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Eating less or more - Mindset induced changes in neural correlates of pre-meal planning

Maike A. Hege, Ralf Veit, Jan Krumsiek, Stephanie Kullmann, Martin Heni, Peter J. Rogers, Jeffrey M. Brunstrom, Andreas Fritsche, Hubert Preissl

Appetite 125 (2018) 492-501

Obesity develops due to an imbalance between energy intake and expenditure. Besides the decision about what to eat, daily energy intake might be even more dependent on the decision about the portion size to be consumed. For decisions between different foods, attentional focus is considered to play a key role in the choice selection. In the current study, we investigated the attentional modulation of portion size selection during pre-meal planning. We designed a functional magnetic resonance task in which healthy participants were directed to adopt different mindsets while selecting their portion size for lunch. Compared with a free choice condition, participants reduced their portion sizes when considering
eating for health or pleasure, which was accompanied by increased activity in left prefrontal cortex and left orbitofrontal cortex, respectively. When planning to be full until dinner, participants selected larger portion sizes and showed a trend for increased activity in left insula. These results provide first evidence that also the cognitive process of pre-meal planning is influenced by the attentional focus at the time of choice, which could provide an opportunity for influencing the control of meal size selection by mindset manipulation.

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A predictive, quantitative model of spiking activity and stimulus-secretion coupling in oxytocin neurons.

Jorge, Maícas-Royo , Gareth Leng , Duncan J MacGregor

Endocrinology 159, 1433-1452 (2018)

Oxytocin neurons of the rat hypothalamus project to the posterior pituitary where they secrete their products into the bloodstream. The pattern and quantity of that release depends on the afferent inputs to the neurons, on their intrinsic membrane properties, and on non-linear interactions between spiking activity and exocytosis: a given number of spikes will trigger more secretion when they arrive close together. Here we present a quantitative computational model of oxytocin neurons that can replicate the results of a wide variety of published experiments. The spiking model mimics electrophysiological data of oxytocin cells responding to cholecystokinin (CCK), a peptide produced in the gut after food intake. The secretion model matches results from in vitro experiments on stimulus-secretion coupling in the posterior pituitary. We mimic the plasma clearance of oxytocin with a two-compartment model, replicating the dynamics observed experimentally after infusion and injection of oxytocin. Combining these models, allows us to infer, from measurements of oxytocin in plasma, the spiking activity of the oxytocin neurons that produced that secretion. These inferences we have tested with experimental data on oxytocin secretion and spiking activity in response to intravenous injections of CCK. We show how intrinsic mechanisms of the oxytocin neurons determine this relationship: in particular, we show that the presence of an after-hyperpolarization (AHP) in oxytocin neurons dramatically reduces the variability of their spiking activity, and even more markedly reduces the variability of oxytocin secretion. The AHP thus acts as a filter, protecting the final product of oxytocin cells from noisy fluctuations.

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A worldwide consensus on Nudging? Not Quite, but almost

Cass.R.Sunstein, Lucia A. Reisch, Julius Sauber

Regulation and Governance (2018) 12, 3-22

 

Nudges are choice-preserving interventions that steer people’s behavior in specific directions while still allowing them to go their own way. Some nudges have been controversial, because they are seen as objectionably paternalistic. This study reports on nationally representative surveys in eight diverse countries, investigating what people actually think about nudges and nudging. The study covers Australia, Brazil, Canada, China, Japan, Russia, South Africa, and South Korea. Generally, we find strong majority support for nudges in all countries, with the important exception of Japan, and with spectacularly high approval rates in China and South Korea. We connect the findings here to earlier studies involving Denmark, France, Germany, Hungary, Italy, the United Kingdom, and the United States. Our primary conclusion is that while citizens generally approve of health and safety nudges, the nations of the world appear to fall into three distinct categories: (i) a group of nations, mostly liberal democracies, where strong majorities approve of nudges whenever they (a) are seen to fit with the interests and values of most citizens and (b) do not have illicit purposes; (ii) a group of nations where overwhelming majorities approve of nearly all nudges; and (iii) a group of nations that usually show majority approval, but markedly reduced approval rates. We offer some speculations about the relationship between approval rates and trust.

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Undervalued and ignored: Are humans poorly adapted to energy-dense foods?

