Neural Correlates Of Happiness

Happiness is the intrinsic need and motivation of individual. It is also the common goal and the common theme of all mankind. In eastern, there are statements on happiness in one of the oldest classic "1Ching: Book of Changes" in China. In western, philosophers in Greek times had deliberated over happiness and developed the profound theories.Nowadays, with the development of empirical research, happiness has been of considerable interest in philosophy, ethics, psychology, sociology, education, economics, anthropology and neuroscience. In psychology, a wealth of research has examined the associations between happiness and a host of diverse subjective and objective factors. The findings enhance people’s understanding of happiness.The brain plays an important role in emergence, maintenance and promotion of happiness. With the development of neuroimaging technique, there is growing interest on neural correlates of happiness. However, limited work has examined the relationship between the brain and happiness and less is known how happiness is reflected in the brain. Studying the neural basis of happiness, will effectively identify the neural markers of happiness and will provide neuroscientific evidence to enhance our knowledge on happiness, which is of great value in the theory and the practice.Given the importance of understanding the relationship between happiness and the brain, we examined the neural mechanisms of happiness. Following previous studies, happiness characterizes individuals’characteristic level of happiness during a particular period of time. From the perspective of multimodal neuroimaging, the current study used the structural magnetic resonance imaging (MRI), resting-state and task-based functional MRI (fMRI) to investigate systematically how trait happiness is reflected in brain structure and function.Few studies were conducted on trait happiness within a neuroscientific framework. Furthermore, most of current neuroscientific studies simply reduced happiness to pleasure. Thus, the study one firstly investigated the neural basis of overall happiness, by conducting three experiments using voxel-based morphometry (VBM) techniques in MRI, and Regional homogeneity (ReHo) and functional connectivity (FC) in the resting-state fMRI, respectively. In this study, happiness was measured by Subjective Happiness Scale (SHS).In experiment one, the structural MR images from169young, healthy adults were analyzed by VBM. In experiment two, regional homogeneity (ReHo) in resting-state fMRI was examined on two groups of young adults:happy and unhappy individuals (N=25per group). In experiment three, functional connectivity (FC) in resting-state fMRI was further examined on data from experiment two. The results showed that the structure and function of the prefrontal cortex, temporal lobe, parietal lobe, the limbic system and the subcortical structures were related to the overall happiness. Importantly, these areas are mostly overlap with the default network, the emotion and reward networks, and executive control network. These findings may indicate that overall happiness were related to people’s self-evaluation, self-reflection, past memories, future imagination, ability to process emotional experiences and rewards, as well as the executive function.Secondly, due to the distinct philosophy, happiness can be divided into hedonic happiness (pleasure attainment and pain avoidance) and eudaimonic happiness (meaning and self-realization). However, less is known how hedonic happiness and eudaimonic happiness are reflected in the brain and their similarities and differences. Therefore, the study two also used VBM in structural MRI and FC in resting-state fMRI to investigate the neural correlates of hedonic happiness and eudaimonic happiness, respectively. Following with previous studies, hedonic happiness was measured by positive affect sub-scales of Positive and Negative Affect Schedule (PANAS), while eudaimonic happiness was measured by Scales of Psychological Well-Being (PWB). In experiment four, the structural MR images from124young, healthy adults were analyzed by VBM. In experiment five, functional connectivity (FC) in resting-state fMRI from118young adults was examined. The results demonstrated that hedonic happiness and eudaimonic happiness have significant correlation (rs>0.32, p<0.001). However, the neural correlates of hedonic happiness and eudaimonic happiness shared some common characteristics and also are different from each other. Specifically, the decreased functional connectivity between Default Mode Network (DMN) and dorsolateral prefrontal cortex (DLPFC), and the increased functional connectivity between DMN and Superior Medial Frontal Gyrus (sMFG) correlated with hedonic happiness and eudaimonic happiness. The functional connectivity between DMN and some regions in temporal lobe and parietal lobe correlated with hedonic happiness, while the functional connectivity between DMN and some regions in prefrontal cortex and cerebellum correlated with eudaimonic happiness. Furthermore, hedonic happiness was positively associated with right middle temporal gyrus gray matter volume, while eudaimonic happiness was positively associated with inferior parietal lobule gray matter volume. Taken together, the similarities and differences between hedonic happiness and eudaimonic happiness may suggest they play different roles and work together to promote the overall happiness.Finally, from the perspective of time, reward processing can be divided into anticipation and experience. Anticipation represents the psychological state when the stimulus is yet to come, and the experience represents the psychological processing of the current stimulus. Most current research on the neural mechanisms of emotional processing among happy and unhappy individuals focused on the experience. However, anticipation is related to approach motivation, which is important to mental health and happiness. Thus, basing on the tasked-based fMRI, the study three investigated the neural correlates of anticipation as a function of trait happiness.40young adults were instructed to conduct the emotional anticipation task. We scanned the participants’brain activity when they were anticipating future positive or neutral events. It was found that bilateral medial prefrontal cortex (MPFC) was activated when people were anticipating the future positive event rather than the future neutral events. More importantly, the activation in medial prefrontal cortex can predict the level of the individual’s trait happiness. These findings may suggest that the approach motivation for the future positive events plays a key role in trait happiness.These studies used a variety of neuroimaging techniques and methods to investigate the neural correlates of happiness. These findings may provide neuroscientific insight into the development of the happiness theories, and give neuroscientific evidence to develop intervention practices on individual’s happiness. However, several limitations and future directions need to be considered. Firstly, the future studies to investigate the happiness in different cultures within neuroscience framework are needed. Secondly, the neural relationships between overall trait happiness and specific happiness are also needed investigated. Lastly, it will be of merit to addressing the causal relationship between the brain and happiness in future study. These directions are our research tasks in future.