Prefrontal cortex transcranial direct current stimulation (tDCS) temporarily reduces food cravings and increases the self-reported ability to resist food in adults with frequent food craving

This study examined whether a 20-min session of prefrontal transcranial direct current stimulation (tDCS) (anode over the right prefrontal cortex and cathode over the left prefrontal cortex) would reduce food cravings and increase the self-reported ability to resist foods in 19 healthy individuals who reported frequent food cravings. Participants viewed computerized images of food and used computerized visual analogue scales to rate food cravings and inability to resist foods before, during, and after receiving either real or sham tDCS. This study employed a randomized within-subject crossover design; participants received both real and sham tDCS and were blind to the condition. Food cravings ratings were reduced in both conditions, however, the percent change in cravings ratings from pre- to post-stimulation was significantly greater for real stimulation than for sham. The percent change in inability to resist food from pre- to post-stimulation also showed a greater decrease in the real condition than for sham. Post hoc analyses suggest that active prefrontal tDCS acutely and significantly decreased food cravings ratings for sweet foods and carbohydrates more so than sham tDCS. No significant differences were seen in the amount of food ingested between real and sham tDCS. These findings in healthy subjects indicate that tDCS is able to temporarily reduce food cravings and improve the self-reported ability to resist foods.     

Prefrontal cortex transcranial direct current stimulation associated with aerobic exercise change aspects of appetite sensation in overweight adults

This study investigated whether transcranial direct current stimulation (tDCS) on dorsolateral prefrontal cortex (DLPFC) isolated or combined with aerobic exercise influenced the desire to eat, hunger, and satiety in overweight subjects. Nine volunteers underwent anodal or sham tDCS (2 mA; 20 min) over DLPFC and isocaloric exercise bouts (70%VO₂R; ∼200 kcal). The appetite sensations were evaluated by visual analogue scales at four moments: I - Baseline; II - After tDCS; III - Post-Exercise and IV - 30-min Post-Exercise. The tDCS on left DLPFC decreased the desire to eat at baseline (tDCS −26% vs. −14% Sham). The tDCS associated with exercise had greater suppressing effect in desire to eat compared to either tDCS or exercise alone (tDCS −39% vs. −27% Sham). Moreover, the tDCS associated with exercise decreased hunger (tDCS −48% vs. 36% Sham) and increased satiety (tDCS 28% vs. 7% Sham) immediately after exercise. The post-exercise 30-min recovery elicited an overall increase in appetite. However the increase in desire to eat and hunger after recovery was lower after tDCS (29% and 13%, respectively) compared to sham stimulation (77% and 113%, respectively). These findings in overweight subjects indicate that the combination of tDCS over DLPFC and aerobic exercise induced greater decrease in appetite sensations compared to anodal tDCS or exercise alone.     

Impact of Psychosocial Occupational Therapy Combined with Anodal Transcranial Direct Current Stimulation to the Left Dorsolateral Prefrontal Cortex on the Cognitive Performance of Patients with Schizophrenia: A Randomized Controlled Trial

BackgroundThe most common cognitive dysfunctions in patients with schizophrenia are information processing, memory, and learning. Based on the hypothesis of rehabilitation and brain stimulation in memory and learning, adding a form of neuromodulation to conventional rehabilitation might increase the effectiveness of treatments.AimsTo explore the effects of psychosocial occupational therapy combined with anodal Transcranial Direct Current Stimulation (tDCS) on cognitive performance in patients with Schizophrenia.MethodsTwenty-four patients diagnosed with schizophrenia were randomized into the experimental and control groups. We used The Cambridge Neuropsychological Test Automated Battery (CANTAB) and the Loewenstein Occupational Therapy Cognitive Assessment battery (LOTCA) to assess spatial recognition, attention, visual memory, learning abilities, and high-level cognitive functions like problem-solving. All participants received customized psychosocial occupational therapy activities. Furthermore, the experimental group received 12 sessions of active anodal tDCS for 20 minutes with 2 mA intensity on the left dorsolateral prefrontal cortex (DLPFC) while the patients in the sham group received sham tDCS.ResultsCombining tDCS to conventional psychosocial occupational therapy resulted in a significant increase in spatial memory, visual learning, and attention.ConclusionsAnodal tDCS on the left DLPFC improved visual memory, attention, and learning abilities. Contrary to our expectations, we could not find any changes in complex and more demanding cognitive functions.     

