Behavioral Correlates of Theta and Delta oscillations in the Hippocampal Formation

Abstract

The goal of this project is to characterize the relationships between the behavioral state of the animal and the frequency phase and the amplitude of theta and delta oscillations observed in the hippocampal formation. The behavioral state of the animal is characterized by its position in space, the velocity, direction and statistical properties of its movement over time. Theta amplitude, frequency and phase re-flects movement properties and may act as carriers of information that bridges the gap between environmental and proprioceptive streams of information in the brain. Our analysis revealed that theta and delta oscillations are indeed important players in the dynamics of hippocampal network and are closely related to the locomotion of the animal. The causal role of movement in theta generation was evident as a gen- eral positive modulation of the oscillatory variables as a function of movement properties. It was also found that spatial cues have modulator power on theta even though we couldn’t pin down the accurate nature of the relationship. Delta power was found to be modulated by the running direction with a six fold symmetry, which could possibly give rise to the symmetry of the network. The study found that these oscillatory bands and associated modulations are important in the dynamics of the network and is intricately associated with the behavioral properties of the animal. This provides a tool by which we can gain insights in to the working of neurons and networks from a behavioral perspective.