Excerpt from Transcript of BS 192: Review of Key Ideas

While I think neuroscience is interesting because it helps us understand ourselves and others, I also think Brain Science is an important podcast because it's a voice for science and how it really works despite the fact that it's done by human beings.

It's actually rather surprising to realize that this is only the second time we've talked about hearing. Back in episode 140, I described a talk I attended about the role that hearing loss plays in the development of dementia. The bottom line is that if you have hearing loss, it is critical to your brain health to get hearing aids that really work. This includes working with a professional to make sure that they are adjusted properly.

As Kraus pointed out, people tend and to take hearing for granted, even though hearing loss is actually much more socially isolating than vision loss. Vision is the most heavily studied of the senses, but hearing presents some interesting contrasts that relate to the difference in the signal.

Visual inputs are relatively static while sound is extremely time sensitive. I learned this as a young teenager when I tried to learn how to play the guitar. After my first year of lessons, I was wondering why nothing I played seemed to sound right. Then I got a new teacher who told me about the beat. Turns out that if you don't play the notes with the correct timing, even a familiar song becomes unrecognizable.

Sound is not only time sensitive, but very rapidly changing. Again, this is something we seldom notice unless we try to listen to another language. Then it sounds like everybody's talking way too fast.

Speech is faster than other sounds, including music. It takes about a hundred milliseconds to tell the difference between notes, but for consonants, the change is like 20 milliseconds. I emphasize this timing element because this is the one key to understanding how sound is processed in the brain.

Despite all the supposed powers of the cortex, it is way too slow to process sound. Most of the processing actually occurs subcortically, and of course, unconsciously. These circuits are ancient because hearing is shared by virtually all vertebrates, even though many lack vision.

Thus, the decoding of the timing of sounds including speech and music occurs at the level of the brain stem and midbrain. I found the discussion of this in the book to be very fascinating, even though we didn't have time to delve into the details during the interview.

Kraus wanted to emphasize the important point that everything we hear changes our brain. In the case of noise, these changes can be damaging, but learning languages and music is highly beneficial.

Besides reading Of Sound Mind: How Our Brain Constructs a Meaningful Sonic World by Nina Kraus, I also want to encourage you to visit Kraus's website at brainvolts.northwestern.edu.

Brain Science comes out the fourth Friday every month. Next month, I plan to talk about why embodiment is so important.

Until then, I hope you'll check out my other podcasts, Graying Rainbows and Books and Ideas. Thanks again for listening. I look forward to talking with you again very soon.

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