Reduction of food cravings through concurrent visuospatial processing

OBJECTIVE: Two experiments adopted a working memory approach to evaluate the effectiveness of visuospatial tasks as a technique for reducing food cravings. METHOD: Dieting and non-dieting women were asked to form images of both food-related and nonfood items, induced by either pictures (Experiment 1) or verbal cues (Experiment 2). They were required to concurrently perform one of three tasks that load on the visuospatial sketch pad of working memory: saccadic eye movements, dynamic visual noise, or spatial tapping. RESULTS: In support of the working memory model of limited visuospatial capacity, concurrent visuospatial activity reduced the vividness of food-related images which, in turn, reduced the intensity of the associated craving. The same pattern of results was observed across dieters and non-dieters and for all stimulus types. DISCUSSION: Visuospatial tasks may provide a useful technique for the treatment of food craving episodes in both nonclinical and clinical populations.     

Food-related Stroop interference in obese and normal-weight individuals: Behavioral and electrophysiological indices

The primary objective of the present study was to investigate differences in the attentional processing of food-related words in a Stroop task, as assessed by means of behavioral (reaction times) and electrophysiological (P200 and P300 amplitudes) indices, between obese and normal-weight individuals. Results revealed a P200 bias to food-related words in obese participants, which was not seen in normal-weight participants. This indicates that, in an early, automatic stage of information processing, obese participants already tend to engage more attention towards food-related stimuli than to neutral stimuli. With respect to reaction times and P300 scores, as alleged indices of more conscious maintained attention, a general food-related bias was observed, with no between-group differences. Further, in the obese group, significant positive correlations were observed between the food-related reaction time bias, food craving, and external eating, whereas in the normal-weight group, food craving scores correlated positively with P200/P300 amplitude biases. It can be concluded that obese individuals display an enhanced automatic, preconscious attentional processing of food-related stimuli, and this can be regarded as an initial expression of a greater responsiveness to food cues. In the current food-abundant environment, such a heightened food cue-responsiveness might contribute substantially to the tendency to overeat.     

Too tempting to resist? Past success at weight control rather than dietary restraint determines exposure-induced disinhibited eating

As the prevalence of obesity is increasing, many people resort to dieting to achieve a healthy body weight. Such dietary restraint has been suggested to cause counterproductive effects leading to disinhibited eating. However, it is more likely that dietary restraint is a by-product of previous difficulties in weight control and disinhibited eating. If so, disinhibition should be related more strongly to unsuccessful weight control than dietary restraint. This possibility was examined in the present study. Participants were exposed to palatable food or to neutral objects. Before and after exposure, we measured craving, general inhibitory control and inhibition of food-related responses with the Stop-Signal Task (SST), and food consumption during a taste test. Results showed that exposure increased craving in both successful and unsuccessful weight regulators. People who were successful at controlling their weight, however, were better able to regulate this temptation compared to unsuccessful weight regulators: while exposure to palatable food reduced inhibitory control over food-related responses and increased food consumption in unsuccessful weight regulators, successful weight regulators did not show such disinhibition. Dietary restraint did not influence any of these findings. Further, the exposure-induced difference in inhibition between successful and unsuccessful weight regulators was specific for food-related responses, as regulatory success did not influence general inhibitory control. Thus, while successful and unsuccessful weight regulators seem equally tempted by palatable food, those who are successful in controlling their weight seem better able to resist these temptations by exerting inhibitory control over appetitive responses toward palatable food.     

