Tag: Matt Smear

Active Olfactomotor Movements in Head-Fixed Mice

Presenter(s): Isabelle Cullen — Neuroscience

Faculty Mentor(s): Dr. Matt Smear, Dr. Avinash Singh

Session: (In-Person) Oral Panel—Stimuli and Response

Olfactomotor responses are respiratory, orofacial, and locomotive movements used during olfactory sampling and in response to odors (Rabell et al. 2017, Kurnikova, Deschênes, and Kleinfeld 2019, Findley et al. 2020, Johnson et al 2003, Wesson et al 2008, Jones and Urban 2018). Altered sensory sampling behaviors, such as eye movement, temperature insensitivity, and excessive sniffing, have been identified in individuals with Autism Spectrum Disorder (ASD). In addition, Rozenkrantz et al. (2015) showed that olfactomotor behavior is affected in children with ASD. These children do not modulate sniffing behavior to aversive odors despite correctly identifying odors as unpleasant, suggesting an altered unconscious motor response. To investigate the neural mechanisms underlying olfactomotor sampling, we investigated respiratory and orofacial responses to odor using wildtype mice. Wildtype mice are exposed to 2-phenylethanol (attractive odor), 2-methylbutyric acid (aversive odor), alpha-pinene (neutral odor), or clear air in the course of a behavioral session. We record respiration with an intranasal thermistor, and track orofacial movements using DeepLabCut. Our preliminary results in wildtype mice (n=2) suggest that mice alter their sniffing speed and nose movement in response to odor stimuli. This work will shed light on active olfaction and help us understand more about naturalistic olfactomotor behaviors.

Utilizing the Optomotor Response to Measure the Effect of Cadaverine on Larval Zebrafish Behavior

Presenter(s): Laura Reich − Biology

Faculty Mentor(s): Adam Miller, Matt Smear

Poster 41

Research Area: Natural Science

Zebrafish behavior is strongly influenced by environmental stimuli, and olfaction (sense of smell) is a powerful driver of behavioral responses. Our overarching goal is to measure an odorant’s effect on a behavioral response and to understand the sensorimotor transformations that occur within the brain as the animal smells its world and reacts accordingly. As a first step towards this goal, we used a repetitive visual stimulus to induce the optomotor response, causing the zebrafish to swim in the direction of perceived motion. This method allows us to orient the larval zebrafish towards a region of water with an odorant of interest. This research specifically focuses on the impact of cadaverine, an odorant known to stimulate an aversive response, on larval zebrafish. We hypothesize that while a repetitive visual stimulus is in use, the distribution of larval zebrafish in a petri dish will differ when cadaverine is administered to a section of the water. Rather than moving with the visual stimulus, we predict that the fish will avoid regions with cadaverine, halting the optomotor response. This research serves to demonstrate that olfaction, the sense that is often forgotten and taken for granted, plays an important role in zebrafish and can potentially overcome visually-directed behavior.

Calcium Imaging of Mice Brains Injected with Glutamate-Sensing Fluorescent Reporter (GluSnFr)

Presenter(s): Nelly Nouboussi − Biology, Human Physiology

Faculty Mentor(s): Matt Smear, Teresa Findley

Poster 63

Research Area: Natural science

One of the most important tasks a sensory system performs is locating the source of a stimulus. However, very little is known about how the olfactory systems localizes odors. The goal of this project is to develop a technique that will allow us to image the glomeruli, the area in the brain where neurons from the brain and the nose connect. We will image using superfolder intensity-based glutamate-sensing fluorescent reporter (referred to as GluSnFR), which localizes to the extracellular surface of neurons and can thus report concentrations of the neurotransmitter glutamate at synapses. A virus carrying the GluSnFr gene will be injected in the brain during survival surgeries. The first step in this project is to confirm that GluSnFr is expressed by the cells of interest, which will be accomplished by sectioning samples of mice brains 2 weeks after injection, and looking for expression using a microscope. Once it is established that GluSnFr is expressed, we will perform glutamate imaging to obtain images of olfactory bulb activity. We predict that GluSnFr will indicate when neurons are firing, and this will be illustrated in the images taken. This is significant because this technique will ultimately be used to image the glomeruli of mice performing olfactory search tasks, in order to establish a correlation between the activity of neurons and the behavior of the animals.

Odor Concentration Change Sensing in Mice

Presenter(s): Antonio Munoz

Faculty Mentor(s): Avinash Singh & Matt Smear

Oral Session 4 CQ

Our brains are constantly tracking dynamic sensory information from our environment. Exactly how the brain computes sensory input over time is not fully understood. The mouse olfactory system provides a great model to study stimuli changes over time because mice utilize odor concentration changes for olfactory navigation. It is not understood how mice optimize sensory information for spatial navigation.

One of the mechanisms guiding odor localization involves changes in odor concentration (ΔC). The ability to track odor concentration gradients is critical for vertebrates like the mouse for survival.
Previous work in the Smear lab has revealed a population of neurons in the olfactory bulb that respond to dynamic stimuli changes. The neural activity in this population of neurons was sensitive to concentration changes in odor.

