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Sunday, September 2, 2007

Chocoholics in the dark

Wanting to eat chocolate isn't the worse thing that can happen, but wanting and seeing chocolate is irresistible. Researchers have identified three brain regions of importance for food craving. They compared cravers to non-cravers focusing on chocolate and tested them during 5 different challenges while being brain scanned in a fMRI.

Brain centers and food craving
They used fMRI to measure the response to the flavour of chocolate,the sight of chocolate and their combination in cravers vs.non-cravers.
The cravers and non-cravers did not differ in activation of the brain regions for tasting (primary taste cortex= anterior insula).
They did differ significantly in the activation of a reward centre in the brain, the center for affective hedonic response, the orbitofrontal cortex. Not only is the affective response greater with the cravers, the combination of sight and taste of chocolate enhances the activation more than only the taste of chocolate or a picture of chocolate compared to the non-cravers.

Two other brain areas connected with the medial orbitofrontal cortex also show different responses between cravers and non cravers.
The pregenual/anterior cingulate cortex showed a greater activation in cravers to the combination of the sight and taste of chocolate. The combination produced a far greater activation than the sum of the separate conditions.
The other center the ventral striatum showed a significant greater activation to the sight of chocolate than the non-cravers. The activation on taste did not differ. The ventral striatum in cravers vs.non-cravers contributes especially to the conditioned,i.e. visual,component of chocolate craving.

The head of the nucleus caudatus also connected to the orbitofrontal cortex also showed a greater activation when the picture and the taste of chocolate were presented than the sum of the components.


Brain regions of interest for food craving:

1. the medial orbitofrontal cortex
2. ventral striatum
3. pregenual cingulate cortex

Eating in the dark when you're on a diet?
A very effective stimulus results when all of the sensory aspects of the stimuli (sight and mouth feel) are combined. This can drive behavior more in cravers than non-cravers.
Understanding individual differences in brain responses to very pleasant foods helps in the understanding of the mechanisms that drive the liking for specific foods and thus intake of those foods.

Another important implication of this research as quoted from an interview with Edmund Rolls and Ciara McCabe at the University of Oxford's experimental psychology department:

This finding might offer a way of making food less pleasurable for people on a diet. "The take-home message is that if you want to limit [food] intake, you could limit the extent to which you are exposed to the combination of sight and taste. For example, you could eat in the dark", he said.

Chocoholics versus carbohydrate craving
These findings are about food craving, chocolate craving may be part of carbohydrate craving. In the publication the overlap or distinction between chocolate craving and carbohydrate craving is not made. The authors mention a questionnaire for selecting their subjects. Question 6 is "Do you crave any other food? If so, what is that food?". The answers to this question are not presented in the publication. This makes it hard to subscribe the findings of this study to chocolate alone.

And for eating in the dark, well it would hinder Dr Shock in pouring his Kopke Port 1963 which goes perfectly well with his dark chocolate.

Other articles about chocolate on this blog:

Is Chocolate an Antidepressant?

Side effects from Chocolate

Article discussed:
Edmund T. Rolls, Ciara McCabe (2007)
Enhanced affective brain representations of chocolate in cravers vs. non-cravers
European Journal of Neuroscience 26 (4), 1067–1076.

Related post on Finding Optimism written by Leo Babauta from zen habits: 5 Powerful Reasons to Eat Slower

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