Research

Histology of brain tissue, comparing young tissues (A and B) to aged tissues (E and F).

The Overarching Question

Why is it difficult to distinguish speech in a noisy environment when a person is aged?

Our Approach

To answer this question, we first identify age-related conditions that affect hearing. Through experimentation, our studies elucidate the underlying mechanisms of such conditions. In turn, these findings allow us to develop a well-rounded understanding of our overarching question that may lead to answers and effective therapies.

Our current project focuses on the organization of the aged auditory cortex to identify which areas are untouched by aging and which are reorganized.

Explore some of our past projects below:

Neural Selectivity in the Temporal Domain of the Auditory Cortex in Aged Brains

Presbycusis is a type of age-related hearing deficit characterized by a gradual decline in hearing and is particularly present in acoustically challenging environments or when involving complex signals such as speech. This project is focused on the hypothesis that neural activity will be more selective in the rostral regions of the temporal domain than in the caudal regions, suggesting that changes in non-spatial auditory processing occur with age.

Effects of Amplitude-modulated Signal-in-noise Auditory Stimuli on the Firing Rates of Auditory Cortical Neurons

The natural acoustic environment is normally very complex, with different types of sounds simultaneously emitted from various source locations. It remains unclear how the auditory system is able to disambiguate the different acoustic signatures into different sound sources. We hypothesize that the addition of a second, or ‘distracter’ stimulus will predictably change firing rates of auditory neurons to a primary, or ‘target’ stimulus. Our findings suggest that the processing of concurrent sounds involves both linear and non-linear properties in the auditory cortex.

Spike Decoding of Signals from Noise Stimuli in the Auditory Cortex

Most natural listening conditions consist of different sounds from various locations. We currently have little understanding of how these different signal streams are decoded by core and belt auditory cortex into perceptually distinct events or objects. We therefore used spike train decoding techniques to determine the effects of various background distractors on the responses of neurons to amplitude-modulated sounds with complex spectra. Our findings suggest that both rate and temporal information in the firing rate patterns of auditory cortical neurons can accurately encode complex, concurrent acoustic stimuli.

Effect of Aging on the Neural Activity of Spatial, Spectral, and Temporal Processing

Diagram of the model species brain with key features highlighted. People with age-related hearing loss often complain of chronic tinnitus, characterized by ringing in the ears without external sensory stimuli. This phantom symptom can result in severe impairment of daily activities. The changes in brain physiology that underlie this condition remain unknown. The objective of this study is to compare the activity of individual neurons in reorganized versus non-reorganized areas of the aged auditory cortex.

Responses to Changes in Amplitude Modulation Rate and Spatial Location in Neurons in the Auditory Cortex

Acoustic signals are commonly thought to be processed in two main pathways, a caudal spatial pathway and a rostral non-spatial pathway. This hypothesis predicts that particular spatial or non-spatial features of an acoustic stimulus are extracted from core auditory areas by belt and parabelt auditory areas, which are then further processed in the parietal and frontal lobes. It may also be that this segregation begins as early as primary auditory cortex (A1). We are currently testing this hypothesis by comparing the responses of the same auditory cortical neurons to complex stimuli that vary only in their temporal properties (amplitude modulation rate, AM) or spatial location.