In a deep hole next to the UCSB Psychology Building, construction continues on a facility to house a machine that will help researchers peer inside working human brains.
Using a powerful magnet, the machine utilizes magnetic resonance imaging (MRI) technology that allows scientists to study active brain function and structure. The MRI scanner, to be purchased and placed in the new building as part of plans to upgrade and expand the psychology facilities on campus, will produce images of human subjects’ brains while the subjects are performing mental tasks. Such tasks include remembering a list of items or calculating a mathematical equation.
Psychology professor and Director of the UCSB Brain Imaging Center Gregory Ashby, and assistant professor of psychology Michael Miller are both involved with conducting brain-imaging studies on groups of human subjects. The brain images collected for these UCSB studies currently come from subjects scanned at Dartmouth through a collaboration between the two universities. If construction on the Psychology Building finishes on time, UCSB faculty will be able to collect their own MRI data on campus, allowing more UCSB researchers to take part in brain imaging studies.
“The building is scheduled to be completed in November — that is assuming everything goes on schedule, and often there are delays,” Ashby said. “Say a year from now, we expect to be in that building. The last little piece is to get funding for the machine. If we can get the money, it should be here in a year.”
Ashby told the Nexus last spring that an MRI scanner suitable for brain research would cost about $2 million. Currently, the Psychology Dept. is still looking to submit a grant that would pay for the machine, but Ashby said he is not worried about finding the funding on time.
Researchers process the scanner’s images to create a map showing what exact parts of the brain are active during particular tasks. These maps can be used in the future by other researchers to help better understand how the human brain is wired and functions as a whole. The term given to this type of research is “functional MRI” (fMRI). The term “functional” refers to the fact that the brain is actively performing some task while being studied. This contrasts structural MRI scanning that would only be used to show the anatomy of a body part.
In addition to the Psychology Dept., the Molecular, Cellular and Developmental Biology Dept. is also interested in having access to the new MRI scanner. Kenneth Kosik was hired to the position of Harriman chair of neuroscience last fall, and is co-director of the Neuroscience Research Institute. He said the MRI scanner will provide valuable insight into the biological aspects of brain research as well as the higher function, psychological aspects.
In cases where a specific aspect of cognition is to be studied, such as the recollection of memorized pictures, a psychological experiment must be designed that will cause the brain to use its memory retrieval functions and not anything else. Kosik said a good experimental design is critical to getting meaningful results from brain imaging research. Acquiring the fMRI data and performing the analysis has become commonplace, so the real burden is creating insightful mental tasks that will uncover a new aspect of brain function.
“It’s a matter of how clever you can be. The physics of it and the actual running of the [MRI machine] is pretty well worked out,” Kosik said. “The limited factor right now for fMRI is our own imagination.”
One important element of experimental design is to have a good “control,” Kosik said. A control is a part of an experiment that is designed to use every brain function except the one being studied. By comparing the brain activation during the experimental part and the control part of the experiment, researchers can draw conclusions about what parts of the brain are utilized by the topic of study. This pattern of resulting brain activation is called an “activation map.”
Miller said his current research interests tend toward investigating memory and the differences between individuals’ brain organization. He has conducted imaging studies with the goal of identifying areas of the brain that are used when performing specific memory tasks.
“I am interested in memory and decision making, so I am interested in the kinds of processes that lead to false memories and the kinds of strategic processing that subjects go through,” Miller said. “I have also been very interested in the individual variability of brain activation.”
Because of random noise present in the images that the MRI scanners produce, it is often necessary to scan a group of subjects and average all of their scans to discover what parts of the brain are really active. Miller has found there are some individual brain activations patterns that are not noise and are worth studying to determine how individual brains differ from group averages.
“Most neuroimaging studies sort of rely on the average across a group of subjects to produce a map. Most of the maps you see in journals are based on a group of subjects,” Miller said. “But what we discovered is that there is a lot of individual variability that goes into those group maps. For some tasks if you look at the individual patterns of brain activity, they can often be very different from the group map.”
Future studies may help to uncover what these individual differences mean for the field of prescription drugs and brain surgery.
How fMRI Works
An MRI machine is essentially a large magnet that has an attached radio transmitter and receiver. The strength of the magnet’s field is measured in tesla and describes the machine’s ability to image small changes in brain activity. Ashby said the MRI machine UCSB is considering will be 3 tesla.
“This would be the most powerful MRI in Santa Barbara,” Ashby said. “There’s nothing over 1.5 tesla in Santa Barbara. We are going to have either a Siemens or Philips [machine]. The main thing that is important for us is we want something that is turn-key, that does not require a lot of physicists around.”
Originally, MRI machines were called “nuclear magnetic resonance imaging” because the strong magnetic field manipulates the nucleus of atoms, but the term was dropped to avoid confusion with radioactive substances.
“When you put a head or a body in this huge magnet, it polarizes some of the hydrogen atoms, and you can sort of knock those atoms off line, and you can measure how long it takes to go back into alignment,” Miller said. “It turns out different [bodily] tissues have different rates of realignment. That’s how you can get an anatomical picture.”
An anatomical picture shows the brain’s structure in detail, but does not include any information about the brain’s activity. To get that information, the fMRI scanning process takes advantage of the unique property of blood.
“It turns out there are also magnetic differences between oxygenated and deoxygenated hemoglobin in the blood. Whenever you have a cognitive thought, we assume there is localized neural activity, and the assumption is that localized neural activity leads to localized differences in blood flow and in the oxygen level of that blood,” Miller said. “fMRI is very good at picking up those local changes in blood flow.”
The changes in blood flow are then shown graphically on a picture of the brain. These graphics frequently appear in journals to demonstrate the parts of the brain used in a specific set of tasks or experiments. As more studies are completed, the overall knowledge base of how the brain works will also grow.
“My feeling is that the insights we are getting from fMRI today are one of maybe two or three [imaging techniques] that are responsible for creating this extraordinary excitement about neuroscience,” Kosik said. “You see people coming out of the woodwork with an interest in neuroscience — like the cover of Time Magazine; and it’s the subject of popular books. I think that because the findings are so extraordinary — and the insights — that it has in many ways captured the public’s imagination.”