Does Neuronal Activity in Auditory Cortex Support Auditory Short Term Memory? Causal Interrogations using Intracranial Direct Current Stimulation

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Auditory perception, cognition, and language critically depend on linking sequential sounds through time. This is because many sounds make sense only when perceived in the context of other sounds before and after. Speech is a prime example. To link sounds the auditory system needs to be capable of memorizing sounds for several seconds in order to compare and integrate them with upcoming sounds. Recent studies suggest that processes required for such short term memory of auditory information involve the highest level of the auditory system, the auditory cortex. Here, it was found that persistent neuronal activity emerged in different subfields of auditory cortex, including the primary auditory cortex, during time periods when subjects needed to hold auditory information in memory in order to perform an auditory memory task. However, because these associations between short term memory and auditory cortex are only of a correlational nature, our project intends to address the more fundamental neuroscientific question of causality, and will test whether auditory cortex is essential for short term memory. In order to test causality we will modify activity in the auditory cortex of monkeys by means of intracranial direct current stimulation and expect that this intervention will change their ability to perform auditory memory tasks. Our project will deepen the understanding of the role of auditory cortex (and perhaps of sensory cortex in general) in short term memory. Our project will also advance the knowledge of the effects of direct current stimulation on the firing of single neurons and local field potentials in cortex. In summary, the present project will generate new knowledge on how direct current stimulation modulates brain activity and brain functions.