When People Actively Listen to Speech, their Eye Movements Decrease

After reaching a specific age, around 40% of individuals encounter varying levels of hearing impairment. Although age-related hearing loss is most common among adults aged 65 and above, it can commence as early as one’s 40s or 50s.

Despite the widespread use of current diagnostic methods, they may not always identify initial signs of hearing impairment, such as struggles with understanding speech in noisy settings. Consequently, researchers are working on developing effective techniques for detecting milder forms of hearing loss early on, before they become irreversible.

In pursuit of this goal, two neuroscientists from the Rotman Research Institute in Canada have been investigating the connection between attentive listening and eye movements. Their recent study, featured in The Journal of Neuroscience, suggests that when young adults exert extra effort to comprehend speech, their eye movements tend to decrease.

Current Hearing Loss Diagnosis Methods and Their Limitations

Björn Herrmann, one of the paper’s co-authors, explained the limitations of current hearing loss diagnosis methods, which rely on pure-tone audiometry. This approach involves individuals listening to pure tones at various sound levels to determine the threshold at which they can just perceive the tone before it becomes too faint. If the hearing threshold is too high, indicating the need for intense sound to hear the tone, hearing aids may be recommended. However, age-related hearing loss typically progresses gradually, often commencing in one’s 40s or 50s.

Many individuals in their 40s or 50s begin to encounter difficulties in comprehending speech amid noisy surroundings, such as crowded restaurants, shopping malls, and other public places. These challenges in hearing speech in noise often precede more pronounced hearing loss that occurs later in life.

Limitations of Pure-Tone Audiometry for Early Detection

Herrmann pointed out that pure-tone audiometric thresholds are not particularly informative when it comes to identifying early-stage issues with speech perception in noisy conditions. Consequently, hearing loss is typically diagnosed using pure-tone audiometry a decade or two after the initial signs of speech perception difficulties emerge.

To detect hearing issues earlier, researchers are striving to create improved diagnostic tools that can capture subtle aspects of a patient’s hearing. These tools aim to identify physiological signs that suggest increased effort when trying to understand speech in noisy environments, potentially indicating early hearing loss. If successful, these measurable physiological markers could enhance hearing loss assessment for new patients and those who have undergone hearing loss treatments.

The Significance of Objective Measures in Assessing Listening Effort

Björn Herrmann, a co-author of the study, explained the importance of objective measures in clinical and research contexts, as subjective assessments of listening effort can influence individual interpretations of the term “effort.” Previous research has highlighted various physiological responses associated with effortful listening, including changes in pupil size, measured through pupillometry, which involves tracking the diameter of pupils over time.

However, measuring pupil size during a hearing test may not be ideal due to sensitivity to changes in light and camera angles, which can confound results. Therefore, Herrmann and colleague M. Eric Cui sought an alternative method to detect effortful listening.

Their hypothesis was based on research indicating that eye movements decrease under cognitive challenges, and reduced eye movements might correspond to higher auditory sensitivity to speech. To test this, they conducted experiments involving 26 young adults aged 18 to 35, monitoring their eye movements while they listened with varying levels of effort.

Assessing Eye Movements Across Varied Visual Stimuli

Participants sat in a soundproof booth, wearing headphones and an eye tracker. They listened to sentences and stories while observing different visuals on a computer screen. The team aimed to determine if changes in eye movements occurred regardless of the visual stimulus.

Their analysis focused on fixation duration (how long the eyes remained fixed on a point) and gaze dispersion (how often the eyes moved across the screen). The results revealed that under more effortful listening conditions, characterized by high speech masking through background noise, participants exhibited reduced eye movements, as seen in longer fixation durations and decreased gaze dispersion.

These findings suggest that eye movement recordings could provide valuable insights into the level of effort individuals exert during listening under different conditions. In the future, this measure of effortful listening could lead to new hearing loss detection tests in clinical settings.

However, further research is needed to understand how changes in eye movements relate to changes in pupil size and to investigate differences in listening effort under various circumstances. The researchers also plan to explore the applicability of this approach in older adults and individuals using hearing aids to assess their benefits.

Read the original aricle on: Medical X Press

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