Dopaminergic and Non-Dopaminergic Value Systems in Conditioning and Outcome-Specific Revaluation

Animals are motivated to choose environmental options that can best satisfy current needs. To explain such choices, this paper introduces the MOTIVATOR (Matching Objects To Internal Values Triggers Option Revaluations) neural model. MOTIVATOR describes cognitiveemotional interactions between higher-order sensory cortices and an evaluative neuraxis composed of the hypothalamus, amygdala, and orbitofrontal cortex. Given a conditioned stimulus (CS), the model amygdala and lateral hypothalamus interact to calculate the expected current value of the subjective outcome that the CS predicts, constrained by the current state of deprivation or satiation. The amygdala relays the expected value information to orbitofrontal cells that receive inputs from anterior inferotemporal cells, and medial orbitofrontal cells that receive inputs from rhinal cortex. The activations of these orbitofrontal cells code the subjective values of objects. These values guide behavioral choices. The model basal ganglia detect errors in CS-specific predictions of the value and timing of rewards. Excitatory inputs from the pedunculopontine nucleus interact with timed inhibitory inputs from model striosomes in the ventral striatum to regulate dopamine burst and dip responses from cells in the substantia nigra pars compacta and ventral tegmental area. Learning in cortical and striatal regions is strongly modulated by dopamine. The model is used to address tasks that examine food-specific satiety, Pavlovian conditioning, reinforcer devaluation, and simultaneous visual discrimination. Model simulations successfully reproduce discharge dynamics of known cell types, including signals that predict saccadic reaction times and CS-dependent changes in systolic blood pressure.Defense Advanced Research Projects Agency and the Office of Naval Research (N00014-95-1-0409); National Institutes of Health (R29-DC02952, R01-DC007683); National Science Foundation (IIS-97-20333, SBE-0354378); Office of Naval Research (N00014-01-1-0624

Self-reported nutritional status, executive functions, and cognitive flexibility in adults

Objectives. The purpose of this study was to investigate the relationship between nutrition status, executive cognitive functions, and cognitive flexibility; and to analyze the role of gender, age, and nutrition status in the prediction of executive cognitive functions and cognitive flexibility in a sample of Iranian adults. Background. This study is based on the hierarchy of needs, health beliefs, developmental, cognitive and psychophysiological conceptualizations of nutrition and their plausible influences on human cognitive functions and cognitive flexibility. Materials and Methods. The randomly selected sample consisted of 200 adult participants (M=99 and F=101) from Eghlid City, the north of Fars province, Iran. A demographic questionnaire, the Nutrition Assessment Inventory (NAI), the Amsterdam Executive Function Inventory (AEFI), and the Cognitive Flexibility Scale (CFS) were used. Results. Findings showed significant positive relationships between healthy nutrition (diet-oriented nutrition and high fat foods subscales of Nutrition Assessment Inventory), the evaluation coping subscale, and the total score of Cognitive Flexibility Inventory. In addition, age and nutritional status had a significant impact with regards to predicting cognitive flexibility and executive cognitive functions. Conclusions. Given the significant positive relationship between nutrition status and cognitive flexibility, and the role of gender and nutrition status on executive cognitive functions and mental flexibility, this study may offer beneficial approaches for nutrition and cognitive health programs by clinicians and health education professionals

