By: Michael Spelman
Hedonism is the idea that we as people have every right to maximize the pleasure we attain from life (Hedonism bot here knows what I'm talking about); and why shouldn't we? Our brains are literally wired in a way that promotes rewarding behaviors. It is because of this wiring that when a commercial comes on TV for a big, juicy, one and a half pound, double Philly-cheesesteak chipotle burger (or maybe a succulent kale salad for the vegetarians out there?) being held/eaten by Kate Upton or Ryan Gosling in minimal clothing, our primal instincts run wild and we find ourselves throwing money in every direction to obtain this pleasure explosion of a sandwich (at least that is how advertising is supposed to work). Or maybe you aren't as "turned on" by food as I am. Perhaps your "go to" pleasure is alcohol, or cigarettes, or shopping. Maybe you are one of those adrenaline junkies that needs to jump out of a perfectly good airplane or mountain in a wing suit and zoom past cliff-sides going 200mph just so that you get through the day with a smile on your face. Personally, that type of thing gives me the heeby-jeebies and my heart drops every time I watch a video like that.
But all differences in pleasure preferences aside (for now), the reason we do these things that may be fattening, life-threatening, malicious, maniacal or anything in between, is due to the fact that we have very specific neural circuitry involved in reward and behavior. Specifically, a complex interconnected network of dopaminergic neurons (neurons that release/respond to dopamine) serve to integrate our senses (thalamus) with our conscious decision-making ability (prefrontal cortex, PFC), our memory (hippocampus), our emotions (amygdala), and even our motor outputs (ventral tegmental area, VTA, and substantial nigra, SN). While this image may seem a bit confusing with all the arrows and brain regions, it is actually quite simplistic in summarizing the intricacies of the circuit. What I mean by saying it is simplistic is that the circuit does not necessarily go only in one direction (from sensory input to motor output) as it seems to show: the sensation of reward can actually arise from an action that generates a pleasurable sensory output. Picture this: as a little kid, you were at a pool (your own, a friend's, doesn't matter really); as you are walking by the edge of the pool, someone picks you up and throws you in; during the pre-splash flight you notice you actually enjoy this feeling of elevation; now whenever you go to a pool, you try and find a way to jump from the highest possible object because you have developed this intrinsic propensity to succumb to gravitational forces. As most of us probably know, this "intrinsic propensity" is due to the release of adrenaline from the sympathetic division of our autonomic nervous system (remember fight or, in this case, flight?). This adrenaline release has now become intricately associated with feelings of pleasure and joy and in order to replicate it, you need to replicate the initial stimulus (heightened elevation and the feeling of falling). So now you spend all of your time jumping out of airplanes.
Those of you who have taken any introductory psychology course can recognize this pattern of paired stimulus with a sensation, or expectation of reward as Pavlovian conditioning 101; the feelings of reward have been conditioned by memory to be associated with the neutral stimulus of high elevation, even in the absence of the rewarding stimulus. This is precisely how individual differences in pleasure preferences can arise. For instance, as a child I learned to associate the sensation of being full to an overall sense of well-being. Obviously different foods have different smells and tastes and appearances so I began pairing certain smells and certain styles of foods to good feelings (that burger description above is still in my mind). Nowadays I don't even need to see or smell food that is within my grasp; I am a sucker for good advertising (I would buy these edible cookie cups in a heartbeat if I knew where to get them).
Obviously not everyone has the same preferences, but the general idea here is that any activity or process or thing can become entrained in our minds as a rewarding behavior through conditioning and learning. This all comes back to the reward circuitry in our brains. We begin to associate memories and emotions with these good feelings and this results in the activation of the circuit even when we just think about the activity or thing or process. You may find yourself asking, "yeah, so what?". The issue arises when people begin to crave these pleasurable feelings beyond a point of self-control and become addicted to chasing them. This can occur when the pleasurable behavior begins to be used to ameliorate some negative event or emotion.
Because the initial conditioning and pairing of stimuli are physiologically engrained in the reward circuit, there should be a physiological explanation for the transition from benevolent hedonism to full-fledged, compulsive addiction, right? Many researchers have focused on elucidating this mechanism, and their results are quite interesting.
