Friday, March 1, 2013

Tuned in



By Mark Hamer



We often list our large brains, opposable thumbs, and developed vocal chords as defining biological traits that make us human. Socially, our combined ability to communicate through speech, develop complex relationships and recognize ourselves as individuals, distance us from all other organisms on earth. But here are more subtle aspects of our existence that go unexplored. Traits of our species that, though heard by most daily, go unnoticed or at least under-appreciated. I’m talking about music. Music is a mysterious thing. Its effects on human behavior can manifest itself as anything from a deep calm to flailing around like a tempestuous banshee. Clearly there is something that exists within these intentionally manipulated vibrations that is altering what goes on in our heads. So let’s take a moment to appreciate music, and its effects on the brain.

An awesome visual of a connectome, which
diagrams neuronal circuits in the brain
Brain physiology is a complex and often convoluted discussion point. We are all aware that, at its core, the functional units of the brain are neurons. The human brain is estimated to contain 100 billion neurons (that’s 100,000,000,000). Neuronal networks within the brain work like telephone lines. They send information back and forth at astonishing rates. Of course, like telephone lines, a single neuron usually is not long enough to reach from the origin of the signal to the destination. Instead, neurons are said to “synapse” with other neurons. That is, once a point is reached where one neuron stops, another neuron picks it up. Telephone poles don’t float in the air without support. They require telephone poles at regular intervals. The telephone poles of the brain consist of a variety of supportive cells known as glial cells. A single neuron is capable of receiving signals from hundreds, even thousands of other neurons and transmitting it through to many more. Signals are received by dendrites and sent through axons. When a signal is being transmitted through a neuron we call it an action potential. Action potentials occur as the result of sufficient stimulation of the neuron by the dendrites that have formed connections (i.e. synapsed) to it. The action potential is then propagated along the axon by exploiting the electrochemical voltage gradient that exists between the interior and exterior of the cell. Think of this as the way electrons are passed from atom to atom in our telephone wire example. Once this signal reaches the end of an axon it stimulates the release of chemicals, known as neurotransmitters. Common neurotransmitters include chemicals such as serotonin, dopamine and acetylcholine. These neurotransmitters have diverse roles in brain physiology but effectively they can be thought of as the intermediate chemical messenger that transfers the signal between neurons.
The basic structure of a neuron

But we we’re talking about music right? What does all this brain stuff have to do with music? Researchers have taken a particular interest recently in the effects that music has on neurons in certain regions of the brain. Direct links can be drawn between changes in brain activity and nearly every aspect of human biology. So, if music is affecting our brains it is very likely that it is affecting our bodies too. The range of topics that could be covered in this blog is overwhelming. Instead of sitting here listing all of the possible effects that music has on brain physiology, I will instead focus on a couple of interesting discoveries that have recently been made.

One of the articles that got me interested in this subject was actually found while searching about the effect of music on bodily physiology, specifically on blood pressure. As I read however it became increasingly clear that what I was really reading was an article that had much broader implications. On the surface, this article titled “Music improves dopaminergic neurotransmission: demonstration based on the effect of music on blood pressure regulation” attempts to explain a pathway through which music is capable of decreasing blood pressure. It got me thinking though: if music is causing a decrease in blood pressure, could it be that stress hormones are the agent responsible? If this is the case, does music increase the capacity of neurogenesis? After a quick search I found another article that answers just this question.


We’ve all heard of something termed the “Mozart effect”. The Mozart effect is the idea that, if exposed to classical music during fetal development, the baby will have a step up on those babies whose mom’s didn’t hold headphones against their bellies. However, it might be better that mom just listen to the music herself. A second study found that a decrease in stress hormones coincides with listening to classical music. As us 502’ers know, decreasing stress has potentially long lasting effects on neurogenesis, the ability for new neurons to form within the brain. So, when mom’s relaxed the baby is too, and this promotes neurogenesis. These two paper’s when read together thus show an extremely important relationship between stress and music.

            The relationship between music and stress is a fairly straightforward concept. I’m sure we all have that favorite band or album that, after a stressful day of writing blog or papers on osmoregulation, instantly lets us chill out and relax. But there’s a question that, in my mind, remained unanswered until I really began to search. That is, why does music exist in the first place? We as people interested in physiology should always ask ourselves what the functional role of a behavior is.

The effect of music on systolic blood pressure 
Currently, scientists are beginning to cite music as being evolutionarily advantageous to humans. But how are these broad claims being supported and what are their implications? Researchers at Stanford may have been the first to support this idea with empirical evidence. In their experiment they scanned the brains of people listening to the English, late-baroque period composer William Boyce. One of the characteristics fundamental to classical music is “the movement, which is defined as the primary self-contained section of a large composition’’. Transitions between movements provide a relevant way of modeling what is known as event segmentation. Event segmentation, as the name suggests, is the partitioning of particular sensory events in to pieces that the brain is capable of then storing or ignoring. Studying movement transitions allowed the authors to discover differences in the activity of certain regions of the brain. In this study activity was observed “in the ventral fronto-temporal network associated with detecting salient events, followed in time by a dorsal fronto-parietal network associated with maintaining attention and updating working memory.” This discovery has fascinating implications. Most importantly is helps to describe a model through which the brain processes salient stimuli. But what I found equally intriguing was the fact that when you are listening to music, especially new music, you are honing your ability to pick up on and pay attention to stimuli. What’s even more amazing is that music is beginning to be discovered to have adult neurogenic properties as well. Chew on that for a moment!

A 20 second video showing some of the interesting changes that 
occur in the brain during a motion transition

At the beginning of this blog I listed some physical and social attributes that are often used to describe human beings. I believe that the beauty of music is that it utilizes all of these and focuses them down in to a coherent manifestation of the human condition. So go listen to some music, it really is good for you.



Some links to music I listened to while writing this:

References:

Ivanov, V.K., J.G. Geake. 2003. The Mozart Effect and primary school children. Psychology of Music 31: 405-413

Peterson, D.A., M.H. Thaut. 2007. Music increases frontal EEG coherence during verbal learning. Neuroscience Letters 412: 217-221.

Sridharan, D., D.J. Levitin, C.H. Chafe, J. Berger, V. Menon. 2007. Neural Dynamics of Event Segmentation in Music: Converging Evidence for Dissociable Ventral and Dorsal Networks. Neuron 55: 521-532.

Sutoo, D., K. Akiyama. 2004. Music improves dopaminergic neurotransmission: demonstration based on the effect of music on blood pressure regulation. Brain Research 1016: 255-262

Suzuki, M., M. Kanamori, S. Nagasawa, I. Tokiko, S. Takayuki. 2007. Music therapy-induced changes in behavioral evaluations, and saliva chromogranin A and immunoglobulin A concentrations in elderly patients with senile dementia. Geriatrics & Gerontology International 7: 61-71.

Photo References

http://treeswingers.files.wordpress.com/2010/05/ratatat.jpg

http://io9.com/5943304/how-to-preserve-your-brain-by-turning-it-into-plastic

http://webspace.ship.edu/cgboer/theneuron.html

http://blog.lib.umn.edu/chamb169/myblog/2011/11/the-mozart-effect.html

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