Quantifying clinical improvements in patients with depression under the treatment of transcranial direct current stimulation using event related potentials

The main goal of this study was to assess the changes in brain activities of patients with severe depression by applying transcranial direct current stimulation (tDCS) using event related potentials (ERPs). Seven patients (four males, with the mean age 34.85?±?4.25) were asked to fill out Beck’s depression questionnaires. EEG signals of subjects were recorded during Stroop test. This test entailed 360 stimulations, which included 120 congruent, 120 incongruent, and 120 neutral stimulations lasting for 12 min. Subsequently, the dorso lateral prefrontal cortex in patients’ left hemisphere was stimulated for six sessions using tDCS. At the end of tDCS treatment period, subjects filled out Beck’s depression questionnaires again and EEG signal recordings were repeated simultaneously with Stroop test. Wavelet coefficients of EEG frequency bands in every stimulation type were extracted from ERP components. The changes in Beck score before and after tDCS were estimated using neural network model. The ERP results showed that the latency period of N400 component after applying tDCS decreased significantly. Moreover, a significant correlation was observed between percentage changes of congruent and incongruent accuracy and the increase in the average energy of wavelet coefficients in alpha band in Pz electrode with p?=?0.0128, r?=?0.9060 and p?=?0.0037, r?=?0.95, respectively. Additionally, the results of neural network model revealed that the changes in Beck score were estimated with an average error of 0.0519. Consequently, the improvement of depressed patients treated with tDCS could be estimated with good accuracy using average energy of wavelet coefficients in alpha band.     

Human cortical specialization for food: a functional magnetic resonance imaging investigation

Although specialized cortical pathways that process specific sensory stimuli and/or execute cognitive functions have been identified, the neuro-specificity for food-related stimuli has not been clearly demonstrated. We employed functional magnetic resonance imaging (fMRI) to compare neural systems associated with the appreciation of foods and nonfoods. Healthy, normal weight, right-handed men and women (n = 12; age 29.8 +/- 1.8 y, BMI 21.8 +/- 0.8 kg/m(2)) were imaged by fMRI while fasting. Real food and nonfood items were presented to subjects both visually and tactilely, during scanning. Subjects were instructed to pay attention to the items. A randomized 2 x 2 block design consisted of 4 conditions: visual food, visual nonfood, tactile food, and tactile nonfood. Brain regions that were significantly activated to a greater extent during the presentation of foods compared with nonfood items included the anterior cingulate, superior temporal gyrus, parahippocampal gyrus, hippocampus, and the insula. These findings support the claim that the presence of food (either seen or felt) elicits a unique cortical response that is differentiated from nonfood items. This neural substrate specialized for processing of foods informs models of food-related behavior.     

Effects of overfeeding on the neuronal response to visual food cues

BACKGROUND: The regulation of energy intake is a complex process involving the integration of homeostatic signals and both internal and external sensory inputs. Environmental visual cues are one of the first and primary inputs signaling the potential availability of food. OBJECTIVE: We examined the effects of short-term overfeeding on the neuronal responses to food-related visual stimuli in thin individuals. DESIGN: Twenty-five thin individuals (13 women, 12 men) were studied. Functional magnetic resonance imaging (fMRI) was performed after 2 days of eucaloric energy intake and after 2 days of 30% overfeeding in a counterbalanced design. fMRI was performed while the subjects were presented with visual stimuli in 3 different categories: neutral control objects, foods of neutral hedonic value, and foods of high hedonic value. Measures of appetite were obtained by using visual analogue scales before and after meals. RESULTS: In the eucaloric state, pictures of foods of high hedonic value elicited greater activation of neuronal regions than did neutrally rated foods, which is consistent with visual processing and attention (inferior temporal visual cortex, posterior parietal cortex, premotor cortex, and hippocampus) and with activation of the hypothalamus. Two days of overfeeding led to significant attenuation of these responses. Overfeeding also resulted in reduced hunger ratings and increased satiety ratings. CONCLUSION: These findings emphasize the important role of external food-related visual cues and suggest that there are interactions between external visual sensory inputs, energy balance status, and brain regions important in the homeostatic regulation of energy intake.     

