Brain's Trigger for Binge Behavior Revealed

Neurologists have discovered that rats that responded to cues for sugar with the speed and excitement of binge-eaters were less motivated for the treat when certain neurons were suppressed.

Rats that responded to cues for sugar with the speed and excitement of binge-eaters were less motivated for the treat when certain neurons were suppressed, researchers discovered.

 

The findings, due to appear in the June 15 issue of the journal Neuron, are now available online.

 

"External cues – anything from a glimpse of powder that looks like cocaine or the jingle of an ice cream truck – can trigger a relapse or binge eating," said lead author Jocelyn M. Richard, a Johns Hopkins University post-doctoral fellow in psychological and brain sciences.

 

"Our findings show where in the brain this connection between environmental stimuli and the seeking of food or drugs is occurring."

 

Researchers trained rats to realize that if they heard a certain sound, either a siren or staccato beeps, and a pushed a lever, they would get a drink of sugar water. Then, as the rats performed the task, the researchers monitored neurons within the ventral pallidum area of the rats' brains, a subcortical structure near the base of the brain.

 

When the rats heard the cue linked to their treat, a much larger-than-expected number of neurons reacted – and vigorously, researchers found. They also found that when the neuron response was particularly robust, the rats were extra quick to go for the sugar. The researchers were able to predict how fast the rats would move for the sugar just by observing how excited the neurons became at the sound of the cue.

 

"We were surprised to see such a high number of neurons showing such a big increase in activity as soon as the sound played," Richard said.

 

Next, the researchers used "optogenetics," a technique that allows the manipulation of cells through targeted beams of light, to temporarily suppress the activity of ventral pallidum neurons while the rats heard the sugar cues. With those neurons inactive, the rats were less likely to pull the sugar lever; when they did pull it, they were much slower to do so.

 

That ability to slow and calm the reaction to cues or triggers for binges could be key for people trying to moderate addictive behaviors, according to Richard: "We don't want to make it so that people don't want rewards. We want to tone down the exaggerated motivation for rewards.”

 

Journal Reference:
Jocelyn M. Richard, Frederic Ambroggi, Patricia H. Janak, Howard L. Fields. Ventral Pallidum Neurons Encode Incentive Value and Promote Cue-Elicited Instrumental Actions. Neuron, 2016; DOI: 10.1016/j.neuron.2016.04.037