Brain tells you whether to stay or go while foraging

June 7th, 2011 - 2:33 pm ICT by IANS  

Washington, June 7 (IANS) Every creature that forages for food decides at some point that the food source it is working on is no richer than the rest of the patch and that it’s time to move on and find something better, a recent study reports.

This kind of foraging decision is a fundamental problem that goes far back in evolutionary history and is dealt with by creatures that don’t even have proper brains, said Michael Platt, professor of neurobiology and director of the Centre for Cognitive Neuroscience at Duke University.

Platt and his colleagues now say they’ve identified a function in the primate brain that appears to be handling this stay-or-go problem, the journal Nature Neuroscience reports.

They have found that the dorsal anterior cingulate cortex (ACC), an area of the brain known to operate while weighing conflicts, steadily increases its activity during foraging decisions until the individual decides it is time to move, according to a Duke statement.

In lab experiments with rhesus macaque monkeys, Platt and postdoctoral fellows Benjamin Hayden and John Pearson put the animals through a series of trials in which they repeatedly had to decide whether to stay with a source that was giving ever-smaller squirts of fruit juice, or move to another, possibly better, source.

The animals were merely gazing at a preferred target on a display screen, not moving from one tree to the next, but the decision-making process was the same, Platt said.

For the other variable in this basic equation, travel time, the researchers added delays when monkeys chose to leave one resource and move to another, simulating short and long travel times.

As the monkeys repeatedly chose to stay with their current source or move to another, the researchers watched a small set of neurons within the anterior cingulate cortex fire with increasing activity for each decision.

The rate of firing in this group of neurons grew until a threshold was reached, at which time the monkey immediately decided to move on.

“It is as if there is a threshold for deciding it’s time to leave set in the brain,” Platt said.

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