Adore D. Ferguson-Richards, Justin Minerva, Jacob A. Krawitz, Nicky Rashkover, Roshan A. Jain

To adapt to our environment, our nervous system is constantly interpreting sensory information allowing us to react to relevant stimuli while ignoring the irrelevant ones. Which allows for the appropriate response to the stimuli based on the current environmental constraints. One of the main contributors to this is a form of non-associative learning called habituation, characterized by a decline in responsiveness to a stimulus after repeated exposure. Habituation learning is evolutionarily conserved across all animals from invertebrates up to humans. Habituation learning can vary in a number of neuropsychiatric conditions in humans including Attention-Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD). There are multiple genes associated with these conditions; the one we chose to focus on is AP2S1. This gene encodes a subunit of the AP2 complex which assists in clathrin mediated endocytosis however its role in behavioral regulation is not well understood. When ap2s1 is mutated in zebrafish, larvae show deficits in habituation of the acoustically-evoked escape response, making this a useful model to understand the mechanism of this learning. The fast escape response of five day old larval zebrafish is controlled by a pair of command neurons called the Mauthner cells. When a Mauthner cell fires, larvae perform a fast escape, so we reason that habituation requires regulating these critical neurons. The Spiral Fiber neurons are excitatory neurons that are presynaptic to the Mauthner cells and are thought to regulate Mauthner firing. We investigated the activity of the Spiral Fiber termini, which bundle together around the start of the Mauthner axon as well as the Spiral Fiber cell bodies. We used a fluorescent calcium indicator (GCaMP5G) to visualize Spiral fiber structure and activity to determine if there is an association between the development of these neuronal structures and the altered habituation of the mutants. For the wild type siblings there is activity at the Spiral Fiber termini which reduces as the fish habituate. In the mutants there is higher activity observed at the Spiral Fiber termini compared to the wild type. To understand why I am measuring the dimensions of the bundle of Spiral Fiber termini as well as counting the cell bodies to determine if there’s a developmental difference between the mutants and the siblings. By characterizing the circuit development of Spiral Fiber neurons we hope to better understand how ap2s1 regulates habituation learning.