Gender specific discrepancies on psychometric examination are
often interpreted to reflect static differences in cerebral
hemisphere specialization, but dynamic alterations relating
to circulating gonadal hormones may also be relevant after puberty.
The often cited inference of a right hemisphere advantage in
males and left hemisphere advantage in females derived from
small but reliable differences on spatial tasks and verbal tasks,
for example, may to some extent relate to gender-specific
differences in circulating gonadal hormones. Performance
fluctuations on other higher order cognitive tasks through the
menstrual cycle tend to support a temporal association between
alterations in cerebral laterality and hormone fluctuations.
A potential left hemisphere advantage after menstruation when
estrogen and progesterone levels are high in contrast to a right
hemisphere advantage at menstruation when estrogen and progesterone
levels are low has also received support from shifts in visual
field perception. The present investigation continues this line
of work by measurement of prospective changes in unirhinal
olfactory acuity in the menstrual, ovulatory, and midluteal
phases of the menstrual cycle in 11 healthy women who agreed
to blood assays of estradiol and progesterone prior to completing
a modified version of the Connecticut Chemosensory Perception
Exam (CCPE). The CCPE detection of n-butanol showed a clear
pattern of changes over the menstrual cycle marked by an asymmetry
favoring the right nostril during menstruation when estradiol
and progesterone levels were low, an asymmetry favoring the
left nostril during ovulation when estradiol levels were high
and progresterone levels were low, and an absence of asymmetry
during the midluteal phase when estradiol levels decreased and
progesterone levels increased. Preliminary correlation analyses
revealed a potential competitive influence of estradiol and
progesterone on this apparent shift in cerebral laterality.
There is thus sufficient evidence to conclude that dynamic changes
in relative cerebral hemisphere advantages have a temporal relation
to fluctuations in circulating gonadal hormones and to suggest
the value of additional investigation of more specific causal
relations. (JINS, 2001, 7, 703–709.)