One of the smallest parts of the brain is
getting a second look after new research suggests it plays a crucial role in
A University of British Columbia study
published today in Nature Neuroscience says the lateral habenula, a region of
the brain linked to depression and avoidance behaviours, has been largely
misunderstood and may be integral in cost-benefit decisions.
"These findings clarify the brain
processes involved in the important decisions that we make on a daily basis,
from choosing between job offers to deciding which house or car to buy,"
says Prof Stan Floresco of UBC's Dept. of Psychology and Brain Research Centre
(BRC). "It also suggests that the scientific community has misunderstood
the true functioning of this mysterious, but important, region of the
Choosing the best option
In the study, scientists trained lab rats
to choose between a consistent small reward (one food pellet) or a potentially
larger reward (four food pellets) that appeared sporadically. Like humans, the
rats tended to choose larger rewards when costs – in this case, the amount of
time they had to wait before receiving food – were low and preferred smaller
rewards when such risks were higher.
Previous studies suggest that turning off
the lateral habenula would cause rats to choose the larger, riskier reward more
often, but that was not the case. Instead, the rats selected either option at
random, no longer showing the ability to choose the best option for them.
The findings have important implications
for depression treatment. "Deep brain stimulation – which is thought to
inactivate the lateral habenula – has been reported to improve depressive
symptoms in humans," Floresco says. "But 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."
Oldest brain regions
Floresco, who conducted the study with PhD
candidate Colin Stopper, says more investigation is needed to understand the
complete brain functions involved in cost-benefit decision processes and
related behaviour. A greater understanding of decision-making processes is also
crucial, they say, because many psychiatric disorders, such as schizophrenia,
stimulant abuse and depression, are associated with impairments in these
The lateral habenula is considered one of
the oldest regions of the brain, evolution-wise.