lack of sleep speeds up risky decisions
Heightened expectations and low risk perception – that is what lack of sleep seems to induce when decisionmaking during gambling was studied in an experimental study.
To understand the neural underpinnings of risky decision making under conditions of sleep deprivation, Vinod Venkatraman and colleagues of Duke University studied healthy volunteers as they underwent functional magnetic resonance imaging (fMRI), the use of MRI to measure the haemodynamic response related to neural activity in the brain or spinal cord of humans.
The authors found that the nucleus accumbens, an area in the brain involved with the anticipation of reward, becomes selectively more active when high risk-high payoff choices were made under conditions of sleep deprivation. Further, the number of high risk decisions did not increase with sleep deprivation, but the expectation of being rewarded for making the high risk gamble was elevated. Allied to this finding was the observation that there was an attenuated response to losses in the insula, a part of the brain involved with evaluating the emotional significance of an event.
According to the authors, the new findings build on prior research that has shown that sleep-deprived participants choose higher-risk decks and exhibit reduced concern for negative consequences when performing a variant of the Iowa Gambling Task. While well-rested participants learn to avoid high-risk decks and to choose from the advantageous decks, sleep-deprived participants tend to continue to choose from the risky decks as the game progresses.
Michael W.L. Chee, one of the authors of the study, noted that disadvantageous decisions were not actually made, but the brain showed response patterns suggesting that going down that path might be the next step. Herein lies the added value of brain imaging — potentially being able to foretell the likelihood of making disadvantageous decisions, added Chee.
“Most of us know of people who have stayed up all night on a gambling table, taking crazy risks that did not make sense and who lost more than they had because they did not walk out when it was sensible to,” said Chee. “Understanding why we make poorer choices when sleep deprived is important not only because of the increasing numbers of persons affected, but also because there exist today unprecedented opportunities to incur damaging losses by means such as online gambling. This work is one of many evaluating the neural correlates of decision making but the first to apply such methods to sleep deprived individuals.”
Sleep Deprivation Elevates Expectation of Gains and Attenuates Response to Losses Following Risky Decisions
Sleep, May 1, 2007, Volume 30 , Issue 05, Pages 603-609
Vinod Venkatraman, MEng1,3; YM Lisa Chuah,PhD1; Scott A Huettel, PhD2,3; Michael WL Chee, MBBS, MRCP(UK)1,2
1Cognitive Neuroscience Laboratory, Duke-NUS Graduate Medical School, Singapore; 2Brain Imaging and Analysis Center and 3Center for Cognitive Neuroscience, Duke University, Durham, NC
Using a gambling task, we investigated how 24 hours of sleep deprivation modulates the neural response to the making of risky decisions with potentially loss-bearing outcomes.
Two experiments involving sleep-deprived subjects were performed. In the first, neural responses to decision making and reward outcome were evaluated. A second control experiment evaluated responses to reward outcome only.
Healthy right-handed adults participated in these experiments (26 [mean age 21.3 years] in Experiment 1 and 13 [mean age 21.7 years] in Experiment 2.)
Measurements and Results:
Following sleep deprivation, choices involving higher relative risk elicited greater activation in the right nucleus accumbens, signifying an elevated expectation of the higher reward once the riskier choice was made. Concurrently, activation for losses in the insular and orbitofrontal cortices was reduced, denoting a diminished response to losses. This latter finding of reduced insular activation to losses was also true when volunteers were merely shown the results of the computer’s decision, that is, without having to make their own choice.
These results suggest that sleep deprivation poses a dual threat to competent decision making by modulating activation in nucleus accumbens and insula, brain regions associated with risky decision making and emotional processing.