A vanishing sex difference

slipperhangingAI and Robotics

Nov 14, 2013 (3 years and 6 months ago)

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A vanishing sex difference

Effects of environmental contingencies in a

virtual Morris water task on male and female spatial navigation




Mühl
, Griego, Kabisch, Kolomiyets, Kunkemöller, James,
Neubauer
,
Liu,
Schumann
, Nagel &
Kreitz

Introduction

Sex

differences

in

spatial

navigation

A

standard

measure

for

spatial

navigation

in

rodents

are

mazes,

like

the

Morris

water

maze,

the

Hebb
-
Williams

maze

or

corridor

mazes
.

Virtual

reality

offers

the

possibility

to

investigate

human

spatial

navigation

behaviour

under

similar

conditions

with

a

high

degree

of

control
.










Astur

et

al
.

(
1998
)

showed

in

various

experiments

a

reliable

sex

difference

in

the

virtual

Morris

water

task
.




The

participants

showed

continual

increase

of

their

performance

to

locate

a

hidden

platform,

that

is

the

swim

latency

decreased
.



Men

were

faster

in

finding

the

hidden

platform,

showed

smaller

heading

errors,

and

a

better

spatial

strategy

(search

in

the

right

quadrant)

in

the

probe

trials

compared

to

women
.




The

sex

difference

was

not

the

result

of

motivational,

motor

or

sensory

differences

regarding

the

computer

program,

rather

it

could

traced

back

to

navigational

ability
.


A

study

applying

the

virtual

MWT

paradigm

showed

differential

cue

use

for

women

and

men

(Sandstrom

et

al
.
,

1998
)
.



Women

rely

on

the

use

of

distal

cues,

e
.
g
.

objects

in

the

background
.



Men

make

use

of

distal

cues

and

geometric

cues,

e
.
g
.

the

ground

plan
.


A

fMRI

study

(Grön

et

al
.
,

2000
)

revealed

significantly

different

activations

between

women

and

men

while

performing

a

complex,

three
-
dimensional,

virtual
-
reality

maze
.




Both,

men

and

women,

showed,

besides

others,

strong

activations

in

the

hippocampus

proper,

the

parahippocampal

gyrus

and

parietal

regions
.



C
ompatible

with

the

differential

cue

use

mentioned

above

woman

showed

stronger

activations

in

a

right

parietal

area

and

a

right

prefrontal

area,

whereas

men

exhibited

stronger

activation

in

the

left

hippocampus
.


In

our

experiment

we

wanted

to

investigate

the

influence

interleaved

non
-
stationary

platform

trials

have

on

sex

differences
.

Subjects

had

to

perform

an

Morris

water

task

with

interleaved

non
-
stationary

platform

blocks

after

each

stationary

platform

block
.

While

the

platform

location

did

not

change

over

the

stationary

platform

blocks,

it

was

randomly

assigned

to

a

different

location

for

each

non
-
stationary

platform

block
.

Stationary

and

non
-
stationary

blocks

differed

in

the

distal

cue

design
.


Abstract


In

tasks

of

spatial

navigation

males

in

general

show

a

superior

performance

compared

to

females,

independent

of

the

species

studied
.

A

study

using

a

virtual

version

of

the

Morris

water

task

(MWT)

to

investigate

human

navigational

behaviour

found

a

reliable

sex

difference

(Astur

et

al
.
,

1998
)
.

To

investigate

this

difference

further

we

used

the

virtual

MWT

similar

in

design

to

that

used

by

Astur

et

al
.
,

but

interleaved

the

stationary

platform

blocks

with

non
-
stationary

platform

blocks
.

The

general

sex

difference

was

replicated

and

there

was

a

stronger

effect

of

the

interleaved

non
-
stationary

blocks

on

male

navigation
.

Materials and Method

Results & Conclusion

References

Astur, R.S., Ortiz, M.L., & Sutherland, R.J. (1998). A characterization of performance by men and women in a virtual Morris w
ate
r task: a large and reliable sex
difference.
Behavioral Brain Research
, 93, 185
-
190.

Grön, G., Wunderlich, A. P., Spitzer, M., Tomczak, R., & Riepe, M. W. (2000), Brain activation during human navigation: gende
r
-
d
ifferent neural networks as
substrate of performance.
Nature Neuroscience
, 3, 404
-
408.

