(PP501) Age-Related Decline in Neural Synchrony and the Frequency-Following Response

It is a known phenomenon that speech understanding in background noise declines with advancing age. Although there is ample evidence of behavioral measures declining with age, there is less physiologic evidence. This study hypothesizes that the FFR will be degraded with advancing age, consistent with poorer phase-locking - even in people with audiograms within normal limits. A second hypothesis is that middle-aged and older adults will have degraded neural representation as frequency increases, compared to a younger normal hearing group which will have better high frequency neural representation than the two older groups. Results could be used in patient counseling.

Summary: 

Objectives:

The purpose of this study is to investigate the neural integrity of the aging population through the Frequency-Following Response (FFR), which is dependent on phase-locked neural synchrony. A secondary purpose is to examine frequency-specific effects of neural degradation among young, middle-aged, and older groups.

Rationale:

As patients age, there are increased incidences of listening difficulties in background noise. This study aims to present a physiological correlate to support this incidence in older populations. This could advance knowledge relating to the difficulty of speech in noise capabilities in older populations, as well as serve as a tool in patient counseling. The results of this study could also aid in more comprehensive prevention and intervention plans for aging individuals.

Methods:

Three age groups will be assessed: Young (21-30 years old), middle-aged (41-50 years old), and older adults (61-70 years old). Participants must have hearing sensitivity within normal limits (< 25 dB HL). The Frequency-Following Response is recorded in four frequencies: 500 Hz, 750 Hz, 1,000 Hz, and 1,125 Hz. Each frequency is recorded in two monaural conditions (for each ear) and a binaural condition, for a total of twelve conditions per person. Psychoacoustic testing (interaural phase differences) and speech-in-noise testing is also being collected in each participant. FFR analyses were performed in Matlab and included measures of amplitude and stimulus-to-response cross correlations.

Results:

Amplitudes were biggest in binaural conditions. Additionally, amplitudes were largest in the lowest frequency (500 Hz) and smallest in the higher frequencies (750-1,125 Hz). The largest correlation was seen binaurally and in the lower frequencies as well. Preliminary data for the two older groups (middle-aged and older adults) show lower amplitudes than the young group- particularly in the highest frequencies. It is expected that we will see lower correlations in the middle-aged an older group as well.

Conclusions:

It is anticipated that the Frequency-Following Response will show poorer phase-locking in middle-aged and older populations, in comparison to a young group. These effects will likely be more pronounced in the higher frequencies. This indicates poorer neural synchrony in middle-aged and older populations, which may contribute to poorer speech-in-noise abilities in aging adults.