The Neuroscience of Happiness

Can neuroscience tell us anything about happiness? With so many people seemingly interested in how to be happy, great utility would exist in being able to measure the emotion objectively through neuroscientific methods. However, happiness can mean many different things and has thus historically been difficult to connect to an objective underlying neurobiology. While considerable progress has been made measuring these constructs of happiness through self-report, recent developments in neuroimaging and meta-analyses have begun to suggest progress in our ability to objectively measure the emotional experience of happiness. Yet, these recent findings are not without controversy. Much debate still exists around whether happiness can be examined as a discrete emotion or a part of a dimensional continuum. Researchers also contest whether happiness can be mapped onto the brain to a specific region or only examined as a part of a dynamic neural network. Below is an overview of the recent findings and debate. The article concludes by integrating these findings, discussing future directions, and taking the view that, unfortunately, we still have a ways to go before neuroscience can consistently identify states of happiness and meaningfully inform better paths toward its obtainment.

Categorical vs. Dimensional Approach

Basic emotions: Activation likelihood maps representing regional activity consistently associated with each discrete emotion. Horiontal lines overlaid on the sagittal image (far right) show locations of axial slices. Left side corresponds to left side of image. Color gradient represents degree of activation consistency.^[5]

Scientists have primarily measured happiness up to now through subjective self-report across two aspects: hedonia (pleasure) and eudaimonia (meaning and a life well-lived).^[1] Researchers also examine happiness in positive affect, analyzing both the state (including physiology and neural substrates) and the subjective experience of emotion (involving cognition).^[2] Yet, debate exists among affective researchers on the biological nature of emotions, such as happiness, and how they should map onto the brain.

Basic Emotions View

Some argue for a categorical approach, stipulating that happiness is one of a number of basic emotions, namely, anger, sadness, happiness, fear, and disgust.^[3] Basic emotion theorists take these discrete emotions to be innate, universal, and to have unique physiological patterns, facial expressions, and neural correlates.^[4] In other words, happiness should exist and be measurable in the brain distinct from the other basic emotions.

A recent meta-analysis by Vytal and Hamann (2010) provide some support for this approach to emotion research. In their analysis of 83 PET and FMRI neuroimaging studies from 1993 to 2008 with activation likelihood estimation, the researchers found that each of the five basic emotions was associated with a consistent and discrete set of neural correlates with regional brain activations.^[5]

Dimensional view

Dimensional approach: Graphical representation of the affective circumplex, with the valence dimension represented horizontally on the x-axis and arousal vertically on the y-axis.

In contrast to the basic emotions view, a dimensional approach claims these discrete emotions are instead categories or elaborated responses arising from more fundamental biological properties such as valence (degree of pleasantness) and arousal (level of intensity), often combined with cognitive processes such as appraisal.^[6] From this perspective, happiness would not be a biologically ingrained, innate emotion, but, the product of an emotional experience of high valence and, depending on cultural context, a reasonably high amount of arousal. Dimensional theorists would then be more interested in looking for the neural correlates of the dimensional axes (e.g., positive or negative valence) than the specific emotions.

Past research on lateralization has suggested that positive and negative emotions may be associated with greater activation in the left and right hemispheres, respectively. For instance, one study of 84 older adults found greater left than right superior frontal activation with electroencephalography was associated higher levels of self-reported both hedonic and eudaimonic well-being^[7] However, one meta-analysis since then found that neural activity associated with positive and negative emotions was found to be relatively symmetrical^[8], and another similarly found limited support for valence-specific lateralization of emotional activity in frontal cortex.^[9]

A different dimensionalist hypothesis for identifying neural correlates of happiness was that subregions of orbitofrontal cortex process positive and negative valence and the amygdala processes level of arousal.^[10] Indeed, past EEG and lesion studies have pointed to at least partially separable neural systems for positive and negative emotions.^[8] More specifically, some researchers have found evidence that the medial edge of the orbitofrontal cortex has been connected to positive and negative valence.^[11] However, the same meta-analyses above would suggest otherwise, as they found that the spatial distributions of positive and negative emotions were not significantly different^[8], and additional studies similarly suggest a more complex dynamic, by which multiple regions represent arousal, valence, and their interaction. ^[10][12]

Brain Regions

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Nucleus Accumbens

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Orbito Frontal Cortex

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Right Superior Temporal Gyrus

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Left Anterior Cingulate Cortex

File:VACC.jpg

Sagittal view of a cluster in the ventral ACC

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Conclusion

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References

1. Waterman, A. S. (1993). Two conceptions of happiness: Contrasts of personal expressiveness (eudaimonia) and hedonic enjoyment. Journal of Personality and Social Psychology, 64(4), 678-691.
2. Kringelbach, M. L., & Berridge, K. C. (2010). The neuroscience of happiness and pleasure. Social Research, 77(2), 659-678.
3. Eckmanm P. (1992). An argument for basic emotions. Cognition and Emotion. 6, 169-200.
4. Panksepp, J. (2007). Neurologizing the psychology of affects: how appraisal-based constructivism and basic emotion theory can coexist. Perspectives on Psychological Science. 2, 281-296.
5. Vytal, K., & Hamann, S. (2010). Neuroimaging support for discrete neural correlates of basic emotions: A voxel-based meta-analysis. Journal of Cognitive Neuroscience, 22(12), 2864-2885.
6. Russell, J. A., & Barrett, L. F. (1999). Core affect, prototypical emotional episodes, and other things called emotion: Dissecting the elephant. Journal of Personality and Social Psychology, 76(5), 805-819.
7. Urry, H. L., Nitschke, J. B., Dolski, I., Jackson, D. C., Dalton, K. M., Mueller, C. J., . . . Davidson, R. J. (2004). Making a life worth living: Neural correlates of well-being. Psychological Science, 15(6), 367-372.
8. Murphy, F. C., Nimmo-Smith, I., & Lawrence, A. D. (2003). Functional neuroanatomy of emotions: A meta-analysis. Cognitive, Affective and Behavioral Neuroscience, 3(3), 207-233.
9. Wager, T. D., Phan, K. L., Liberzon, I., & Taylor, S. F. (2003). Valence, gender, and lateralization of functional brain anatomy in emotion: A meta-analysis of findings from neuroimaging. NeuroImage, 19(3), 513-531.
10. Lewis, P. A., Critchley, H. D., Rotshtein, P., & Dolan, R. J. (2007). Neural correlates of processing valence and arousal in affective words. Cerebral Cortex, 17(3), 742-748.
11. Kringelbach, M. L., & Berridge, K. C. (2009). Towards a functional neuroanatomy of pleasure and happiness. Trends in Cognitive Sciences, 13(11), 479-487.
12. Colibazzi, T., Posner, J., Wang, Z., Gorman, D., Gerber, A., Yu, S., . . . Peterson, B. S. (2010). Neural systems subserving valence and arousal during the experience of induced emotions. Emotion, 10(3), 377-389.