hemisphere of men and women who stutter, when compared to a non-stuttering control group. Anatomical connectivity of the speech motor and planning regions is less vigorous in adults who stutter, especially women. Men who stutter seem to have more right-sided motor connectivity. On the other hand, stuttering women have less connectivity with the right motor regions. In non-stuttering, normal speech, PET scans show that both hemispheres are active but that the left hemisphere may be more active. By contrast, people who stutter yield more activity on the right hemisphere, suggesting that it might be interfering with left-hemisphere speech production. Another comparison of scans anterior forebrain regions are disproportionately active in stuttering subjects, while post-rolandic regions are relatively inactive. Bilateral increases and unusual right-left asymmetry has been found in the planum temporale when comparing people who stutter and people who do not. These studies have also found that there are anatomical differences in the Rolandic operculum and arcuate fasciculus. Denis Drayna suggests that brain imaging studies of people who stutter do not tell if the differences in the brain anatomy caused stuttering or if they are the effect of stuttering;In the mouse model for stuttering created by Drayna and team, they noticed significant similarities between the vocalizations in mice (carrying GNPTAB mutation) and human stuttering. Researchers investigated the brain tissue from the mice mutants and reported a significant decrease in the number and density of astrocytes in their corpus callosum. Astrocyte is a star-shaped cell in the brain that supports the nerve cells by supplying oxygen and nutrients, and taking away the waste. The corpus callosum enables the communication between the left and right hemispheres of the brain. Follow-up experiments with the GNPTAB mutation introduced to brain cell types showed that the vocalization defects in mice were specific to the loss of astrocytes. Mice did not show stuttering-like vocalization defects when the mutation is engineered to other brain cell types. Other anatomical differences The corpus callosum transfers information between the left and right cerebral hemispheres. The corpus callosum, rostrum, and the anterior mid-body sections are larger in adults who stutter as compared to normally fluent adults. This difference may be due to unusual functions of brain organization in stuttering adults and may be a result of how the stuttering adults performed language-relevant tasks. Furthermore, previous research has found that adults who stutter show cerebral hemispheres that contain uncommon brain proportions and