Sandstrom, N.J., Kaufman, J., & Huettel, S.A. (1998). Differential cue use by males and females in a virtual environment navi
gat
ion task.
Cognitive Brain Research
,
6, 351
-
360.


O'Keefe, J., & Nadel, L. (1978). The hippocampus as a cognitive map. Oxford University Press.

Colby, C.L., & Goldberg, M.E. (1999). Space and attention in parietal cortex. Annual Review Neuroscience, 22, 319
-
349.



A

large

sex

difference

was

observed
:

men

had

significantly


faster

swim

latencies

across

stationary

blocks

F(
1
,

308
)

=

42
.
94
,

p

<

.
01

than

women

performing

the

Morris

water

maze
.





T
his

differences

vanished,

or

became

non
-
significant,

when

only

the

performance

in

the

first

trials

of

the

stationary

blocks

was

compared
,

p

=

.
10
.

Design



Independent

variables
:

sex,

platform

stability,

block,

environment



Dependent

variables
:

swim

latency

to

find

target

Procedure
:

The

experiment

consisted

of

14

blocks,

7

stationary

platform

blocks

interleaved

with

7

non
-
stationary

platform

blocks,

with

4

trials

in

each

block
.

T
he

starting

positions

within

the

pool

was

randomly

determined

for

each

trial
.

Stationary

platform

block

:

the

platform

was

tied

to

the

same

location

within

the

pool

over

all

blocks

Non
-
stationary

platform

trial

:

the

location

was

randomly

reassigned

for

each

block

The

two

conditions

used

different

sets

of

distal

cues

(abstract

objects

vs
.

concrete

objects)

which

made

it

possible

for

the

subject

to

discriminate

between

the

conditions,

though

they

were

not

told

about

the

design
.

The

association

of

stationary

and

non
-
stationary

blocks

with

either

abstract

and

concrete

cues

were

evenly

distributed

over

the

subjects
.




A

possible

interpretation
:

use

of

different

spatial

representations
.

Men

are

more

effective

in

construction

and

use

of

an

allocentric

representation

of

the

environment

(cognitive

map)

relying

on

geometrical

and

distal

cues,

while

women,

at

least

initially,

rely

instead

on

an

egocentric

representation
.

This

leads

to

an

advantage

of

men

in

spatial

navigation

tasks
.



The

advantage

turns

into

disadvantage,

when

differential

environments

are

alternating
.

The

cognitive

maps

are

interfering

with

each

other,

maybe

due

to

an

automatic

process

of

generalization

based

on

similar

geometric

cues
.

Women,

on

the

other

hand,

were

less

affected

by

the

change

of

the

environment,

as

the

egocentric

representation

is

based

on

the

use

of

clearly

distinguishable

distal

cues
.



Assuming

egocentric

representation

to

be

mainly

supported

by

parietal

cortex

(Colby

&

Goldberg,

1999
),

and

allocentric

representations

by

the

hippocampus

(O'Keefe

&

Nadel,

1978
),

differential

brain

activations
,

with

women

showing

stronger

activation

in

prefrontal

and

right

parietal

areas

and

men

in

the

left

hippocampus

(Grön

et

al
.
,

2000
),

indicate

the

use

of

differential

representations
.

Additional

support

for

differential

representation

use

comes

from

studies

exploring

sex

differences

in

cue

use

(
Sandstrom,

Kaufmann,

&

Heuttel,

1998
),

with

women

relying

mainly

on

distal

cues

and

men

on

distal

and

geometric

cues
.


0
5
10
15
20
25
30
sec
Over all trials
Over 1. trials
Swim latency in stationary blocks
Women
Men
A

classical

Morris

water

task


Subjects

are

supposed

to

find

a

stationary

hidden

platform

in

a

circular

pool

filled

with

opaque

water
.

Orientation

is

only

possible

by

the

use

of

distal

cues

distributed

around

the

pool
.

The

subjects

are

finding

the

target

faster

with

every

trial,

indicating

a

continuous

learning

process
.

This

is

thought

to

indicate

the

construction

of

an

cognitive

map

of

the

environment
.

To

navigate

through

the

environment

subjects

initially

have

to

rely

on

egocentric

representations
.

By

continuous

exposure

to

the

environment,

it

becomes

possible

to

form

relations

between

the

various

cues
.

An

allocentric

representation

(cognitive

map)

is

built

and

refined

gradually,

supporting

the

navigation

process
.

Fig. 1 Male example of an stationary platform block
demonstrating learning