Gender Differences Structural Brain WeightMaleFemale Klekamp et al 1989, n=18;16) Zilles (1972) Wessely (1970; n=18,13) Witelson (1985; n=12;30) Unweighted Mean 1,3581,193 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 Times18 Ancient Greece20 Middle Ages, England , Massachusetts35 19 th century, England , USA , USA , USA , USA75 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

0 Canonical Effect for LH Specialization (RVFA)

TARGET + (DISTRACTER) LDT With Distractors

LDT with Distractors + parkstop

Control for reading scan bias by using Hebrew readers

+ - Pre 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 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

Alerting Network (Norepinephrine) Orienting Network (Acetylcholine) Conflict Network (Dopamine)

CONGRUENT TARGET time VALID CUE *

INCONGRUENT TARGETDOUBLE CUE ** time

LANT-RH PrePostPrePostPrePost * * * * PrePostPrePostPrePost LANT-LH * * * ‡