Aging Clinical Research CenterAging Clinical Research Center

Brain Imaging Studies:Brain Imaging Studies:Gender EffectsGender Effects

Ruth O’HaraRuth O’HaraAssistant Professor,Assistant Professor,

Department of Psychiatry and Behavioral Sciences,Department of Psychiatry and Behavioral Sciences,Stanford UniversityStanford University

Neurophysiology of Cognitive Functioning

AREA FUNCTION Prefrontal Cortex Executive Functioning

Attentional Abilities Information Processing Speed

Medial Temporal Working Memory Lobe/ Hippocampus Verbal Memory Occipital Lobe/ Visuospatial Memory Medial Temporal Lobe Motor Cortex Psychomotor Speed

Center for Neurological Skills

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

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)

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)

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)

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

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)

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