Neurobiological Correlates of Pathological Gambling: Temporo-Spatial Evidence Derived from fMRI and EEG Studies

Abstract

In the first study functional magnetic resonance imaging (fMRI) data in occasional gamblers (OG) and pathological gamblers (PG) were obtained during a quasi-realistic blackjack game. The present experiment focused on neuronal correlates of risk assessment and reward processing. Participants had to decide whether to draw or not to draw a card in a high-risk or low-risk blackjack situation. It was assumed, that PG would show differences in prefrontal and ventral striatal brain regions in comparison to OG during risk assessment and as a consequence of winning or losing money. Although both groups did not differ with respect to behavioral data, blood oxygen level dependent (BOLD) signals in PG and OG significantly differed in thalamic, inferior frontal, and superior temporal regions. Whereas PG demonstrated a consistent signal increase during high-risk situations and a decrease in low-risk situations, OG presented the opposite pattern. During reward processing as derived from contrasting winning vs. losing situations, both PG and OG groups showed an enhancement of ventral striatal and posterior cingulate activity. Furthermore, PG demonstrated a distinct fronto-parietal activation pattern which has been discussed to reflect a cue-induced addiction memory network triggered by gambling-related cues. The second experiment investigated event-related potentials (ERPs) in occasional gamblers (OG) and pathological gamblers (PG) during a quasi-realistic blackjack scenario to examine regional source (RS) models of risk assessment and reward processing based on fMRI activation patterns from experiment 1. Participants had to decide whether (to draw) or not to draw a card in a high-risk or low-risk blackjack situation. Although both groups did not differ in behavioral data, ERP signals in PG and OG significantly differed in P3b and late positive potential (LPP) amplitudes on high-risk vs. low-risk decisions. An fMRI constrained RS model during risk assessment yielded larger source moments in PG in the high-risk vs. low-risk comparison during early time windows in frontal and temporal brain regions, followed by thalamic, frontal, and temporal activations within later time windows. During reward processing, as derived from contrasting winning vs. losing situations, PG demonstrated enhanced fronto-central N1 amplitude and centro-parietal differences in the P3b time window. There were larger source moments in PG during early time windows in fronto-central and parietal networks, followed by middle frontal source activity in the 400-450 ms (millisecond) time window. Pathological gambling (PGG) is suggested to be reflected by early risk-related frontal and temporal modulations, which became not significant in ERPs, followed by enhanced P3b amplitude, probably associated with intensified evaluation processing or context updating in high-risk decisions. LPP enhancement in high-risk decisions in PG might represent stronger cue-related craving or arousal, potentially triggered by thalamic, frontal, and temporal generators. Early N1 enhancement in PG during win trials might reflect early attentional processing, probably generated in anterior cingulate cortex. Later valence-related P3b modulations in PG point to increased context updating with underlying frontal sources. To conclude, high-risk as well as win situations might serve as cues in PG reflected in stronger activations in arousal-related brain networks.