Regret in Rats and Humans

Regret is a very common human emotion that we tend to experience from time to time when we feel as though we have failed to make a good decision. Although we, as humans, feel regret, we had not associated that feeling previously with any other animal until the Redish lab, consisting of Loyola alumnus and current MD/PhD student, Brian Sweis, studied it in rats. 

In their study, the Redish lab was able to determine that rats do indeed experience the feeling of regret. They were able to determine this by setting up a neuroeconomic task, which was designed to act as a stimulus  to induce regret. The rats also had electrodes implanted into their brains to monitor their brain activity. The areas of the brain that were mostly focused upon in this study were the orbitofrontal cortex, which is involved in decision making, as well as the ventral striatum, which is associated with the reward circuit in the brain.  

The task, "Restaurant Row", was set up as a restaurant model and consisted of four different zones in which four different flavors of food were offered to the rats and it was up to the rat's discretion to choose which flavor it wished to eat within a set amount of time. There were also various pitched tones associated with each flavor that sounded to indicate the delay the rat had to wait for that flavor to be dispensed. The rat, then had to make an economic decision about whether it should wait for that reward or go to a different zone without knowledge of how long the delay would be for the next reward. If the rat arrived in a zone with a longer delay time, then it was observed that the rat would look back at the previous reward zone, which was indicative of its feeling of regret. When the rat felt regret upon entering a high cost and low value reward zone, it was also seen that  the ventral striatum and the OFC exhibited activity that was similar to that, which is seen in if the rat had achieved the previous low cost and high value reward.  

Similar to this study of regret in rats, there was a recent study conducted by Stefanie Brassen and her research team on older individuals to assess whether regret increases or decreases with age. According to the study, as people age, they generally have less regrets due to the fact that they begin to let go of minor problems in their lives. To simulate the feeling of regret in this study, the older participants were placed in an fMRI to monitor their neural activity and were then given a game to play in which there were seven boxes with gold and one with a devil. The game entailed the participant choosing one box to open at a time to earn money, with the option to walk away with the money they had at any point. Regret was assessed when the participants were told how many more boxes they could have opened if they did not walk away with the amount of money they did and continued playing.  

From the fMRI results, it was determined that the ventral striatum activity decreased in older, healthy adults  only when they opened up a box with the demon, in contrast to depressed individuals who exhibited low ventral striatum activity when they opened a box with a devil as well as when they discontinued playing the game, exhibiting regret. This indicates that the healthy older adults were able to effectively suppress their feelings of regret as seen from the fMRI results and the control with the older depressed participants. 

This study relates to that of Brian Sweis' in that the ventral striatum activity was assessed in both studies and it appears that the activity of the ventral striatum decreased during feelings of regret for both the rat and for humans. In addition, similar to Sweis' study, where the rat spent more time at the reward center following making a bad decision, in the study by Stefanie Brassen, the elderly that had depression made riskier choices in relation to the game they played after experiencing regret. This parallel allows for rats to serve as stronger models for neural activity in humans, which has great implications for future neuroscience research.

Sources:
Jabr, Ferris. "The Rue Age: Older Adults Disengage from Regrets, Young People Fixate on Them." Scientific American. N.p., 19 Apr. 2012. Web. 04 Mar. 2016.
Steiner, Adam P., and A David Redish. "Neur300." Box. July 2014. Web. 04 Mar. 2016