Individual variation of fMRT responses to eye opening, motor, and speech tests in healthy subjects

Functional magnetic resonance imaging (fMRI) was used to study the variation of functional changes that arise in the brain in response to similar tests in healthy subjects. The approach was assumed to demonstrate diverse individual strategies of achieving the same external (behavioral) response via different brain mechanisms and to identify the factors responsible for the diversity. Hemodynamic (fMRI) responses to activation of attention while opening the eyes or performing motor (consecutively moving the fingers of the right and left hands) and speech (mentally repeating the months of the year or the days of the week in the backward order) tests were determined in 21 healthy subjects aged 21–30 years, including 14 males and 7 females. A variation in fMRI responses was observed, i.e., three or four types of reactive hemodynamic changes were seen in the same test in the group, the prevalence of each type varying from 40 to 10% in one test. The responses showed distinct gender differences, and their specifics depended on the nature of the functional test. In motor and speech tests performed with the eyes closed, the fMRI responses in the females were more specific and local than in the males. In motor tests, the fMRI responses of the males compared with the females were characterized by a greater involvement of the frontal regions, which are responsible for regulatory functions. In the activation test (eye opening), the fMRI responses were more diffuse in the females and more local in the males.