Interactions of gamma frequency rhythms in computational models of primary auditory cortex

Many animals rely on the ability to perceive and process sounds for communication and survival. The brain must be able to accurately and reliably perceive relevant sounds in the environment and synthesize auditory information to extract meaning. Electrical oscillations have been observed throughout in the brain, and these rhythms have been investigated to understand their relation to auditory function. Experimental evidence suggests that a class of these rhythms in the gamma frequency range (30--90 Hz) is important in behavioral learning and physiological plasticity, which is thought to be a neural correlate for memory. In the primary auditory cortex, dual gamma rhythm generators have been observed in different laminae, but the role of these gamma rhythms in auditory processing is not fully understood. In this work, mathematical models of gamma rhythm generation were used to help understand how gamma rhythms support auditory plasticity and how dual gamma rhythms interact, with implications for interlaminar communication.;Here, a simplified model of gamma rhythms was developed to consider how synaptic potentiation is affected by an independent gamma-periodic input representing an encoded auditory signal. The results suggested a mechanism by which both potentiation and depression could occur, dependent on the frequency of the input. Furthermore, an optimal duration of potentiation may be influenced by the time constant for decay of the N-methyl-D-aspartate receptor (NMDAR) mediated currents.;To understand how laminar gamma rhythms may operate in support of auditory function, a biophysically detailed mathematical model of gamma rhythms in a column of auditory cortex was developed. The model replicated a wide range of experimental constraints and demonstrated a role for feedforward inhibition in disrupting synchrony between laminar networks. The detailed model was further optimized for computational efficiency and demonstrated conditions under which observed frequency relationships between laminar rhythms were robust.;Together, the results of these simulations have contributed to the understanding of auditory function by showing how different gamma frequency rhythms in primary auditory cortex may support interlaminar communication and regulate plasticity underlying learning and memory.