The Stimulus Preceding Negativity as a psychophysiological marker of uncertainty learning in gambling disorder patients
Alberto Megías, Juan F. Navas, & José C. Perales
Mind, Brain, and Behavior Research Center. University of Granada, Spain.
Background. The Stimulus Preceding Negativity (SPN) is an EEG slow cortical potential that mounts before the onset of a motivationally relevant outcome. SPN magnitude correlates both with the appetitive value and the uncertainty level of the outcome. On the other hand, gambling disorder patients (GDP) present anomalies in learning processes about uncertain outcomes, but little is known about the biological substrate of such anomalies.
Hypothesis. We hypothesized SPN to be heightened in GDPs, compared against healthy controls (HCs), in a classical conditioning analogue in which a cue either validly predicted an outcome (medium-uncertainty condition, MU) or bore no predictive value regarding the outcome (high-uncertainty condition, HU).
Methods. 26 HCs and 24 GDPs were exposed to two causal learning tasks, each consisting of 256 trials. In the MU condition the probability of the outcome was .75 in presence of the cue, and .25 in its absence (DP=.50), whereas in the HU condition the probability of the outcome was .50 regardless of whether the cue was present or absent (DP=.50). Cue-outcome contingency judgments, and trial-by-trial yes/no predictions of the outcome were collected. The SPN was measured the average voltage of frontocentral electrodes in the 200ms preceding the outcome.
Results. As expected, HC showed a stronger SPN in the HU condition than in the MU one as the task progressed (as they progressively behaviorally discriminated between the conditions). Gamblers SPN, however, remained high and constant regardless of task block and condition.
Discussion. Gambling disorder models stress the importance of uncertainty-driven motivation. In parallel, animal studies show that the appetitive properties of rewards are modulated by their uncertainty level, with individuals preferring uncertain rewards over certain ones also showing stronger risk propensity. This is the first demonstration so far that this mechanism could be involved in actual pathological gambling behavior.