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CV: Dr. Andrew Dimitrijevic

By Matthew Pariselli  •  July 6, 2017

Bio basics: A scientist in Evaluative Clinical Sciences and the Hurvitz Brain Sciences Research Program at Sunnybrook Research Institute (SRI), research director of the Sunnybrook Cochlear Implant Program, and an assistant professor in the department of otolaryngology – head and neck surgery at the University of Toronto. Did postdoctoral fellowships at the University of British Columbia and the University of California, Irvine. Completed his M.Sc. in zoology and PhD in neuroscience, both at U of T. Born and raised in Toronto, Ont. Joined SRI in September 2016. Resides in Toronto with his wife and two kids.

What prompted you to become a scientist?

I’ve always been interested in neuroscience, but realistically it was my grandfather who had Parkinson’s disease. I saw the personality change over the years and wanted to know what was happening in the brain. Up until my PhD I was doing animal work, but for my PhD I totally switched and studied humans, looking at language and speech. What’s cooler than studying the brain processes that help us define who we are as human beings?

What sparked your interest in hearing, specifically?

I’m interested in what defines us as humans. What are we as humans? What is thought? These philosophical digressions have always interested me. I began looking at them from a neuroscientific point of view and that’s how I got into the higher-order stuff—so from cognition and listening, to speech and language. Hearing is considered many different things, but as you get higher and higher in the brain, it gets more and more complex, and hearing becomes part of the working memory for speech and language.

What is your research focus?

We try to understand variability of [cochlear implant] surgical outcome. Let’s say you have two people who are medically identical; they both have hearing loss, and they both get cochlear implants. One year later, one person is doing awesome, whereas the other person struggles, and yet we have no way of predicting why these two people respond differently even though everything tells us they’re medically identical. If we understand where the problem is occurring—is it encoding or is it a cognition problem?—[then] we can target rehabilitation.

What is a cochlear implant?

There are electrodes that go into the cochlea, which is your hearing organ that looks like a snail. When the organ dies—maybe a virus attacked it; maybe there were malformations—the person becomes deaf. Normally, the auditory nerve innervates the cochlea, and that [stimulation] goes on to the brain. With a cochlear implant, we insert these electrodes and they mimic what is normally happening in the cochlea. High frequencies and low pitches are coded in different areas of the cochlea, and then these electrodes stimulate the auditory nerve. We put a microphone on the outside of the ear and we do some signal processing. What happens is that sound output is transformed into pulses and those pulses now stimulate the auditory nerve, [so] these people can hear again. It’s the most successful implantable device that we know of. We’ve taken people who’ve never heard anything in their lives, who have no concept of sound, and when we put the implant in, they can hear.

How would you describe being in the presence of someone who hears for the first time?

It’s profound. These people are just profoundly changed. For the first time they can hear their baby or their grandkids. People become more involved in their community as they re-enter life. [Until this point], their life has been on pause.

What are you working on?

We’re in collaboration with [U of T’s] faculty of music. We’re getting patients to do music lessons. Music therapy is a really big field, not just for hearing, but also for patients with Parkinson’s disease, and Alzheimer’s disease and other dementias.

We’re also doing projects that look at the cognitive aspects of hearing, like effort. It’s called listening effort. When you’re in a noisy situation and you’re trying to focus, you exert a lot of mental effort to pay attention. We can do this up until a certain point, but then afterward we end up conking out. We, as normal hearing people, are in this environment in a bar, whereas people with cochlear implants are in it all day. The input going into their brain is not perfectly crisp sound. They can understand, but it’s not perfect. What happens then is that these people with cochlear implants do fine, but if they have to listen for an entire day at a conference or at work, they feel exhausted, and sometimes they just take out the implant. We often think of hearing loss as just hearing loss, but it has a lot of implications. There are higher rates of depression and suicide because these people can be really socially isolated.

What attracted you to SRI?

SRI is very diverse in terms of covering the whole spectrum of research, varying from cognition­­—which I’m really into—and aging, to genetics. Eventually, I’d like to try to merge those two [cognition and genetics], and the resources are here to do that. Sunnybrook also has the largest adult cochlear implant centre in the country, so being here is an amazing opportunity.

What are some advantages associated with being at SRI?

When I was in Cincinnati, Ohio [looking at hearing disorders in children with cochlear implants], it was hard to get patients, and we were separate from the clinic. Now, my lab is actually in the clinic. Here at Sunnybrook it’s mostly adults with cochlear implants and because it’s adults, there are a lot more interesting things I can do in terms of cognition. The scope of work here is much more diverse, and I can merge with other fields and researchers. Historically, we have always thought of hearing and cognition as two separate entities, but in the past 10 years we’ve realized they are actually dependent on each other. Sunnybrook has an amazing team working on dementia, so this is perfect. There are experts I can talk to in cognition and psychology, so coming here was a no-brainer. Also, I like Toronto. I’ve been trying to come back to Canada for a while.

What do you like about Toronto?

When I left Toronto 13 years ago, I thought, ‘Oh yeah; it’s time to leave. I’ve been here my whole life, and I’m ready to try something else.’ Then I went other places and realized, ‘Yeah, the music scene [in Toronto] is awesome. My family and friends are there.’ Every city has pros and cons, but Toronto is an awesome city. We’ve lived in L.A., Calif., we’ve lived in Cincinnati and traveled abroad, but the diversity in Toronto and Canada versus the U.S. is great. Going in, I didn’t realize how big of a difference there was, but then after living there I was like, ‘Wow.’ Living in Canada after living in the U.S. is a blessing.

What do you enjoy about your research?

One of the main things I enjoy is the translational aspect. When I was doing stuff in the animal world, I felt like I was a few steps removed from something actually happening. It’s different now. For example, with my PhD, we developed certain types of sounds to diagnose hearing loss in a sleeping baby without relying on feedback. Companies are now using this technology. I can actually see the fruits of my labour. I’ve been to hospitals and said, ‘Oh, I helped develop that machine!’ [laughs] This was a motivator for me. It’s translational in my lifetime. There are certain areas of research where you may see something happen 20 years later, but the time from bench to bedside in my field is really quick.

How do you maintain a work-life balance?

When I’m home my kids are my number one priority. Ask my wife about grant season, though, and she’ll tell you grants become my number one priority and I’m up until 2 a.m. every night. Overall, I try to set aside time for family and kiteboarding. I haven’t figured out the secret to balance, but if you find it let me know. [laughs]

If you weren’t a scientist, how would you fill your days?

I can’t see myself doing anything else. I love coming to work and thinking of new experiments. It’s always a game. If I weren’t a scientist, though, I’d probably be a snowboarding bum or a kiteboarding bum. [laughs] I’d probably live in Whistler, B.C. and be a hippie there or be a surfer hippie in California, U.S. I definitely couldn’t do 9–5 in an office.