J. Biomedical Science and Engineering, 2011, 4, 196-199 JBiSE
doi:10.4236/jbise.2011.43027 Published Online March 2011 (http://www.SciRP.org/journal/jbise/).
Published Online March 2011 in SciRes. http://www.scirp.org/jour nal/JBiSE
Brain activation patterns associated with sexual orientation in
homosexual male and female: preliminary study with 3.0T
fMRI
Gwang-Won Kim1, Jong-Chul Yang2, Gwang-Woo Jeong 3
1Interdisciplinary Program of Biomedical Engineering, Chonnam National University, Gwangju, Republic of Korea;
2Department of Psychiatry, Chonbuk National University Medical School, Jeonju, Republic of Korea;
3Department of Radiology, Chonnam National University Medical School, Chonnam National University Hospital, Gwangju, Repub-
lic of Korea.
Received 22 November 2010; revised 8 January 2011; accepted 12 January 2011.
ABSTRACT
This study was performed to clarify the sexual orien-
tation in a 19-year-old homosexual male and a
20-year-old homosexual female by using a functional
magnetic resonance imaging (fMRI) with viewing
male and female erotic nude pictures. The sex hor-
mone levels of the homosexual male and female were
in the normal range of healthy heterosexual males
and females, respectively. In both homosexuals more
significant brain activities were observed while view-
ing the nude pictures of the same genetic sex than
those of the opposite sex in the frontal cortex, parietal
cortex, occipital cortex, anterior cingulate gyrus,
amygdala, midbrain, hippocampus, orbitofrontal
cortex, parahippocampal gyrus, thalamus, globus
pallidus, and putamen, which are known to be re-
sponsive to sexual arousal. The homosexual male and
female showed a tendency toward higher sexual
arousal to the same genetic sex as comparison with
the opposite sex. This finding may be useful to un-
derstand the different neural mechanisms on sexual
arousal in homosexuals.
Keywords: Sexual Orientation; Homosexual Male;
Homosexual Female; Functional Magnetic
Resonance Imaging (fMRI)
1. INTRODUCTION
The sex is defined by genes and physical characteristics
of the body. The decision of sexual orientation is likely
to be related with complex correlations between cul-
tural, psychological, social-environmental, and bio-
logical factors. Sexual orientation involves the expres-
sion of sexual arousal as a biological factor rather than
the voluntary selection of the opposite sex [1-3]. Ho-
mosexual persons are characterized by a persistent dis-
comfort with their natal body and a stated desire to be
the opposite sex. In addition, they can experience sexual
arousal and attraction to the same genetic sex [1].
The most influential biological theory of sexual ori-
entation is that hormones influence the development of
neural structures that regulate sexual behavior [2]. The
sexual hormones show different degrees of variability
between males and females. The major male and female
hormones can be classified as estrogen and testosterone
[4]. Estrogen leads to the growth of the female sex or-
gans and feminization, whereas testosterone is response-
ble for development of the male reproductive structures
and masculinity. Although, the levels of free testosterone
and estradiol (E2) in the homosexual male and female in
our study were in the normal range of healthy hetero-
sexual males and females, respectively, they are sexually
interested in members of their genetic sex.
In this study, the differential brain activation patterns
in response to visual sexual stimuli with male and fe-
male erotic nude pictures in both homosexual male and
female subjects were compared to discriminate the sex-
ual orientation for homosexual persons by using 3.0
Tesla functional magnetic resonance imaging (fMRI).
2. CASE REPORT AND RESULTS
The first case deals with a homosexual male whose
name is YS. He is 19 years old and is sexually interested
in male. He has received any hormonal and/or surgical
therapy. At present he lives with his parents and is a
freshman in a university with a major tied of the early
childhood education. YS has had a difficult time adjust-
ing to school life since primary school because of sexual
identity. Growing up, YS did not feel socially isolated,

G.-W. Kim et al. / J. Biomedical Science and Engineering 4 (2011) 196-199 197
but he had more female friends than male friends. He
had firstly fallen in love with a boy-friend when he was
a middle school. During the interview, he was calm and
appeared to be introversive. YS expressed discomfort
about his sex at birth. He exhibited a passion for female
traits such as long hair and female clothes. YS visited the
hospital with his boyfriend, whom he has been dating for
6 months and seems to accept him as a girl. YS gave
fully informed consent and the experiment contents in
accordance with the Declaration of Helsinki.