According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) addiction can be defined as "a maladaptive pattern of substance use resulting in significant negative physical, social, interpersonal or legal consequences". Here I am modifying the term "substance" to include any behavior that promotes hedonic pleasure. As I mentioned above, when one such hedonic pleasure becomes an outlet for escaping negative life events, things can get bad. For example, after a bad break-up from a long relationship, you go to the store and buy a gallon tub of ice cream and then proceed to eat the whole thing at home while watching some sappy love movie based on a cheesy novel. Now, that isn't so bad (other than the potential health consequences of eating a gallon of ice cream in one sitting). But what about when other negative life events occur and you begin doing this every time something goes wrong? Without even consciously doing it, you begin to ignore your health/weight, shunt your responsibilities, and severely limit your social interactions for fear of more bad things happening. So now this hedonic pleasure (enjoying ice cream) no longer is a source of happiness, but has become a way of escaping the negative events in your life. Not only that, but that 1 gallon of ice cream is no longer enough because you've started building a tolerance to its soothing effects. This tolerance leads to compulsive ice-cream buying and consumption and now you can't get through the day without it anymore! (I am probably dramatizing this for effect, but this really does happen)
Volkow and colleagues have shown that exactly this type of behavior is what ensues in drug addicts, and it is due to a physiological change in the pattern of activation of this reward circuit. A progression from making conscious decisions (PFC) to ameliorate some negative emotion, to an unconscious reward-seeking pattern of behaviors results in compulsive behaviors that serve to promote relief from withdrawals and negative emotions. As shown in the image below, there is a change from activation of the more anterior brain structures in the non-addict, to the more posterior brain structures in the addict.
Initially, the anterior brain structures serve as a physiological mechanism of self-control and inhibit poor decision making. However after repeated learning or substance use, these inhibitory controls become overridden and the posterior brain structures act similarly to a reflex pathway: without even consciously thinking about it or choosing to, an addict will respond to stress or aversion by carrying out reward-seeking behaviors.
Now you may again be thinking to yourself, "So what? I eat ice cream/jump out of planes all the time and I am not physiologically addicted". And my first response would be to tell you to attempt to put down the carton/parachute and see how long you can go without it. All jokes aside though, it is likely because you have a well-established sense of self-control and can resist the urge to give in to your hedonic pleasures. For other people however, it may not be as simple as that (many adrenaline junkies die every year by trying to achieve the ultimate rush).
Researchers have hypothesized that there are many potential risk factors that predispose certain individuals to developing addictions. These include such things as stress, violence, aggression, developmental environment, social environments, and even genetics (we talked about the nAChR subunit alleles in the lateral habenular nucleus in our physiology lecture; for information on this and other neurotransmitter receptor influences, check this out). Many of these risk factors have been shown to be very influential in the development of addiction using mouse models and various conditioning paradigms.
All-in-all, we inherently strive to make ourselves feel good by doing those things that we have learned to promote our own happiness. It would seem to insult the intensive and complex process of evolution that led to the development of this physiological reward circuit in our brains were we to not use it for hedonic pleasure. The key to maintaining this pleasure however, seems to lie in the maintenance of an appropriate level of self-control. When this self-control is diminished, our brain circuitry can cause us to do some unbelievably malevolent things without even really being conscious of it. That is unless someone develops a way in which to abolish such reward-seeking/addictive behavior and cures them with lasers.
1. Classical Conditioning- Ivan Pavlov. 2008. video. youtube.com. Web. 20 Jan 2014. <http://www.youtube.com/watch?v=hhqumfpxuzI>.
2. Sommer, W. H., and R. Spanagel. 2013. Behavioral neurobiology of alcohol addiction. Springer 13. Retrieved from http://www.springer.com/biomed/neuroscience/book/978-3-642-28719-0
3. Dubuc, B. (2014). [Web log message]. Retrieved from http://thebrain.mcgill.ca/flash/a/a_03/a_03_cr/a_03_cr_que/a_03_cr_que.html
4. DSM. 2012. Clinical Practice Guidelines. American Psychiatric Association. Arlington, VA: Retrieved from http://www.psych.org/practice/dsm
5. Miller, M. C., and J. Segal. Understanding addiction: How addiction hijacks the brain. HelpGuide.org. Retrieved from http://www.helpguide.org/harvard/addiction_hijacks_brain.htm
6. Lynch, W. J., K. L Nicholson., M. E. Dance, R. W. Morgan, and P. L. Foley. 2010. Animal models of substance abuse and addiction: Implications for science, animal welfare, and society. Comp Med 60: 177-188. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2890392/
7. Dick, D. M., and A. Agrawal. 2008. The genetics of alcohol and other drug dependence. Alcohol Research & Health 31: 111-118. Retrieved from http://pubs.niaaa.nih.gov/publications/arh312/111-118.pdf
8. Volkow, N. D., G. Wang, J.S. Fowler, D. Tomasi, and F. Telang. 2011. Addiction: Beyond dopamine reward circuitry. Proceedings of the National Academy of Sciences 108: 15037-15042. Retrieved from http://www.pnas.org/content/108/37/15037.full.pdf html
9. Chen, B. T., H. Yao, C. Hatch, I. Kusumoto-Yoshida, S.L Cho, F.W. Hopf, and A. Bonci. 2013. Rescuing cocaine-induced prefrontal cortex hypoactivity prevents compulsive cocaine seeking. Nature 496: 359-362. doi: 10.1038/nature12024
10. Cottone, P.. Laboratory of addictive disorders. Retrieved from http://www.bumc.bu.edu/busm-pm/research/laboratories/lad/