Sex Differences in Brain Activation During Virtual Navigation: A Functional MRI Study

over half of the studies; a female advantage was found in approximately 18 percent of the studies which involved map learning and memory, but women as a group never outperformed men in real or simulated environments. The effect size (Cohen’s d) of the sex difference varies from small to large. For example, a moderate effect size favoring males was reported for a map-based route learning task (Galea & Kimura, 1993), while a large effect size was found for an orienteering drill (Malinowski & Gillespie, 2001). Effect sizes favoring men during performance of computerized maze navigation are moderate to large (e.g., Gron, Wunderlich, Spitzer, Tomczak, & Riepe, 2000; Moffat, Hampson, & Hatzipantelis, 1998). A sex difference favoring men in virtual Morris Water Task (vMWT) performance has also been reported (Astur, Ortiz, & Sutherland, 1998; Driscoll, Hamilton, Yeo, Brooks, & Sutherland, 2005; Nowak & Moffat, 2010; Sandstrom, Kaufman, & Huettel, 1998) with several effect sizes as large as or larger than one standard deviation (e.g., Astur et al., 1998; Nowak & Moffat, 2010). Sex differences at the behavioral level imply that sex differences at the neural level may be one source of explanation for this group difference; therefore, it is logical to hypothesize that men and women may be recruiting different brain regions to solve navigation tasks. To our knowledge, only two papers have addressed sex differences in blood oxygen level dependent response (BOLD; i.e., brain activation) during the performance of VE tasks in samples of healthy young participants. In the first fMRI study of this nature, men and women were tested while they navigated as quickly as possible through a number of unfamiliar computerized mazes (Gron et al. 2000). Behaviorally, men found their way to the goal location of the mazes significantly faster than women, and the effect size of this sex difference was large. During maze navigation, activation in the right prefrontal cortex and right inferior and superior parietal lobes was greater for women than men. Activation during navigation was greater for men than women in the regions of the left hippocampus, right parahippocampal gyrus, and left posterior cingulate/retrosplenial cortex. The authors interpreted the sex difference in brain activation as a product of the differential use of egocentric and allocentric strategies. However, due to the large, statistically uncontrolled sex difference in navigation performance, this study cannot rule out the possibility that men and women matched in navigation accuracy and speed may show a more similar pattern of brain activation during maze performance. Ohnishi et al. (2006) categorized participants by sex and navigation ability, which provided the opportunity to test the main effects and interactions of each of these variables on brain activation during passive maze navigation. Sex Differences in Brain Activation During Virtual Navigation: A Functional MRI Study Nicole T. Nowak (at3125@wayne.edu) Department of Psychology 5057 Woodward Ave. 7 th Floor Detroit, MI 48202 Susan M. Resnick (resnicks@grc.nia.nih.gov) Laboratory of Behavioral Neuroscience Biomedical Research Center, room 04B317 251 Bayview Boulevard, Suite 100 Baltimore, MD 21224-6825 Wendy Elkins (wendy.elkins@nih.gov) Laboratory of Behavioral Neuroscience Biomedical Research Center, room 04C106 251 Bayview Boulevard Baltimore, MD 21224-6825 Scott D. Moffat (moffat@wayne.edu) Institute of Gerontology and Department of Psychology 87 E. Ferry St. Detroit, MI 48202 Abstract A male advantage is often reported for measures of visuospatial performance, including measures of spatial navigation; however, few papers have addressed sex differences in brain activity during performance of these navigation tasks. We used functional MRI to compare the brain activation between young adult men and women during performance in a virtual environment (VE). Men and women did not differ in performance, but sex differences were apparent in the functional neuroanatomical correlates of navigation. In particular there was increased activation of the posterior cingulate retrosplenial cortex in men, and, in women with perfect recall performance, increased activation of the parahippocampal gyrus. These two areas are keys to successful navigation. Our results demonstrate that even when men and woman are well-matched on navigation performance, they appear to use different brain mechanisms to achieve the same behavioral end point. Keywords: virtual navigation; sex differences; functional MRI Spatial navigation is one domain of human cognition where a male advantage has been reported. In a review of sex differences in navigational performance Coluccia and Louse (2004) reported that a male advantage was found in