Stephan F. Miedl

Neurobiological correlates of problem gambling in a quasi-realistic blackjack scenario as revealed by fMRI

In the present study we obtained functional magnetic resonance imaging (fMRI) data in occasional gamblers (OG) and problem gamblers (PG) during a quasi-realistic blackjack game. We 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. We assumed PG would show differences in prefrontal and ventral striatal brain regions in comparison to OG during risk assessment and due to the winning or losing of money. Although both groups did not differ in 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 which was triggered by gambling-related cues.

Elevated functional connectivity in a striatal-amygdala circuit in pathological gamblers.

Both substance-based addiction and behavioural impulse control disorders (ICDs) have been associated with dysfunctions of the ventral striatum. Recent studies using functional connectivity techniques have revealed increased coupling of the ventral striatum with other limbic regions such as amygdala and orbitofrontal cortex in patients with substance abuse disorders and attention-deficit hyperactivity disorder. In the present study, we re-analyzed previously published functional magnetic resonance imaging data acquired in pathological gamblers and controls during value-based decision-making to investigate whether PG is associated with similar functional connectivity effects. In line with previous studies in other ICDs, we observed reliable increases in functional coupling between striatum and bilateral amygdala in gamblers vs. controls. Implications of these findings for neural models of self-control and addiction are discussed.

The neural basis of impulsive discounting in pathological gamblers

Pathological gambling is thought to result from a shift of balance between two competing neurobiological mechanisms: on the one hand the reward system involved in the regulation of the urge to get rewards and on the other hand the top-down control system. Fifteen pathological gamblers (PG) and fifteen healthy controls (HC) were studied in an event-related functional magnetic resonance imaging experiment where participants had to choose either a smaller, but immediately available monetary reward (SIR) or a larger delayed reward (LDR). We examined contrasts between LDR and SIR decisions. Additionally, we contrasted choices near the individual indifference point (indifferent decisions) and clear SIR or LDR choices (sure decisions). Behavioral data confirmed former results of steeper discount rates in PG. Contrasting choices of LDR vs. SIR showed widespread bilateral activations in PG, including postcentral gyrus, thalamus, superior/medial frontal gyrus and cingulate gyrus, whereas HC demonstrated only focal left-sided pre/postcentral activity. Forgoing an immediate reward thus recruits a widespread brain network including typical control areas. Indifferent vs. sure decisions were associated with widespread activation in PG, including the bilateral fronto-parietal cortex, insula, anterior cingulate gyrus, and striatum, whereas in HC, only bilateral frontal cortex and insula were activated. The reverse contrast demonstrated more activity for sure decisions in the cingulate gyrus, insula, and medial frontal gyrus in HC, whereas PG showed inferior parietal and superior temporal activity. The present study demonstrates that pathological gambling is associated with a shift in the interplay between a prefrontal-parietal control network and a brain network involved in immediate reward consumption.

Intertemporal choice behavior is constrained by brain structure in healthy participants and pathological gamblers

The steepness of the delay discounting function shows considerable interindividual differences. Moreover, faster devaluation of future rewards has been consistently observed in pathological gamblers (PGs). Here, we asked whether variability in delay discounting is at least partially driven by differences in the anatomy of gray and white matter. For 40 healthy young subjects (study 1) as well as 15 PG and 15 age-matched healthy controls (HCs, study 2), the individual discounting parameter k was obtained. Based on 3D T1-weighted high-resolution magnetic resonance scans and diffusion tensor imaging, we performed voxel-based morphometry and tract-based spatial statistics, respectively, to examine the relation of gray matter volume (GMV) and white matter properties (as indicated by fractional anisotropy, FA) to k. Healthy groups from both studies showed a negative correlation between k and FA for the superior longitudinal fascicle and inferior longitudinal fascicle, whereas a positive correlation was found in the PG group for the inferior longitudinal fascicle and left inferior fronto-occipital fascicle. The latter also was significantly different between HC and PG in the group statistics (albeit on the right side), thus suggesting that this is a significant structure for the development of pathological gambling. GMV of the right frontal orbital cortex, left insular cortex and right lateral occipital cortex showed a positive correlation to k HC (studies 1 and 2) and PG, whereas a negative correlation was found for the left frontal pole in all three groups. Group comparison of GMV (study 2) revealed a decrease in PG for several cortical and subcortical areas.

