Listening Linked To Attention In Older Adults

The elderly cannot hear properly not only because of their ears but also because of changes in the attention processes in their brains, new research has shown.

Researchers at the Max Planck Institute for Cognitive and Brain Sciences in Leipzig have made this discovery which attaches particular importance to the alpha waves whose adaption to altered hearing situations improves speech comprehension. The currents constantly flowing in our brain can be measured using an electroencephalogram in the form of voltage fluctuations on the scalp. Regular alpha waves shape the signal measured in this way. In hearing tasks, the strength of these alpha waves indicates the effort made during listening.

Led by Jonas Obleser at the Max Planck Institute, the researchers have recorded the alpha waves of 20- to 30-year-olds and 60- to 70-year-olds during a hearing task. The participants listened to spoken numbers and had to press a number if the second number they heard was higher than the first. The numbers were presented in background noise to simulate the type of hearing situation experienced in daily life. The scientists tested the hearing acuity of all participants prior to the task and adapted the speech material to the requirements of each individual. This made the task equally difficult for younger and older participants.

While the participants were solving the number task, the researchers manipulated the acoustic quality by removing certain frequencies from the speech signal. They also varied the predictability of the task’s solution. If a very low number was given first, there is a greater probability that the second number will be higher.

With better predictability, the participants became quicker at completing the tasks. The outcome was, however, different when the acoustic quality was changed. Older participants benefited to a greater extent from better quality and completed the tasks more quickly. A major significance in acoustic quality for older participants was reflected in the alpha waves. With better speech quality, the amplitude of the alpha waves among the older participants was significantly lower than among the younger participants.

Attention in old age evidently shifts to acoustic aspects of the speech signal. Participants who adapted their alpha waves better to the acoustic quality of speech and to the predictability of speech in the experiment found it easier to listen despite the background noise.

Outcomes of this research could include adapting hearing aids to the listener’s brain activity individually to improve speech comprehension in changing situations.

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