The brain is an amazing organ. It gives us conscious control over our actions and is the seat of our thoughts and experiences. There are millions of things in our environment that enter our world everyday, but only a few of them get past the steely discrimination of our perception. Take a minute to pause your reading and think about the feeling of your clothes against your skin. You weren't quite consciously aware of this until I mentioned it, right? That is just one example of how the brain deals with many different types of sensory inputs every day, taking the relevant stimuli and bringing them to conscious experience while simultaneously discarding the irrelevant ones so you aren't constantly overwhelmed with all the sights, sounds, and other sources of sensory input that constantly bombard your person. This discrimination is a matter of how the brain pays attention. It is simply impossible to pay attention to everything at once, so the brain has to choose what gets into our perception and what is kept out. Of course, what gets in and what stays out can change from moment to moment, and from environment to environment.
The Kraus lab at Northwestern has spent time working on the effects of musical training on the brain. A few months prior, they published a study that showed that among aging and older people, musicians had a better ability to hear speech in a noisy, distracting environment. This ability to pick out speech in the face of many interfering noises or competing speech is a cognitive ability that tends to decline in most older people, so the fact that they found that musicians were better at it was promising evidence for the positive effects of musical training on age-related decline.
They build on that promising finding in a new paper where they explore the wider implications of ability to pick out speech in a noisy environment, or as they call it, speech-in-noise. The next step in their experimental process was to determine how this greater attentional ability to speech-in-noise translated to actual differences in the brains of musicians versus non-musicians.
In order to measure attention objectively, the Kraus lab recruited people who were willing to put on a strange-looking cap that measures the electricity of brain activity through the scalp.
The technique of measuring and recording electric activity through the scalp is called electroencephalography, or EEG for short. The experiments consisted of getting two groups of subjects, one with musical training and one without, and strapping those lovely caps onto their heads. Next, the subjects were placed in a room with two speakers on opposite sides. A voice reading a story was playing from the speaker on one side of the participants, and a different voice reading a different story was playing from the other speaker mounted on the opposite side of the room. They were asked to listen to one story and not the other, and then given a short quiz on the story after the readings. While they listened to the story the EEG cap did its work recording their brain waves.
The two big questions that this study wanted to answer were 1) whether paying attention to one voice over the other would produce an increase in attention that they could measure using EEG 2) whether this measured increase in attention would be greater in musicians. In other words, can we measure how much attention these people are paying to a voice despite the noisy environment in which it exists? And can musicians pay better attention to this speech-in-noise than non-musicians?
The lab was looking closely at the attention networks of the brain while the people tried to focus on one voice over the other. They were specifically looking for how much the activation of attention centers in the brain varied over the eight minutes that the two competing voices played. They had a fancy name for how much the EEG recordings of the attention centers varied over time: response variation. Any time the variation in activation of attention centers is LOW, it seems that people are paying a greater amount of attention to one particular thing. So low variation in attention, or low response variation, is a good thing. It means that the subject's brains are paying better attention!
So what did they find? People with musical training were better able to hear the speech-in-noise than people without musical training. Musicians also had a better recorded EEG auditory attention score than non-musicians. All this data was pretty much old news from the last paper the Kraus lab published on aging adults, but the really interesting stuff comes from more of the data from the EEG recordings.
Here in a figure from the paper, red indicates a greater amount of attention paid to the correct voice (the "attend" labeled in the graph) in the study. Notice that only musicians have red scores in the front of the brain, where the prefrontal cortex electrical activity is measured.
When looking at the data from all of the study participants, the lab saw no overall differences in brain response variation between musicians and non-musicians. It seemed, at least on the measurable brain activity level, that both groups were paying equal amounts of attention. But the one brain area that seemed to be "listening harder" in musicians was the prefrontal cortex.
The prefrontal cortex is often called the "CEO" of the brain. It's responsible for higher judgements, planning, focusing attention, and control of social behavior. It's the part of the brain that develops the most slowly throughout life, not maturing fully until age 25. In non-musicians, there was no difference in prefrontal cortex EEG recordings between attention paid to the intended voice versus the unintended voice. But in musicians, the EEG of the prefrontal cortex showed it was paying better attention to the intended voice!
The most fascinating part of this study was that the magnitude of the effect correlated to how long the musicians had played music. People with more years of musical training had a prefrontal cortex that "paid better attention" than people who had less years of musical training. It seemed that people who had spent more time training their brains via musical study had prefrontal cortexes that were better at locking their attention into the intended voice.
This paper has some exciting implications. It's the first paper to present direct evidence that musicians and non-musicians have different patterns of brain activation when paying selective attention to speech. It shows that the prefrontal cortex, an area of the brain that is thought to be greatly responsible for attention and control, gets better at voice discrimination with more musical training. This could mean that music training at an age before the prefrontal cortex fully develops could potentially strengthen attentional capabilities, which might be helpful in the treatment of disorders like ADHD. As is often the case in science, more answers lead to more questions. Exactly how does musical training shape the attention centers of the brain? Is there an age at which musical training fails to cause this effect in the brain? I'm looking forward to reading more studies that attempt to get at these answers.
Strait DL, & Kraus N (2011). Can you hear me now? Musical training shapes functional brain networks for selective auditory attention and hearing speech in noise. Frontiers in psychology, 2 PMID: 21716636