1. Performance in Piaget’s Water Level Task Across the Menstrual Cycle
Alexandra E. Silva, Mariah A. Sullivan, Anastasia Oliferovskiy, Tomoki Ishibashi, Sandra M. Narvaez, Gabriela Nordeman
San Diego State University, Department of Psychology
Hypotheses and Results
Piaget’s Water Level Task (WLT) shows a consistent sex difference
favoring men (Vasta & Lieben, 1996). While some investigators have
assumed the basis is genetic, others argue for a major role for environment,
and still others for an organizational effect of early sex steroids.
Another possibility is that the sex difference reflects a contribution of the
activational influences of estrogen on neural circuits as the levels change
across the menstrual cycle. This possibility that has not been studied
previously. However, it receives some support from studies of menstrual
cycle effects on other types of tasks that show cognitive sex differences,
including space relations, explicit working memory and verbal fluency.
Improvement in female performance is observed in the early follicular
phase compared with the mid-luteal phase, periods when estrogen levels are
relatively low and high, respectively (Epting & Overman, 1996).
Because estrogen is a mediator of neuroplasticity, effects of the hormone on
cognition may not be due solely to high versus low levels. In the adult
brain, rapid rises in circulating estrogen stimulate the production of
dendritic spines in neurons that express the estrogen receptor. This can
result in the neuron making 30% more connections to neurons within its
network, a phenomenon assumed to influence behaviors regulated by that
network (Luine, 2014). Behavioral changes may also occur following a
rapid decline in circulating estrogen because the retraction of the estrogen-
induced spines also requires a temporary reorganization of circuit
connectivity. This means that neural circuits affected by estrogen may be
potentially disrupted by rapid rises or decreases in circulating estrogen.
In this study, we examined the association of dynamic changes in plasma
estrogen across the menstrual cycle with WLT performance by using a
cross-sectional design that included normally cycling women (n=218) and
those on oral contraceptives (OC; n=141). Males (n=81) were included for
comparison.
Hypothesis 1: The rapid decrease in estrogen levels prior to or the rapid increase between days 9 and 16 will be
associated with significant increases in WLT error compared to days 5-8 when estrogen levels have stabilized at
a low level. This was confirmed using a 1-Way ANOVA with a quadratic trend analysis comparing the WLT
scores from women tested between the onset of menses to the peri-ovulatory period (days 1 through 16). The
ANOVA yielded a main effect for period (F[3,21]= 2.72; p<0.05) as well as a significant effect for the quadratic
trend (F[1] = 5.75; p<0.02) that is shown in the figure below. Although estrogen levels are low from days 1-8,
WLT error was significantly higher on days 1-4 compared to days 5-8 (t[66]=3.09; p<0.002). WLT error also
increased as estrogen levels increased linearly between days 9 and 16, and was significantly higher in women
tested on days 13-16 compared to days 5-8 (t[35] = 3.21; p<0.002).
Hypothesis 2: Stable, but high estrogen levels in the post ovulatory period will result in lower WLT error
compared with periods of rapid changes in estrogen levels. This was not confirmed. Although average WLT error
during this period was lower compared to the peri-ovulatory group, the difference was not significant.
Hypothesis 3: WLT error in OC women will be significantly higher during menses compared to performance
during the three weeks when they are taking the oral contraceptive. During this three week period we expected
WLT performance to be stable due to constant low levels of estrogen. This was not confirmed. We observed no
significant differences across the cycle in OC women. In addition, no single OC group at different periods of the
cycle the differed significantly in the error observed in males.
Hypothesis 4: Based on results from previous studies, WLT error will be significantly lower in men compared to
women when scores are collapsed across the cycle. As shown below, this was confirmed in planned comparisons
using t-tests (males vs normal cycling women; (t[297] = 2.86, p<0.01); males vs OC women t[220] = 2.42;
p<0.03).
Participants were recruited from San Diego State undergraduate psychology
classes and compensated with class credit. Procedures were approved by the
SDSU Human Subjects Committee. At the beginning of testing, participants
were presented with an example showing a water bottle sitting horizontally on a
table with the water level marked by a horizontal line. They were then presented
with a sequence of 6 pictures, each depicting a bottle (upright or upside down)
tilted to the left or right 0, or 45 degrees from horizontal and asked to draw a
line where the water level would be. Examples of the first 3 test upright figures
are shown below.
Scoring was done by determining the degrees of deviation from horizontal of
the line drawn by the participant. Analyses used the sum of the errors across the
6 drawings. Separate analyses were performed for normally cycling women
versus those on oral contraceptives.
To accommodate the inherent error in estimating the day of the menstrual cycle
in normally cycling women (Epting & Overman, 1998), scores from individual
participants were collapsed into 7 groups of 4 consecutive days that covered a
28 day cycle. Cycle phase was determined by having participants report the
onset of the next cycle after testing or by self report of menses at the time of
testing. Normally cycling women with period lengths as long as 32 days were
included in the study and their data were collapsed as part of the group
containing data from participants tested on days 25-28 of their cycle.
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Introduction
References
Discussion
Methods
As hypothesized, we found that WLT error is greater during periods of rapid
rises or decreases in plasma estrogen levels in normally cycling women.
When estrogen levels were low and stable during days 5-8 of the cycle,
female WLT performance was the same as men. This suggests that the
mediating variable affecting WLT performance is related to estrogen-induced
neuroplasticity.
When estrogen levels stabilized at a relatively high level in the post ovulatory
period, WLT error was consistently higher than that observed for days 5-8,
but the differences did not reach statistical significance (p<0.07). Further
research is need to clarify the degree to which stable, relatively high levels of
estrogen impair WLT performance. Possible effects of progesterone should
also be considered.
Where estrogen acts in the brain to influence WLT performance is unknown.
One area to consider is the prefrontal cortex (PFC), where estrogen receptors
are widely distributed (Arevelo et al., 2015). This area is also implicated by
findings that show structural changes within the PFC across the menstrual
cycle that are associated with concomitant cognitive and emotional changes
(Konrad et al., 2008; Little, 2013; Luine, 2014).
Within the PFC, there are discrete, interconnected areas that process two
basic aspects of perception essential to WLT performance. Object processing
related to the conscious perception of the water container relies on ventral
stream processing originating in the inferior temporal lobe. The second aspect
involves the position of the water container relative to the table top, as well as
the dynamic aspects of water movement. This processing is accomplished
within the intraparietal lobule portion of the dorsal stream and its connection
with the superior temporal sulcus (Kravitz et al. 2011). Results from the
present study suggest that estrogen may alter the organization of dorsal and
ventral stream input being integrated within the PFC.