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Ifat Levy

Flawed decision-making processes might be at the core of several pathological behaviors, including obesity. Our lab combines behavioral methods from experimental economics with functional MRI to study choice behavior and its neural correlates in humans, and to look for markers for pathological behavior that could lead to obesity. Two main approaches are employed: the first is to study the effect of risk and ambiguity regarding possible outcomes on choice behavior in general; the second approach is to focus specifically on food choices and the neural representation of the value of food.

Choice under risk and ambiguity

When choosing between different gains most people prefer smaller but more certain gains to larger but less certain ones. For example, a certain gain of $10 is usually preferred to a 50% chance of winning $25, even though the latter option offers more money on average ($12.5 vs. $10). This behavioral tendency is called “risk aversion”. Similarly, a 50% chance of winning $25 is often preferred to an unknown probability of winning much more than $25, a tendency which is termed “ambiguity aversion”. An opposite pattern of behavior is observed when losses are involved: most people prefer a 50% chance of losing $25 to a sure loss of $10, thus exhibiting “risk seeking”.

Typical brain activation in response to food images. Shades of orange and yellow denote above-baseline activity. Shades of blue and green denote below-baseline activity.
Although most people exhibit those traits, they differ significantly in their degree. An interesting question is whether differences in eating behavior might be explained, at least partially, by differences in attitudes towards risk and ambiguity. For example, overeating implies an immediate certain reward (food), accompanied by a future, uncertain punishment (gaining weight). Overweight individuals might therefore be more risk seeking in the realm of losses compared to lean individuals. We have previously identified brain areas whose activation tracks the “subjective value” of options that were presented to normal-weight young adults. Following these results we are now running similar experiments in lean and obese individuals, looking for weight-related differences both in behavior and in the neural activation.
Areas of the striatum and the medial prefrontal cortex (MPFC) encode the subjective value of options that we encounter.

Food choice and the value of food

In this set of experiments we study how food choices are affected by different kinds of inputs, such as warnings regarding the potential negative consequences of consuming high fat food, and food product placement in movies. We also study how people learn to associate neutral cues with food rewards, behaviorally and neurally. In all of these studies we include subjects of different weight groups, to look for potential differences in behavior and neural correlates between lean and overweight individuals.