Jeffrey M.Brunstrom Alex C.L.Drake Ciarán G.Forde and Peter J.Rogers   

Appetite 120 (2018) 589-595

In many species the capacity to accurately differentiate the energy density (kcal/g) of foods is critical because it greatly improves efficiency in foraging. In modern humans this ability remains intact and is expressed in a selective preference for types of fruit and vegetables that contain more calories. However, humans evolved consuming these low energy-dense foods (typically < 1.75 kcal/g) and it remains unclear whether they can also discriminate more energy-dense foods that now feature in modern Western diets. In two experiments participants (both N ¼ 40) completed four tasks that assessed the ‘value’ of different sets of 22 foods that ranged in energy density (0.1 kcal/g to 5.3 kcal/g and range 0.1 kcal/g to 6.2 kcal/g in Experiment 1 and 2, respectively). In Experiment 1 three measures (expected fullness, calorie estimation, and food choice), and in foods less than approximately 1.5 kcal/g (typically fruits and vegetables), the relationship between perceived value and energy density is linear. Above this, we
observed clear compressive functions, indicating relative and progressive undervaluation of higher energy-dense foods. The fourth task (rated liking) failed to provide evidence for any relationship with energy density. In Experiment 2 the same pattern was replicated in measures of expected fullness, and in two different assessments of subjective calorie content. Consistent with the concept of ‘evolutionary discordance,’ this work indicates that modern human physiology is poorly adapted to evaluate foods that have a historically unusual (high) energy density. This has implications both for our understanding of how ‘modern’ energy-dense foods affect choice and energy intake, and for strategies aimed at removing calories from highly energy-rich foods.

 

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Does activation of midbrain dopamine neurons promote or reduce feeding?

L Boekhoudt, TJM Roelofs, JW de Jong, AE de Leeuw, MCM Luijendijk, IG Wolterink-Donselaar, G van der Plasseand RAH Adan

International Journal of Obesity (2017) 41, 1131–1140

BACKGROUND: Dopamine (DA) signalling in the brain is necessary for feeding behaviour, and alterations in the DA system havebeen linked to obesity. However, the precise role of DA in the control of food intake remains debated. On the one hand, food reward and motivation are associated with enhanced DA activity. On the other hand, psychostimulant drugs that increase DA signalling suppress food intake. This poses the questions of how endogenous DA neuronal activity regulates feeding, and whether enhancing DA neuronal activity would either promote or reduce food intake.


METHODS: Here, we used designer receptors exclusively activated by designer drugs (DREADD) technology to determine the effects of enhancing DA neuronal activity on feeding behaviour. We chemogenetically activated selective midbrain DA neuronal subpopulations and assessed the effects on feeding microstructure in rats.


RESULTS: Treatment with the psychostimulant drug amphetamine or the selective DA reuptake inhibitor GBR 12909 significantlysuppressed food intake. Selective chemogenetic activation of DA neurons in the ventral tegmental area (VTA) was found to reduce meal size, but had less impact on total food intake. Targeting distinct VTA neuronal pathways revealed that specific activation of the mesolimbic pathway towards nucleus accumbens (NAc) resulted in smaller and shorter meals. In addition, the meal frequency was increased, rendering total food intake unaffected. The disrupted feeding patterns following activation of VTA DA neurons or VTA to NAc projection neurons were accompanied by locomotor hyperactivity. Activation of VTA neurons projecting towards prefrontal cortex or amygdala, or of DA neurons in the substantia nigra, did not affect feeding behaviour.


CONCLUSIONS: Chemogenetic activation of VTA DA neurons or VTA to NAc pathway disrupts feeding patterns. Increased activity of mesolimbic DA neurons appears to both promote and reduce food intake, by facilitating both the initiation and cessation of feeding behaviour.

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Chemogenetic Activation of Midbrain Dopamine Neurons Affects Attention, but not Impulsivity, in the Five-Choice Serial Reaction Time Task in Rats

Linde Boekhoudt, Elisa S Voets, Jacques P Flores-Dourojeanni, Mieneke CM Luijendijk, Louk JMJ Vanderschuren and Roger AH Adan

Neuropsychopharmacology (2017) 42, 1315-1325

Attentional impairments and exaggerated impulsivity are key features of psychiatric disorders, such as attention-deficit/hyperactivity disorder, schizophrenia, and addiction. These deficits in attentional performance and impulsive behaviors have been associated with aberrant dopamine (DA) signaling, but it remains unknown  whether these deficits result from enhanced DA neuronal activity in the midbrain. Here, we took a  novel approach by testing the impact of chemogenetically activating DA neurons in the ventral  tegmental area (VTA) or substantia nigra pars compacta (SNc) on attention and impulsivity in the  five-choice serial reaction time task (5-CSRTT) in rats. We found that activation of DA neurons in  both the VTA and SNc impaired attention by increasing trial omissions. In addition, SNc DA neuron  activation decreased attentional accuracy. Surprisingly, enhanced DA neuron activity did not affect
impulsive action in this task. These results show that enhanced midbrain DA neuronal activity  induces deficits in attentional performance, but not impulsivity. Furthermore, DA neurons in the  VTA and SNc have different roles in regulating attention. These findings contribute to our  understanding of the neural substrates underlying attention deficits and impulsivity, and provide  valuable insights to improve treatment of these symptoms.