Food cue-elicited brain potentials in obese and healthy-weight individuals

The main objective of this study was to investigate, by means of event-related potentials (ERPs), whether obese individuals process food-related information differently as compared to normal-weight individuals. Because amplitudes of late positive ERP components (P3, LPP) reflect motivational tendencies, obese participants were expected to display enlarged P3 and LPP amplitudes towards food pictures. Obese and normal-weight adults were exposed to pictures of food and control items, while EEG was recorded. Subjective levels of food craving and hunger were also assessed. While there were no differences in ERP amplitudes between obese and normal-weight individuals, significantly larger P3 and LPP amplitudes were elicited by pictures of food items as compared to control pictures. Positive correlations were found between P3 and LPP amplitudes and self-reported increases of hunger. It was concluded that food-related information is processed differently in the brain as compared to non-food-related information, in a manner that reflects the natural motivational value of food. In the present study, there was no indication of an electrophysiological or subjective hyper-reactivity to food cues in obese adults.     

The phenomenology of food cravings: the role of mental imagery

The study aimed to investigate the role of mental imagery in the experience of food cravings. A sample of 130 undergraduate students was first asked to recall and rate a previous food craving experience. Second, they were asked to imagine themselves eating their favourite food and to rate the involvement of different sensory modalities. It was found that mental imagery was a key element in both the retrospective craving experience and the current food induction. In particular, craving intensity was related to the vividness of the food image (r = .46). The specific sensory modalities most involved were visual (39.7%) and gustatory (30.6%), followed by olfactory (15.8%). There was little involvement of auditory or tactile modalities. It was concluded that cognitive experimental techniques aimed at reducing the vividness of visual, gustatory or olfactory imagery, might usefully be deployed to reduce unwanted food cravings.     

State of expectancy modulates the neural response to visual food stimuli in humans

Human brain imaging studies demonstrate distributed activation of limbic, paralimbic and sensory systems to food and food-associated cues. Activity in this circuit may be modulated by internal factors, such as hunger, and cognitive factors. Anticipation to eat is one such factor, which likely impacts consummatory behavior. Here, the neural substrates of food expectancy were identified in 10 healthy male participants who underwent two whole-brain functional Magnetic Resonance Imaging scans on separate days. Fasted subjects viewed images of food and scenery, in two counterbalanced states. During one condition, subjects were 'expecting' to eat right after the scan and during the other they were 'not expecting' to eat for 1 h after the scan. Food pictures compared with scenery yielded bilateral activation in visual areas as well as in the left insula and amygdala in both conditions. The left dorsolateral prefrontal cortex, hippocampus and putamen were additionally activated in the 'not expecting' condition while right orbitofrontal cortex activity was enhanced in the 'expecting' condition. These data suggest that cognitive manipulations affect the response to food cues in the prefrontal cortex, in areas involved in the planning and control of motivated behaviors, while the amygdala and insula responded equally in both conditions, consistent with a more basic role in homeostatically driven appetitive behavior.     

L-tryptophan does not affect food intake during recovery from depression

L-tryptophan administration did not affect food intake or premeal ratings of hunger, satiety, sweet craving, or starch craving, during test meals in 13 depressed inpatients before, and 2 weeks after beginning treatment with desipramine (DMI), or in nine age-matched normal subjects. Partial recovery from depression and/or treatment with DMI for 2 weeks were not associated with a significant change in body weight or food intake. The implications and limitations of these findings with respect to antidepressant-induced weight gain are discussed.     

Use of high-frequency repetitive transcranial magnetic stimulation to probe the neural circuitry of food choice in anorexia nervosa: A proof-of-concept study

