Previous neuroimaging studies on romantic love have focused on determining how the visual stimuli that serve as a representation of loved ones induce the neural activation patterns of romantic love. The purpose of this study was to investigate the temporal changes in romantic love over a period of 6 months and their correlated neurophysiological changes.
Five heterosexual couples (n=10, mean age 21.1±1.97) who started dating not less than 100 days previously were recruited to measure their blood oxygen level dependent (BOLD) signals using functional magnetic resonance imaging (fMRI) while showing them pictures of their loved ones and their previously identified, opposite-sex friends. Subsequently, the subjects were scanned under the same experimental conditions to assess possible changes in their brain activities after 180 days.
We found that their Passionate Love Score (PLS) values (M: 118.6±9.1, F: 120.2±7.0) were significantly reduced after 6 months (M: 110.8±4.0, F: 106.2±3.0). Furthermore, significantly increased activations were found in the cingulate gyri, inferior frontal gyri, supramarginal gyri, etc., after 6 months, whereas the head and tail of the right caudate nucleus were deactivated, which is indicative of the inhibition of expression and sensory neglect.
These findings suggest that dynamic neural processes in the cortical-subcortical regions are involved in temporal changes in romantic love.
Romantic love is often simply associated with human sexual activity for mate choices and the willing, and even eager, participation of the individuals, and yet it is a profound emotion that prevails in human activity throughout the world.
The first work on the neural basis of romantic love suggested that distinct networks of brain areas are responsible, such as the anterior cingulate gyrus and caudate nucleus.
Regions known to have rich vasopressin and oxytocin receptor levels in the human brain are activated by both maternal and romantic love.
Although romantic love is a dynamic process, neuroimaging studies on temporal changes in neural activity during romantic love have not yet been performed. The aim of this work was to investigate the neural substrates at an early stage of romantic love within 100 days of its inception using fMRI and to determine any temporal changes in neural activities after 180 days compared with the early stages of love. This study was initiated at the request of the Korea Broadcasting System (KBS), Korea's public broadcaster, for a nationally televised documentary film entitled "Love". Part of this study, particularly the experimental procedure and the result, appeared in this film and was broadcast nationally in 2006.
Five heterosexual, right-handed couples exhibiting passionate love for each other (n=10, mean age: 21.1±1.97 years, range: 18-24 years) were recruited by advertisements placed by KBS. We screened approximately 200 volunteers after initial rounds of professional interviews by psychologists. They were deemed to be psychologically, medically and neurologically healthy, as determined by the diagnostic procedures of two psychiatrists. The levels of passionate love of all of the volunteers were scaled using the Passionate Love Scale (PLS),
The PLS is a 15- or 30- item Likert type scale, designed to measure the level of passionate love, which is defined as "a state of intense longing for union with another". It taps the cognitive, emotional, and behavioral indicants of passionate love. We used the short 15-item scale. Each item scores from 1 to 9, so the highest total score is 135. This evaluation was made before the fMRI scanning at the baseline and after 6 months.
Photo strips of various facial expressions of the participant's lover, friends of the same sex, blurred human faces, and a gray background without face were made as visual stimuli for each subject. The friends of the same sex were the oldest and closest ones chosen by the participants. They all had the same age as their friend and their friendship existed for at least 5 years.
To make the photo strips, all of the subjects were asked to bring friends of the same sex and their lovers to the broadcasting studio, and all of the photos were taken at the same place, at the same time and under the same conditions. The task paradigm was as follows: 5 still photos depicting various facial expressions of a friend of the same gender running for 30 seconds, blurred human faces for 30 seconds, 5 still photos portraying different facial expressions of the lover displayed for another 30 seconds, and finally a gray background without face for the last half minute. This six-minute sequence was repeated to form a 12-minute movie clip. We performed the fMRI experiment and the PLS twice at the end of May and the beginning of December, 2005 (i.e. with a 6-month interval between the two).
Echo-planar images were collected on a 1.5 T MRI scanner (Magnetom Vision, Siemens, Erlangen, Germany) using a standard head coil and Siemens Magnetom gradient overdrive. For each subject, four time series (friend, blurred human face, lover and no object against gray background) of the whole-brain images were obtained with a gradient-echo and echo-planar scanning sequence (EPI; TR 3 s, TE 60 ms, flip angle 90°; FOV 240 mm2, acquisition matrix 64×64 , 30 axial slices, slice thickness 5 mm, gap 0 mm). The first five images were discarded to account for spin saturation effects. A T1-weighted 3D magnetization prepared rapid acquisition gradient-echo sequence (MP RAGE) scan (voxel size=1.0×1.0×1.0 mm3) lasting 7 minutes and 14 seconds was recorded in the same session as a functional measurement for the recording of the subject's individual brain anatomy.
