Day 5

Today starts week two of my internship. I'm going to start this entry with an introduction, because I never did that earlier. Also, if anything I say in this blog is unclear, confusing, etc. please tell me in the comments so that I can clear it up.

This summer I am interning at an fMRI lab at Columbia. I will be working with grad students in the lab and contributing to current research. It's pretty cool. You may be saying right now, "Well, I've heard of an MRI, but how is an fMRI different?" An MRI is the most basic form of magnetic imaging. Standard MRIs (also known as T1 scans) take pictures of slices of the brain. They are mainly used for structural imaging. fMRIs (also known as T2* scans) measure blood flow in the brain. (The 'f' stands for functional) The way that fMRIs work is that they track the BOLD Signal (Blood Oxygen Level Dependency) in each voxel (3D pixel) of the brain over time. In other words, it tracks where blood goes when you do a certain task. In this way, we can see what specific parts of the brain are used for. fMRIs are often used for research, but they are also commonly used pre-brain surgery to see what parts of the patients brain are used for what. For example, most people process language on the left side of the brain, but if the patient processes language on the right side, the person operating needs to know that. (Fun fact for those who know what WADA is, the WADA test is still the gold standard for pre-surgery testing. Even though Pouget said it is rarely used, he was wrong.)
One of the tricker things about fMRI is the hemodynamic lag, or the time it takes for blood to go to an activated brain area. Once a part of the brain is activated by a certain stimulus, it takes about 1-5 seconds for blood flow in that area to increase. This must be factored in and averaged out while analyzing the results. I will talk more about this later when I am actually looking at real fMRI data.


Today the rest of the summer students came. I like them! After Grace (a grad student in the lab who is head of summer students) talked to us for a bit, I started to teach the three other students how to use UNIX and some MATLAB commands. I was impressed by how well I knew the material. After a while, Grace told us that there was a study subject who was about to go into the scanner and, if we wanted to, we could go watch the study.
This study had to do with how exposure to emotional faces can affect visual perception, specifically in the periphery. The task was extremely difficult (in my opinion). First, a face which portrayed an emotion (happy, fearful, or neutral) flashed on the screen for less than a second (maybe even less than half a second.) Immediately after, eight groups of lines showed up on the screen for about the same amount of time. Half of the lines were red and the other half were blue; they were arranged in a circle around the center of the screen. One of the groups of blue lines were slanted either left or right, and the task was to determine that direction.
The first section of the experiment was basically a practice round, except that the program calibrated the angle at which the lines were slanted so that the task was not too easy and not too difficult. After that, the subject had to do four trails of about ten minutes each. The task was exactly the same for all four trials. Next, the subject got a retinotopic scan, which mapped out how his visual cortex is set up. Lastly, as in all fMRI scans, the subject got a structural scan. (The reason that everyone gets a structural scan is so that the results can be projected onto a high resolution picture of the subject's brain.) That was the end of the first of two days of scanning for this subject. In addition to the fMRI, the subject's heart rate and galvanic skin response were measured, and he was also connected to an eye tracker. (Given that the study was measuring his periphery, any trial in which his eyes left the middle of the screen will be discarded.)
While we were watching the scan, we were able to ask Michelle (the grad student running this study) a lot of questions about her study, how the stimuli worked, how the scanner worked, etc. She and the tech, Steve, answered every one of our questions in great detail, which was extremely helpful.  It is possible that we may be subjects for this study in the future.

I finished the day talking to Spiro about the script we are writing. I haven't gotten to far in the tutorials I need to do, so a lot of what he was saying was way over my head, but I feel like after I run through some of these tutorials tomorrow I will understand it a lot better.