Face Perception is Modulation by Sexual Preference (Kranz & Ishai, 2006) Melody Sinclair-Brooks PSYC 260
Overview • Introduction • Hypothesis • Methods • Results • Discussion • My Opinion
Introduction • 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
However, the effects of gender and sexual orientation on peoples response to faces is currently unknown.
Hypothesis • 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: The brain’s “pleasure center” • 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.
Methods • Researchers used fMRI to test whether subjects would respond more to their sexually preferred faces...
Subjects • 40 normal, right-handed subjects with normal vision (Mean age ± SD= 26 ± 3years) • 10 heterosexual women & 10 homosexual women • 10 heterosexual men & 10 homosexual men
Procedure • Stimuli were projected onto a translucent screen placed at the feet of the subject Subjects viewed: • Grayscalephotographs of faces (3 runs each) and • Assessed facial attractiveness (5 runs each)
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
Face (3s) Phase-scrambled face (3s) Each stimulus was presented for 3 seconds, with no blank periods between the stimuli
Procedure 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
Independent Variables: • Face or Phase-Scrambled face • Sexual Preference Dependent Variables: • Attractiveness rating • Brain activation
Data Acquisition • 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 Analysis • 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.
Anatomical Regions Observed • inferior occipital gyrus (IOG) • lateral fusiformgyrus (FG) • superior temporal sulcus (STS) • amygdala • intraparietalsulcus (IPS) • caudate • putamen • mediodorsal nucleus of the thalamus (mdT) • anterior cingulate cortex (ACC) • insula • inferior frontal gyrus (IFG) • medial orbitofrontal cortex (OFC)
Data Analysis • 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
How were the trials sorted for each subject? • 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
What were the parameter estimates used for? • Between-subjects random-effects analyses to control for any random effects between subjects
Results • 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
Results • Regardless of gender or sexual orientation, participants had very similar assessments of attractiveness of both male and female faces.
Discussion 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...
...... especially for reproductive success in sexually-relevant faces I I WANT YOUR BABIES.
Conclusion • 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
My Opinion • 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
Questions? Thank you.