Binge drinking, the ingestion of large amounts of ethanol followed by intermittent withdrawals, is associated with increased reflection impulsivity, the tendency to make decisions before enough evidence is accumulated. This was revealed by a study recently published in Addiction Biology by researchers in the BCNI.
The researchers also showed that this increased reflection impulsivity was associated with a reduction in the volume of the dorso-lateral prefrontal cortex (DLPFC) and the inferior parietal cortex.
The study, authored by Dr Paula Banca, tested thirty healthy volunteers and thirty binge drinkers, defined as consuming more than 4 drinks (5 for men) in the space of 2 hours, at least once a week for a period of three months. They did a structural scan of the participants’ brains.
Reflection impulsivity was assessed with two tasks. The first required participants to tell whether a sequence of red or blue beads was drawn from one of two bags, one of which contained 80% blue beads and 20% red beads. The other bag held 20% blue and 80% red beads.
The second task asked participants to turn over grey squares in a grid of 25 squares. The squares could either be blue or yellow, and participants had to determine which colour was predominant in the grid. In both tasks, the number of beads or squares the participants looked at before they made a decision reflected the amount of evidence they required to make a decision.
As Dr Banca stated: “reflection impulsivity measures the amount of information gathered before taking a decision or the tendency to make rapid decisions without a proper evaluation of options.”
The study found that binge drinkers made decisions with less evidence in the beads task, whereas there was no difference in the grey squares task. Reflection impulsivity as measured by the two tasks was linked to different brain changes. For the beads task, DLPFC and inferior parietal cortex were reduced in volume in people who showed higher impulsivity. On the other hand, in the grey squares task, higher impulsivity was linked to increases in other brain areas: the dorsal cingulate and precuneus.
The researchers highlight that these findings have important implications for how binge-drinking is treated: “These findings emphasize the role of possible therapeutic interventions targeting decision-making deficits.”
This study comes in light of longstanding interest in decision making in substance abuse. Decision making is often modelled as a process following Bayesian principles: an individual will make a decision based on prior beliefs about the true state of their surroundings, and evidence they acquire. In this study, reflection impulsivity, or the tendency to acquire less evidence, was reduced in binge drinkers.
When the researchers modelled the decisions of participants with a computational model, they found that binge drinkers experienced more “cognitive noise”. In the words of the authors: “The ‘cognitive noise’ parameter […] provides a measure of how much decision making is influenced by the more cognitively difficult process of ‘thinking ahead’.”
Decision making will remain an important area of research in substance abuse. Another recent paper, by one of the co-authors and colleagues, Dr Michael Moutoussis, showed that beliefs about your own ability to succeed in a task heavily influence decision making – something which may play an important role in decision making in substance abuse. However, Dr Banca states: “However, more research is needed before this can be confidently applied to clinical groups and related to the currently more robust approach in this study.”
But, the current paper highlights the importance of studying decision making in binge drinkers.