Anodal stimulation of inhibitory control and craving in satiated restrained eaters

Modality Matters: Fasted Individuals Inhibit Food Stimuli Better Than Neutral Stimuli for Words, but Not for Pictures

The current study aimed to evaluate the effect different modalities (pictures and words) of food stimuli have on inhibitory control under different homeostatic states. To this end, the homeostatic state was altered by asking participants to fast for 16 h (n = 67) or eat lunch as usual (n = 76) before completing an online stop-signal task with modal (pictures) and amodal (words) food and valenced-matched non-food stimuli. The inclusion of non-food stimuli allowed us to test the food specificity of the effect. We found a significant Group × Modality × Stimulus Type interaction (F(1,141) = 5.29, p = 0.023, ηp2 = 0.036): fasted individuals had similar inhibitory capacity for modal and amodal food stimuli but better inhibitory capacity for non-food words compared to images, while there were no inhibitory differences in dependence on either modality or stimulus type in satiated individuals. Thus, we were able to show that inhibitory capacities to modal compared to amodal stimuli depend on participants' current state of fasting. Future studies should focus on how this lowered inhibitory capacity influences food intake, as well as the role of stimulus valence in cognitive processing, to clarify potential implications for dieting and weight loss training.

Regional specificity of cathodal transcranial direct current stimulation effects on spatial-numerical associations: Comparison of four stimulation sites

Neuromodulation with transcranial direct current stimulation (tDCS) is an increasingly popular research tool to experimentally manipulate cortical areas and probe their causal involvements in behavior, but its replicability and regional specificity are not clear. This registered report investigated cathodal tDCS effects on spatial-numerical associations (i.e., the SNARC effect), the numerical distance effect (NDE), and inhibitory control (i.e., stop-signal reaction time; SSRT). Healthy adults (N = 160) were randomly assigned to one of five groups to receive sham tDCS or 1 mA cathodal tDCS to one of four stimulation sites (left/right prefrontal cortex [PFC], left/right posterior parietal cortex) with extracephalic return. We replicated that cathodal tDCS over the left PFC reduced the SNARC effect compared to sham tDCS and to tDCS over the left parietal cortex. However, neither NDE nor SSRT were modulated in the main analyses. Post hoc contrasts and exploratory analyses showed that cathodal tDCS over the right PFC had a time-dependent effect by delayed practice-related improvements in SSRT. Math anxiety moderated changes in the NDE in the groups receiving tDCS to the right parietal cortex. With few exceptions, the replicability and regional specificity of tDCS effects on behavior were weak and partially moderated by individual differences. Future research needs to characterize the parameter settings for effective neuromodulation.

Practice makes perfect: Restrained eaters' heightened control for food images

OBJECTIVE

Restrained eaters (RE) show behaviourally unregulated food intake, which is often explained by a deficit in inhibitory control. Despite evidence for general inhibitory deficits in RE, it remains unclear how the variety of (food) cues in our environment can influence cognitive control.

METHOD

In this re-analysis, we explored the inhibitory capacity of RE and unrestrained eaters (URE) on a stop-signal task with modal (pictures) and amodal (word) food and non-food stimuli.

RESULTS

Although we did not find the expected inhibitory deficits in RE compared to URE, we found a significant Group × Modality × Stimulus Type interaction. This indicated that RE have relatively good inhibitory control for food, compared to non-food modal cues, and that this relationship is reversed for amodal cues.

CONCLUSIONS

Hence, we showed differential processing of information based on food-specificity and presentation format in RE. The format of food cues is thus an important new avenue to understand how the food environment impedes those struggling with regulating their eating behaviour.

No effect of prefrontal transcranial direct current stimulation (tDCS) on food craving, food reward and subjective appetite in females displaying mild-to-moderate binge-type behaviour

Previous work suggests there may be an effect of transcranial direct current stimulation (tDCS) on appetite control in people at risk of overconsumption, however findings are inconsistent. This study aimed to further understand the potential eating behaviour trait-dependent effect of tDCS, specifically in those with binge-type behaviour. Seventeen females (23 ± 7 years, 25.4 ± 3.8 kg m-2) with mild-to-moderate binge eating behaviour completed two sessions of double-blind, randomised and counterbalanced anodal and sham tDCS applied over the right dorsolateral prefrontal cortex at 2.0 mA for 20 min. Subjective appetite visual analogue scales (VAS), the Food Craving Questionnaire-State (FCQ-S), and Leeds Food Preference Questionnaire (LFPQ) were completed pre- and post-tDCS. Participants then consumed a fixed-energy meal, followed by the VAS, FCQ-S and LFPQ. No difference between pre- and post-tDCS scores were found across fullness (p = 0.275, BF10 = 0.040), prospective consumption (p = 0.127, BF10 = 0.063), desire to eat (p = 0.247, BF10 = 0.054) or FCQ-S measures (p = 0.918, BF10 = 0.040) when comparing active and sham protocols. Only explicit liking and wanting for high-fat sweet foods were significantly different between conditions, with increased scores following active tDCS. When controlling for baseline hunger, the significant differences were removed (p = 0.138 to 0.161, BF10 = 0.810 to 1.074). The present data does not support the eating behaviour trait dependency of tDCS in a specific cohort of female participants with mild-to-moderate binge eating scores, and results align with those from individuals with healthy trait scores. This suggests participants with sub-clinical binge eating behaviour do not respond to tDCS. Future work should further explore effects in clinical and sub-clinical populations displaying susceptibility to overconsumption and weight gain.

Playing with temptation: Stopping abilities to chocolate are superior, but also more extensive

Cue-specific inhibitory control is assumed to support balanced food intake, but previous studies with established measures showed inconsistent results. We developed a novel kinematic stop task in virtual reality (VR) and report results from trajectory recordings. The primary objective of this explorative study was to assess the interrelationships between validated measures of food-related inhibitory control and novel measures from the VR task. We hypothesized that healthy female participants show worse inhibitory control when grasping attractive virtual chocolate, compared to non-edible color-and-shape matched objects. We further aimed to quantify the construct validity of kinematic measures (e.g., reaching extent/spatial displacement, movement time after stop-signal, velocity) with established measures of inhibitory control in a keyboard-based adaptive stop-signal task (SST). In total, 79 females with varying levels of chocolate craving participated in an experimental study consisting of self-report questionnaires, subjective chocolate craving, the conventional SST and the kinematic task in VR. Results showed superior stopping ability to chocolate in both tasks. In VR, participants successfully interrupted an initiated approach trajectory but terminated slightly closer to chocolate targets. Stop-signal delay (SSD) was adapted relative to movement onset and appeared later in chocolate trials, during which participants still stopped faster, as was also confirmed by shorter stop-signal reaction time (SSRT) in the conventional task. Yet, SSRT did not correlate with stopping in VR. Moreover, SSRT was related to depressive symptoms whereas measures from VR were related to chocolate craving and subjective hunger. Thus, VR stopping can provide deeper insights into healthy weight individuals' capacity to inhibit cue-specific approach behavior towards appetitive stimuli in simulated interactions. Furthermore, the results support a multi-faceted view of food-specific inhibitory control and behavioral impulsivity.