Brain Imaging Studies: Gender Effects

1
Brain Imaging StudiesGender Effects
Aging Clinical Research Center
Ruth OHara 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 GendersStructural
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 GendersProcessing
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 GendersProcessing
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 (AB)
• Gender Difference
• CMale 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