If you’ve ever
had to cook dinner, prepare for the next day’s work meeting, while also listen
to a friend complain over the phone, then you know all too well the importance
of multitasking. But what's actually going on inside our brains that allows for
us to strategically focus on one task over another? That's remained largely a
mystery, at least until recently. Earlier this week, researchers at New York
University identified one small region of the brain—the thalamic reticular
nucleus (TRN)—as the one that controls our ability to multitask. Working as a
task switchboard, the TRN enables our brains to focus on the sensory stimulus
that is most vital at any given moment. Now, with a better understanding of how
the process works, researchers hope to use the information to study diseases in
which multitasking or sensory overload goes awry—autism, schizophrenia, and
ADHD, for example. The ability to multitask is a vital part of life, as it's
needed to perform everyday functions like driving, cooking, or even socializing
with a group of friends. But at any given time, our brains are bombarded with a
multitude of sensory information, and we're forced to decide what's important
in that instant, focus on it, and tune out everything else. Researchers have
known about this process for years, but they weren't sure exactly how it worked
because they couldn't come up with a reliable experiment for identifying what
parts of the brain were involved.
By putting
laboratory mice through a game-like experiment, they were able to show that
different neurons within the TRN regulated which senses the brain should focus
on and which should be set aside. The experiment involved training mice to
respond to a specific sensory stimulus, either light or sound. If the mice
observed and followed the correct stimulus, they received milk as a reward. At
the same time, the researchers would attempt to distract the mice with the
opposite stimulus (the mice trained to respond to light would be distracted
with sound, for example). In real time, the researchers would record electrical
signals that came from the TRN neurons in the mice’s brain. They were also able
to inactivate various parts of the neural network—specifically the prefrontal
cortex, which seeks out certain stimulus over others. When the mice were
trained to pay attention to a particular sound and ignore light, the TRN
neurons that control vision were highly active, meaning that they were
suppressing visual signals so that the mice could focus more intensely on the
sound. The opposite happened when they were trained to follow the light in
order to receive their milk reward. Further, when the researchers inactivated
the prefrontal cortex—the area of the brain responsible for higher level
functioning—using a laser beam, the TRN neural signaling went completely out of
whack. This shows that the prefrontal cortex stores incoming sensory
information.
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