Face Perception is Modulation by Sexual Preference
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Transcript of Face Perception is Modulation by Sexual Preference
Face Perception is Modulation by
Sexual Preference(Kranz & Ishai, 2006)
Melody Sinclair-Brooks PSYC 260
Introduction Hypothesis Methods Results Discussion My Opinion
Overview
Face perception is mediated by a distributed neural system in the human brain
Introduction
The response to faces is modulated by cognitive factors such as:
attention visual imagery emotion
Introduction
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
Hypothesis
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
The reward circuitry: The brain’s “pleasure center”
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...
Methods
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
Subjects
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)
Procedure
Procedure 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
Each stimulus was presented for 3 seconds, with no blank periods between the stimuli
Face (3s) Phase-scrambled face (3s)
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.
Procedure
ii. Attractiveness assessment (cont’d):
Subjects pressed 1 of 3 buttons to indicate whether a face was:
attractive neutral unattractive
Procedure
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
Data Acquisition
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.
Data Analysis
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)
Anatomical Regions Observed
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
Data Analysis
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
How were the trials sorted for each subject?
Between-subjects random-effects analyses to control for any random effects between subjects
What were the parameter estimates used for?
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
Results
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.
Results
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
Discussion
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
Discussion
Recent studies have reported that facial beauty evokes activation in the reward circuitry regions of the brain...
Discussion
...... especially for reproductive success in sexually-relevant faces
I I WANT 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
Conclusion
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
My Opinion
Questions?
Thank you.