Scientists discover brain part that drives decision-making

25 November 2013

A tiny part of the brain may be what’s behind your big

Canadian scientists say they’ve discovered that a part of
the brain called the lateral habenula may help us make major cost-benefit decisions
like buying a new house.

The study “suggests that the scientific community has
misunderstood the true functioning of this mysterious, but important, region of
the brain,” study author Dr. Stan Floresco, a behavioral neuroscientist at the
University of British Columbia in Vancouver, said in a statement.

The new research was published Nov. 24 in Nature Neuroscience.

The lateral habenula is one of the smallest parts of the brain. Scientists previously linked it to depressive symptoms when they saw patients improve when the part was turned
off through deep brain stimulation, a procedure where electrodes are
implanted in the brain and controlled by a pacemaker.

The structure had also been thought to be involved in avoidance behavior.

Evolutionarily, the lateral habenula had been considered to
be one of the oldest regions of the brain, according to the scientists — they just might not have realized what it actually did.

In a lab experiment, scientists led by Floresco and UBC
colleague Colin Stopper trained rats to pick between a task that gave them a
consistent, but small reward of one food pellet or a task that took longer but
could potentially give them a larger haul of four pellets.

The rats acted like people would: They tended to choose the
larger rewards when the amount of time they had to wait before receiving the
pellets — the “costs” — were low, but they picked the smaller rewards as the
time lags increased.

Essentially they decided “what’s better for me?” according to the researchers.

However when the scientists turned off the lateral habenula, the
rats selected either option equally, no longer showing the ability to pick
the best option.

That surprised the researchers, who expected the rats to
choose the larger, riskier reward more often due to the previous research that has linked the
brain region to avoidance behaviors.

Previous studies that found the depression benefits may have also
been misinterpreted, they said. What may have been happening in those patients were changes in decision-making. 

“Our findings suggest these improvements may not be because
patients feel happier. They may simply no longer care as much about what is
making them feel depressed.”

It may sound surprising scientists are finding out new
information about something so studied like the brain, but it’s not totally foreign
for researchers to discover new functions for body parts.

In Nov., Belgian surgeons discovered a “new” ligament in the
knee, the anterolateral ligament (ALL), that previously was thought to be a
part of the ACL that may tear during knee injuries.

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