The brain somehow maintains a neural representation of odor across sniffs, and this is the behavior I want to observe. A behavioral representation of these ΔC neurons had previously not been studied before. By investigating ΔC tracking behaviors in mice, my goal is to relate the neural activity we see in this neuronal population with a behavioral representation in mice and increase our understanding of sensory optimization.

Glomerular Signals Underlying Olfactory Navigation

Presenter(s): Nelly Nouboussi—Biology

Faculty Mentor(s): Matt Smear, Amanda Welch

Session 3: The Substance of Us

The olfactory system is the least studied sense although it is very important for our existence . Our lab has examined the behavioral structure of olfactory navigation . Our next goal is to compare sampling movements directly against sensory input in order to establish a correlation between neural activity and behavior . The first step in this goal, which is the topic of my thesis, is to successfully express fluorescence indicators in the olfactory bulb and to detect this expression using our imaging apparatus . We are focusing specifically in the glomeruli, which contains the neurons responsible for converting odor information into action potentials . To achieve the expression of our fluorescence sensor GCaMP, we either injected a virus encoding the fluorescence protein into mice brains or engineered mice to encode the sensor gene in their genome . We worked with three mice strains:
B6 mice which can express GCaMP anywhere, Tbet-Cre mice which can express the virus only in the mitral layer and Tbet-Cre-Ai148D mice which contain the GCaMP gene in their genome . Histology revealed that we successfully expressed GCaMP in B6 mice, but we could only observe background fluorescence in Tbet-Cre and Tbet-Cre-Ai148D mice . This could result from the frying of the bulb due to continuous expression of the protein or the degradation of the virus . Despite the difficulty of the surgeries, we could visualize activity in the glomeruli of live mice with the two-photon microscope, although our success rate remains low . We are continuously adjusting our protocol to improve our techniques, so we can move on to the next stage of our project .

Imaging Glomerular Signaling of Unrestrained Olfactory Search in Mice

Presenter(s): Isabelle Cullen—Biology

Faculty Mentor(s): Matt Smear, David McCormick

Session: Prerecorded Poster Presentation

Olfaction is vital for many crucial animal behaviors such as social interaction, avoiding predators, and locating food . Our goal is to understand how an animal navigates toward the source of an odor . However, little is known about how odors are coded to inform olfactory search behavior . Air turbulence can cause odor distributions to be highly variable and unpredictable . Although we have previously characterized specific behavioral patterns in turbulent odor plumes, little is known about how odors are translated into movements . Our goal is to capture and understand the sensory input that informs these previously observed behaviors . We do this by injecting iGluSnFR, a fluorescent glutamate reporter, into the mitral cell layer of the olfactory bulb . This reporter tells us how glutamate released from olfactory sensory neuron terminals influences activity of mitral cells . iGluSnFR’s fast kinetics allows us to observe and measure glutamate levels as the mouse performs olfactory navigation . By revealing activity in olfactory sensory neurons during olfactory navigation, this technique can tell us how odor informs the mouse’s brain during active sampling . Following the development of this technique, we will image from iGluSnFR mice performing our olfactory search task to determine the neural computation that connects movement and sensation . Understanding how mice translate odor into behavior will inform our understanding of active sensory sampling behaviors in humans .

Altered Motor Response to Aversive and Attractive Odors as Potential Biomarker for Autism Spectrum Disorders

Presenter(s): Isabelle Cullen—Biology

Faculty Mentor(s): Matt Smear, David McCormick

Session 2: Cells R Us

Active sensing in olfaction is the modulation in sampling behavior (inhalation patterns, or sniffing)
to modulate sensory input . Previous studies in humans and mice observed pleasant odors are sampled at a higher inhalation magnitude, while aversive odors are sampled at lower magnitudes when compared to the clean air control . However, this sniffing modulation is not present in those with autism . Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by deficits in social behaviors, communication skills, narrowed interests, and repetitive behaviors . Rozenkrantz et al . (2015) showed that children with ASD did not modulate sniffing behavior to aversive or attractive odors despite correctly identifying odors as pleasant or unpleasant, suggesting an innate altered motor response rather than perceptual differences . While studying the basis of this behavior in humans is limited, we can access the neural mechanism that underlies this behavior through transgenic mouse lines . With the support of the Smear lab, we will repeat Rozenkratz’s (2015) paradigm using Fragile X-Knockout mice to investigate the neurological mechanisms driving this phenomenon along with orofacial movements during olfaction . Due to COVID-19, data collection is limited, however, we have developed a small raspberry pi based system combined with a camera to track orofacial movements through the experiment . We then use Deep Lab Cut, an AI network, to extract facial patterns and movements of the nose during olfaction . This work will establish a behavioral paradigm for studying autism-related symptoms in mice, and will thus lay the groundwork for understanding the neural mechanisms underlying this disorder, which may serve as a potential biomarker to aid in earlier detection .