Network encoding of short-term memory in primary auditory cortex

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Project Summary/Abstract Short-term memory (STM) is a fundamental component of hearing that is critical to speech comprehension and auditory communication. Mounting evidence has indicated that the activity in primary auditory cortex (A1) changes when we perform auditory tasks. In this project, our long-term objective is to understand how A1 changes its neural activity and connectivity during the maintenance of auditory STM. We will study how auditory STM is encoded in the structure of neural networks in A1 layer 2/3 (L2/3). We choose to study L2/3 because auditory STM involves an intracortical circuit, and L2/3 is dense in intracortical connectivity. To the best of our knowledge, the representation of STM in neural network structure has not been studied in A1. To explore this topic, we will have animals compare two sequential sounds that are separated by a silent delay. The animals must memorize the first sound to compare with the second sound to give a correct behavioral response during the task. We will record neuronal responses in A1 L2/3 while the animals perform this task. We hypothesize that the neural networks that arise during the first sound will be sustained during the delay until the second sound. We will use both simple and complex sounds to understand how acoustic complexity affects neuronal network structure. Furthermore, we will determine if there exists a stimulus-invariant representation of acoustic periodicity, i.e., `pitch', in neuronal networks. Our preliminary results suggest that neural activity in auditory cortex depends on if the animal successfully discriminates between high vs. low frequency pure-tones. Thus, our results shed light on how the brain's auditory responsiveness depends on how we listen and react to sound. Listening can be challenging for both healthy and hearing-impaired people. Our studies will help clarify the basic understanding of how the brain allows us to listen. As a result, our work will contribute to future therapies designed to enable better hearing in every-day settings.