Comprehending masked words: the role of alpha brain frequencies

Understanding speech in a noisy environment can be challenging for people, especially those with speech perception deficits. Studies could already show that brain activity correlates with the perception and memorization of words. This study investigated the ongoing brain activity using Electroencephalography (EEG) and its correlation to the comprehension of noise-masked words in healthy subjects.

Houweling and his team worked with 32 German-speaking probands (mean age 23.5). They tested their ability to comprehend spoken monosyllabic digits (i.e. zero to nine, except seven) masked by speech-like background noise and how the comprehension developed when subsequentially enhancing or reducing the background noise, respectively.

The EEG activity was measured before and after the noise set in (but before the digits were spoken). The results show that an enhanced α frequency previous to the stimuli enhances the chance of comprehending the digits when they are weakly masked but decreases the probability of comprehending strongly masked words.

Further studies are necessary to see if these findings apply also to complex speech rather than single-syllable words. Nevertheless, the findings of this study represent a stepping-stone in the development of non-invasive interventions based on the modulation of ongoing brain activity. These interventions should not just focus on enhancing or decreasing the α frequency but finding the right amount for each patient in each environment.

Reference:

Houweling, T., Becker, R., Hervais-Adelman, An Elevated pre-target EEG alpha power enhances the probability of comprehending weakly noise masked words and decreases the probability of comprehending strongly masked words. Brain and Language, Vol. 247 (2023)
https://doi.org/10.1016/j.bandl.2023.105356

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