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.
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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
OTHER
Masking
SINGLE
Enrollment
19
Brain Stimulation Laboratory, Institute of Psychiatry
Charleston, South Carolina, United States
Food Cravings
Twenty-four images of food were presented in random order using a custom developed computer program. While viewing the food images, participants used a computerized visual analog scale to rate how much they would like to eat each food right now if it were actually available to them, how much they liked the food, and how much would they be able to resist tasting the food if it were in front of them. They viewed the pictures and rated before treatment and after real tDCS and Sham tDCS. The scale ranged from 0 (no food cravings) to 100 (extreme food cravings). The before treatment after treatment food craving ratings were used to calculate percent change.
Time frame: before treatment, after treatment
Cravings for Sweet Foods
Twenty-four images of food were presented in random order using a custom developed computer program. While viewing the food images, participants used a computerized visual analog scale to rate how much they would like to eat each food right now if it were actually available to them, how much they liked the food, and how much would they be able to resist tasting the food if it were in front of them. They viewed the pictures and rated before treatment and after real tDCS and Sham tDCS. The scale ranged from 0 (no sweet food cravings) to 100 (extreme sweet food cravings). The before treatment after treatment ratings for sweet food craving were used to calculate percent change.
Time frame: before treatment, after treatment
Cravings for Carbohydrate Foods
Twenty-four images of food were presented in random order using a custom developed computer program. While viewing the food images, participants used a computerized visual analog scale to rate how much they would like to eat each food right now if it were actually available to them, how much they liked the food, and how much would they be able to resist tasting the food if it were in front of them. They viewed the pictures and rated before treatment, during, and after real tDCS and Sham tDCS. The scale ranged from 0 (no food cravings) to 100 (extreme food cravings). The before treatment, during treatment, and after treatment ratings for carbohydrates were used to calculate percent change.
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Time frame: before treatment, during treatment, after treatment
Inability to Resist Food and tDCS Condition
Twenty-four images of food were presented in random order using a custom developed computer program. While viewing the food images, participants used a computerized visual analog scale to rate how much they would like to eat each food right now if it were actually available to them, how much they liked the food, and how much would they be able to resist tasting the food if it were in front of them. They viewed the pictures and rated before, during, and after real tDCS and Sham tDCS. The scale ranged from 0 (no food cravings, completely resist food) to 100 (extreme food cravings, unable to resist food). The before treatment, during treatment, and after treatment resist ratings for carbohydrates were used to calculate percent change.
Time frame: before treatment, during treatment, after treatment
Food Ingested and tDCS Condition
Food was presented on a plate for the participants to eat after treatment. Each participant received a Chocolate Plate, Donut Plate, Cookie Plate, and a Potatoe Chip Plate. Each participant received the same amount of food on each plate. Each plate was weighed in grams separately before and after eating the food. A difference score was calculated to determine how much food was eaten for each type of food. The mean difference score was calculated for each type of food for the Sham tDCS group \& the Real tDCS group. The means and standard deviations of percent change in the decrease of food (weighed in grams) ingested post-tDCS treatment are reported below for the real tDCS group and the sham tDCS group.
Time frame: After treatment
Confidence Ratings in Guessing of Treatment Condition
At the end of the participants' second appointment, they were asked to guess which tDCS session was real and which was sham. 0=completely guessing. 10=absolutely sure. We calculated how many participants correctly guessed when they received real and when they received sham. A composite index was created to control for correct-guessing in the mixed model analysis. A new variable was created wherein the "guess correct" value (0=incorrect guess, 1=correct guess) was multiplied by the guess confidence rating for each participant. Thus, those that guess incorrectly had a guess-composite value of 0 whereas those that guessed correctly had a value equal to their guess confidence.
Time frame: After treatment