Gender Differences Structural

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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

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

1900 1940 1980 2040

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

LVF RVF10

Target

Unilateral Lexical Decision

Left RightVF

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

LVF RVFVF

racy (

Post NF

Lexical Decision Results: Example of Treatment Effects

Within Condition

Nonsense (nonverbal) Shapes

Between Condition

Primary Color Task

Shade Task

Faces - Head-on

Faces - Rotated

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

150 200 250 300 350

Reaction Times

LVF-Lh RVF-Lh Race

Alerting Network (Norepinephrine)

Orienting Network (Acetylcholine)

Conflict Network (Dopamine)

CONGRUENT TARGET

VALID CUE

INCONGRUENT TARGETDOUBLE CUE

LANT-RH

Pre PostPre PostPre Post

Pre PostPre Post Pre Post

LANT-LH** *

Gender Differences Structural

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