Pre-processing and statistical analysis of the fMRI data was performed using Statistical Parametric Mapping software (SPM99; Wellcome Department of Cognitive Neurology;
We estimated the degree of romantic love for the subjects using the PLS and professional interviews twice at an interval of 180 days (at the end of May and the beginning of December, 2005). During the interviews, the participants stated that their love would undoubtedly last for a long time. This passionate feeling was supported by the corresponding PLS scores. We found high PLS scores (M: 118.6±9.1, F: 120.2±7.0) at the early stage of intense love. This indicates that the couples were all deeply and passionately in love. However, after 180 days, we found that their PLS values were decreased (M: 110.8±4.0, F: 106.2±3.0), although this reduction was not statistically significant. All of the couples stated that their relation remained unchanged during the 180 days, but three out of ten participants told us secretly that they had sometimes considered separation during this time.
From the BOLD signal obtained by subtraction of the neural response that occurred while the subjects were shown pictures of their lovers and viewing their friends, we found statistically significant activations at an early stage of love. The left superior frontal gyrus, left medial frontal gyrus {Brodmann area (BA) 6}, left cingulate gyrus (BA 32), left subgyrus, right pons and right precentral gyrus, right frontal gyrus, right parietal postcentral gyrus, and anterior lobe of right cerebellum were significantly activated (p<0.05) when the participants were viewing the pictures of their lovers, compared with when they were viewing the pictures of their friends. Among these activations, those which reached the most significant level were the left superior frontal gyrus, left cingulate gyrus (BA 32), and anterior lobe of the right cerebellum (p<0.001)(
The same paradigm was used at the second scan 180 days after the initial fMRI scanning. Significant activations were found in this experiment at the corpus callosum, left inferior frontal gyrus, left middle frontal gyrus (BA 11), left middle frontal gyrus, right medial frontal gyrus (BA 6), right temporal gyrus, left superior frontal gyrus, right parietal postcentral gyrus (BA 3), right middle occipital lobe, and certain areas of the cerebellum (p<0.05) when the participants were viewing the pictures of their lovers, compared with those when they were viewing the pictures of their friends. Particularly, the corpus callosum reached the most significant level of activation (p<0.001)(
The neural activity patterns between the two measurements (May and December, 2005) were compared. We found that the left middle frontal gyrus, right inferior frontal gyrus, both cingulate gyrus areas (BA 31 and BA 33), the corpus callosum, both parietal supramarginal gyrus areas, both parietal precuneus areas and the left middle occipital gyrus (BA 18) showed significantly increased levels of activation when the participants were viewing the pictures of their lovers after 180 days (December 2005) compared with those measured initially (May 2005; p<0.05)(
The aim of this study was to investigate the neural systems underlying the later stages of romantic love as compared to its early stages. To the best of our knowledge, this is the first study to carry out a follow-up fMRI scan in order to investigate the temporal changes in the neural activity of enduring love. In this comparison with an interval of 180 days for the same romantic couples, we found that the activation of the caudate was significantly reduced, while that of the cortical regions including the cingulate gyrus was increased when the participants were viewing the pictures of their loved ones after 180 days, as compared with the initial measurements. Their PLS values were also significantly reduced after 6 months. This result suggests that the anterior cingulate gyrus and the caudate nucleus are likely the major regions involved in romantic love and that they exhibit a dynamic alteration over time as the degree of their romantic love evolves. This finding supports the hypothesis that romantic love is a dynamic process in the brain.
The early stage of romantic love in this study is marked by activations in the left superior frontal gyrus, left cingulate gyrus, left subgyrus, and sub-lobar regions, and the anterior lobe of the right cerebellum, while the participant is viewing his or her lover's face as compared to those of his or her friends. The left cingulate gyrus, which is located in the dorsal region of the anterior cingulate, is reportedly associated with various emotional states including happiness and pain.
The most significant finding of this study is that the neural correlates of romantic love change over time. It is commonly known that the fire of passionate love cools down over time. Changes in neural activation associated with romantic love over time have previously been suggested.
The significant decrease in fMRI activation in the head and tail of the right caudate nucleus after 180 days is consistent with previous studies which reported that the caudate nucleus is an important region in romantic love.
Our results show the cingulate gyrus to be more activated after 180 days than at the initial measurement, which is consistent with the previous finding of larger activation in the cingulate gyrus for couples having longer durations of love.
Previous fMRI studies on romantic love used participants heterogeneous in age and the duration of love. For instance, Aron and his colleagues
This study was supported by a grant of the Specific Research Program (
Neural activation sites for romantic-love related stimuli (A) at the early stage within 100 days from the first meeting (May 2005) and (B) in 6 months (December 2005).
Temporal changes in (A) neural activations and (B) deactivations between initial fMRI measurement and the measurement in 6 months. fMRI: functional magnetic resonance imaging.
Neural activation sites for romantic-love related stimuli at the early stage within 100 days from the first meeting (May 2005)
Neural activation sites for romantic-love related stimuli in 6 months (December 2005)
Temporal changes in neural activations between initial fMRI measurement and the measurement in 6 months
fMRI: functional magnetic resonance imaging
Temporal changes in neural deactivations between initial fMRI measurement and the measurement in 6 months
fMRI: functional magnetic resonance imaging