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INVESTIGATING THE ROLE OF SEROTONIN IN OLFACTORY GUIDED BEHAVIOR AND NEUROPHYSIOLOGY

Author
Lewis, Matt
Abstract
The work presented in this thesis is a series of investigations relating to how serotonin
(5-HT) modulates for olfactory behavior and network physiology. 5-HT is a
neuromodulator which has been associated with a variety of neural functions including
rhythmic pattern generation, reward processing, and sensory processing. I first focused
my attention on how 5-HT may modulate olfactory guided behavior using a behavioral
pharmacological approach. Within the habituation task we found that infusion of a 5-
HT2 receptor antagonist, cinanserin, impaired habituation memory at low (0.001 Pa)
odor concentrations, and impaired spontaneous discrimination at all odor
concentrations test (0.001, 0.01, and 0.1 Pa). Within the forced choice discrimination
task we found a significant reduction in task performance following cinanserin
infusion. When sampling behavior and decision times were analyzed, we found that
cinanserin infusion significantly increased decision latencies only at one carbon
difference tests at 0.01 and 0.1 Pa concentrations. While rats were slower to choose
the odor pots at these odor concentrations they were equivalent in accuracy in the task.
Put in a speed/accuracy tradeoff context, we found that when animals were asked to
discriminate between similar odorants, accuracy is maintained and the expense of
speed. Later in my Ph.D. work I moved to studying how 5-HT modulates the olfactory
bulb network activity using an extracellular multi-electrode array. Utilizing a
horizontal brain slice preparation, I performed extracellular recordings followingserotonin application and the use the 5-HT2 receptor antagonist, cinanserin. Using
signal processing techniques, we analyzed the effects of 5-HT on multiunit activity
(MUA) and local field potentials (LFP). Within the LFP we focused our analysis on
two frequency bands, theta (1-10 Hz) and gamma (20-55 Hz). We found that 5-HT
increased MUA and increased power in both the theta and gamma bands. These
effects were shown to be 5-HT2 receptor dependent because they were not detected
when slices were first perfused with cinanserin. These behavioral and physiological
results demonstrate that 5-HT2 receptors are necessary for non-associative and
associative odor memory and that 5-HT plays an important role in the modulation of
olfactory bulb network dynamics.
Date Issued
2017-12-30Subject
Neurosciences; local field potentials; neural oscillations; odor learning; olfactory perception; rat cognition; Serotonin
Committee Chair
Linster, Christiane
Committee Member
Harris-Warrick, Ronald Morgan; Smith, David M.; Cleland, Thomas A.
Degree Discipline
Neurobiology and Behavior
Degree Name
Ph. D., Neurobiology and Behavior
Degree Level
Doctor of Philosophy
Type
dissertation or thesis