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Our Research Focus
A reduction of GABA, a key inhibitory neurotransmitter, occurs throughout the brain as we age. The age-related loss of GABA is a prominent feature in numerous neurodegenerative disorders. In the central auditory pathways, the age-related loss of GABA impairs our ability to detect fine differences in the timing of sounds. It is this disruption to temporal processing that often characterizes age-related hearing loss (ARHL). Understanding the mechanisms of ARHL and finding treatments is of the utmost importance as ARHL is one of the most common disabilities of industrialized countries as 1 out of every 3 people over the age of 65 will experience ARHL.

Specifically, we examine pre- and postsynaptic GABAergic changes across multiple ages in the auditory midbrain, where the age-related loss of GABA is well documented. Furthermore, we examine these synaptic changes on ascending and descending pathways that originate in the auditory midbrain as these pathways carry temporally precise signals and play a critical roles in perception and the interpretation of speech in a noisy environment. We also examine presynaptic mitochondrial changes as literature has been increasingly emphasizing the role of mitochondrial dysfunction in a variety of hearing disorders.

Much of our current data and recent publications demonstrate significant changes to GABAergic neurotransmission occurring well before old age, when temporal processing and hearing thresholds are diminished. Thus, our experiments and current funding pay special attention to GABAergic changes occurring during middle-age groups, prior to age-related deficits in temporal processing and hearing thresholds.

We use transmission electron microscopy (TEM) to examine the ultrastructural and synaptic changes with age in the auditory midbrain. Furthermore, we combine TEM with intersectional viral tract-tracing to understand the age-related synaptic changes that are occurring on specific ascending and descending pathways. To examine temporal processing abilities and hearing thresholds we employ prepulse inhibition of the acoustic startle, envelope following responses and auditory brainstem responses. We also use and combine receptor immunohistochemistry, fluorescent tract-tracing, single molecule in situ fluorescent hybridization, and optically sectioned light microscopy to examine age-related changes to subunit composition of GABAA receptors and GABAergic mRNA expression on specific ascending and descending pathways of the auditory midbrain.