The study revealed that repetitive stress changes the way the brain processes sounds, reducing the perception of loudness over time. This is because stress increases the spontaneous activity of the auditory cortex, but reduces the responses to sounds in certain neurons and intensifies them in others.
Repetitive stress has a significant impact on mental health and can contribute to the development of psychiatric disorders and sensory difficulties. This happens because, when we are under constant stress, our body and brain go through a series of changes to try to adapt to this situation.
These changes affect behavior and the way we perceive the world around us. Unlike acute stress, which is a quick and temporary reaction to a specific threat, repetitive stress persists even after the initial cause has passed.
Scientists already know that chronic stress can affect important cognitive functions, such as learning, memory and decision-making. However, there are still many questions about how it influences our sensory processing, that is, the way we perceive sounds, smells, images and touches.
Our perception of the senses is deeply linked to our emotional state. For example, when we are stressed, a sound may seem louder or a smell may seem more unpleasant than when we are calm. But does repeated stress really change the way we experience the world around us?
Previous research has shown that chronic stress can increase sensitivity to pain, alter our perception of smells and even change the way our brain functions.
This is because stress causes inflammation in the nervous system and affects brain regions such as the amygdala and anterior cingulate cortex, which are involved in emotions and sensory perception.
Despite these advances, little is known about how stress affects the perception of neutral stimuli, such as a common sound or a simple texture, which, in theory, would not have a positive or negative emotional charge.
Some studies suggest that stress can decrease the ability to recognize new smells and textures, but separating this effect from the impact on memory has been a major challenge.
Other research suggests that chronic stress can alter primary areas of the brain responsible for the senses, such as the piriform cortex, which processes smells. But there are still no direct measurements of how repeated stress affects the activity of these regions over time.
To better understand this relationship, scientists at the University of the Negev in Israel decided to focus on the auditory cortex, which is responsible for processing sounds.
They chose this area because previous research shows that stressful experiences in childhood can impair auditory perception and because this region of the brain is influenced by the limbic system, which regulates emotions and stress.
To test this hypothesis, the researchers conducted experiments on mice, subjecting them to repeated stress and analyzing how this affected their auditory processing over time.
They found that stress increased spontaneous activity in the auditory cortex, but reduced the response to sounds in certain types of neurons, while increasing the response in others. As a result, the mice began to perceive sounds as less intense than they actually were.
Furthermore, the effects of stress on perception did not occur immediately but developed gradually as exposure to stress persisted.
Repetitive stress causes a reduction in neural contrast in stressed animals when compared to controls.
These findings suggest that repetitive stress can directly modify the functioning of sensory areas of the brain, affecting how we perceive the world.
This challenges the idea that stress only impacts emotionally charged stimuli, showing that it can alter even the perception of neutral everyday sounds.
This study paves the way for further research into how stress may be related to sensory and psychiatric disorders, helping to better understand its effects on the brain and behavior.
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Repeated stress gradually impairs auditory processing and perception
Ghattas Bisharat, Ekaterina Kaganovski, Hila Sapir, Anita Temnogorod, Tal Levy, Jennifer Resnik
PLOS Biology. Published: February 11, 2025
Abstract:
Repetitive stress, a common feature of modern life, is a major risk factor for psychiatric and sensory disorders. Despite the prevalence of perceptual abnormalities in these disorders, little is known about how repetitive stress affects sensory processing and perception. Here, we combine repetitive stress in mice, longitudinal measurement of cortical activity, and auditory-guided behaviors to test if sound processing and perception of neutral sounds in adults are modulated by repetitive stress. We found that repetitive stress alters sound processing, increasing spontaneous cortical activity while dampening sound-evoked responses in pyramidal and PV cells and heightening sound-evoked responses in SST cells. These alterations in auditory processing culminated in perceptual shifts, particularly a reduction in loudness perception. Additionally, our work reveals that the impact of stress on perception evolves gradually as the stressor persists over time, emphasizing the dynamic and evolving nature of this mechanism. Our findings provide insight into a possible mechanism by which repetitive stress alters sensory processing and behavior, challenging the idea that stress primarily modulates emotionally charged stimuli.
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