Functional magnetic resonance imaging of the human brain in males und females during mental rotation

Introduction: The aim of the present study was to investigate cortical activation and sex differences during mental rotation using functional magnetic resonance imaging (fMRI) and functional transcranial Doppler sonography (fTCD).

Methods: Twenty healthy subjects (50% female) were investigated using fMRI (block design, TR 4000ms, TE 50ms, FoV 256×256, 36 slices, slice thickness 3mm) and fTCD (M1 segment of both MCAs, 2MHz ultrasonic probes). During the activation period, subjects were asked to perform a mental rotation task consisting of pairs of identical threedimensional cubes shown from different perspectives (cube perspective test). Subjects were instructed to decide from which perspective the second cube showed the first. Rest was used as control condition.

Results: Men performed slightly better on the mental rotation task than women. Significant BOLD signal changes could be observed in the superior parietal lobe as well as in areas at the parieto-occipital border bilaterally. Additionally, areas in the middle and superior frontal gyrus bilaterally and the right inferior frontal gyrus, the insular cortex bilaterally and thalamus, mesencephalon and cerebellum bilaterally were activated during mental rotation. There was no significant lateralization to the non-dominant hemisphere, but a tendency towards a more right hemispheric activation in men. Men tended to show more activation in frontal and parieto-occipital regions of the right hemisphere as compared to women.

Discussion: Our results confirm earlier studies showing activation especially in the superior parietal lobe and the parieto-occipital border, as well as in several frontal and occipital areas during mental rotation. Furthermore, there was more activation in several right hemispheric brain regions in men which gives support to the hypothesis of a stronger right hemispheric lateralization in men. The clinical application for the presurgical evaluation of patients undergoing neurosurgery is currently investigated in an ongoing study.