#psych135

Don’t these pictures just make your mouth water?

I’m guessing you’re thinking about rushing to the nearest food place already.

Did you know that concepts such as foods are represented as distributed circuits of information across different areas of our brain? These varied modality-specific responses by our brain create our food knowledge. It’s no wonder that a mere picture of a yummy food drive us to immediately eat, savor relish from its taste!

Different and relevant modalities represent different sets of information during perception and action. As the object is processed, its properties are captured by our senses so that this information can be reactivated during conceptual processing and whenever the object is unavailable. This perceptual reenactment is different from mental imagery for mental imagery results from attempts of consciously recovering a vivid image from our working memory. On the other hand, perceptual reenactment is a conceptual processing that often lies outside our awareness and so, it’s is said to be relatively automatic and implicit. 

In a study conducted by Simmons, Martin and Barsalou entitled Pictures of Appetizing Foods Activate Gustatory Cortices for Taste and Reward the researchers explored the distributed properties of foods. They focused on high-caloric, high-fat processed foods such as cheeseburgers and cookies because they are the usual diet of people nowadays. Inevitably, it will have a strong gustatory and appetitive responses that will lead to immediate consumption (Yum!).  

They further hypothesized that if there is indeed a distributed circuit for food knowledge then, viewing a food picture won’t stimulate the visual areas alone but also brain areas on taste and rewards. Furthermore, the researchers hold that once a part of the distributed circuit becomes activated, it will have a domino effect in the sense that the remainder of the parts will become activated via conceptual and inference processing of that particular food. 

The study is experimental in nature. The researchers had sixteen native-English-speaking volunteers from Emory University where ten of which are female while six were male. The participants’ ages range from 19-46 years old. These first set of subjects, participated in the stimulus selection of the study. And then, the researchers presented the food and location pictures that resulted from the selection process to the second set of subjects that underwent an event-related fMRI and they look on to the active and distributed circuit of brain areas. Nine right-handed, native-English-speaking volunteers from the same university participated in the scanning study. Six of which were female while the remaining were male. All of the participants’ ages range from 18-45 years old. 

During the scanning procedure, subjects viewed food, location and scrambled pictures (as shown below). They instructed the subjects to respond whether the picture that they are viewing is similar or different from the preceding photo with the help of a response pad. The subjects were given 2 seconds of viewing time for each picture. 

The researchers confirmed through a simple picture-matching task that viewing pictures activated gustatory cortex. Food pictures, relative to location pictures, activated the insula/operculum which represents the tastes of foods. Moreover, it also activated two regions in the orbitofrontal cortex (OFC) which represent the reward values for tastes. Food pictures also produced an activity in the occipitotemporal cortex. 

These finding support the hypothesis of the researchers that there is a distributed circuit across brain areas that represent food knowledge:  

“Food pictures activated the insula/operculum very near regions that become active when people actually taste glucose, sucrose, salt, or umami. (See Figure a) Food pictures also activate OFC very near regions that become active when people experience taste stimuli directly. The close proximity of the regions active for food pictures to well-established gustatory areas suggests that food pictures automatically activate gustatory areas to produce conceptual inferences about taste properties (See Figure b.) ... The insula/operculum receives projections from the ventroposterior medial nuclues of the thalamus which has been associated with tastes per se. The OFC, in contrast, receives projections from the insula/operculum and has been associated with the reward values of specific tastes only.” 

It was further discovered that the firing rate of neurons in insula/operculum of monkeys is independent of hunger and satiety. On the other hand, firing rate of neurons in OFC are regulated by hunger and satiety which said to suggest the reward value of tastes:

“Thus, when a monkey is hungry, the firing rate of OFC neurons is high, given that the reward value of food is high. Similarly in humans, greater activation occurs in gustatory OFC before participants are satiated than after.”

To end, due to a distributed coding of our modalities in our brain that produce our food knowledge, it activates our gustatory system both in mere viewing pictures of food and when we actually eat them. So better be careful and try out a healthy diet! 

By: Char Bustamante

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