Brain imaging is always used in planned brain surgeries. For example, before neurosurgeons will consider operating on a patient with uncontrolled focal epilepsy they require a multitude of tests; a fMRI is one of the most important. I am going to through it so that every function is location can be identified, as well as determining whether or not the risks of damage being caused by surgery are too great. The fMRI is even able to pinpoint functions, including memory and language, to the hemisphere that they are most prominently used in.
In the context of the cerebral cortex, hemispheres can be defined as the identical twins of one another. They both have the same lobes, which in an average brain usually serve the same functions as its “twin”. However, the two hemispheres are a bit interesting because they control the opposite side of a person’s body than the side that they are located. In other words, the right hemisphere of a person’s brain controls the functions of the left side of the body, while the left one controls the right side of a person’s body.
The fMRI evaluations provide information about both hemispheres, as well as the lobes. During the evaluation that is used for surgery, the patient is asked to do a multitude of tasks that are recorded using the FMRI. The technician may ask the person to do something related to voluntary motor function, using one side of the person’s body at a time, in order to pinpoint the exact location within the lobe(s) of voluntary motor function control, not just its general location. As for functions like memory, the doctors are more interested in where memories are mainly stored and processed. Those functions are usually mostly stored on one of the hemispheres.
If performing surgery on the focal point, also known as the origin of the person’s seizures, will cause major damage to these areas then the person is told that they are not a candidate for surgery. However, if it seems that surgery will cause no major damage to these areas then the person is told that they may be a candidate for surgery. I say may be because some patients require further testing.
As we learned in lesson two, functional magnetic resonance imaging (fMRI) is a neuroimaging technique that measures the amount of blood flow to areas of the brain. It can be used to study which part of the brain is active when performing specific cognitive tasks, such as solving a math problem. An active area of the brain will require more blood flow. The fMRI is a non-evasive procedure that is similar to a PET scan, without the injections of radioactive material, and it’s not a static image like the MRI. The fMRI also has good spatial resolution. (Goldstein, 2015)
I’ve always been amazed the way the two hemispheres of the brain work. As you mentioned, the left side of the brain controls functions on the right side of the body and vice versa. I had a client that I worked with at my former job who suffered from hemiparesis as the result of a stroke that damaged the right side of their brain, which caused limited movement of their left arm and leg. In regards to neurosurgery, I recall reading in chapter six of the course text on long-term memory, the story of patient H.M. who had his hippocampus removed on both sides of his brain to reduce the severity of his seizures (Goldstein, 2015). The surgery was successful in decreasing seizures, but unfortunately also prevented him from forming any new long-term memories (Goldstein, 2015). This surgery took place in 1953. The fMRI and other modern neuroimaging techniques would not be introduced to the world for a few more decades. I wonder how patient H.M.’s outcome could have been different, if better technology was available to his surgeon(s) at the time for use in pre-surgical evaluation.
If you are interested in reading more about evaluations performed prior to or during neurosurgery, I would highly recommend the article, “The Seahorse and the Almond” written by British neuropsychologist Paul Broks. The seahorse refers to the hippocampus and the almond is the amygdala (both parts of the brain responsible for different functions). The case profiles a young woman named Naomi who also undergoes surgery for epileptic seizures. (Broks, 2003)
References
Broks, P. (2003). The Seahorse and the Almond. Into the Silent Land. New York. Atlantic Monthly Press. pp. 22-38
Goldstein, E. B. (2015). Cognitive psychology: Connecting mind, research, and everyday experience (4th ed.). Australia: Wadsworth Cengage Learning.