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Food Decision-Making: Effects of Weight Status and Age

Floor van Meer, Lisette Charbonnier, and Paul A. M. Smeets

Current Diabetes Reports (2016) 16: 84

Food decisions determine energy intake. Since overconsumption is the main driver of obesity, the effects of weight status on food decision-making are of increasing interest. An additional factor of interest is age, given the rise in childhood obesity, weight gain with aging, and the increased chance of type 2 diabetes in the elderly. The effects of weight status and age on food preference, food cue sensitivity, and self-control are discussed, as these are important components of food decision-making. Furthermore, the neural correlates of food anticipation and choice and how these are affected by weight status and age are discussed. Behavioral studies show that in particular, poor self-control may have an adverse effect on food choice in children and adults with overweight and obesity. Neuroimaging studies show that overweight and obese individuals have altered neural responses to food in brain areas related to reward, self-control, and interoception. Longitudinal studies across the lifespan will be invaluable to unravel the causal factors driving (changes in) food choice, overconsumption, and weight gain.

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Do Europeans like Nudges?

Lucia A. Reisch and Cass R Sunstein

Judgement and Decision Making Vol 11 No 4 July 2016 310-325

In recent years, many governments have shown a keen interest in “nudges” — approaches to law and policy that maintain freedom of choice, but that steer people in certain directions. Yet to date, there has been little evidence on whether citizens of various societies support nudges and nudging. We report the results of nationally representative surveys in six European nations: Denmark, France, Germany, Hungary, Italy, and the United Kingdom. We find strong majority support for nudges of the sort that have been adopted, or under serious consideration, in democratic nations. Despite the general European consensus, we find markedly lower levels of support for nudges in two nations: Hungary and Denmark. We are not, in general, able to connect support for nudges with distinct party affiliations.

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Brain Insulin Resistance at the Crossroads of Metabolic and Cognitive Disorders in Humans

Stephanie Kullmann, Martin Heni, Manfred Hallschmid, Andreas Fritsche, Hubert Preissl, and Hans-Ulrich Häring

Physiological Reviews 96: 1169-1209 2016

Ever since the brain was identified as an insulin-sensitive organ, evidence has rapidly accumulated that insulin action in the brain produces multiple behavioral and metabolic effects, influencing eating behavior, peripheral metabolism, and cognition. Disturbances in brain insulin action can be observed in obesity and type 2 diabetes (T2D), as well as in aging and dementia. Decreases in insulin sensitivity of central nervous pathways, i.e., brain insulin resistance, may therefore constitute a joint pathological feature of metabolic and cognitive dysfunctions. Modern neuroimaging methods have provided new means of probing brain insulin action, revealing the influence of insulin on both global and regional brain function. In this review, we highlight recent findings on brain insulin action in humans and its impact on metabolism and cognition. Furthermore, we elaborate on the most prominent factors associated with brain insulin resistance, i.e., obesity, T2D, genes, maternal metabolism, normal aging, inflammation, and dementia, and on their roles regarding causes and consequences of brain insulin resistance. We also describe the beneficial effects of enhanced brain insulin signaling on human eating behavior and cognition and discuss potential applications in the treatment of metabolic and cognitive disorders.

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Modulation of attentional networks by food-related disinhibition

Maike A. Hege, Krunoslav T. Stingl, Ralf Veit, and Hubert Preissl

Physiology & Behaviour 176 (2017) 84-92

The risk of weight gain is especially related to disinhibition, which indicates the responsiveness to external food stimuli with associated disruptions in eating control. We adapted a food-related version of the attention network task and used functional magnetic resonance imaging to study the effects of disinhibition on attentional networks in 19 normal-weight participants. High disinhibition scores were associated with a rapid reorienting response to food pictures after invalid cueing and with an enhanced alerting effect of awarning cue signalizing the upcoming appearance of a food picture. Imaging data revealed activation of a right-lateralized ventral attention network during reorienting. The faster the reorienting and the higher the disinhibition score, the less activation of this network was observed. The alerting contrast showed activation in visual, temporo-parietal and anterior sites. These modulations of attentional networks by food-related disinhibition might be related to an attentional bias to energy dense and palatable food and increased intake of food in disinhibited individuals.

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