Dissertations, Theses, and Capstone Projects

Date of Degree

6-2023

Document Type

Thesis

Degree Name

M.S.

Program

Cognitive Neuroscience

Advisor

Thomas Preuss

Subject Categories

Behavioral Neurobiology | Behavior and Ethology

Keywords

Startle Plasticity, PPI, Acute Stress, Alarm Pheromone, Mauthner Cell

Abstract

Fish face a variety of stressors in nature, a prominent one being a predatory threat to which they respond with an adaptive behavioral response thus maximizing their chances of survival. A primary anti-predatory behavior is a startle response or C-start. This behavior is controlled by two large reticulospinal neurons, the Mauthner cells (M-cells) which integrate multimodal sensory inputs. Detecting a predator involves various sensory information such as visual and mechanosensory cues but also olfaction. Indeed, following an attack, an injured fish will release an alarm pheromone (Schreckstoff) and thus acutely alert close by conspecifics. However, whether the alarm pheromone in fact modulates the startle response is not clear. In fish, startle behavior shows remarkable plasticity in response to changes in the environment and/or internal physiological states. One powerful modulator of startle is prepulse inhibition (PPI), a sensorimotor gating process that largely reduces the expression of startle behavior. PPI was shown to be disrupted in African cichlid fish exposed to a chronic social stressor (bullying). Here we asked how an acute stressor namely, an alarm pheromone (Schreckstoff), will affect the auditory startle response and PPI in goldfish using high-speed recordings. Our results showed that the pheromone decreased baseline startle latency. In contrast, startle responsiveness and PPI were not affected. A change in startle latency independent of the responsiveness potentially suggests a presynaptic or a downstream effect in the startle circuit. Taken together, the results indicate that the alarm pheromone does modify startle but in a differential manner from a chronic stressor.

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