Now in Neuropsychopharmacology: How Impulsivity and Disrupted Decision-Making Relate to Suicidal Behavior
Research has demonstrated that impaired decision-making is a key factor in the onset of suicidal behavior and can manifest as difficulty choosing between two similarly valued options or as impulsivity in decision-making. To better understand the potential relationship between decision-making and suicidal behavior, scientists have examined the neural underpinnings of each and found disrupted ventromedial prefrontal cortex encoding of value—which can be associated with impulsivity—in people who have attempted suicide.
In a study recently published in Neuropsychopharmacology, researchers including post-doctoral fellow Vanessa Brown, PhD, Katalin Szanto, MD, and senior author Alexandre Dombrovski, MD, from the University of Pittsburgh hypothesized that in suicidal individuals, disrupted ventromedial prefrontal cortex value signals and reduced ventromedial prefrontal cortex-frontostriatal connectivity may result in a compromised decision-making ability and impulsivity. To better understand how impulsivity and disrupted decision-making relate to suicidal behavior, the scientists sought to distinguish disrupted value signals from other learning deficits, investigate correlates of suicidal behavior beyond ideation, and measure impulsivity along facets that distinguish suicide attempts from suicidal ideation. The team assembled a cohort of participants ages 47–79 years, who were recruited into four groups: suicide attempters, suicide ideators, depressed non-suicidal controls and non-depressed non-suicidal controls.
Participants completed 300 trials of a task requiring continual learning and updating of expected value during functional magnetic resonance imaging that assessed each individual’s value-based learning.
“Based on participants’ responses on the task, we used a reinforcement learning algorithm to estimate the value of each choice they made, and then correlated these values with brain activity,” explained Dr. Brown, the study’s first author. “This analysis showed us what areas in the brain responded to expected value. We then examined how these value-related brain areas, particularly the ventromedial prefrontal cortex, differed in activity as well as connectivity to other brain areas when we compared people who had attempted suicide versus people who had not. In terms of connectivity, we were particularly interested in areas in the frontoparietal network, which is responsible for cognitive control; highly impulsive people have been shown to have reduced frontoparietal – ventromedial prefrontal cortex activity.”
In the current study, the team reported an altered pattern of ventromedial prefrontal cortex-frontoparietal connectivity—rather than a reduced pattern of connectivity in this region—in impulsive people who exhibit suicidal behavior, in addition to reduced ventromedial prefrontal cortex value signals. The relationship between ventromedial prefrontal cortex-frontoparietal connectivity, previous rewards on the task, and participants’ future task choices was also disrupted in people who had attempted suicide, suggesting that people with a history of suicidal behavior fail to use recent rewards to guide behavior. This study adds to earlier research on impaired valuation and decision-making and moderation of these impairments by impulsivity in suicidal behavior, and contributes enhanced understanding by using a task that offers improved isolation of value signals and is more sensitive to cognitive control demands.
Regarding the study’s significance, Dr. Dombrovski said, “These findings shed new light on how impulsivity and value-based decision-making impairments – both risk factors for suicide – interact in older adults who have attempted suicide. The neural correlates of impulsivity differ in people who attempt suicide and affect learning, suggesting that the neural processes underlying impulsivity in suicide are distinct, and require more understanding, than in people who do not attempt suicide. Overall, these findings suggest that, in a crisis, suicide can emerge as an accident in the decision process, and that disrupted communication between value-oriented ventral and ‘cognitive’ dorsal prefrontal cortex can give rise to such accidents.”
Ventromedial prefrontal value signals and functional connectivity during decision-making in suicidal behavior and impulsivity
Brown VM, Wilson J, Hallquist MN, Szanto K, Dombrovski AY
Neuropsychopharmacology 45 (2020) doi: 10.1038/s41386-020-0632-0