Repetitive transcranial magnetic stimulation (rTMS) is used to modulate neural systems and provides the opportunity for experimental tests of hypotheses regarding mechanisms underlying anorexia nervosa (AN). The present pilot study has investigated whether high-frequency repetitive transcranial magnetic stimulation (HF-rTMS) to a region of the right dorsolateral prefrontal cortex (DLPFC) might be associated with change in food selection among adult inpatients with AN. Ten women received one session of sham and one session of HF-rTMS targeting the right DLPFC while completing a computerized Food Choice Task. Compared to sham, HF-rTMS was associated with changes in food ratings and food choice: inpatients reported higher healthiness ratings of low- and high-fat foods and selected a significantly greater proportion of high-fat foods over a neutrally rated reference item while receiving HF-rTMS. Findings suggest that HF-rTMS to the right DLPFC was associated with a reduction of fat avoidance on a food choice task among inpatients with AN and provide additional support for the possibility that this region, and related neural circuits, may underlie restrictive food choice. Research using rTMS to experimentally test neural mechanisms is needed to elucidate the underpinnings of AN and supports the development of novel treatment targets.     

Second meal effect: modified sham feeding does not provoke the release of stored triacylglycerol from a previous high-fat meal

The present study was carried out to determine whether cephalic stimulation, associated with eating a meal, was sufficient stimulus to provoke the release of stored triacylglycerol (TAG) from a previous high-fat meal. Ten subjects were studied on three separate occasions. Following a 12 h overnight fast, subjects were given a standard mixed test meal which contained 56 g fat. Blood samples were taken before the meal and for 5 h after the meal when the subjects were randomly allocated to receive either water (control) or were modified sham fed a low-fat (6 g fat) or moderate-fat (38 g fat) meal. Blood samples were collected for a further 3 h. Compared with the control, modified sham feeding a low- or moderate-fat meal did not provoke an early entry of TAG, analysed in either plasma or TAG-rich lipoprotein (TRL) fraction (density <1.006 kg/l). The TRL-retinyl ester data showed similar findings. A cephalic phase secretion of pancreatic polypeptide, without a significant increase in cholecystokinin levels, was observed on modified sham feeding. Although these data indicate that modified sham feeding was carried out successfully, analysis of the fat content of the expectorant showed that our subjects may have accidentally ingested a small amount of fat (0.7 g for the low-fat meal and 2.4 g for the moderate-fat meal). Nevertheless, an early TAG peak following modified sham feeding was not demonstrated in the present study, suggesting that significant ingestion of food, and not just oro-sensory stimulation, is necessary to provoke the release of any TAG stored from a previous meal.     

Relation between food intake and visual analogue scale ratings of appetite and other sensations in healthy older and young subjects

OBJECTIVE: Visual analogue scales are widely used in appetite research, yet the validity of these scales to evaluate appetite and mood has not been assessed in older subjects. The aim of this study was to determine the relations between food intake and visual analogue scale (VAS) ratings of appetite and nonappetite sensations in healthy older and young subjects. DESIGN: Retrospective combined analysis of four single-blind, randomised, controlled appetite studies. SETTING: All studies were conducted in the University of Adelaide, Department of Medicine, Adelaide, Australia. SUBJECTS: A total of 45 healthy young men (n=24) and women (n=21) aged 18-35 y and 45 healthy older men (n=24) and women (n=21) aged 65-85 y were recruited by advertisement. INTERVENTIONS: Oral, intraduodenal or intravenous administration of treatments which suppressed food intake were compared to control. Up to 90 min after treatment, a test meal was offered and subjects ate freely for between 30 and 60 min. Perceptions were assessed by 100-mm visual analogue scales administered at regular intervals. RESULTS: Food intake at the test meal was positively related to perceptions of hunger, drowsiness, and calmness at both baseline and premeal (r>0.16, P<0.05), and inversely related to premeal ratings of fullness (r> 0.2, P<0.05) in both older and young subjects. Food intake was related to VAS ratings at least as strongly, if not more so, in older as in young subjects. CONCLUSIONS: These observations (i) confirm that food intake is related to perceptions of hunger and fullness as assessed by VAS in healthy older and young subjects, and (ii) suggest that sensations, not obviously associated with appetite, including 'drowsiness' and 'calmness', are also associated with food intake.     

