Effect of Forward Masking on Frequency Following Response as a Function of Age

Background: Forward masking occurs when noise is presented before the target signal, making the latter difficult to be perceived. It is related to temporal auditory processing and consequently to speech recognition in noisy environments, which may decline with age. Interest in forward masking has grown in the last years. Studies investigate psychoacoustic and electrophysiological recordings in different age- groups.

Purpose: The purpose of the study was to investigate the effect of forward masking on frequency following response (FFR) as a function of age.

Research design: Cross-sectional analytical observational study.

Study sample: We assessed 69 normal-hearing participants of both genders assigned to three groups: 40 young individuals (aged 18-25 years, mean age = 22 years 8 months), 21 middle-age individuals (aged 25-55 years, mean age = 37 years 2 months), and 8 seniors (aged <55 years, mean age = 65 years 3 months).

Intervention: FFRs were recorded using the /da/ syllable with and without noise.

Data collection and analysis: The /da/ syllable and speech-shaped noise were monaurally presented to the participants' right ears through ER-3a insert earphones. Electrodes were placed in M1 and M2 (-), Fz (+), and Fpz (ground). Acquisition occurred under two conditions: (1) the/da/ syllable presented without the noise and (2) the /da/ syllable presented 4 msec after the noise.

Results: Data show that (1) considering the mean values of all participants, there was a significant latency delay of all waves (PV, A, PW, PX, PY, PZ, and O) when the /da/ syllable was presented 4 msec after the masking noise as compared with the condition without noise, that is, forward masking occurred in all components of the FFR responses, and (2) for the youngest group and the middle-age group, forward masking was seen for all waves, except PX in the latter one; for the senior group, an irregular pattern was observed (presence of forward masking in PA, PY, PZ, and O). This pattern may be due to an aging effect on FFR responses even without noise presence, which makes it more difficult to identify forward masking effect in this population. Although it is well documented in the literature that forward masking increases with age, this is less evident on FFR recordings in the senior population.

Conclusions: An aging effect was identified in FFR responses. Forward masking was identified in FFR responses of all groups but less evident in senior population.