Elsevier

Appetite

Volume 51, Issue 1, July 2008, Pages 34-41
Appetite

Transcranial direct current stimulation of the prefrontal cortex modulates the desire for specific foods

https://doi.org/10.1016/j.appet.2007.09.016Get rights and content

Abstract

We aimed to assess whether modulation of the dorsolateral prefrontal cortex (DLFPC) with noninvasive brain stimulation, namely transcranial direct current stimulation (tDCS), modifies food craving in healthy subjects. We performed a randomized sham-controlled cross-over study in which 23 subjects received sham and active tDCS (anode left/cathode right and anode right/cathode left) of the DLPFC. Subjects were exposed to food and also watched a movie of food associated with strong craving. Desire for food consumption was evaluated by visual analogue scales (VAS) and food consumption before and after treatment. In addition we measured visual attention to food using an eye tracking system. Craving for viewed foods as indexed by VAS was reduced by anode right/cathode left tDCS. After sham stimulation, exposure to real food or food-related movie increased craving; whereas after anode left/cathode right tDCS, the food-related stimuli did not increase craving levels, as revealed by the VAS scale. Moreover, compared with sham stimulation, subjects fixated food-related pictures less frequently after anode right/cathode left tDCS and consumed less food after both active stimulation conditions. These changes were not related to mood changes after any type of tDCS treatment. The effects of tDCS on food craving might be related to a modulation of neural circuits associated with reward and decision-making.

Introduction

Increasing evidence suggests that the control of eating origins in neural networks associated with decision-making (Pignatti et al., 2006). Although several factors influence the decision of food consumption, such as levels of blood sugar, hormonal changes, food availability, emotional state (including anxiety and depression), physical activity, memory, this information is finally processed in the neural networks associated with decision-making such as the prefrontal cortex, resulting in a final action. Therefore one possible approach to regulate food craving might be to interfere with this decision-making process by changing the activity of the dorsolateral prefrontal cortex (DLPFC).

Several studies from our and other groups have already shown that the prefrontal cortex modulates drug craving and decision-making. For instance, noninvasive brain stimulation, namely repetitive transcranial magnetic stimulation (rTMS), of the DLPFC significantly reduces smoking (Eichhammer et al., 2003, Fregni et al., in press), cocaine (Camprodon, Martinez-Raga, Alonso-Alonso, Shih, & Pascual-Leone, 2007) and alcohol (Boggio et al., 2008) craving. Indeed, one of the most important areas participating in the cue-associated anticipation and planning of drug use involves DLPFC, an area involved in planning and memory (Wilson, Sayette, & Fiez, 2004). For food craving, it was shown that high-frequency (10 Hz) rTMS of the left dorsolateral prefrontal cortex decreases food craving in women with frequent cravings for food. Specifically, the results of this study demonstrated that food craving during exposure to foods remained constant in the active treatment group but increased in the sham treatment group (Uher et al., 2005) after exposure to real food. Finally, we showed that stimulation of the dorsolateral prefrontal cortex is associated with decreased risk-taking in the BART task (Fecteau et al., 2007a). Indeed it has been shown that craving (particularly for cocaine) is associated with specific sensations similar to those of individuals engaged in risky behavior (Goeders, 2002).

In the present study, we tested whether modulation of prefrontal cortex with another technique of noninvasive brain stimulation, transcranial direct current stimulation (tDCS), modulates food craving-related behavior. We chose this technique because it modulates brain activity significantly in a safe, powerful and painless way and its effects can last for more than an hour (Nitsche et al., 2003, Nitsche and Paulus, 2000, Nitsche and Paulus, 2001). It is a technically simple tool in which a continuous weak electric current is applied to the brain via large electrodes that are placed on the scalp of the subject. The effects of tDCS depend on the direction of the electric current, anodal stimulation increases brain activity and excitability and cathodal stimulation reduces it (Nitsche et al., 2003, Antal et al., 2001). Several well-conducted studies in animals and humans confirmed the behavioral and neurophysiological effects of tDCS (Bindman, Lippold, & Redfearn, 1964; Nitsche et al., 2003, Purpura and McMurtry, 1965). In fact, in humans, it has been shown that: anodal stimulation increases cortical excitability in the motor and visual cortex and cathodal stimulation decreases it (Nitsche & Paulus, 2000, 2001). Furthermore the effects of 13 min of tDCS on cortical excitability can last up to 90 min after the end of the stimulation (Nitsche & Paulus, 2001), most probably due to changes of NMDA receptor-efficacy (Nitsche et al., 2003). TDCS, as used in current protocols, is safe in humans as shown by neuropsychological testing (Fregni, Boggio, Lima et al., 2006; Iyer et al., 2005), EEG assessment (Iyer et al., 2005), a neuroimaging study (Nitsche et al., 2004) and brain metabolites evaluation (Nitsche & Paulus, 2001). Finally, recent modeling studies have shown that the amount of electric current going to the brain is large enough to induce a modulation of brain activity (Miranda, Lomarev, & Hallett, 2006; Wagner et al., 2007).

In this study, we tested the hypothesis that bilateral stimulation of prefrontal cortex with tDCS is suited to reduce food craving. Therefore a placebo-tDCS-controlled, randomized, double-blind, crossover study was performed.

Section snippets

Study subjects

Subjects were recruited by local advertising in websites, flyers and notices distributed throughout local universities. We used the same inclusion criteria as the study of Uher et al. (2005): subjects had frequent (≥3 times/day) and strong urges to eat one of the foods we chose for our experiment (see the list). We included healthy subjects aged between 18 and 55 years. Subjects were excluded if they had any neuropsychiatric disorder, current or past history of alcohol or other drugs abuse, were

Results

Subjects tolerated tDCS well. The adverse effects were mild and similar in the three conditions of stimulation (Table 1 lists the adverse effects). The most frequent adverse effects were scalp burning, headache, local itching, burning sensation and somnolence. They were not significantly different across the three conditions of stimulation (p = 0.98).

Discussion

The results of our study demonstrate that active anode right/cathode left DLPFC stimulation reduced food craving significantly. After sham stimulation, craving was significantly increased by presentation of food-related cues, whereas after anode left/cathode right tDCS, craving levels did not change. These results suggest that both active tDCS conditions had an effect in reducing food craving. Moreover, subjects consumed a smaller amount of food after both active stimulation conditions and,

Conclusion

In conclusion, our study demonstrates that anodal tDCS of the DLPFC can suppress food craving. This finding extends the results of a previous study using rTMS to inhibit craving as it suggests that excitability enhancing strategies of brain stimulation of the right hemisphere might be more effective to reduce food craving and therefore opens an avenue for the exploration of noninvasive brain stimulation for eating disorders.

Acknowledgements

This work was supported by a grant from the Harvard Medical School Scholars in Clinical Science Program (NIH K30 HL04095) to F.F. The authors are thankful to MackPesquisa (Sao Paulo, Brazil) that supported part of this study. The authors are thankful to Barbara Bonnetti for the administrative support.

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