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Neural Plasticity, Cochlear Implants, Vision, and More: Interview with Sandra Aamodt, PhD

Neural Plasticity, Cochlear Implants, Vision, and More: Interview with Sandra Aamodt, PhD

March 16, 2009 Interviews

Douglas L. Beck, AuD, speaks with Dr. Aamodt, neuroscientist, author, and co-author of Welcome to Your Brain - Why You Lose Your Keys But Never Forget How to Drive, neural plasticity, cochlear implants, vision, cognitive reserve, Alzheimer’s Disease, regular exercise, rapid eye movement, sleep , memory, and more.

Academy: Hi, Sandra. Thanks so much for taking time to speak with me.

Aamodt: Hi, Doug. It’s my pleasure.

Academy: Sandra, I know you’re currently sailing around the Pacific, and I believe you’re in New Zealand at this moment?

Aamodt: That’s right. My husband and I sailed from San Francisco to New Zealand. It’s about a 6,000-mile journey if you go straight, but we didn’t go straight! We stopped at dozens of islands, took our time, and enjoyed the trip. We’ll be heading back to the United States after the hurricane season passes, probably in April.

Academy: What type of boat are you sailing?

Aamodt: It’s a 45-foot ketch.

Academy: Wow, it really sounds fabulous. I am so jealous. But okay — I’ll get past it. Let’s start with your bio. Can you tell me where and when you earned your doctorate?

Aamodt: I earned my PhD in neuroscience from the University of Rochester in 1994. After that, I did a four-year post-doc fellowship at Yale. My work focused on studying how the timing of critical periods for learning during development is controlled by maturational changes in young neurons.

Academy: And then I believe you were the editor-in-chief of Nature Neuroscience for a few years?

Aamodt: That’s right. After my post-doc, I went to Nature Neuroscience. It was a brand new journal at that time, and I started as an assistant editor. Five years later, I became editor-in-chief in May 2003. I stayed there for five years, and then we started to sail across the Pacific.

Academy: I totally loved your 2008 book with Sam Wang, titled Welcome to Your Brain. I can imagine how difficult it must be to take the most advanced ideas in neuroscience, and present them at a level that everyone can understand.

Aamodt: Well, that’s a challenge, but that’s also part of the fun. One key to connecting with people is expressing ideas in terms the other person can relate to.

Academy: Agreed. And I think you clearly succeeded. For example, I really enjoyed your notes about people learning second languages. Please tell me about that?

Aamodt: Well, that’s a fairly broad topic, but the main point is that different types of learning have different critical periods. For example, if the goal is to speak without an accent, you need to learn the second language, or third, or fourth language, before the end of the critical period for learning phonemes. So, in essence, you need to learn the new language before you’re three or four years old. However, if you want to speak correctly with respect to grammar of the language, you can learn it up to about ages 10 to 12 or so.

Academy: What about neural plasticity as it relates to audition? One thing I often talk about is that with regard to audiologists, our most common patients have already undergone negative neural plasticity as they lost hearing due to aging or noise exposure. In other words, their brains have changed as they have received less auditory input over the years.

Aamodt: That’s correct. And then when you use cochlear implants or hearing aids to replace those lost sounds, they undergo additional neural plasticity changes, as their brain gets used to hearing the sounds again. To me, cochlear implants are an amazing example of neural plasticity. People have some 25,000-30,000 nerve fibers on each auditory nerve. Yet we can replace that with 20-25 channels of auditory stimulation, and most recipients can use that absolutely minimal auditory information to make sense of sound in meaningful ways.

Academy: Yes, that’s true. And, in fact, the vast majority of cochlear implant recipients from the last few years can use their telephones successfully. It certainly has come a long way from the early days of simply adding amplitude and temporal cues to speech reading.

Aamodt: Yes, and even that little bit of information, those 20 channels or so sending information to the brain facilitates re-organization to interpret that information as meaningful speech. Of course it’s not an instant result, but it usually does happen over weeks and months of exposure and learning.

