Q: Can you give us a brief background about yourself?
Dr. Zach: I was a postdoc at Rockefeller University and I came to here to work as a lecturer. I never actually went to an American school so I learned a lot about American higher education system. I’m from Israel. I’m from suburbs of Tel Aviv but I did my PhD in Jerusalem. I came to New York to do postdoc in Rockefeller and this July I came to Penn.
Q: How have you found the education systems to be different?
Dr. Zach: I think compared to my undergraduate experience in Israel it’s a lot more focused on the experience of the student. Take small loads, take a lot of electives in different fields. When I went to school, you didn’t take any electives in different fields. You can do a minor, double major, but all this, like taking a lot o courses outside your major, is very strong here and it’s a lot of focus about having an enriched experience. I really value this. When I went to college you chose the major, that’s a choice, but once you chose it, there aren’t that many more choices. I also work as an advisor. Learning all the rules of the advising, you see that the policy is to help the students still have free time for extracurricular activities and summer programs abroad, etc. There’s a lot of emphasis of how we’d like a student to be as opposed to what you have to know to get a degree.
Q: How did your interest in neuroscience develop?
A: I always wanted to be a scientist, ever since I was a child. I grew up in a suburban environment. I remember when I was five or six they were showing a pathologist in a courtroom – I guess it was like law and order or something. I thought I would have to work with corpses. I was always fascinated with the concept – the very analytical and methodical approach. So I always kind of knew I wanted to be a scientist but this was before I knew any sciences. It was really the scientific method that I liked. As a teenager, I was really interested in the human mind. So I thought it would be perfect that I would get good biological answers instead of vague answers. I did a double major in Biology and Psychology and PhD in Neuroscience. I learned there are very few answers when you try to be rigorous about it, but I still like the effort. Even when I teach BBB109 I still rethink things that I didn’t study myself. There are many great ideas and approaches.
It’s like that in science in general. If you take biology or preliminary genetics course and then do PhD in it, it crumbles into islands of knowledge in oceans of unclarity. And you learn to focus on things you can progress in. Even when I was a postdoc, I’ve seen portions of oceans turn into islands, of people approaching, giving preliminary questions, and then developing them into better answers. It’s very exciting. I think in very few jobs you get to see a big change in knowledge. Most people’s jobs are probably not very different from 3 years ago. In science it’s very different. Even now, to keep with the work I did as a postdoc is an effort. Because things change and I sometimes hear not even the facts but how they’re organizing the theories. It’s nice to feel that the passing of time is meaningful.
Q: What kind of research have you been participating in?
Dr. Zach: In my PhD, I worked on learning new tasks and changes in the primary motor cortex that follow learning. And it was usually motor tasks and how the primary motor cortex representation changes once you learn something. Not so much memory in long term but how is memory being formed. Immediately after you learn something, there’s a process of consolidation and if consolidation is interrupted, you forget, and if consolidation is good, you retain the memory. So how could we look at consolidation and if you talk about brain activity, how are different neurons changing to enable long-term activation? We already know that representation of body changes with practice, connection between cells changes with practice. But what happens within short few hours time to enable memory is interesting and we studied that.
If you compare the primary motor cortex to the primary visual cortex, our level of knowledge is very different. Regarding the visual cortex, information about organization is a lot more known so you can talk a lot more about changes in the organization. Once you know how it’s supposed to be you can talk a lot more about how it changed, while the other the connections are not as well known so it’s a lot harder to talk about change. Therefore, when I moved to do my postdoc, I wanted to look at the same kind of questions of learning and consolidation but with a higher level of detail. In my PhD, I looked at cell activity. Now I wanted to move to a better perspective and more specific connection at the cellular level. This was more complex so in order to do that I moved to working on visual cortex, where more is known.
Q: How did you tackle the research questions you had?
Dr. Zach: So the methods were a big change for me when I began my postdoc. I moved to a method that is still relatively new, called two-photon microscopy. You use a microscope to track changes in fluorescence. What is special about this technique is the “two-photon: part because you project light on tissue and when two photons of light converge, they change wavelength and the meaning of this is that you can detect changes of one photon, allowing very fine resolution. What we did was, we used viruses with construct that will only be expressed in certain cell types – and what will be expressed are fluorescent molecules. So specific cell types in the brain produce genes that give out specific products and now some are fluorescent and we can therefore track these cells. We looked at the shape of the axons of these cells. We looked at them before and right after learning and then looked at them after every week for two months to see the changes formed and every week to see if they were retained. We trained animals to learn something to see changes in connection between cells and to see if they’re maintained throughout the long period of time.
Q: Have you had any interesting discoveries in your research?
A: There are two sides of the spectrum regarding theories on this matter. One theory is that every cell represents a small region. For example, in the primary motor cortex, a cell will control a small group of muscles computing some small subsets of activity. Other theory is that the cells act together to compute all possible movements. According to this theory, one cell can, in different context, generate different movements. We tried to advocate for a different theory that different cells take on different properties at different times. So for example, if a brain region is responsible for the arm movement and you’re trained to move your hand when you see the color green as opposed to the color red or you’re told to move to a certain sound, the cells in the motor cortex will respond to color green or sound with movement. So system will respond to whatever is important for behavior; they respond to whatever guides movement. But this changes in different contexts. Cells in the primary motor cortex originally didn’t respond to green light but after learning that it guides movement, the cells suddenly respond to green more than red. And if [monkeys] move to another task in which green light is meaningless cells don’t respond at all. If [monkeys] go back to the same task, then cells respond immediately. So we showed that the behavior of cells is dynamic, they represent different things at different times.
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