6 - STRUCTURAL SEX DIFFERENCES

Question 1

corpus callosum

one explanation of hemispheric lateralisation

Answer 1

assumptions:

• corpus callosum as a whole larger in women?
• more connections between hemispheres?
• explain less lateralised brain
• splenium more bulbous in women?
• isthmus relatively larger in women? (relative to brain size)
• but mixed evidence - could be due to measurement methods

Question 2

overall brain size

one explanation of hemispheric lateralisation

Answer 2

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Question 3

cortical structures

other candidate structures for hemispheric specialisation

Answer 3

• posterior temporal cortex - higher neuron density in women?
• temporal plane (roof of temporal lobe - different size in each hemisphere) - larger size asymmetry in men?

evidence not very convincing

Question 4

subcortical structures

other candidate structures for hemispheric specialisation

Answer 4

• sub cortical candidate structures
• INAH-3 of hypothalamus larger in men?
• cut through anterior hypothalamus
• Levay says this plays a similar role in humans as the SDN-POA un rats
• homosexual male and female similar size
• but Levay used a small sample size and homosexuals died of AIDs which could affect brain

Question 5

information:

no clear evidence for gender difference in the anatomy of the forebrain

• but anatomical differences might be too subtle to be detected easily and reliably
• perhaps differences in local patterns of connectivity? (but can assess patterns of synaptic connections)
• or differences in relative density of different neuron types in some brain areas?
• or differences at the level of neurotransmitter and receptor molecules?

Answer 5

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Question 6

brain mosaic

Answer 6

Joel et al (2015)

• several brain structures so show sex difference on average
• but differences not distributed in an internally consistent way (within the individual)
• have different levels of being ‘male-typical’ or ‘female-typical’
• same for the body parts
• no specific male or female pattern
• very few have a purely male or female brain pattern