Chronic Stress Changes How We Hear Everyday Sounds, Study Finds
Chronic stress not only affects emotions and decision-making but also changes how the brain interprets sounds, according to a groundbreaking study conducted at Ben-Gurion University of the Negev (Israel). Researchers found that prolonged stress dampens the brain’s response to quieter sounds while preserving its sensitivity to louder ones. This discovery sheds new light on the broader effects of stress on sensory processing and its potential links to sensory disorders.
How the Study Was Conducted
The study was led by Dr. Jennifer Resnik from the Department of Life Sciences at Ben-Gurion University and was recently published in PLOS Biology. Her research team included Ghattas Bisharat, Ekaterina Kaganovski, Hila Sapir, Anita Temnogorod, and Tal Levy. Dr. Resnik is also a member of the Zelman Center for Brain Science Research.
Study Design and Methodology
According to Neuroscience News, the research was conducted using a mouse model to investigate the effects of chronic stress on auditory processing. The team focused not on how stress impacts the ear but on how it alters brain function in response to sound.
- Stress Induction: Mice were exposed to repeated stressors over a prolonged period. The stressors were designed to mimic real-life chronic stress conditions, ensuring a gradual and persistent physiological response.
- Brain Activity Measurement: Researchers used longitudinal cortical recordings, a technique that allowed them to track neural activity over time. Electrodes were implanted in the auditory cortex of the mice, enabling the team to monitor how neurons responded to different sound stimuli before, during, and after prolonged stress exposure.
- Auditory Stimuli Testing: The mice were presented with a variety of sounds at different decibel levels. The researchers analyzed how stress altered their ability to detect and respond to low, medium, and high-intensity sounds.
- Neuron-Specific Investigations: The team focused on SST inhibitory neurons (brain cells that slow down activity in other neurons to help control sensory processing; SST stands for somatostatin, a substance these neurons produce to regulate signals in the brain), known to regulate other neurons involved in auditory processing. They observed how these neurons responded under stress and how their overactivity suppressed responses in other neural populations, particularly pyramidal and PV cells (parvalbumin-expressing neurons that help control brain activity by fast inhibition of other neurons, improving signal timing and sensory processing).
- Behavioral Assessments: In addition to neural recordings, the study included behavioral experiments where mice had to respond to auditory cues. By tracking behavioral changes alongside brain activity, the researchers confirmed that chronic stress not only altered neural processing but also influenced perception and reaction to sound.
- Gradual Effects Over Time: The researchers observed that the changes in auditory perception did not appear immediately but developed progressively, suggesting a long-term adaptation in the brain’s auditory processing mechanisms.
While previous research has linked stress to cognitive impairments and emotional dysregulation, fewer studies have explored its impact on sensory processing. This study is unique because it highlights how stress affects the perception of neutral stimuli, such as everyday sounds, rather than just emotionally charged signals.
This research differs from previous studies in several ways:
- Focus on Neutral Sensory Processing – Unlike past studies that mainly explored stress’s effect on emotional or threat-related stimuli, this research examined how the brain processes everyday sounds.
- Neuronal Mechanisms Identified – The study revealed that SST inhibitory neurons become hyperactive under chronic stress, suppressing other neural responses to quieter sounds.
- Gradual Change Over Time – The findings showed that stress-induced alterations in sound processing develop progressively, suggesting long-term effects rather than immediate shifts.
- Implications for Sensory Disorders – The research connects chronic stress to potential auditory issues, such as hypersensitivity or difficulty filtering background noise.
- Use of Longitudinal Cortical Recordings – By tracking neural activity over time, the study provided insights into how stress-induced changes in the brain accumulate.
Key Findings of the Study
1. Reduced Sensitivity to Quiet Sounds
Mice under chronic stress exhibited significantly weaker responses to low-decibel sounds. This suggests that stress makes the brain less responsive to subtle auditory inputs, potentially affecting how people hear background noises or soft conversations.
Example: A stressed individual may struggle to hear someone speaking softly in a noisy café.
2. Increased Sensitivity to Loud Noises
Despite weakened responses to quiet sounds, the mice maintained normal or heightened sensitivity to louder stimuli. This may explain why people under chronic stress often feel more easily startled by sudden or loud noises.
Example: A person experiencing high stress may jump at the sound of a door slamming even if they usually wouldn’t.
3. Overactivity of SST Inhibitory Cells
SST cells, a type of inhibitory neuron in the brain, became hyperactive under stress. These cells suppressed responses to quieter sounds, dampening overall auditory sensitivity.
Example: This mechanism may contribute to conditions like sensory overload, where background noise becomes overwhelming.
4. Stress Alters Perception Over Time
The study demonstrated that the effects of stress on auditory processing were not immediate but developed gradually, suggesting cumulative changes in brain function over prolonged stress exposure.
Example: A person under continuous workplace stress might not notice changes in their hearing at first but could gradually find it harder to focus in noisy environments.
5. Broader Sensory Implications
These findings suggest that chronic stress doesn’t just affect emotional reactions but alters how the brain interprets neutral sensory information, potentially influencing sight, touch, and taste as well.
Example: Someone under stress might find bright lights more irritating or certain textures more uncomfortable than they did before.
Connection Between Stress and Brain Function
The study highlights the link between stress and cognitive processing, particularly in how the brain prioritizes information. If stress alters basic sensory perception, it could also impact learning, concentration, and decision-making.
- Attention and Focus – Individuals experiencing chronic stress may struggle to focus in noisy environments due to difficulty filtering out background sounds.
- Memory Impairment – Changes in sensory perception may disrupt how the brain encodes auditory information, leading to memory problems.
- Emotional Regulation – Heightened sensitivity to loud noises may contribute to irritability and emotional dysregulation.
Significance for Science, Medicine, and Society
Scientific Advancements
This research advances our understanding of how chronic stress affects the brain beyond emotional responses, offering new perspectives on sensory processing disorders.
Medical Implications
- The findings may help explain sensory sensitivities seen in stress-related conditions such as PTSD (Post-Traumatic Stress Disorder) and anxiety disorders.
- They suggest potential pathways for developing treatments to counteract stress-induced sensory changes.
Educational and Workplace Relevance
- In learning environments, stressed students may struggle to process verbal instructions in noisy classrooms.
- Workplace productivity could be affected if employees under chronic stress find it harder to focus due to altered auditory perception.
Societal Impact
Understanding the broader effects of stress on perception may lead to improved stress management strategies, helping individuals cope with noisy or overstimulating environments.
Conclusion
The study conducted by Dr. Jennifer Resnik and her team at Ben-Gurion University provides groundbreaking insights into how chronic stress reshapes auditory perception. By demonstrating that stress dampens the brain’s response to quiet sounds while maintaining sensitivity to louder ones, the research opens new avenues for exploring stress-related sensory disorders.
These findings have broad implications for neuroscience, medicine, education, and workplace productivity. As scientists continue to unravel the complexities of stress on the brain, this study serves as a crucial step toward understanding and mitigating its hidden effects on everyday perception.