To examine the underlying the functional brain activa-
tion patterns associated with sexual orientation, an fMRI
examination was performed as follows: The visual stim-
uli were presented in a block design fashion. The para-
digm for visual stimulation consisted of 3 times rest
condition and 2 times activation condition; each lasted
for 60 and 90 seconds, respectively. During the activa-
tion period, each subject viewed male and female erotic
nude pictures. Functional MRI was performed using a
3.0T Magnetom Trio MR Scanner with a bird cage head
coil. Functional images were acquired using a gradi-
ent-echo echo planar pulse sequence with the following
parameters: repetition time/echo time = 3000 ms/30 ms,
flip angle = 90, field of view = 22 cm × 22 cm, matrix
size = 64 × 64, and slice thickness = 5 mm. Data were
analyzed using Statistical Parametric Mapping (SPM02,
Wellcome Department of Cognitive Neurology, Univer-
sity College London, London, UK). Prior to statistical
analysis, images were realigned to correct for head
movement between scans. Preprocessed functional vol-
umes of subject were spatially normalized to the Mont-
real Neurological Institute (MNI) space. Images were
smoothed with an 8 mm full-width-half-maximum
Gaussian filter. After specification of the appropriate
design matrix, signal changes in the haemodynamic re-
sponse produced by the different experimental condi-
tions were assessed at each voxel using a general linear
model (GLM). Significant signal changes for each con-
trast were assessed by independent t-test (P < 0.01) on a
voxel-by-voxel basis.
The average levels of free testosterone (Free T), de-
hydroepiandrosterone sulfate (DHEA-S), sex hormone
binding globuline (SHBG), estradiol (E2), estriol (E3),
follicle stimulating hormone (FSH), and luteinizing
hormone (LH) in the homosexual male were 13.5 pg/ml,
34.6 μg/dl, 26.0 nmol/L, 21 pg/ml, 4.9 ng/ml, 4.06
mlU/ml, and 3.45 mlU/ml, respectively. The levels of
Free T, SHBG, E2, FSH, and LH were in the normal rage
of male [5]. Compared to the female erotic nude pictures,
viewing the male pictures in the homosexual male
yielded higher brain activities in the frontal cortex, pa-
rietal cortex, occipital cortex, hippocampus, parahippo-
campal gyrus, amygdala, anterior cingulate gyrus, puta-
men, globus pallidus, caudate nucleus, thalamus, insula,
and midbrain (Figure 1, Table 1).
Second case is for a homosexual female whose name
is JY. She is 20 years old and she feels an exclusive at-
traction to female. She has received any hormonal and/or
surgical therapy. At present she lives with her girlfriend
Figure 1. Differential brain activation patterns in response to
the visual sexual stimulation with the female (A) and male (B)
erotic nude pictures in a homosexual male, resulting from the
one sample t-test (P < 0.01).
Table 1. Differential brain activities (peak t-value, P < 0.01)
associated with visual sexual arousal between homosexual
male and female.
Activity (t - value)
Homosexual male Homosexual female
Brain areas
FemaleaMaleb FemaleaMaleb
Neocortex
Frontal cortex 3.55 5.45 5.25 3.86
Parietal cortex 3.65 5.08 4.11 3.38
Occipital cortex 6.23 8.17 10.31 8.23
Orbitofrontal cortex3.79 4.25 3.60 2.79
Temporal cortex 3.76 3.77 9.07 7.66
Limbic-system and
others
Amygdala - 2.56 3.09 -
Cingulate cortex - 2.42 3.36 -
Globus pallidus - 3.18 2.70 -
Hippocampus - 3.01 3.30 2.47
Parahippocampal
gyrus - 2.55 3.38 -
Putamen - 3.37 3.46 -
Thalamus - 2.79 3.38 -
Cerebellum 5.56 7.29 10.03 5.86
Insula - 4.19 - 3.14
Midbrain - 2.60 2.78 -
a. Female = female erotic nude pictures
b. Male = male erotic nude pictures

G.-W. Kim et al. / J. Biomedical Science and Engineering 4 (2011) 196-199 198
who she met one year ago. She reported that her father
abused her physically during her childhood and her pa-
rents got divorced. Her behavior has become more mas-
culine and often aggressive. She wishes she were a male
and has applied a bandage to her breast to appear more
masculine. She has not had the surgery to change her sex
because of the high cost, although she is currently
working at a transgender bar to earn money for a sex
reassignment surgery. JY stated that she was displeased
with her parents during the interview. Furthermore, she
stated that if she is upset, she cannot control herself and
she showed signs of impulsive behavior. She also com-
plained about things often and was easily angered by her
girlfriend during the interview. She expressed discomfort
about her sex at birth. JY gave fully informed consent
and the experiment contents in accordance with the
Declaration of Helsinki.