Working memory and food-related decision making

Dual-process theories argue that cognitive processes, and executive functions in particular, underpin controlled, goal-directed, decisions about food intake and choice. A considerable amount of research has been devoted to understanding the role of one executive function, inhibitory control, in appetite control. In addition, there has been interest in whether inhibitory control can be trained to improve dietary decisions. A systematic review and meta-analysis, however, casts doubt over the efficacy of training inhibitory control to change eating behaviour (Chapter 2). The importance of another executive function to eating behaviour, working memory, has been less well-studied. The aim of this thesis was to assess the role of working memory in food-related decision making in healthy volunteers and patients with type 2 diabetes. The results of Study 1 (Chapter 3) suggest that visuospatial working memory is important for decisions about the consumption of low energy dense foods and dieting success. The findings from Study 1 also provide support for the suggestion that dietary restraint has detrimental effects on central executive functioning. Study 2 (Chapters 4 and 5) found that working memory training can improve working memory and non-trained aspects of working memory in adults with type 2 diabetes. Transfer effects to eating behaviour were limited to those high in restraint (the higher the restraint the greater the reduction in saturated fat intake from pre-training to post-training). The results from Study 3 (Chapter 6) suggest that cognition (including one component of working memory) may be less important to food intake decisions in the context of other demographic, physical and psychological health factors. The importance of working memory to food intake decisions can be observed in controlled laboratory experiments. However, further research is needed to establish whether training working memory is a useful strategy to help bring about behaviour change to improve dietary choices

Allatostatin-A neurons inhibit feeding behavior in adult Drosophila

How the brain translates changes in internal metabolic state or perceived food quality into alterations in feeding behavior remains poorly understood. Studies in Drosophila larvae have yielded information about neuropeptides and circuits that promote feeding, but a peptidergic neuron subset whose activation inhibits feeding in adult flies, without promoting metabolic changes that mimic the state of satiety, has not been identified. Using genetically based manipulations of neuronal activity, we show that activation of neurons (or neuroendocrine cells) expressing the neuropeptide allatostatin A (AstA) inhibits or limits several starvation-induced changes in feeding behavior in adult Drosophila, including increased food intake and enhanced behavioral responsiveness to sugar. Importantly, these effects on feeding behavior are observed in the absence of any measurable effects on metabolism or energy reserves, suggesting that AstA neuron activation is likely a consequence, not a cause, of metabolic changes that induce the state of satiety. These data suggest that activation of AstA-expressing neurons promotes food aversion and/or exerts an inhibitory influence on the motivation to feed and implicate these neurons and their associated circuitry in the mechanisms that translate the state of satiety into alterations in feeding behavior

A Randomized Study of Food Pictures-Influenced Decision-Making Under Ambiguity in Individuals With Morbid Obesity

Background and Aims In addition to craving responses to salient food cues, the anticipation of short-term rewarding consumption of palatable food may overrun the anticipation of long-term negative consequences of obesity. The present investigation addressed the potential interplay of food cravings and decision-making abilities in individuals with obesity. Method Study 1 included 107 bariatric surgery candidates with class 2/3 obesity (OB-group) and study 2 included 54 individuals with normal weight/pre-obesity (nonOB-group). In both studies, standardized questionnaires concerning food cravings, food addiction, and psychopathology were administered. A cue-reactivity paradigm was used to measure craving responses toward semi-individualized images of highly palatable, processed food/fruit (appetitive food cues) compared to images of raw vegetables (non-appetitive food cues). Decision-making was measured with a modified computerized version of the Iowa Gambling Task (IGT) with food pictures. Both groups were divided into two subgroups that were randomized to different IGT conditions. In one IGT condition the advantageous IGT card decks were covered by pictures of palatable, processed food or fruit and the disadvantageous decks by images of raw vegetables (= congruent condition), and in the other IGT conditionvice versa. Results Participants in the OB-group admitted on average higher craving responses toward palatable, processed food or fruit cues compared to pictures of raw vegetables. This was not the case in the nonOB-group. Contrary to our hypothesis, decision-making performance in both groups was worse when pictures of palatable, processed food or fruit were associated with advantageous IGT card decks compared to performance when those pictures were linked to the disadvantageous decks. The interference effect of food pictures processing on advantageous decision-making has been observed particularly in those individuals of the OB-group who exhibited high craving responses toward palatable, processed food cues or high levels of food addiction. Discussion The results indicate that food pictures processing interferes with decision-making, regardless of weight status. Opposed to the hypothesis, stronger tendencies to avoid than to approach pictures presenting processed, tasty food were observed. Further research should examine how cognitive avoidance tendencies toward processed, high energy food and approach tendencies toward healthy food can be transferred to real life situations

