ANDRZEJ KRAUZENOTEBOOKprimates process visual information over
time, as the brain maintains attention.
For the first study, the team trained two
macaque monkeys to complete a com-
puter monitor–based task. In each trial,
a small, c-shaped cue flashed somewhere
on the screen. Then, between 300 mil-
liseconds and 1600 milliseconds later, a
square appeared. If that square appeared
in the same position as the cue—which it
did in around 78 percent of the trials—
the monkeys could earn a juice reward by
releasing a lever within about half a sec-
ond of the square appearing.As they waited for the square to
appear, the monkeys focused their atten-
tion on the location where the cue had
just flashed on the screen, all while
the researchers recorded the animals’
neural activity in the frontal and pari-
etal regions of the brain. Data from 97
recording sessions revealed cyclical pat-
terns of neural activity in these areas,
with peaks occurring at approximately
250-millisecond intervals after the cue
appeared in a well-described pattern of
oscillations known as a theta rhythm
(Neuron, 99:P842–53.e8, 2018).Kastner’s team found that, in trials
where the square appeared at the same
location as the cue, the monkeys were
most likely to lift the lever at the moments
corresponding to peaks in those activ-
ity cycles. The results directly link brain
activity and behavior, and indicate that
“rhythms in brain regions that direct
the attentional spotlight are predictive
of behavioral outcomes,” says study co-
author Ian Fiebelkorn, a neuroscientist
at Princeton University.In the second study, this time with
human participants, Kastner and col-
leagues worked in collaboration with
a group led by Robert Knight at the
University of California, Berkeley.
The team recorded neurophysiologi-
cal data from 15 presurgical epilep-
tic patients, each of whom had up to
100 electrodes placed over their fron-
tal and parietal brain areas. In two
experiments, patients performed the
same basic target-detection task that
the macaques had carried out. Data
from this study, too, showed a direct
link between neural activity oscilla-
tions in the frontal and parietal lobes
and performance on the task (Neuron,
99:P854–65.e5, 2018).
The studies are the first to reveal that,
although paying attention might feel like
a constant process, this cognitive state is
governed by waves of activation gener-
ated inside the brain. “This disconnect
between what’s going on in our brains
and what we experience was very sur-
prising,” Kastner tells The Scientist.
The spotlight of attention could
therefore be thought of as a strobe
light, says Michael Posner, an emeri-
tus professor at the University of Ore-
gon who is often credited as the origi-
nator of the spotlight metaphor. “WeThe brain doesn’t run in
parallel when it comes to
paying attention.
—Ran dolph Helfrich, UC Berkeley16 THE SCIENTIST | the-scientist.com