To analyse gender related pattern of brain activation and deactivation during movement execution.

Unlike sexual characteristics, which are the physical qualities that separate the two sexes of an organism, the neurological differences are not visually apparent and therefore hard to study. Psychological sex differences are thought by some to reflect the interaction of genes, hormones and social learning on brain development throughout the lifespan. More and more evidences arise showing the gender related human brain differences in terms of functional organization¹ and even brain volume². Some differences are subtle, but just some of them appear to be more prominent. Sex differences in human behavior show adaptive complementarity: males have better motor and spatial abilities, whereas females have superior memory and social cognition skills³. In all supratentorial regions, males had greater within-hemispheric connectivity, whereas between-hemispheric connectivity predominated in females. This effect was reversed in the cerebellar connections³. Some of the brain diseases demonstrate distinct gender-related specificity and prevalence, e.g. MS – two times, often occur in females than in males, autism, PD and AD occur more often in males². However, this field of research has spurred an equally long history of debate as to whether inherent differences in the brains of males and females predispose the sexes to stereotypical behaviors, or whether such claims reinforce and legitimate traditional gender stereotypes and roles in ways that are not scientifically justified — so-called neurosexism⁴.Functional MRI is often used in fundamental and clinical studies. Because of its robust physiologic basis and good spatial resolution to date FMRI is widely used for brain mapping in thousands of clinical and scientific departments all over the world, and accepted as the standard clinical procedure for brain mapping in the USA as preoperative brain mapping approach and in cases of epilepsy. Brain mapping of motor regions in the cortex appears to be one of the oldest and most widespread fMRI techniques in clinical practice. Nevertheless a presence of huge amount of studies utilizing this task for brain mapping – gender differences in patterns of brain activation under motor task execution seems to be underinvestigated. We propose fMRI visualization of the brain activated by a movement task for estimation of gender specific motor brain network peculiarities.

12 healthy subjects (6M, 6F, 20-39 years old) were studied by fMRI with 1.5T SIGNA EXCITE (GE). FMRI data were obtained using GE EPI pulse sequence with following parameters: TR/TE=3000/73 ms, voxel size=4x4x6 mm. The task paradigm lasted 3 minutes and consisted of three blocks of simple finger tapping task separated with rest periods, each started with the voice command. The brain maps with the regions of activation were built with GLM model. Model based ICA analyses was done using GLM design matrix (software package FSL5.0).

From the analysis of the brain maps gender differences in total brain activation were found. In males the volume of activation was much smaller (17.6 cm³) in comparison to females (53.1 cm³). Also we have found out high linear correlation of the general volume of activation and maximum task-related BOLD signal change in masculine and feminine subpopulations (Fig.1). Common regions of activation in contralateral primary sensory-motor cortex (SMN), supplementary motor area, and ipsilateral cerebellum were found. Also we have found out additional activation of bilateral ventral premotor cortex, bilateral frontal cortex and contralateral hemisphere of the cerebellum in females (Fig.2). Deactivation occurred in the region of the default mode network (DMN) – precuneus, posterior cingulate, medial prefrontal and bilateral parietal cortex. Two modes of DMN functioning during motor activity were found: task related deactivation and task independent functioning. Our results showed that females need more neural substrates for motor control and some cognitive support and enlarged brain activation, while the men use less cognitive control of movement execution. Selective deactivation of the left amygdala (-28, -18, -16, MNI152) was found in males, while amygdala activation was found in several females (Fig.3). Left amygdala deactivation in men supposes specific emotional suppression during the movement execution, its activation in women supposes reward-related activity during the successful movement execution⁵. Amygdala exhibits structural differences in males and females including size, sex hormone receptors⁵. Movement execution and power also differ in different sexes.

Our results suppose new evidence for gender related differences in the functional brain organization. Results also give us background for further subdivision of the fMRI normative basis from which we investigate functional brain changes in patient population.