The Role of Photoreceptor Light Sensitivity in Expression of Classical Conditioning

George Mason University, Fairfax VA

Investigators

Abstract

Lay Summary Blackwell IBN-0077509 The seaslug, Hermissenda crassicornis, is a model system for studying associative learning because it shares properties of classical conditioning with mammals. In Hermissenda, individual brain cells have been identified in which a change in cell properties is correlated with a change in animal learning behavior . Specifically, the type B class of photoreceptors shows an increase in excitability consequent to classical conditioning with light and turbulence. The excitability of the type B photoreceptor is affected by current flowing across the cell membrane in response to light. The measurement of this current, which has not been adequately characterized, is one goal of this project. The expression of associative learning behavior depends on the interaction between type A and type B photoreceptors in response to light. This interaction is affected by the light-induced current flowing across the membrane of the type A photoreceptors. Thus, a second goal of this project is to measure this current in response to light of various intensities and durations. The third and final goal of this research is to develop a computer model of both (type A and type B) classes of photoreceptors and their interaction. Model simulations are used to evaluate the output of both types of photoreceptors in response to light, and the change in output consequent to an increase in excitability in the type B photoreceptor. This project will significantly contribute to our knowledge of how people learn. Classical conditioning, also known as Pavlovian conditioning, is studied extensively because it is a form of associative learning present in many different species. A change in cell excitability is thought to be a general mechanism of associative learning because it has been detected in brain cells of mammals which have been classically conditioned. However, the pathway between change in cell excitability and change in animal behavior is not fully understood. These is evidence that expression of learning behavior emanates from modulation of the complex interaction between groups of neurons. This project begins to elucidate how changes in cell properties modulate neuronal networks involved in classical conditioning behavior.