The effect of hunger state on hypothalamic functional connectivity in response to food cues

ACKNOWLEDGMENT The authors thank Lisette Charbonnier for her relentless efforts in setting up the study at all three sites and collecting the Dutch data. Open Access funding enabled and organized by Projekt DEAL. FUNDING INFORMATION This work was financially supported by the European Union Seventh Framework Programme (FP7/2007–2013) for research, technological development, and demonstration under grant agreement 266408 (Full4Health, www.full4health.eu). Furthermore, the study was supported in parts by a grant (01GI0925) from the Federal Ministry of Education and Research (BMBF) to the German Center for Diabetes Research (DZD e.V.).Peer reviewedPublisher PD

Hippocampal-dependent appetitive control is impaired by experimental exposure to a Western-style diet

Animals fed a Western-style diet (WS-diet) demonstrate rapid impairments in hippocampal function and poorer appetitive control. We examined if this also occurs in humans. One-hundred and ten healthy lean adults were randomised to either a 1-week WS-diet intervention or a habitual-diet control group. Measures of hippocampal dependent learning and memory (HDLM) and of appetitive control were obtained pre- and post-intervention. HDLM was retested at 3-weeks follow-up. Relative to controls, HDLM performance declined in the WS-diet group (d=0.43), but was not different at follow-up. Appetitive control also declined in the WS-diet group (d=0.47) and this was strongly correlated with HDLM decline (d=1.01). These findings demonstrate that a WS-diet can rapidly impair appetitive control in humans - an effect that could promote overeating in consumers of a WS-diet. The study also suggests a functional role for the hippocampus in appetitive control and provides new evidence for the adverse neurocognitive effects of a WS-diet

Increased Brain Reward Responsivity to Food-Related Odors in Obesity

Objective Food odors serve as powerful stimuli signaling the food quality and energy density and direct food-specific appetite and consumption. This study explored obesity-related brain activation in response to odors related to high- or low-energy-dense foods. Methods Seventeen participants with obesity (BMI > 30 kg/m2 ; 4 males and 13 females) and twenty-one with normal weight (BMI < 25 kg/m2 ; 9 males and 12 females) underwent a functional magnetic resonance imaging scan in which they received chocolate (high-energy-dense food) and cucumber (low-energy-dense food) odor stimuli. Participants' olfactory and gustatory functions were assessed by the "Sniffin' Sticks" and "Taste Strips" tests, respectively. Results Compared with normal-weight controls, participants with obesity had lower odor sensitivity (phenylethyl alcohol) and decreased odor discrimination ability. However, participants with obesity demonstrated greater brain activation in response to chocolate compared with cucumber odors in the bilateral inferior frontal operculum and cerebellar vermis, right ventral anterior insula extending to putamen, right middle temporal gyrus, and right supramarginal areas. Conclusions The present study provides preliminary evidence that obesity is associated with heightened brain activation of the reward and flavor processing areas in response to chocolate versus cucumber odors, possibly because of the higher energy density and reinforcing value of chocolate compared with cucumber.Peer reviewe

Mitochondrial ROS Signaling in Organismal Homeostasis

Generation, transformation, and utilization of organic molecules in support of cellular differentiation, growth, and maintenance are basic tenets that define life. In eukaryotes, mitochondrial oxygen consumption plays a central role in these processes. During the process of oxidative phosphorylation, mitochondria utilize oxygen to generate ATP from organic fuel molecules but in the process also produce reactive oxygen species (ROS). While ROS have long been appreciated for their damage-promoting, detrimental effects, there is now a greater understanding of their roles as signaling molecules. Here, we review mitochondrial ROS-mediated signaling pathways with an emphasis on how they are involved in various basal and adaptive physiological responses that control organismal homeostasis