gender differences structural brain weightmalefemale klekamp et al 1989, n=18;16) 12761104 zilles...
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Gender DifferencesStructural
Brain Weight Male Female
Klekamp et al 1989, n=18;16) 1276 1104
Zilles (1972) 1308 1178
Wessely (1970; n=18,13) 1379 1231
Witelson (1985; n=12;30) 1471 1258
Unweighted Mean 1,358 1,193 grams
• Male rh = 1442g (n=7), callosal area 672 mm^2• Male MH (n=5) 1511g, 801 (differs sign from
Male RH)• Females RH (n=20) 1269g, 655• Fem MH (n=10), 1237g, 697 (differs from fem
RH)
Absolute vs Relative Size Differences
• Bermudez & Zatorre (2001, n=137) found larger splenium (back of corpus callosum) in females.
• FEMALES
• Larger language areas -Harasty et al, 1997
• Larger lateral frontal area – Schlaepfer et al, 1995
• More densely packed neurons in temporal lobe, Witelson et al 1995
• MALES
• Larger medial frontal, Goldstein et al, 2001
• Larger cingulate, Paus et al 1996
• Larger amygdala and hypothalamus, Swaab et al, 1985
• More white matter volume, Gur et al, 1999
• More neurons overall, Pakkenberg & Gunderson, 1997
Prehistoric Times 18
Ancient Greece 20
Middle Ages, England 33
1620, Massachusetts 35
19th century, England 41
1900, USA 47
1915, USA 54
1954, USA 70
1992, USA 75
Aging of America
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5
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1900 1940 1980 2040
Year
Milli
ons o
ver a
ge 65 Male
Female
Gender Difference: Functional
Reliable Functional Sex Differences
• Men are better at– Visuospatial tasks– Higher mathematics– Aggression
• Females are better at:– Verbal tasks
Hemispheric asymmetries may be less marked in females compared to males
• APHASIAS occur most often in women with LH anterior damage. In men, they occur more frequently with LH posterior damage.
• APRAXIA, or difficulty in selecting hand movements, is associated with LH frontal damage in women and with LH posterior damage in men.
Functional Neuroimaging Differences
• EEG males more asym – Corsi-Cabrera et al, 1997; MEG Reite et al, 1995
Gender differences
VHS: Brain Sex #1 (Anything you…)
Problem-Solving Tasks Favoring Women
• Women tend to perform better than men on tests of perceptual speed, in which subjects must rapidly identify matching items for example, pairing the house on the far left with its twin
• In addition, women remember whether an object, or a series of objects, has been displaced
• On some tests of ideational fluency, for example, those in which subjects must list objects that are the same color, and on tests of verbal fluency, in which participants must list words that begin with the same letter, women also outperform men
• Women do better on precision manual tasks-that is, those involving fine-motor coordination-such as placing the pegs in holes on a board:
• And women do better than men on mathematical calculation tests:
Problem-Solving Tasks Favoring Men
• Men tend to perform better than women on certain spatial tasks. They do well on tests that involve mentally rotating an object or manipulating it in some fashion, such as imagining turning this three-dimensional object
Block Design
• or determining where the holes punched in a folded piece of paper will fall when the paper is unfolded:
• Men also are more accurate than women in target-directed motor skills, such as guiding or intercepting projectiles:
• They do better on disembedding tests, in which they have to find a simple shape, such as the one on the left, once it is hidden within a more complex figure:
• And men tend to do better than women on tests of mathematical reasoning:
• Cognitive behavior• MOTOR • Target throwing & catching M>F Hall & Kimura, 1995• Fine motor skills F>M Nicholson & Kimura, 1996• SPATIAL• Mental rotation M>F Collins & Kimura, 1997• Spatial navigation M>F Astur et al, 2002• Geographical knowledge M>F Beatty & Troster, 1987• Spatial memory F>M McBurney et al, 1997• MATH APTITUDE• Computation F>M Hyde et al, 1990• Mathematical Reasoning M>F Benbow, 1988• PERCEPTION• Sensory sensitivity F>M Velle, 1987• Perceptual speed F>M Majeres, 1983• Facial/Body expression F>M, Hall 1984• Visual Recognition memory F>M McGivern et al, 1998• VERBAL• Fluency F>M Hyde & Linn, 1988• Verbal Memory F>M McGuinness et al, 1990
Mechanism(s) responsible for Gender Differences
• Interhemispheric: Females have greater callosal connectivity
• Intrahemispheric: Language organization differs by gender
• Strategic: Females employ verbal strategies more often (even for spatial tasks)
• Mediated: Difference due to other trait variables such as handedness, familial hand, cognitive style, maturation, hormonal!)
TESTOSTERONE LEVELS• On a test in which women
usually excel (bottom), no relation is found between testosterone and performance.
Methodologies
Frequency Effects
Note: Contralateral Pathway
Dichotic Listening
This and following slides from Eran Zaidel
+ home
Lexical Decision Task :Word or not?
toyn +
Lexical Decision Task -- example nonword
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J
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LVF RVF10
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35P
erce
nt E
rror
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Target
Unilateral Lexical Decision
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Left RightVF
Mean
Late
ncy (
msec)
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Canonical Effect for LH Specialization (RVFA)
TARGET + (DISTRACTER)
LDT With Distractors
LDT with Distractors
+park stop
Control for reading scan bias by using Hebrew readers
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LVF RVFVF
Mean
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racy (
%)
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Pre
Post NF
Lexical Decision Results: Example of Treatment Effects
Within Condition
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Nonsense (nonverbal) Shapes
Between Condition
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Primary Color Task
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Shade Task
Faces - Head-on
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Faces - Rotated
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Abstract Concepts
Concrete Concepts
Info is processed by the hemisphere specialized for the material or task. – input transferred to
specialized hemisphere– VF Differences reflect
interhemispheric transfer time and info degradation.
Callosal Relay ModelCallosal Relay Model
Hemisphere that gets the stimulus processes it
• VF differences reflect relative ability/efficiency of hemispheres.
• Both hemispheres do everything more or less well
Direct Access
Uncrossed, LVF-Lh
Crossed, RVF-Lh
Redundant Target, Between, Uncrossed
Race Inequality
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Per
cent
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Reaction Times
LVF-Lh RVF-Lh Race
Alerting Network (Norepinephrine)
Orienting Network (Acetylcholine)
Conflict Network (Dopamine)
CONGRUENT TARGET
time
VALID CUE
*
INCONGRUENT TARGETDOUBLE CUE
* *
time
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C O A
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sec)
LANT-RH
Pre PostPre PostPre Post
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C O A
Mean
Laten
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sec)
Pre PostPre Post Pre Post
LANT-LH** *
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