ANHB3323 Lecture Notes - Lecture 15: Sex Steroid, Senescence, Follicular Phase
3 Jun 2018
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LECTURE FIFTEEN: Sexual Differentiation of the Brain
Anatomical Differences:
• Female brains smaller than male brains → minor once corrected for size
• Male brains → more white matter
• Female brains → more grey matter
• Grey/white ratio increased in female brains in frontal, temporal, parietal
and occipital lobes
• Differences relative to cerebrum size
• Probably no true difference in grey matter ratio between males and
females
• Male brains → size of frontal and parietal lobes related to IQ
• Female brains → size of frontal lobe and Brocas area related to IQ
• True differences are in subcortical areas → hippocampus and amygdala
Hippocampus Differences:
• Sexually dimorphic → intimately involved in learning and memory
• Larger in females than males
• Doesnt include → CA1 region, pyramidal cells, dendate gyrus → structure
• Differences are in neurotransmitter systems, steroid binding, effects on
things like long term potentiation
Amygdala Differences:
• Complex structure → involved in organization of emotional responses
• Right and left amygdalae respond differently in males vs. females to
emotional stimuli
• Differences do not involve all nuclei of the amygdala
Functional Differences:
• Female brains → higher blood flows and glucose utilization
• Differences somewhat, but not completely associated with size
• Estrogen → probable mediator of these differences
Neurochemical Differences:
• Serotonin (5HT)
o Very clear sex differences
o Whole blood 5HT → females > males
o 5HT synthesis and metabolism → males > females
o 5HT transporters → females > males
o 5HT receptors → 1A and 2 receptors higher in females
• Dopamine
o Concentrations higher in females
o Release, transport and synthesis all higher in females
Physiological/Pathophysiological Correlations:
• Differences in serotonin
o Relationship to depression
o More common in females
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