bulb tracks breathing rhythms and place in freely behaving mice

Vertebrates sniff to control the odor samples that enter their nose. These samples can not only help identify odorous objects, but also locations and events. However, there is no receptor for place or time. Therefore, to take full advantage of olfactory information, an animals brain must contextualize odor-driven activity with information about when, where, and how they sniffed. To better understand contextual information in the olfactory system, we captured the breathing and movements of mice while recording from their olfactory bulb. In stimulus- and task-free experiments, mice structure their breathing into persistent rhythmic states which are synchronous with statelike structure in ongoing neuronal population activity. These population states reflect a strong dependence of individual neuron activity on variation in sniff frequency, which we display using "sniff fields" and quantify using generalized linear models. In addition, many olfactory bulb neurons have "place fields" that display significant dependence of firing on allocentric location, which were comparable with hippocampal neurons recorded under the same conditions. At the population level, a mouses location can be decoded from olfactory bulb with similar accuracy to hippocampus. Olfactory bulb place sensitivity cannot be explained by breathing rhythms or scent marks. Taken together, we show that the mouse olfactory bulb tracks breathing rhythms and self-location, which may help unite internal models of self and environment with olfactory information as soon as that information enters the brain.

neuroscience↗

A dynamic sequence of visual processing initiated by gaze shifts

Animals move their head and eyes as they explore and sample the visual scene. Previous studies have demonstrated neural correlates of head and eye movements in rodent primary visual cortex (V1), but the sources and computational roles of these signals are unclear. We addressed this by combining measurement of head and eye movements with high density neural recordings in freely moving mice. V1 neurons responded primarily to gaze shifts, where head movements are accompanied by saccadic eye movements, but not to head movements where compensatory eye movements stabilize gaze. A variety of activity patterns immediately followed gaze shifts, including units with positive, biphasic, or negative responses, and together these responses formed a temporal sequence following the gaze shift. These responses were greatly diminished in the dark for the vast majority of units, replaced by a uniform suppression of activity, and were similar to those evoked by sequentially flashed stimuli in head-fixed conditions, suggesting that gaze shift transients represent the temporal response to the rapid onset of new visual input. Notably, neurons responded in a sequence that matches their spatial frequency preference, from low to high spatial frequency tuning, consistent with coarse-to-fine processing of the visual scene following each gaze shift. Recordings in foveal V1 of freely gazing head-fixed marmosets revealed a similar sequence of temporal response following a saccade, as well as the progression of spatial frequency tuning. Together, our results demonstrate that active vision in both mice and marmosets consists of a dynamic temporal sequence of neural activity associated with visual sampling. HighlightsO_LIDuring free movement, neurons in mouse V1 respond to head movements that are accompanied by a gaze-shifting saccadic eye movement, but not a compensatory eye movement. C_LIO_LINeurons respond to gaze shifts with diverse temporal dynamics that form a sequence across the population, from early positive responses to biphasic and negative responses. C_LIO_LIIn darkness, most neurons show a uniform suppression following a gaze shift. C_LIO_LITemporal dynamics of responses correspond to a neurons temporal and spatial frequency preferences, consistent with a coarse-to-fine processing sequence. C_LIO_LIA similar temporal sequence following saccades is observed in foveal V1 of freely gazing head-fixed marmosets, demonstrating shared aspects of active visual processing across species. C_LI

neuroscience↗

Sniff-synchronized, gradient-guided olfactory search by freely-moving mice

For many organisms, searching for relevant targets such as food or mates entails active, strategic sampling of the environment. Finding odorous targets may be the most ancient search problem that motile organisms evolved to solve. While chemosensory navigation has been well characterized in micro-organisms and invertebrates, spatial olfaction in vertebrates is poorly understood. We have established an olfactory search assay in which freely-moving mice navigate noisy concentration gradients of airborne odor. Mice solve this task using concentration gradient cues and do not require stereo olfaction for performance. During task performance, respiration and nose movement are synchronized with tens of milliseconds precision. This synchrony is present during trials and largely absent during inter-trial intervals, suggesting that sniff-synchronized nose movement is a strategic behavioral state rather than simply a constant accompaniment to fast breathing. To investigate the spatiotemporal structure of these active sensing movements, we used machine learning methods to parse motion trajectories into elementary movement motifs. Motifs fall into two clusters, which correspond to investigation and approach states. Investigation motifs lock precisely to sniffing, such that the individual motifs preferentially occur at specific phases of the sniff cycle. This work clarifies sensorimotor strategies for mouse olfactory search and guides ongoing work into the underlying neural mechanisms.

neuroscience↗

Sniff invariant odor coding

Sampling regulates stimulus intensity and temporal dynamics at the sense organ. Despite variations in sampling behavior, animals must make veridical perceptual judgments about external stimuli. In olfaction, odor sampling varies with respiration, which influences neural responses at the olfactory periphery. Nevertheless, rats were able to perform fine odor intensity judgments despite variations in sniff kinetics. To identify the features of neural activity supporting stable intensity perception, in awake mice we measured responses of Mitral/Tufted (MT) cells to different odors and concentrations across a range of sniff frequencies. Amplitude and latency of the MT cells responses vary with sniff duration. A fluid dynamics (FD) model based on odor concentration kinetics in the intranasal cavity can account for this variability. Eliminating sniff waveform dependence of MT cell responses using the FD model significantly improves concentration decoding. This suggests potential schemes for sniff waveform invariant odor concentration coding.\n\nHighlightsO_LIOdor concentration discrimination does not depend on sniff frequency\nC_LIO_LIAmplitude and latency of MT cell responses vary with sniff frequency\nC_LIO_LIA fluid dynamic based model accounts for sniff dependent variability in the responses\nC_LIO_LITransforming MT cell responses with this model achieves sniff invariant coding\nC_LI

neuroscience↗

Odor concentration change detectors in the Olfactory Bulb

Dynamical changes in the environment strongly impact our perception 1,2. Consistent with this, sensory systems preferentially represent stimulus changes, enhancing temporal contrast 3,4. In olfaction, odor concentration changes across consecutive inhalations ({Delta}Ct) can guide odor source localization. Yet the neural representation of {Delta}Ct has not been studied in vertebrates. We have found that a subset of mitral/tufted (M/T) cells in the olfactory bulb explicitly represent {Delta}Ct. These concentration change detectors are direction selective: some respond to positive {Delta}Ct, while others represent negative {Delta}Ct. This change detection enhances the contrast between different concentrations and the magnitude of contrast enhancement scales with the size of the concentration step. Further, {Delta}Ct can be read out from the total spike count per sniff, unlike odor identity and intensity, which are represented by fast temporal spike patterns. Our results demonstrate that a subset of M/T cells explicitly represents {Delta}Ct, providing a signal that may instruct navigational decisions in downstream olfactory circuits.

neuroscience↗