Brain substrates of craving to alcohol cues in subjects with alcohol use disorder

AIMS: This study's purpose was to identify the neural substrates and mechanisms responsible for craving among subjects with alcohol use disorders (AUDs) using functional magnetic resonance imaging (fMRI). METHODS: Alcohol abusers with AUD (n = 9) and demographically similar non-abusers (n = 9) participated in this study. After given 5 cc of alcohol, subjects were exposed to different types of stimuli [i.e. alcohol, non-alcoholic beverage, and visual control pictures and one rest (cross-hair)]. Craving levels were rated through self-report on a Likert scale immediately after the presentation of visual cues. RESULTS: Brain activations in the fusiform gyri, temporal gyri, parahippocampal gyrus, uncus, frontal gyri, and precuneus were correlated with the level of craving among subjects with AUD in response to alcohol cues. CONCLUSIONS: In conclusion, specific brain regions were identified that are associated with craving among subjects with AUD.     

The relationship between eating-related individual differences and visual attention to foods high in added fat and sugar

ObjectiveAttentional biases for food-related stimuli may be associated separately with obesity, disordered eating, and hunger. We tested an integrative model that simultaneously examines the association of body mass index (BMI), disordered eating and hunger with food-related visual attention to processed foods that differ in added fat/sugar level (e.g., sweets, candies, fried foods) relative to minimally processed foods (e.g., fruits, meats/nuts, vegetables) that are lower in fat/sugar content.MethodsOne-hundred overweight or obese women, ages 18–50, completed a food-related visual search task and measures associated with eating behavior. Height and weight were measured.ResultsHigher levels of hunger significantly predicted increased vigilance for sweets and candy and increased vigilance for fried foods at a trend level. Elevated hunger was associated significantly with decreased dwell time on fried foods and, at a trend level, with decreased dwell time on sweets. Higher BMIs emerged as a significant predictor of decreased vigilance for fried foods, but BMI was not related to dwell time. Disordered eating was unrelated to vigilance for or dwell time on unhealthy food types.ConclusionsThis pattern of findings suggests that low-level attentional biases may contribute to difficulties making healthier food choices in the current food environment and may point toward useful strategies to reduce excess food consumption.     

State and trait food craving in people with bulimic eating disorders

In two studies, we examined trait and state food craving levels in people with a bulimic disorder (BD) (bulimia nervosa and related disorders) and healthy controls (HC) using multidimensional self-report assessments. In study 1, trait food craving was assessed in 70 people with a BD and 69 HC using the Food Craving Questionnaire — Trait. Participants also completed the Eating Disorder Examination — Questionnaire (EDE-Q). In study 2, 45 people with a BD and 29 HC completed the Food Craving Questionnaire — State and the EDE-Q following exposure to visual and real high-caloric food cues. The results showed that both trait and state food cravings were significantly higher in people with a BD, compared to HC. Trait food craving was associated with eating disorder symptomatology in both the HC and BD groups. State food craving was associated with eating disorder psychopathology, but only in the BD group. This research underscores the importance of food craving in the study and conceptualization of BD.     

Cue-elicited craving for food: a fresh approach to the study of binge eating

Recent research has indicated that craving for food can be elicited by exposure to food cues, suggesting that exposure to food cues may represent a useful experimental paradigm to investigate mechanisms related to binge eating. The first objective of the present research was to replicate previous reports that exposure to food cues elicits craving for food. In addition, this investigation was designed to extend the extant literature by testing the effects of 'priming' portions of food, by examining the association between reactivity to food cues and indicators of binge eating, and to examine the role of a putative genetic factor previously found to be associated with cue-elicited craving for alcohol and tobacco. In Study 1, 48 individuals completed measures of craving and mood after exposure to control cues, after exposure to food cues, and after consuming each of three small portions of food. In Study 2, 31 individuals with subclinical symptoms of binge eating completed the same procedures. The results suggested that food cues reliably elicited craving, increased attention to the cues, and decreased positive affect in both samples, although reactivity was greater among the sample with greater eating pathology. Correlational analyses suggested that reactivity to food cues was correlated with binge eating and body mass index among women but not men. Results also suggest that the DRD4 VNTR polymorphism influences cue-elicited craving for food, although the influence of the DRD4 may depend on the population under study.