Effects of Emotion on Neural Encoding of Sound

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DESCRIPTION (provided by applicant): Traditional views of the brainstem have assumed a static and passive role in relaying the auditory signal to higher regions of the brain, but recent evidence indicates a far more dynamic and malleable system than previously thought. In the visual system, there is a plethora of evidence pointing to parallel pathways in the recognition of faces, a high-resolution system in the cortex that processes fine-grained data, and a fast, evolutionary ancient pathway to the limbic system that relays spatially coarse but highly biologically relevant information like facial expression. Anatomically, there is known to be direct and widespread connections between the auditory brainstem and the limbic system as well, and these have been characterized, anatomically, in rodents and primates. However, these connections have not been functionally characterized. The focus of our research is to understand how the neural representation of sounds is affected by emotional stimuli, such as emotion-evoking images, at the earliest stages of the auditory processing stream and to define the growth and transformation of this interaction throughout the auditory pathway. We are interested in determining how a listener's emotional state, induced by emotion-evoking visual stimuli, influences the listener's physiological response to speech. To do this, physiological responses to auditory speech are measured after inducing three emotional states (including a "neutral" state) in the listener with the use of images from a standardized database of emotional visual stimuli. Far-field and near-field recordings (brainstem and cortical responses, respectively) will assess the relative contributions of subcortical and cortical processes to the interaction of the two input modes and illuminate timing of the interactions. Our preliminary data show statistically significant differences between emotional conditions. We currently know that the brainstem is far more malleable than previously thought, which gives promise to the potential effects of therapies for disorders as well as the potential to enhance the learning of language and music, but there are other aspects to this malleability as well. It is known that anxiety disorders have a high comorbidity with depression, and that emotional health is hugely interactive with general mental health. If the brainstem is malleable on the time-scale of hours, it is reasonable to believe that anxiety disorders not only influence one's emotional health, it can also adversely affect sensory processing at a very basic level.