Transcript Sex Differences in the neurocognition of language

Sex Differences in the
Neurocognition of
Language
Michael T. Ullman, Ivy V. Estabrooke,
Karsten Steinhauer, Claudia Brovetto
Language Processing
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Language Processing depends on 2 neurocognitive
systems
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Temporal-lobe based declarative memory system
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Includes…
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Mental lexicon, which contains idiosyncratic word-specific information
 E.g. for irregular past tense; break-broke
Frontal/basal-ganglia procedural system
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Includes…
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Mental grammar underlying the real-time rule-based composition of
complex linguistic representation
 E.g. regular past tenses; play + ed
Also used in motor skills
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Females are better than males at remembering
words
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Females tend to memorize previously encountered
complex representations
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E.g. regular past-tenses; played
Males generally compose it on-line
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E.g. play + -ed
Prediction…
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Both sexes should memorize idiosyncratic lexical
knowledge
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Both should rule compute new complex forms
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E.g. break-broke
E.g. proy-ed
Why?
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Because these could not be memorized
Previous studies
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Frequency Effects
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Hypothesis: if past-tense representations are retrieved
from memory, more frequent ones should be remembered
faster. If they are rule products, such past-tense
frequency effects are not expected
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16 men and 17 women produced regular/irregular past tenses
 DV: reaction-time
Men showed past tense frequency effects for irregulars but not
regulars
Women showed past tense frequency effects for both verb types
Same results for both English and Spanish
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Parkinson’s Disease
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Associated with the Basal-ganglia degeneration leading to
hypokinesia (suppressed movement)
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Study: 15 men and 14 women with Parkinson’s disease produced past
tenses
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For men, past-tense production rates of regulars but not irregulars
correlated with hypokinesia and production rates for irregulars but not
regulars correlated with lexical abilities (object naming)
For women, production rate for both past-tense types correlated with
lexical abilities but not hypokinesia
 Most hypokinetic males were impaired only at regulars
 Most hypokinetic women were impaired at neither
The Effect of Sex Hormones on
Language Processing
Ivy V. Estabrooke, Kristen Mordecai, Pauline Maki, and Michale T. Ullman
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As stated before, women are better than men at
remembering words
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This advantage appears to depend upon the temporal-lobe
declarative memory system
Hypothesis: Because of women’s superior
lexical/declarative memory ability, girls and women
may tend to memorize and/or retrieve at least
certain complex representations that men composed
on-line
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From this, two questions arise
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1. Do females memorize complex forms at a higher rate than
males and/or do both sexes store tense forms, while females
have superior lexical retrieval/processing abilities
2. Do sex hormones, and estrogen in particular, contribute
to the sex differences?
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Previous data supports this hypothesis
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Estrogen improves word and declarative memory abilities in women;
more over, this improvement depends on the part of the temporal lobe
that underlies declarative memory
 Furthermore, testosterone improves men’s word memory
Methods
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10 post-menopausal women and 12 age-matched men
participate in study of the effects of hormone therapy
on language processing
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Subjects were given hormone replacement therapy
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After each three months, subjects were given past-tense
production task containing…
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Regular (sway-swayed) , irregular (break-broke), novel regular (plagplagged) and novel irregular (spling-splung)
Verbs were presented in sentence contexts
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Women-estrogen, Men-testosterone, and placebo group
E.g. Every day I sleep in bed. Yesterday, I ________ in bed.
Accuracy was the DV
Results
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Hormone therapy yielded increased estrogen levels in
both sexes
It also induced an increase in both sexes in the
production rate of real and novel irregular past tenses
Performance at novel regulars decreased with hormone
therapy in both sexes
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Likely due to an increased irregularizations (plag-plog)
Accuracy at real regulars INCREASED in women but
DECREASED in men, as a result of hormone therapy
Accuracy at Past Tense Production
Analysis
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Increase in both women and men in production
rate of real/novel irregular past-tense forms
suggests that sex hormones improve the
retrieval/processing of existing memorized
lexical representations
And of novel forms whose processing depends
on preexisting similar memory traces
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E.g. fling-flung, wring-wrung
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The decrease in performance of novel regulars
with hormone therapy in both sexes..
Supports view that these forms are computed by
neural mechanisms distinct from those that underlie
the processing of real and novel irregulars
 It also supports the dual-system
“declarative/procedural model”
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The fact that hormone therapy led to an
increase in the production rate of regular pasttenses in women, but a decrease in men shows
that in women these forms patttern with the
mempry-dependent irregulars and in men, they
pattern with the compositional novel regulars
Conclusion
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The sex differences just observed may be
attributable to the prior memorization of
complex forms by girls
This may be explained by sex-differences in
estrogen levels, which could affect brain
organization in utero and or learning during
childhood