Psychological and Physical Functions of the Ear that you Might Not have “Heard” About
Seth Horowitz, a renowned auditory neuroscientist referred to hearing as the universal sense. We cannot shut off our ears like we can close our eyelids, thereby making it a sense that ever-present, ever-active. Hearing has evolved as a fundamental sense, back to days when “hearing” was merely the ability amongst proto-animals to sense vibrations. Since then, the ability to hear acute sounds has defined the line between survival and extinction for numerous species. Hence, even though we might continue to take our sense of hearing for granted, what with all that random chaos of noise around us at all times, there are deep-seated psychological and physiological functions that depend this sense of ours.
Our ears merely collect the sounds from our surroundings. The entire hearing apparatus is actually much more complex and deep-rooted than the ears and involves several biological and psychological systems. In this article, we take a look at certain functional aspects and associations of the ear that might surprise you!
Hearing and Emotion
One of the most important biological links that define the hearing apparatus in our body is its connection to the amygdala, the primal centre of emotion. The amygdala can be best described as an “urgency meter” of your body which prioritizes sensory inputs to the brain in terms of the urgency of reaction required for the same. The auditory cortex, the part of our brain which processes auditory information coming in through our ears, has a strong connection with our amygdala. This biological connection is a result of our ancestors having to listen and react to sounds out there in the wild. For early humans, the fight or flight response kicking in due to the amygdala being activated by the sound of a prowling predator in the bushes played a crucial role in their survival.
However, in modern times, without any predators waiting for us in the alleyways (not the animal kind anyhow), the amygdala and auditory cortex connection still plays a fundamental role in helping us cross a road during traffic and other such scenarios. The amygdala is responsible for the strong emotional reaction that we have when we hear the cry of an infant in distress, or when we hear an especially unsavory sound, like loud bangs, angry voices, etc. In some cases, the amygdala takes over the auditory cortex and changes our very perception of sound itself. This is when disorders like Misophonia can emerge, wherein individuals develop strong fight or flight reactions towards specific sounds which might not really be threatening at all. Misophonia cases have included people who have visceral reactions to sounds such as those emanating from someone chewing, typing on a keyboard, fidgeting, etc. In such cases, the amygdala is basically telling the auditory cortex that the sound coming in, even though it is not really a threat, is a fundamental enemy and hence, demands a powerful emotional reaction against it. People with Misophonia often develop Phonophobia, which is the irrevocable fear of certain sounds.
Hearing and Memory
Another major connection between the hearing apparatus and the rest of the brain is its deep-rooted relationship with the hippocampus, the seat of memory in the human organism. We all have the experiential understanding that certain sounds can trigger specific memories, often in a considerably vivid manner. This is especially true when we listen to music or hear a recognizable voice. A study associated with Johns Hopkins University, conducted over a period of six years, constantly monitored the hearing capabilities and cognitive development of a group of 2000 senior adults. The findings clearly showed that as hearing capacity decreased in the individuals, their ability to retain memories and process them decreased substantially. Hearing loss was almost always accompanied by an inability to recollect memories.
The explanation for this was that as an individual loses the ability to hear stimuli from their immediate environment, the brain tries to compensate for the lack of external auditory stimulus by changing fundamental systems of processing in the brain to “fill in the gaps” of environmental awareness. In this case, a lot of processing resources, such as nutrients, energy, and other foundational aspects are diverted to other areas of the brain, away from memory processing centers, in an attempt to compensate for the lack of hearing. This inadvertently leads to memory loss as a direct result of hearing loss.
Hearing loss has also been associated with inability to maintain rich social interactions. Humans being social animals require interactions with other members of the species, a lack of which can result in a definitive impairment of core cognitive functions. Several studies throughout the years have found that as an individual loses the ability to hear, their interactions with those around them decreases, thereby not only increasing isolation, depressive symptoms, and self-confidence, but also causing reduction of memory and mood regulation capabilities.
Hearing and Sleep Patterns
According to experts, we do not stop hearing even when we are asleep. Our ears are always open; it is just the processing systems in the brain for auditory stimuli that shuts down temporarily during sleep. Due to the fact that our ears continue to receive stimuli even during the night, there are subconscious impacts and processes that continue to be impacted by what we hear in the midst of sleep. One of the foundational subconscious impacts of noises acting as stimulus during our sleep cycles is the reduction of time spent is specific phases of the natural cycle. Fairly loud, irritating and consistent noise can cause us to spend less time in two of the most crucial parts of the sleep cycle, namely that of REM (Rapid Eye Movement) phase where dreaming occurs, and deep sleep or slow wave sleep, which is crucial for repairing and resetting of bodily systems. On the contrary, we tend to spend more time in the lighter phases of the sleep, such as hypnagogic phase which is the transition phase between wakefulness and sleep.
This essentially means that noise can disrupt our ability to get peaceful and satisfactory sleep, resulting in grogginess and irritability the next day. A study conducted on workers exposed to loud levels of noise due to their occupation showed that their sleep cycles were continually disrupted, with some individuals even showing signs of insomnia or the complete inability to sleep. Another important aspect that was discovered by scientists fairly recently was that during normal waking stages of life, especially during the day, our bodies secrete the hormone known as brain derived-neurotrophic factor or BDNF, which plays the crucial role of protecting our auditory nerves. At night, owing to the fact that noises tend to be much lower in frequency and diversity, this protecting hormone is not secreted, making the auditory nerves vulnerable to damage during such phases. This is a direct explanation of increased noise sensitivity observed among people as well as creatures like mice during night-time sleep cycles.
Hearing and Body Posture
Other than picking up on auditory signals, another fundamental function that the ear performs is that of maintaining body balance. A specific part of the middle ear, known as the vestibular canal or the middle ear “labyrinth” does not pick up or respond to auditory stimulus, but rather to body movements. The vestibular system of the ear is responsible for anchoring the center of mass in the body and thereby, allowing an individual to maintain equilibrium during activities such as walking, sitting, climbing, etc. It is due to visual and vestibular inputs that the body can maintain an upright posture. Hence, scientists have investigated the role of hearing loss and aging of the vestibular system in terms of the change in body posture that occurs in several individuals as they grow older. The fundamental role of the vestibular system pertains to the orientation of the head and its posture with regards to the body and the neck. Hence, a dysfunction in the vestibular system is often associated with illnesses or psychological disorders such as vertigo and accompanying symptoms, such as dizziness and nausea. Dysfunction in the vestibular system also results in blurred vision and can also lead to increase in the frequency of falls during old age. In some cases, patients have also been shown to display other physical symptoms, such as diarrhea, due to the malfunction of their internal balance system in the ear.
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