Criticism hurts everybody, praise only some: common and specific neural responses to approving and disapproving social-evaluative videos

Social evaluation is a ubiquitous feature of daily interpersonal interactions and can produce strong positive or negative emotional reactions. While previous research has highlighted neural correlates of static or dynamic facial expressions, little is known about neural processing of more naturalistic social interaction simulations or the modulating role of inter-individual differences such as trait fear of negative/positive evaluation. The present fMRI study investigated neural activity of 37 (21 female) healthy participants while watching videos of posers expressing a range of positive, negative, and neutral statements tapping into several basic and social emotions. Unpleasantness ratings linearly increased in response to positive to neutral to negative videos whereas arousal ratings were elevated in both emotional video conditions. At the whole brain level, medial prefrontal and rostral anterior cingulate cortex activated strongly in both emotional conditions which may be attributed to the cognitive processing demands of responding to complex social evaluation. Region of interest analysis for basic emotion processing areas revealed enhanced amygdala activation in both emotional conditions, whereas anterior and posterior insula showed stronger activity during negative evaluations only. Individuals with high fear of positive evaluation were characterized by increased posterior insula activity during positive videos, suggesting heightened interoception. Taken together, these results replicate and extend studies that used facial expression stimuli and reveal neurobiological systems involved in processing of more complex social-evaluative videos. Results also point to vulnerability factors for social-interaction related psychopathologies.

Neural activity during traumatic film viewing is linked to endogenous estradiol and hormonal contraception

Women are at higher risk for Posttraumatic Stress Disorder (PTSD) and recent research has highlighted a modulating role of female sex hormones for cognitive and emotional processes potentially underlying PTSD symptoms. However, studies combining fMRI recordings of brain activity during trauma film viewing with assessment of female sex hormones are missing. The trauma film paradigm - a widely used experimental analogue for trauma exposure - confronts healthy participants with traumatic film clips and thus allows studying peritraumatic processing under laboratory conditions. Following this paradigm, the current fMRI study examined the role of endogenous estradiol and synthetic sex hormones for the neural processing of traumatic (i.e., depicting interpersonal violence) vs. neutral films in 53 healthy women (mean age 22.3 years; 23 using hormonal contraception, HC). As predicted, traumatic films strongly activated areas of the fear processing network, such as amygdala, insula, and dorsal anterior cingulate cortex. Estradiol levels in women not using HC were positively correlated with ventromedial prefrontal activity. Furthermore, women using HC as compared to women without HC demonstrated heightened insula and dorsal anterior cingulate cortex activity during traumatic film viewing. These experimental results highlight the effects of both gonadal hormone status and HC intake on peritraumatic processing in neural regions relevant for emotion generation and regulation that have been found to be abnormal in PTSD.

Suppressing images of desire: Neural correlates of chocolate-related thoughts in high and low trait chocolate cravers

Chocolate is the most often craved food in Western societies and many individuals try to resist its temptation due to weight concerns. Suppressing chocolate-related thoughts might, however, lead to paradoxical enhancements of these thoughts and this effect might be more pronounced in individuals with frequent chocolate cravings. In the current study, neural and cognitive correlates of chocolate thought suppression were investigated as a function of trait chocolate craving. Specifically, 20 high and 20 low trait chocolate cravers followed suppression vs. free thinking instructions after being exposed to chocolate and neutral images. Enhanced cue reactivity was evident in high trait chocolate cravers in that they reported more chocolate-related thoughts selectively after chocolate images compared to their low trait craving counterparts. This cue reactivity was mirrored neurally by higher activation in the ventral and dorsal striatum, demonstrating enhanced reward system activity. Unexpectedly, high trait chocolate cravers successfully reduced their elevated chocolate thoughts in the suppression condition. This lends support for the use of thought suppression as a means of regulating unwanted thoughts, cravings and imagery. Whether this thought manipulation is able to curb the elevated cue reactivity and the underlying reward sensitivity in chocolate cravers in applied settings remains to be shown.