Transcript ClassPresentation05

(Kranz & Ishai, 2006)
Melody Sinclair-Brooks
PSYC 260

Introduction

Hypothesis

Methods

Results

Discussion

My Opinion

Face perception is mediated by a distributed
neural system in the human brain
The response to faces is modulated by
cognitive factors such as:
attention
 visual imagery
 emotion


However, the effects of gender and
sexual orientation on peoples
response to faces is currently
unknown.


Kranz & Ishai expected a significant relationship
between the gender of the image presented and
the sexual preference of the participant.
Greater response to an image will correspond to
a greater activation in the reward circuitry
regions of the brain
Sexual Preference  Brain activation  Response


The reward circuitry consists of the dopaminergic
pathways in the brain
These circuits are evolutionarily important for
natural rewards such as food, music, and sex
Heterosexual men and homosexual
women are expected to respond more
to female faces.

Heterosexual women and homosexual men
are expected to respond more to male faces.

Researchers used fMRI to test whether
subjects would respond more to their
sexually preferred faces...

40 normal, right-handed subjects with normal
vision (Mean age ± SD = 26 ± 3 years)

10 heterosexual women & 10 homosexual women

10 heterosexual men & 10 homosexual men

Stimuli were projected onto a translucent
screen placed at the feet of the subject
Subjects viewed:
 Grayscale photographs of faces (3 runs each)
and
 Assessed facial attractiveness (5 runs each)
Each run:
Participants were shown images of faces
alternating with images of phase scrambled faces
within a period of 30s

They had 21s for viewing and 12s for
attractiveness rating
Face (3s)
Phase-scrambled face (3s)
Each stimulus was presented for 3 seconds,
with no blank periods between the stimuli
i. Viewing Condition:

During the viewing condition, 60 male and 60
female unfamiliar, famous, and emotional faces
were presented
ii. Attractiveness assessment:

During the assessment of facial attractiveness, 100
male and 100 female faces were presented
Reaction times were recorded. The order of runs
was randomized across subjects.
ii. Attractiveness assessment (cont’d):
Subjects pressed 1 of 3 buttons to indicate
whether a face was:



attractive
neutral
unattractive
Independent Variables:
Face or Phase-Scrambled face
 Sexual Preference

Dependent Variables:
Attractiveness rating
 Brain activation


Whole body MR scanner
(Philips Medical Systems, Best, The Netherlands)



Changes in the blood-oxygenation-level-dependent
MRI signal were measured
High resolution structural images were collected in the
same session for all the subjects
(180 axial slices)
The high-resolution anatomical images were used to
build a 3D brain atlas

fMRI data analyzed in BrainVoyager QX Version 1.3
(Brain Innovation, Maastricht, The Netherlands)

All volumes were corrected for motion artifacts,
realigned, and spatially smoothed with a 5mm
FWHM Gaussian filter.












inferior occipital gyrus (IOG)
lateral fusiform gyrus (FG)
superior temporal sulcus (STS)
amygdala
intraparietal sulcus (IPS)
caudate
putamen
mediodorsal nucleus of the thalamus (mdT)
anterior cingulate cortex (ACC)
insula
inferior frontal gyrus (IFG)
medial orbitofrontal cortex (OFC)


The fMRI images for faces were subtracted
from the fMRI images of the scrambled faces
This difference indicated the activation for the
brain areas when faces were being viewed
Scrambled Face signal
– Face signal =Activation


According to their attractiveness score
According to the mean of the parameter
estimates that was calculated for attractive,
neutral, and unattractive male and female
faces

Between-subjects random-effects analyses to
control for any random effects between
subjects



There was a significant interaction between
stimulus gender and the sexual preference of
the subject in the thalamus (mdT) and medial
orbitofrontal cortex (OFC)
Heterosexual men and homosexual women
responded more to female faces
Heterosexual women and homosexual men
responded more to male faces
mdT=
mediodorsal
nucleus of the
thalamus
OFC = medial
orbitofrontal
cortex

Regardless of gender or sexual orientation,
participants had very similar assessments of
attractiveness of both male and female faces.
Activation in the medial orbitofrontal cortex (OFC):
The OFC is involved in representing the reward
value of sensory stimuli:
 including beautiful faces, abstract positive and
negative reinforcers
Activation in the thalamus (mdT) :
it is reciprocally connected to the OFC and will
therefore show similar patterns of activation

Facial beauty is considered an indicator of
reproductive fitness – perhaps why men and
women equally notice and respond to beauty
of the same and opposite sex
 Recent
studies have reported that
facial beauty evokes activation in
the reward circuitry regions of the
brain...
I WANT
I
YOUR
BABIES.


Male and female face stimuli evoke similar
neural activation within a distributed cortical
network that includes: Visual, Limbic, and
Prefrontal regions
Sexually relevant faces elicit stronger neural
responses in the reward circuitry



Kranz & Ishai analyzed many brain regions,
doing a thorough investigation
Perhaps they could have included diagrams
for the procedure when explaining the steps
as it was not crystal clear and provide an
example of the phase-scrambled faces used
Future research could investigate the effect of
peoples’ ethnic background on assessing
attractiveness and activating certain brain
areas
Thank you.