2016年4月10日日曜日

PNAS誌から論文が出版!

新しい論文がPNAS誌から出版されました。

Shinsuke Suzuki, Emily L. S. Jensen, Peter Bossaerts, John P. O’Doherty, "Behavioral contagion during learning about another agent's risk-preferences acts on the neural representation of decision risk", PNAS, Vol. 113, pp. 3755-3760, 2016.
http://www.pnas.org/content/113/14/3755

「他者の行動を観察/学習することで、(1)自分自身のリスク選好が変化する、(2)また、それに伴い線条体(尾状核)のリスクに対する反応も変化する」ことを示しました。

2016年2月18日木曜日

Behavioral and Neural Valuation of Foods Is Driven by Implicit Knowledge of Caloric Content

Deborah W. Tang, Lesley K. Fellows, Alain Dagher
Psychological Science, October 10, 2014 0956797614552081

The factors that affect food choices are critical to understanding obesity. In the present study, healthy participants were shown pictures of foods to determine the impact of caloric content on food choice. Brain activity was then measured while participants bid for a chance to purchase and eat one item. True caloric density, but not individual estimates of calorie content, predicted how much participants were willing to pay for each item. Caloric density also correlated with the neural response to food pictures in the ventromedial prefrontal cortex, a brain area that encodes the value of stimuli and predicts immediate consumption. That same region exhibited functional connectivity with an appetitive brain network, and this connectivity was modulated by willingness to pay. Despite the fact that participants were poor at explicitly judging caloric content, their willingness to pay and brain activity both correlated with actual caloric density. This suggests that the reward value of a familiar food is dependent on implicit knowledge of its caloric content.

2016年2月8日月曜日

Nutritional and behavioral regulators of choice behavior

Joram D Mul, Susanne E la Fleur
Current Opinion in Behavioral Sciences, Available online 3 February 2016
http://www.sciencedirect.com/science/article/pii/S235215461630016X

Added sugar, often consumed in the form of sweetened beverages, is currently labeled as a big evil that increases our risk to develop obesity, cardiovascular diseases, and diabetes. Only a few decades ago, however, saturated fat received a similar negative label. Instead of singling out one of these factors we here explore how fat and sugar intake interact, thus influencing brain function and behavior. We first review current literature on how free choice during simultaneous fat and sugar consumption increases subsequent overeating and thus the risk of obesity. Next we propose neural mechanisms how simultaneous access to both fat and sugar could promote cross-sentizisation and increase total caloric intake. On the basis of our current knowledge we hypothesize that independent drinking of sugar, before or concurrent with fat intake, enhances subsequent fat-intake and total caloric intake by altering dopamine, opioid, and NPY signaling within a neural circuitry comprising of the central amygdala, the ventral tegmental area, and the nucleus accumbens.

2016年2月3日水曜日

Acute Stress Impairs Self-Control in Goal-Directed Choice by Altering Multiple Functional Connections within the Brain’s Decision Circuits

Silvia U. Maier, Aidan B. Makwana, Todd A. Hare
Neuron, Volume 87, Issue 3, p621–631, 5 August 2015
http://www.cell.com/neuron/abstract/S0896-6273(15)00627-3

Important decisions are often made under stressful circumstances that might compromise self-regulatory behavior. Yet the neural mechanisms by which stress influences self-control choices are unclear. We investigated these mechanisms in human participants who faced self-control dilemmas over food reward while undergoing fMRI following stress. We found that stress increased the influence of immediately rewarding taste attributes on choice and reduced self-control. This choice pattern was accompanied by increased functional connectivity between ventromedial prefrontal cortex (vmPFC) and amygdala and striatal regions encoding tastiness. Furthermore, stress was associated with reduced connectivity between the vmPFC and dorsolateral prefrontal cortex regions linked to self-control success. Notably, alterations in connectivity pathways could be dissociated by their differential relationships with cortisol and perceived stress. Our results indicate that stress may compromise self-control decisions by both enhancing the impact of immediately rewarding attributes and reducing the efficacy of regions promoting behaviors that are consistent with long-term goals.

2016年2月2日火曜日

Separate circuitries encode the hedonic and nutritional values of sugar

Tellez LA, Han W, Zhang X, Ferreira TL, Perez IO, Shammah-Lagnado SJ, van den Pol AN, de Araujo IE
Nat Neurosci. 2016 Jan 25. doi: 10.1038/nn.4224.
http://www.ncbi.nlm.nih.gov/pubmed/26807950

Sugar exerts its potent reinforcing effects via both gustatory and post-ingestive pathways. It is, however, unknown whether sweetness and nutritional signals engage segregated brain networks to motivate ingestion. We found in mice that separate basal ganglia circuitries mediated the hedonic and nutritional actions of sugar. During sugar intake, suppressing hedonic value inhibited dopamine release in ventral, but not dorsal, striatum, whereas suppressing nutritional value inhibited dopamine release in dorsal, but not ventral, striatum. Consistently, cell-specific ablation of dopamine-excitable cells in dorsal, but not ventral, striatum inhibited sugar's ability to drive the ingestion of unpalatable solutions. Conversely, optogenetic stimulation of dopamine-excitable cells in dorsal, but not ventral, striatum substituted for sugar in its ability to drive the ingestion of unpalatable solutions. Our data indicate that sugar recruits a distributed dopamine-excitable striatal circuitry that acts to prioritize energy-seeking over taste quality.