The average levels of Free T, DHEA-S, SHBG, E2, E3,
FSH, and LH in the homosexual female were 0.98 pg/ml,
247 μg/dl, 34.6 nmol/L, 87 pg/ml, 4.7 ng/ml, 2.74 mlU/ml,
and 4.53 mlU/ml, respectively. The levels of Free T,
DHEA-S, SHBG, E2, FSH, and LH were in the normal
rage of female [5]. The brain areas showing higher ac-
tivities in viewing the female erotic nude pictures over
the male pictures included the frontal cortex, parietal
cortex, occipital cortex, hippocampus, parahip-pocampal
gyrus, amygdala, anterior cingulate gyrus, putamen,
globus pallidus, caudate nucleus, thalamus, and midbrain
(Figure 2, Table 1).
3. DISCUSSION
This study identified whether the sexual orientation in-
fluenced the neural activation in response to viewing the
male or female erotic nude pictures in homosexual male
and female. In our study, distinct brain activation with
higher signal intensities in both homosexual male and
female was induced by sexual stimuli with the same ge-
netic sex pictures especially in the occipital cortex, fron-
tal cortex, and parietal cortex. These results are pre-
sumably related to the subject’s attention and concentra-
tion on the preferable nude pictures [2,6,7]. It is well
known that the vision-related cortices play important
roles in the perception of visual information.
The predominantly activated brain areas, others inter-
esting areas in our study, observed in viewing the erotic
nude pictures of the same genetic sex over those of the
opposite sex in both subjects included the anterior cin-
gulate gyrus, amygdala, parahippocampal gyrus, thalamus,
hippocampus, globus pallidus, putamen, and midbrain.
Safron et al. [2] reported that the brain areas associated
with sexual arousal were organized a priori into a hy-
pothesized network supporting sexual arousal, which
included the anterior cingulate gyrus, amygdala, hippo-
Figure 2. Differential brain activation patterns in response to
the visual sexual stimulation with the female (A) and male (B)
erotic nude pictures in a homosexual female, resulting from the
one sample t-test (P < 0.01).
campus, hypothalamus, midbrain, orbitofrontal cortex,
and visual areas. Based on the previously published pa-
pers [6-10], visual sexual stimulation affects the thala-
mus along the optic nerve transmits to the parahippo-
campal gyrus through the visual cortex and a object is
recognized. Subsequently, the visual information affects
the thalamus, hippocampus and amgydala, the auto-
nomic nervous system which adjusts sexual behavior in
the hypothalamus was responded. At this time, increased
sexual arousal affects the frontal lobe through the cingu-
late gyrus, and sexual arousal and pleasure are consid-
ered to be felt. In addition, Ponseti et al. [6] reported that
the preferred sexual stimuli induced activation of the
anterior cingulate gyrus, orbitofrontal cortex, thalamus
and ventral striatum relative to the non-preferred sexual
stimuli. Note that the homosexual male and female in
our study showed a tendency toward higher sexual
arousal to the same genetic sex than those of the oppo-
site sex.
Although the homosexual subjects maintain the sex
hormone levels of their born sex in the normal ranges,
the neural activation associated with sexual arousal re-
flected their sexual orientation, giving higher activities
being observed in response to viewing the erotic nude
pictures of their genetic sex. Consequently, the brain
activation patterns in response to visual sexual stimuli
were not considered as the sex hormones, and the neural
mechanisms on sexual arousal correlate with their sexual
preference.
This study provided in valuable information that the
homosexual subjects showed a tendency towards higher
brain activation in response to the visual stimuli with the
erotic nude pictures of the same genetic sex over those
of the opposite sex. Future studies are needed to clarify
how the brain activation patterns associated with sexual
arousal in homosexual persons is changed with the levels
of the sex hormones, and how the brain activation pat-
terns between homosexual persons and transgender are
different to each other.

G.-W. Kim et al. / J. Biomedical Science and Engineering 4 (2011) 196-199 199
4. ACKNOWLEDGEMENTS
This work was supported by the Korea Science and Engineering
Foundation (KOSEF) grant funded by the Korea government (MEST)
(No. 2009-0077677).
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