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Ahmed et al. (2008). Pubertal hormones modulate the
addition of new cells to sexually dimorphic brain
regions. Nature Neuroscience, 11, pp. 995-997.
By David Guzman, Alicia Witter, Jordy Serwin, and
Michelle Greenberg
Ahmed et al. (2008). Pubertal hormones
modulate the addition of new cells to sexually
dimorphic brain regions.
Sexual Dimorphism of the Brain

Males
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Localized areas of function
Visuospatial tasks
Hypothalamus in men
contains both aggression
and sexual drive
Females
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Diffused areas of function
Verbal tasks
Corpus Callosum is larger
Ahmed et al. (2008). Pubertal hormones
modulate the addition of new cells to sexually
dimorphic brain regions.
Effect of Hormones on Sexual
Dimorphism

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Genes (chromosomes) determine response
to hormones
Fetus is female by default
SRY gene causes a response to androgens
which leads to defeminization of fetus
Hormones develop our sex organs, body
development, and brains
Ahmed et al. (2008). Pubertal hormones
modulate the addition of new cells to sexually
dimorphic brain regions.
Does it end there?


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New research shows
sexual dimorphism of
brain may continue in
puberty
Brain is not
permanently
hardwired at birth
Gonadal hormones
Ahmed et al. (2008). Pubertal hormones
modulate the addition of new cells to sexually
dimorphic brain regions.
Method

Rat brains were viewed in four stages
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
Three sexually dimorphic brain areas
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Pre-puberty, Puberty, Mid-puberty, and Adulthood
Anteroventral petriventricular nucleus of the hypothalamus
(AVPV)
Sexually dimorphic area of the preoptic area (SDN)
Medial amygdala
AVPV is larger in females, SDN and Medial Amygdala is
larger in males
Removal of Gonads (Control)
Ahmed et al. (2008). Pubertal hormones
modulate the addition of new cells to sexually
dimorphic brain regions.
Adapted from Ahmed et al. (2008)
Ahmed et al. (2008). Pubertal hormones
modulate the addition of new cells to sexually
dimorphic brain regions.
Results

Cell and Neuron count increase in sexually
dimorphic areas of brain


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Females: More cell growth in AVPV
Males: More cell growth in SDN and Medial Amgydala
Removal of Gonads (gonodal hormones)
prevented cell and neuron growth
Gonadal hormones are necessary in cell growth
for function and development of the sexually
dimorphic areas of the brain during adolescence
and emerging adulthood.
Ahmed et al. (2008). Pubertal hormones
modulate the addition of new cells to sexually
dimorphic brain regions.
Critical Review

Strengths
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Focus on sexually dimorphic areas of the brain. Gonads had a
significant impact on development
Evidence corresponds with behavior and properties we see.
Such as influx of hormones in puberty that we know create
secondary sex characteristics might also effect the brain
Evidence is objective and purely scientific
Weaknesses
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Subjects were rats
Cannot be performed on humans as death is necessary to view
the hypothalamus
More research is needed to see if this relates to humans and
their more complex, social behavior
Ahmed et al. (2008). Pubertal hormones
modulate the addition of new cells to sexually
dimorphic brain regions.