1. Aging Clinical Research Center Brain Imaging Studies: Gender Effects Ruth O’Hara Assistant Professor, Department of Psychiatry and Behavioral Sciences, Stanford University

2. Neurophysiology of Cognitive Functioning Center for Neurological Skills

3. Cognitive Domains _ Executive Function _ Psychomotor Speed _ Attention and Inhibition _ Speed of Information Processing _ Language Abilities _ Phonological Processing _ Semantic Processing _ Verbal Fluency _ Working Memory _ Verbal Memory _ Visuospatial memory _ Visuospatial Ability _ Visuoconstruction _ Mathematical Ability

4. Brain Differences between Genders: Structural Findings (MRI and MRS) _ Males have larger brains (6-8% larger) _ (Reiss et al., 1996; DeCarli et al., 2005) _ No differences in grey/white matter proportions _ (Nopolous et al., 2000; Lunders et al., 2002; DeCarli et al., 2005) _ Females have greater cortical complexity? _ (Lunders et al., 2004) _ Corpus Callosum larger in Females? _ (Johnson et al., 1994; Lunders et al., 2003; Ng et al., 2004; Rauch et al., 1994; Steinmetz et al., 1995; Suganthy et al., 2003) _ Neuronal density does not differ according to Gender? _ (Nagae-Poetscher et al., 2004)

5. Brain Differences between Genders: Processing Differences (fMRI and PET) _ Mathematical Abilities _ Limited number of imaging studies conducted _ To date gender differences typically not considered (Delazer et al., 2004; Gruber et al., 2001; Rickard et al., 2000; Kazui et al., 2000; Menon et al., 2000; 2002) _ Memory Function _ Significant number of studies _ Few gender differences observed although the hippocampus region which subserves memory function may exhibit greater age-related change in younger males than females (Pruessner et al., 2001)

6. Brain Differences between Genders: Processing Differences (fMRI and PET) _ Visuospatial Abilities _ Limited number of imaging studies _ Differential patterns of brain processing observed between gender in some but not all studies (Blanch et al., 2004; Grom et al., 2000; Gur et al., 2000; Jordan et al., 2002; Seurinck et al., 2004; Thomsen et al., 2000; Unterrainer et al., 2000; 2005; Weiss et al., 2003) _ Few statistically significant performance differences between genders observed in these studies _ Language Abilities _ Significant numbers of studies have been conducted _ Differential patterns of brain processing observed in some but not all studies (Shaywitz et al., 1995; Pugh et al., 1996; Grabowski et al., 2003; Weiss et al., 2003). _ Regional differences observed are not accompanied by performance differences between genders (Shaywitz et al., 1995; Pugh et al., 1996) _ Larger study finds no regional or behavioral differences (Frost et al., 1999)

7. Functional Imaging _ Language Areas (A&B) _ Gender Difference _ C=Male & D= Female _ Some studies observe bilateral activation in females relative to males but no performance differences are observed

8. Limitations on Current Studies _ Samples often small _ Variability in technologies, techniques and measurements _ Variability in Cognitive Tasks Assessed _ Variability among subjects being studied _ Studies need to consider impact of potential enhanced blood oxygenation level-dependent (BOLD) response in females (Kastrup et al., 1999; Marcar et al., 2004; Parkes et al., 2004) _ Studies need to consider the impact of increased regional cerebral glucose metabolism in females (Andreason et al., 1994; Kawachi et al., 2002)

9. Conclusions _ Few consistent gender differences noted across imaging studies _ Differential patterns of brain activation between genders do not reflect differential performance _ Regional Brain activation during any task does not necessarily reflect hardwired cognitive processes