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Intrinsic and Synaptic Properties of Olfactory Bulb Neurons and Their Relation to Olfactory Sensory Processing
| Title: | Intrinsic and Synaptic Properties of Olfactory Bulb Neurons and Their Relation to Olfactory Sensory Processing |
| Author: | Balu, Ramani |
| Description: | The elucidation of how sensory information is represented in the brain is a fundamental challenge in neuroscience. Numerous theories exist to explain the encoding of sensory perceptions by brain activity; however, the cellular mechanisms of sensory perception remain a mystery. Because of its stereotyped and relatively simple anatomy, the olfactory bulb represents an ideal system to study sensory coding. This project used cellular electrophysiological and optical imaging methods to investigate how local circuits within the olfactory bulb process information from olfactory sensory afferents to produce a coded representation of smell that is relayed to higher centers. First, I studied the intrinsic membrane currents in mitral cells—the principal output neurons of the olfactory bulb—that shape their response properties. Mitral cells have unique intrinsic electrophysiological properties that actively sculpt their responses to depolarizing and hyperpolarizing stimuli. One class of slowly inactivating voltage gated potassium currents (D-type) controls the generation of action potential clusters in response to depolarizing stimuli and ensures precise spiking in response to phasic depolarizations that mimic trains of olfactory sensory nerve mediated excitatory postsynaptic potentials (EPSPs). A different class of inactivating voltage gated potassium currents (A-type) regulates the ability of mitral cells to fire rebound action potentials in response to inhibitory postsynaptic potentials (IPSPs) and hyperpolarizing stimuli. These results suggest that the intrinsic electrophysiological properties of mitral cells actively regulate the temporal pattern of mitral cell action potentials during odor processing I next investigated the properties of excitatory glutamatergic inputs onto granule cells. Granule cells are the most common interneuron in the olfactory bulb and make reciprocal dendrodendritic synapses with mitral cells. These interneurons possess two functionally distinct classes of synapses that differ in their short term plasticity properties: dendrodendritic inputs from mitral cells that show prominent depression in response to trains of stimuli, and feedback inputs from the piriform cortex that strongly facilitate. These results suggest that oscillatory activity in the piriform cortex—a prominent feature of odor processing—may gate the activity of dendrodendritic inputs, and has important consequences for how feedback inhibition onto mitral cells is regulated. |
| Permanent Link: |
http://rave.ohiolink.edu/etdc/view?acc_num=case1173540900
http://hdl.handle.net/2374.OX/16096 |
| Date: | 2007 |
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