Diana Coomes Peterson, Ph.D. - US grants

DESCRIPTION (provided by applicant): Descending projections from auditory cortex have been postulated to play a role in a wide variety of functions including selective attention, sound localization, gain control, and frequency selectivity. One of the largest of the descending projections is to the inferior colliculus. We intend to use a combination of anatomical tracing and electron microscopic techniques to elucidate the targets of these projections. Cortical projections terminate in the same area of the inferior colliculus as collicular cells that have ascending projections and cells that have descending projections. Therefore our first two goals are to identify if these cortical projections contact cells in the inferior colliculus that have ascending projections to the medial geniculate, or cells that have descending projections to the superior olivary complex and cochlear nucleus. To better understand the functional role of the pathways, our third goal is to determine whether cells in the inferior colliculus that contain y-aminobutyric acid (GABA), an important inhibitory neurotransmitter, are also contacted by cortical projections. Answers to these questions are necessary to ascertain which brainstem circuits are modulated by cortical projections and what role they may play in both normal and diseased auditory systems.

[unreadable] DESCRIPTION (provided by applicant): The long-term goal of this research application is to identify how the amygdala influences auditory perception and function. Specifically it focuses on identifying the effect(s) of amygdalo-collicular projections on cells in the inferior colliculus (IC). The amygdala is thought to play a major role in functions such as emotion, memory, and learning. How such circuitry could influence auditory processing is unknown. The amygdalar projection to the IC influences auditory perception due to previous auditory experience or the emotional state of the animal. The experiments in this application will identify: 1) the physiological response of amygdalar and amygdalo-collicular cells; 2) the morphology and termination pattern of amygdalar projections; and 3) what specific effect(s) amygdalo-collicular projections have on IC cells. This information will contribute to a greater understanding of how descending systems modulate and control auditory processing. It may also provide information about how the auditory system affects the normal aspects of mood, emotion, memory, communication, and learning, as well as pathological conditions associated with tinnitus, depression, bipolar disorders, panic disorders, Alzheimer's, and learning disorders. [unreadable] [unreadable]

DESCRIPTION (provided by applicant): The goal of this research is to understand how the amygdala (AM; a brain center that processes the emotional significance of sensory stimuli) influences the processing of auditory information in auditory cortex (AC). Individuals/animals pay more attention to significant versus insignificant stimuli. The mechanisms associated with this process have not been determined. It is presumed that information about the significance of auditory stimuli is transmitted to AC via direct and indirect projections from the AM, and that subsequent changes in cortical activity alter the attention of the animal to relevant auditory cues. Conditioning experiments that enhance the behavioral relevance of auditory cues have been shown to elicit both short and long-term changes in the spiking activity of neurons in auditory cortex (reviewed by Weinberger, 2007; Suga, 2008). The specific goals of this proposal are to provide information about the morphology and termination pattern of the direct amygdalo-auditory cortex projection and begin to clarify the function of amygdalar inputs on cortical processing. My general hypothesis is that the direct AM-AC projection terminated throughout the AC and influences the spiking response of AC neurons to sound. Relevance: The amygdala mediates emotion, and influences memory and learning. Abnormal processing in the amygdala has been linked to numerous psychiatric disorders that include auditory hallucinations (e.g., schizophrenia, bipolar disorder). It is likely that these auditory hallucinations are initiated by amygdalar projections to AC. By understanding the role of amygdalo-cortical projections, we can obtain a clearer picture of: 1) how normal auditory perception is processed, and 2) how abnormal processing can results in these auditory dysfunctions. PUBLIC HEALTH RELEVANCE: These studies will provide a better understanding of how processing of acoustic signals, including speech, is modified by an individual's emotional state. They may also further our understanding of abnormal auditory perceptions such as tinnitus or the auditory hallucinations associated with psychiatric disorders such as schizophrenia and bipolar disorder.