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soothing or shrill - the relationship between sounds and emotions

The limbic system, the brain’s emotional center, colors our high level cognition like decision making, with fairly basic emotions of either fear or reward, maybe especially when we are experiencing bias. An example of this is when a woman’s voice is described as either soothing or shrill. It could make the difference, and does make the difference in who you listen to, who you consider a leader, in hiring decisions, or who you might vote for. Any kind of negative behavior based on a sound or a particular tone probably will involve the amygdala, which is much more than a simple fear center and might be better described as an alertness center. We have already started to explore this pathway and will revisit that conversation. But remember that there is another pathway in the limbic system. The reward system of the brain motivates our decisions in entirely different ways and has a really interesting and unique way of interacting with the auditory cortex. Let’s spend a little time studying how sounds perceived in the auditory cortex interact with different parts of the limbic system.

The mesolimbic pathway for reward

A study of bias should include why we prefer things, such as certain sounds, like a favorite song. Let’s define a “feel good” area of the brain, before we explore how sounds interact there. First, it’s important to understand - Functions in the brain don’t really reside in places, but rather the connections between places. A group of cells can have multiple functions, depending on who they’re talking to. In other words, it is the brain’s pathways that allow us to have cognition. The mesolimbic pathway connects the ventral tegmental area, or VTA, in the midbrain, and the nucleus accumbens in the ventral striatum. The VTA is one of the few groups of cells in the brain that create dopamine, the powerful reward neurotransmitter. When the VTA inputs dopamine to the nucleus accumbens, this mesolimbic pathway elicits a strong sense of reward and enhances motivation. The fact that dopamine is the prominent chemical here, makes this one of the most powerful reward connections in the brain, and anything that enhances this connection will likely produce a strong, sometimes addictive, sense of reward. Let’s study how sounds can interact with these structures and this pathway.

Pleasant music is ... pleasant. The mesolimbic pathway agrees.

To further understand preferences and bias, let’s study the connection between sound and reward. This 2005 paper demonstrated that listening to good music caused activity in both the ventral tegmental area and the nucleus accumbens. It was one of the first times that it was demonstrated that, at a neurobiological level, pleasant music is … pleasant. The mesolimbic system lights up, so we feel rewarded listening to nice music. It’s kind of an obvious conclusion, but, someone had to do the work and put pen to paper, and this Stanford research group did the work. It seems that 20 years ago, reward centers were usually studied in terms of their role in addictions, or inhibiting negative stimuli, and not so much on simple pleasantness. This was still early days of discovering the roles of the VTA and nucleus accumbens, and utilizing fMRI for this simple type of study was novel. A similar study came out the previous year involving PET technology. Does music light up the reward centers in the brain? yes. But where does the auditory cortex, which perceives sounds but was not mentioned in the paper, fit into this picture?

Is consciousness even real?

There’s a new theory about consciousness, that the conscious brain is not there o sophisticat thought processes, but rather that cognition mostly occurs at a subconscious level, and the conscious brain simply stores memories after the fact to make future predictions. That the cerebral cortex is not for high level human logical rational thought, but only records the subcortex. The auditory cortex is not really perceiving sounds, but simply remembering sounds already perceived at subcortical levels. Consciousness is an illusion? It somewhat makes sense. Subconscious thought occurs about 30 msec after stimulus, and conscious thought about 500 msec, a half second, pretty long in physiological terms, thus the conscious brain is often too slow to participate in real-time events, like playing music or driving a car. But the subconscious is not entirely in charge - when decisions need to be thoughtfully carefully carried out, primitive subcortical reactions are supplanted with cortical processing. But according to this theory, that’s an afterthought. Literally.

I'm never going to like the electric guitar: amygdala, auditory cortex, thalamic reticular nucleus

I don’t like the sound of electric guitar. It reminds me of hair bands. Yuk. Through the years, I’ve developed an appciation of the talent an ha wok that can go into a solid electric guitar riff. However, although I’ve learned better at an intellectual level, my first reaction to hearing electric guitar is always aversion. Unconscious emotions can be more powerful than conscious reasoning. The amygdala, responsible for negative valence or simple dislike, activates long before there is any conscious understanding at the cerebral cortex. The auditory cortex is activated almost half a second after the amygdala, well after aversion begins. And, the amygdala actually sends further signals to the auditory cortex through the thalamic reticular nucleus, meant to amplify the salience of the repulsive sound. This emotion-driven control of sensory perception, signals to the cortex to pay particular attention to how awful the sound is. All this to say, if we dislike something at an unconscious, emotional level, it’s really hard to reason our way out of it. Im never going to like the electric guitar.

I'm husband is always going to like the electric guitar: ventral tagmental area and auditory cortex

My husband is opposite from me. He loves the sound of the electric guitar, and he is befuddled that I don't like it. So let's explore that: what is the relationship between the unconscious sub-cortical areas, and the conscious auditory cortex, when you like a sound? It was suspected for some time that the ventral tagmental area (VTA) which induces a feeling of reward when activated, somehow sharpens sound perception in the auditory cortex. The VTA was thought to be connected in such a way to amplify pleasure in hearing certain sounds; and, induce a feeling of reward when hearing those same sounds in future. Three years ago, a landmark publication gave clear evidence to support this. The activation of the ventral tagmental area enhances pleasure brought about by the thalamus and increase the activity of circuits, between layers within the auditory cortexs. Basically, the VTA teaches the auditory cortex that a pleasurable sound is more likely to be remembered as pleasurable. My husband is always going to like the electric guitar.

Bias is unconscious and wired in - can we turn it around?

My last two videos described the brain areas involved in liking or disliking particular things. In this case, the fact that I really don't like the sound of the electric guitar, and my husband really does like it. Our perceptions of sounds, our biased opinions about them, and even the amplification of these biases ... all these processes begin long before we've had a conscious understanding that we've even heard a sound. The greatest advancement in understanding specifically how these brain pathways work have only been sorted out in the last three years. Pulling back the curtain on these esoteric stores and making them available to the general public, hopefully resolves some of the mystery around some of these cognitive processes. Bias is a physical construct, and to some extent, it's wired in. Thus it can feel hopeless to turn it around. But remember, the brain is plastic. You can create new pathways and let go of your biases. It must be purposeful, but it can be done.

Can women's voices be respected?

Have you ever had that thing where you hear somebody speak and automatically think, I don’t think I’ll listen to what they have to say? Is it possible that you do that more often with women? Do we have an unconscious bias that women’s voices are not the voices of leaders? As I continue to explore the brain’s bias activity, I want to continue to focus for the moment on sensations and how they are processed in the human brain. Down the line I’m going to consider how the experience of bias influences our information processing centers and our decision making, and even influences our own behaviors and reactions, even before we have consciously decided to act. But we have work to do at the sensory level first. Even at this first, sesnory level of brain processing, where information is coming in about the world, the way that we perceive sensations can be influenced heavily by our emotions, and our sensations are kind of not true, they are processed in a biased manner. The sensations one person experiences may be quite different than the way someone else might experience the same things, because of the way an external stimulus comes into the brain.