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Belluscio, L.

Publications and source records attributed to Belluscio, L..

4 recordsLinked to original sources

The influence of stimulus duration on olfactory identity

Duration of a stimulus plays an important role in coding of sensory information. The role of stimulus duration is extensively studied in tactile, visual and auditory system. In the olfactory system, how the stimulus duration influences the identity of an olfactory information is not well understood. To test this, we activated the olfactory bulbs with blue light in mice expressing channelrhodopsin and behaviorally assessed the relevance of stimulus duration on olfactory identity. Our behavior data demonstrate that stimulus duration changes the olfactory information and the associated behavior.

neuroscience↗

Functional relevance of dual olfactory bulb in olfactory coding

Bilateral convergence of external stimuli is a common feature of vertebrate sensory systems. This convergence of inputs from the bilateral receptive fields allows higher order sensory perception, such as depth perception in the vertebrate visual system and stimulus localization in the auditory system. The functional role of such bilateral convergence in the olfactory system is mostly unknown. To test whether each olfactory bulb contributes a separate piece of olfactory information, and whether information from the bilateral olfactory bulb is integrated, we synchronized the activation of olfactory bulbs with blue light in mice expressing channelrhodopsin in the olfactory sensory neurons and behaviorally assessed the relevance of dual olfactory bulb in olfactory perception. Our findings suggest that each olfactory bulb contributes separate components of olfactory information and mice integrate the olfactory information from each olfactory bulb to identify an olfactory stimulus. Significance statementIdentifying an odor is the first step in olfactory coding, as it is critical for the survival of most animals. Previous studies have shown that bilateral olfactory bulbs help rodents to localize the odor source and navigate accordingly. But It is still unclear whether the bilateral olfactory information plays any role in determining odor identity. Here for the first time, using optogenetics and behavioral experiments, we demonstrate that each olfactory bulb provides distinct olfactory information, and rodents integrate information from the two bulbs to identify an odor.

neuroscience↗

Complement 3 signaling is necessary for the developmental refinement of olfactory bulb circuitry

The olfactory system depends upon organizational maps that are developmentally refined and maintained, however the cellular and molecular mechanisms that underlie these processes are unknown. Studies have shown that microglia and complement molecules are important for the developmental refinement of circuitry within the visual system, thus we asked whether they played a similar role in the olfactory system through the formation of the olfactory bulb (OB) maps, the glomerular and intrabulbar maps. Our findings revealed that microglia in mature animals engulf olfactory sensory neuron (OSN) axons and the synaptic terminals of tufted cells in the glomerular and intrabulbar maps respectively, suggesting microglia could anatomically shape the mature OB circuitry. To determine the mechanisms underlying this axonal pruning activity we used complement 3 (C3) and complement receptor 3 (CR3) knockout mice to investigate if C3 signaling was necessary for precise OB map development. Our results demonstrate that glomerular and intrabulbar map disorganization as typically present in early postnatal mice persists into adulthood when C3 signaling is disrupted. These data clearly establish the C3/CR3 pathway as necessary for the proper developmental refinement of both olfactory maps. We further present the olfactory system as a unique platform to study the role of glia in the development and adult refinement of regenerating circuits.

neuroscience↗

Electron Microscopy Analysis of hAPP-Induced Neurodegeneration in the Glomerular Network

Loss of smell is an early indicator of Alzheimers disease (AD), making the olfactory system an accessible model to study the effect of AD related proteins such as Amyloid Precursor Protein (APP). The regenerative capacity of the system further enables studies of circuit recovery after APP-induced degeneration. While the cellular effects of APP are well documented, little is known about its effects on brain circuits at the ultrastructural level. To study circuitry changes, we overexpressed humanized APP with familial AD mutations (hAPP) in olfactory sensory neurons and performed serial electron microscopy on olfactory bulb glomeruli from both control and hAPP expressing mice. We found that hAPP-expressing mice showed a striking decrease in glomerular connectivity along with widespread changes of subcellular structures. By then turning off hAPP expression for 6 weeks we tested the capacity of glomerular circuits to recover and found clear restoration of both connectivity and subcellular features, including an increase in post-synaptic density to above the control level. These data provide an important ultrastructural view of olfactory regions associated with AD and suggest that circuit recovery is possible in brain tissue that has experienced APP-induced neurodegeneration.

neuroscience↗