Academy: One example of neural plasticity I speak about is the fact that my vision is 20/20 for everything about 36 inches and farther from my eyes. Nonetheless, for everything less than 36 inches or so, I need to wear reading glasses. Of course after 10 years of glasses, I had sat on and misplaced far too many pairs of glasses, and so I started wearing contacts. Contacts were great, but I couldn’t drive comfortably at night due to the glare and reflections. So, I started wearing one contact. Of course the one contact immediately corrected my visual acuity, but it was pretty weird. I had a hard time with depth perception for a few weeks and reading was not at all comfortable as I could see both the clear image and the fuzzy image. Fortunately, after about a month, it all cleared-up. I wear one contact in the left and I can read up close without any problem and I can see perfectly clearly at a distance, too.

Aamodt: You basically retrained your brain to use the different information from the two eyes, and to merge them into one useful image. That’s plasticity. A laboratory example along those lines has to do with prisms. Don’t try this at home! When you give adults prism glasses that displace their vision by a couple of feet in one direction, it takes a few days for them to adapt to the new information. However, most adults can adjust their brains, and then they can correctly locate objects in the world while wearing the prism glasses. When you take the prism glasses away, their brains shift back to the original condition more quickly, so the brain seems to be biased toward the more normal situation.

Academy: Sandra, I’ve been reading lately about “cognitive reserve” and how it appears that people who have achieved higher academic accomplishments, and those who actively participate in cognitive activities as they age tend to acquire Alzheimer’s disease at a later age, and it appears to come on more slowly. Can you comment on that?

Aamodt: Yes, that’s true. Education is clearly one of the best protections against dementia from aging. Certain kinds of lifestyles do seem to be protective, and as it turns out, having a healthy brain has a lot to do with having a healthy heart. The brain is clearly the most sensitive organ in the body with regard to oxygen, and a healthy circulatory system helps assure the brain gets the oxygen it needs.

Academy: Let me quote you from your book, on page 212 you said… ”It may surprise you that our bottom line recommendation is that instead of using brain training software, get regular physical exercise. Fitness training can have an effect that is several times larger than any demonstrated benefit from computer-based brain exercise…”

Aamodt: Yes, that’s correct, and that’s still true.

Academy: Sandra, I know you’re time is limited, and I very much appreciate chatting with you. Before I let you go, would you review your thoughts on rapid eye movement (REM) and memory?

Aamodt: Sure. No one knows for certain why we dream during REM sleep. There are some interesting patterns in the physiology that suggest a leading hypothesis, which is that patterns of neural activity that occur during the day are perhaps replayed in “fast forward” (so to speak) while one sleeps, for the purpose of memory consolidation. And as you may know Doug, there’s a huge amount of behavioral evidence showing that people who are prevented from sleeping after learning a new task don’t retain it as well as those who are allowed to sleep.

Academy: What about memory and reconstructing events?

Aamodt: Well, nobody actually remembers their life quite like a movie. I know people think they do. They think they can select a memory and play it back, but that’s not how it really works. A huge amount of what we refer to as memory is your brain picking and choosing a few milestones or ideas and reconstructing a story around it. Of course, the more you reconstruct one memory or milestone the quicker you can access that same sequence of neuronal activity, and the more you reconstruct it, the more you reinforce that particular memory. But that doesn’t make it true or factual. In fact, there’s evidence that recalling memories changes their content. We know that even with regard to very dramatic events such as 9/11. If you ask people their recollections a week later versus a few years later, their memory of the event changes. One of my colleagues says that as we age, our memory tends to recall things in more useful ways. That is, as we age, we remember in ways that are more beneficial to who we are and where we are in our lives at the particular moment of recollection. So it may be a protective mechanism, allowing us to see the more useful and more positive side of things.

Academy: Sandra, it’s absolutely fascinating to speak with you. Thanks so much for your time.

Aamodt: Thanks for your interest, Doug.

Academy: My pleasure, Sandra. I wish you smooth seas and safe sailing as you make your way back to the United States.

Sandra Aamodt, PhD, is a neuroscientist, author, and co-author of Welcome to Your BRAIN (2008), published by Bloomsbury, ISBN 10: 1-59691-523-4.

Douglas L. Beck, AuD, Board Certified in Audiology, is the Web content editor for the American Academy of Audiology.

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