The Effectiveness of Transcranial Direct Current Stimulation (tDCS) in Decreasing Food Cravings

Recently, the use of low amplitude direct current stimulation of the human cortex has received attention as a possible for treatment for depression and pain (Been et al, 2007). This technique (called transcranial direct current stimulation or tDCS) involves the placement of two sponge electrodes over separate areas of the scalp. tDCS has been shown to be capable of changing the excitability of the superficial neurons immediately beneath the sponge electrodes. Evidence suggests that anodal stimulation is associated with increased cortical excitability and cathodal stimulation is associated with decreased cortical excitability (Been et al, 2007).

Brain imaging studies are beginning to elucidate the functional neuroanatomy of cravings (George, Anton, Bloomer, Teneback, Drobes, Lorberbaum, et al., 2001; Myrick, Anton, Li, Henderson, Drobes, Voronin, et al., 2004). While the role of the prefrontal cortex in regulating cravings remains somewhat unclear, frontal cortical areas appear to be involved in integrating incoming sensory information (such as sights, smells, and sounds) with affective/emotional information in the brain, and may be involved in regulating emotional reactions to various stimuli (Alexander, DeLong, \& Strick, 1986; Lorenz, Minoshima, \& Casey, 2003). The dorsal lateral prefrontal cortex may become activated when an individual is presented with cues that trigger reward memories associated with certain consumptive behaviors (Anton, 1999). One fMRI study found that when alcoholic subjects were presented with alcohol related cues, there was greater activation in the left prefrontal cortex and anterior thalamus, compared to when they viewed non-alcohol cues (George et al., 2001). Other studies on bulimia and drug cravings have identified hyperactivity in the orbitofrontal cortex and anterior cingulate cortex associated with increases in cravings ratings (Goldstein \& Volkow, 2002; Uher, et al., 2004).

Very few studies have attempted to directly manipulate activation of brain structures that might be involved in cravings. tDCS allows researchers to selectively activate or inhibit different brain structures that might play a role in craving behaviors. Previous research with manipulating the activation of brain structures found that alcohol cravings decreased among individuals with alcohol dependence who received either left or right anodal stimulation of the dorsolateral prefrontal cortex (Boggio et al., 2008). This finding, combined with prior functional neuroanatomical work, and research on the relation of food cravings and nicotine cravings suggesting they share a common biologic mechanism (Pepino, Finkbiener, Menella 2009, 2007), suggests that the prefrontal cortex may be a reasonable preliminary tDCS cortical target for potentially inhibiting food cravings.

To date, there has only been one published study examining the relationship between tDCS and food craving. Fregni and colleagues (2008) found cravings to be reduced by anode right/cathode left tDCS and cravings did not increase after anode left/cathode right tDCS. The evidence on the effectiveness of tDCS for decreasing food craving indicates relatively short-lived effects (lasting only a few weeks). While this may ultimately limit the utility of tDCS, it may have a place in the prevention and management of obesity.

This study aims to evaluate the effectiveness of transcranial direct current stimulation (tDCS) in decreasing food cravings. Specifically, this study will determine whether healthy subjects will report decreased food craving following a single 20-minute session of tDCS (compared to sham tDCS) delivered during and immediately following the exposure to food stimuli.