The connections between sound 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. 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. ************************** 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? *************************** 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 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.