Motivation

The Neuroscience of Wanting and Pleasure

Wanting and liking are the basis of motivation, our psychological oxygen.

Posted Feb 23, 2017

Humans must find motivation to continue the journey of life. Motivation to go to work, to parent, to invest in costly long-term relationships, and motivation to wake up every morning and give life another shot. Some aspects of these life tasks must be rewarding for people to keep investing in them. In other words, motivation is our psychological oxygen to be. Every moment is measured against a biological motivation meter. Some moments, we are so motivated to be the best parent. Some moments, we are so unmotivated to keep working on our marriage. Some moments, we are putting in insane hours at work. Motivation oscillates from moment to moment, and the thought of reward compels us to renew our motivation to keep trying.

Our brains, moment by moment support this journey by dedicating some of its limited landscape to processing reward and motivation. It has gotten really proficient at this task and has paved multiple pathways to ignite us to keep going. These are the "wanting" and "liking" components of motivation. They are represented in separate networks (although overlapping) and involve different neurochemicals1. Most of us want what we like, but these different pathways in the brain suggest that want is separate from liking or pleasure. For example, a mother might have to interrupt her night sleep every two hours to feed her infant, a student might have to laboriously study for an exam, a night-person might have to wake up at 6 a.m. to go to work. In all of these examples, we are motivated to complete these tasks, but might not enjoy them. Thus, we can be motivated by things that we want but don’t like, which would activate the ‘want’ brain pathway. Of course, we are also motivated by things we enjoy doing, which would activate the ‘like’ pathway. Fortunately, both systems make social interactions worth the risk.

The "Want" Pathway:

Buried underneath the logical cortex is a structure called the "nucleus accumbens" in the ventral striatum. This area facilitates wanting and pursuing desired behaviors. Push this "wanting" system to the maximum and you get addictive behaviors. When this system is activated, motivation to pursue a stimulus increases. This system receives important information from the amygdala, and the hippocampus. The amygdala provides information about the emotional intensity of the situation and the hippocampus provides past memories that convince us to go for it. Then, the ventral striatum summarizes all this information and sends it to the hypothalamus. The hypothalamus controls our drives such as sex, food, and sleep, our hormonal system (via intimate connections with the pituitary gland) and aspects of the autonomic nervous system such as the sympathetic nervous system. It is important to note that these biological computations don’t always make it to our stream of consciousness. In other words, some of our wants are non-conscious.

The chemical soup that this system stews in is saturated with the neurotransmitter dopamine. Any stimulus that manages to release dopamine, is rewarding and produces the motivation to seek it in the future. Needless to say, any drug that is addictive involves an increase in dopaminergic levels2. One of the central areas for dopaminergic release is the "want" region, the nucleus accumbens. Lesions in nucleus accumbens of the ventral striatum, reduce motivation, such as the motivation to work for reward3. More to the point, people suffering from depression struggle to maintain activation in the nucleus accumbens when asked to maintain focus on positive emotions in positive slides compared with non-depressed individuals4. Positive emotions activate this system, in other words these emotions are rewarding.

This system is a key player is convincing us to invest in long-term relationships such as marriage. In an fMRI study investigating the neural correlates of long-term love5, the researchers found activation in the dopamine "want" reward system when participants viewed pictures of their spouse (average marriage was over 21 years) but not when viewing a picture of a friend. In sum, this dopamine rich pathway is activated in anticipation of reward, positive emotions, and relationships.

The "Like" Pathway:

Whereas the "want" system is activated in pursuing a rewarding stimulus, the "like" system is activated in the actual experience of the reward. The feel-good chemicals here are opiates (have analgesic effects) and not dopamine. While dopamine is released in anticipation of a pleasurable event, opiates are released when actually experiencing the pleasure. So, dopamine is what compels you to drive at midnight to get your favorite ice cream, and opiates are involved in the intense pleasure you experience while eating it. Dopamine leads to seeking behaviors, to pursue at any expense and makes the chase feel good. Opiates produce a stagnant state of pleasant calmness and quiescence and also feels good.

An important region in the "like" pathway is the periaqueductal gray subcortical region, which is super responsive to opiates. It is involved in blocking pain signals. This is why we cannot feel pain and pleasure at the same time, one experience predominates. But, this is also why people might medicate social pain by engaging in pleasures, to release pain-inhibiting opiates.

The "like" pathway is also critical to social relationships. For example, opiates are released when mothers look at pictures of their infants but not to others6. Soothing touches and sounds also activate the release of opiates. So, what happens if this system is blocked? When human females are given naltrexone to block opiate release, they spend more time alone and less time with friends and don’t enjoy social interactions. These studies suggest that opiates release is crucial for making social interactions feel pleasurable and therefore motivate us to pursue them, even if at the expense of painful rejections.

So, if it seems as though you have run out of steam, don't be hard on yourself! It is the very nature of motivation to disappear every once in a while. If the tide was high all the time, we would fail to see the beauty of calm oceans. However, studies suggest that dysfunctions in these pathway might lead to depression, social anxiety, or even suicide.

References

(1) Haber, S. N., & Knutson, B. (2010). The reward circuit; Linking primate anatomy and human imaging. Neuropsychopharmacology, 35, 4-26.

(2) Di Ciano, P., Blaha, C. D., & Phillips, A. G. (1998). Conditioned changes in dopamine oxidation currents in the nucleus accumbens of rats by stimuli paired with self-administration or yoked-administration of d-amphetamine. European Journal of Neuroscience, 10(3), 1121-1127.

(3) Caine, S., & Koob, G. (1993). Modulation of cocaine self-administration in the rat through D-3 dopamine receptors. Science, 260, 1814-1816.

(4) Heller, A. S., Johnstone, T., Shackman, A. J., Light, S., Peterson, M., Kolden, G., Kalin, N., & Davidson, R. J. (2009). Reduced capacity to sustain positive emotion in major depression reflects diminished maintenance of fronto-striatal brain activation. Proceedings of the National Academy of Sciences, 106(52), 22445-22450.

(5) Acevedo, B. P., Aron, A., Fisher, H. E., & Brown, L. L. (2012). Neural correlates of long-term intense romantic love. Social Cognitive and Affective Neuroscience, 7(2): 145-159.

(6) Noriuchi, M., Kikuchi, Y., & Senoo, A. (2008). The functional neuroanatomy of maternal love: Mother’s response to infant’s attachment behaviors. Biological Psychiatry, 63(4), 415-423.