🧠 neuroscience

Distinct Neural Signatures of Auditory Processing in Contact versus Non-contact Sports Athletes

This study identifies reduced cortical N100 amplitudes in contact sport athletes compared to non-contact athletes as an objective EEG biomarker of early auditory cortical dysfunction resulting from repetitive sub-concussive head impacts, linking these neural changes to real-world speech perception deficits.

Original authors: Andrew, J. R., Dean, E., Thomas, A., Plack, C. J., Gaffney, C. J., Nuttall, H. E.

Published 2026-02-16

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CC BY 4.0

Original authors: Andrew, J. R., Dean, E., Thomas, A., Plack, C. J., Gaffney, C. J., Nuttall, H. E.

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ⚕️ This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer

Imagine your brain as a high-tech radio station. Its job is to pick up signals (sounds) from the outside world, tune them in clearly, and broadcast them to your conscious mind so you can understand what's being said.

This study looked at two groups of athletes: those who play contact sports (like football or rugby, where bumps and hits are part of the game) and those who play non-contact sports (like swimming or track). The researchers wanted to see if the constant, smaller bumps in contact sports—called "sub-concussive impacts"—were quietly damaging the brain's radio station, even if the players didn't feel a concussion.

Here is the breakdown of what they found, using simple analogies:

1. The "Static" in the Signal

The researchers played a speech sound to the athletes and measured their brainwaves using EEG (a cap that reads electrical activity). They tested two scenarios:

Quiet Room: Like listening to a radio in a silent library.
Crowded Room: Like listening to that same radio in a noisy, crowded bar with six people talking at once.

The Result: The contact athletes' brains struggled to process the sound, especially in the noisy environment. It was as if their radio station had developed a layer of static that made the signal weaker and harder to hear.

2. The "Volume Knob" vs. The "Tuner"

The study found a specific problem with the cortical N100 response. Think of this part of the brain as the volume knob on your radio.

In the contact athletes, this "volume knob" was turned down significantly lower than in the non-contact athletes.
This means their brains were physically less responsive to the sound, even though the sound itself was the same.

However, the subcortical response (the part of the brain that acts like the tuner or the antenna, catching the signal from the ear) was working perfectly fine.

The Analogy: Imagine a radio where the antenna is perfectly tuned and catching the signal clearly, but the volume knob is broken and stuck on "low." The signal is there, but the brain isn't turning it up loud enough to process it clearly.

3. The Real-World Consequence

Because the "volume knob" was turned down, the contact athletes reported real-life trouble. They found it harder to understand speech in noisy places (like a locker room or a party).

The Metaphor: It's like trying to have a conversation at a loud party while wearing earplugs that you didn't realize you had on. You know people are talking, but the words are just muddy and hard to catch.

4. Why This Matters

Previously, doctors could only detect brain damage if an athlete had a clear, dramatic concussion (like a car crash). But this study shows that repeated, smaller bumps (like fender benders) can still cause damage over time.

The researchers found a specific "fingerprint" in the brainwaves (the low volume knob) that acts as an early warning light.

The Takeaway: Just like a mechanic can use a diagnostic tool to see a problem with a car's engine before it breaks down completely, doctors can now use this EEG test to see if an athlete's brain is getting "tired" or damaged from too many hits, long before it causes a major injury.

In short: This paper proves that the constant, small hits in contact sports can quietly turn down the "volume" on how the brain processes sound, making it harder to communicate in noisy places. This discovery gives us a new, objective tool to keep athletes safe by spotting these hidden issues early.

Technical Summary: Distinct Neural Signatures of Auditory Processing in Contact versus Non-contact Sports Athletes

1. Problem Statement

Repetitive sub-concussive head impacts (RSHI) represent a critical and often overlooked neurotrauma challenge, particularly in contact sports. While evidence suggests these impacts cause neurological consequences, the field currently lacks a validated, objective biomarker for the early and reliable detection of such injuries. The study aims to address this gap by investigating whether RSHI exposure manifests as measurable neural deficits in auditory processing, specifically distinguishing between contact and non-contact sport athletes.

2. Methodology

The study employed a rigorous experimental design utilizing electroencephalography (EEG) to assess auditory processing capabilities.

Participants: A cohort of 60 tier-2 athletes was recruited and divided into two groups:
- Contact Group: 30 athletes involved in contact sports.
- Non-contact Group: 30 athletes involved in non-contact sports.
- Matching: Groups were strictly matched for age, sex, height, body mass, and Body Mass Index (BMI) to control for confounding variables.
Stimuli & Conditions: Participants were exposed to a speech syllable under two distinct listening conditions:
1. Quiet: Presentation in a silent environment.
2. Noise: Presentation in a six-talker background noise environment.
Neural Metrics: The study measured two primary neural responses:
- Cortical Response: The N100 amplitude (an event-related potential component).
- Subcortical Response: Frequency Following Responses (FFR), which reflect the brainstem's encoding of sound.

3. Key Contributions

Identification of a Specific Biomarker: The study provides evidence that reduced cortical N100 amplitudes serve as a measurable biomarker specifically linked to early auditory cortical dysfunction caused by sub-concussive exposure.
Differentiation of Neural Pathways: It establishes that peripheral and cortical auditory changes may occur independently following repetitive head impacts, as subcortical encoding remained intact while cortical processing was impaired.
Real-World Correlation: The research links neural deficits to functional outcomes, demonstrating that contact athletes exhibit subtle hearing deficits and impaired self-reported speech perception.

4. Results

Statistical analysis yielded the following significant findings:

Cortical Dysfunction: A significant group effect was observed for cortical N100 amplitudes ( $F(1,54) = 9.16, p = .004$ ). Contact athletes demonstrated significantly reduced N100 amplitudes compared to non-contact athletes, indicating early dysfunction in the auditory cortex.
Subcortical Integrity: Unlike the cortical responses, response timing and subcortical encoding (FFR) remained unaffected in contact athletes under both quiet and noisy listening conditions.
Behavioral Correlation: Contact athletes reported difficulties in speech perception and exhibited subtle hearing deficits, which correlated with the observed neural changes.
Independence of Mechanisms: The data suggests that the observed peripheral and cortical changes are not directly related to one another, implying distinct mechanisms of injury or compensation following RSHI.

5. Significance

This research holds substantial implications for sports medicine and neurotrauma research:

Objective Monitoring Tool: The findings validate the N100 amplitude as a potential objective, EEG-based monitoring tool. This could be deployed to track athlete brain health and safety over time, offering a non-invasive method to detect early signs of injury before clinical symptoms appear.
Targeted Intervention: By identifying a selective vulnerability in the auditory cortex, the study informs future research into the specific neural mechanisms damaged by sub-concussive hits, potentially leading to better protective equipment or return-to-play protocols.
Clinical Relevance: Linking neural biomarkers to real-world communication deficits underscores the functional impact of sub-concussive trauma, moving the conversation beyond acute concussions to the cumulative effects of repetitive head impacts.