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The cerebrum is the largest area of the human brain, containing a high concentration of neurons, or cells that form the "grey matter" of the brain. It is divided into several distinct areas, known as lobes, handling distinct functions of thought and sensory processing. In the frontal lobe, there is a major ridge known as the superior frontal gyrus, that is located on top of the brain, running down toward the front and adjacent to the fold that divides the right and left hemispheres of the brain. This massive gyrus comprises about a third of the lobe's area, and it plays a role in several higher-level cognitive processes.
Many of the exact functions of the parts of the frontal lobe, including the superior frontal gyrus, are still being discovered. Studies have revealed some processes that this gyrus is involved in, however. A type of brain imaging known as functional magnetic resonance imaging (fMRI) has demonstrated that this region is involved in sensory processing. During motor tasks that involve intense levels of concentration, this portion of the brain actually decreases in activity. The results of this study suggest that when individuals describe activities that cause them to "lose themselves" in concentration, it is due to a lower level of self-awareness from this inactivation.
Stimulation and activation of a section of the superior frontal gyrus on the left side of the brain may be involved in the feeling of amusement. Upon electrically stimulating this area, researchers were able to induce smiling and laughter in subjects. Subjects attributed their laughter to any external stimuli that were present, and laughed at incidents that they would not have found funny otherwise. In one case, a subject told researchers that the sight of them standing in the room amused her.
Another essential function of the superior frontal gyrus seems to be its role in working memory. This refers to pieces of information that are held for short lengths of time, allowing for the completion of complex mental tasks. Research performed on individuals with lesions or damage to the superior frontal gyrus found that they had difficulties performing tasks requiring the use of this form of memory. Larger lesions corresponded to greater deficits in working memory, along with damage that was specific to the part of the cerebrum just behind the eyes. Specifically, this seemed to play a role in reviewing the items in working memory, as well as manipulating these items to accomplish cognitive tasks.