Sensory
cortices
processing areas directly to the amygdala. And the amygdala shares elaborate
communications channels with the prefrontal cortex — the brain’s control center
for planning and decision making.
Its strategic location allows the amygdala to act as a spotlight, calling attention
to sensory input that is new, exciting and
important. In this way, it helps predict the
timing and location of potential dangers,
helping you dodge many of the things you
dread. But those same connections also
help you acquire the good things in life, by
identifying and assessing rewards such as
food, sex and other delights.
Though much more is known about
its fear job, researchers are now vigorously gathering evidence about how the
amygdala evaluates information and
events for their reward potential. Recent
studies offer clues to how the amygdala
assigns value to rewards and adjusts
that value as circumstances change.
Other work provides insights into how
the amygdala links actions and rewards,
suggesting that the amygdala plays a role
in goal-directed behavior. Still others are
finding out how neural circuits in the
highly connected human amygdala work
with other brain structures to recognize
good things and find ways to get them.
Such studies may help scientists
understand how rewards can sway attention or learning and help people make
choices. Recent results may also lead to
new therapies for those suffering from
depression and anxiety disorders, as well
as providing insights into reward-seek-ing behaviors such as addiction.
system, alerting the body to respond.
Chemical messengers are then
released into the bloodstream to
ready a flight-or-fight response,
providing the energy needed to
run faster or hit harder.
Early humans relied
on this system to avoid
all types of deadly threats,
from saber-toothed tigers to
falling trees.
But being able to identify
potential rewards is also crucial
for survival, says Elisabeth Murray, a
neurobiologist at the National Institute of Mental Health in Bethesda, Md.
People, and other animals, face countless reward-related decisions as they
go about their daily business, foraging
for food, finding mates and passing on
genes. Identifying pleasant situations
and avoiding aversive ones can boost
well-being and chances for survival.
Murray says many scientists are now
coming to understand that at least part
of that reward-based behavior is driven
by some sort of interaction between the
amygdala and the frontal lobe, known
to be involved in thought, memory and
consciousness. Her lab is especially
interested in circuits connecting the
amygdala with the orbitofrontal cortex,
a part of the prefrontal cortex that sits
just behind the eyes.
“Those parts of the brain are anatomically interconnected, and we think
that they’re interconnected in this way
to help animals make good decisions,”
Murray says.
In recent years, Murray and others
have initiated studies to better understand how the amygdala processes information that feeds into decisions.
In 2006, researchers at Columbia University provided a clue, showing how the
amygdala judges the emotional value of
stimuli. A team led by C. Daniel Salzman
taught monkeys to associate two patterns
on a TV monitor with either a rewarding
sip of water or an irksome puff of air to
the face. By recording the electrical activity in the amygdala as animals watched
the screen, the scientists showed that different amygdala nerve cells are tuned to
Anterior
cingulate
cortex
Central
nucleus
Orbitofrontal
cortex
Sensory
cortices
Prefrontal
cortex
Intercalated
masses
Lateral
nucleus
Basal and
accessory
basal nuclei Amygdala
Hippocampus
Hormonal responses
Autonomic
nervous system
Inhibitory
connections
Excitatory
connections
Linked in two clumps of cells, one
on each side of the brain, the amyg-
dala has many connections with
parts of the prefrontal cortex and
brain areas involved in the senses.
C.D. salzman anD s. Fusi/annual review of neuroscience 2010
Recognizing reward
The amygdala is part of the limbic system, a primitive set of brain structures
involved in emotion and arousal. Studies going back to the mid-1950s show
that the amygdala, located near the
hippocampus in the front part of the temporal lobe, serves as a type of watchdog
to identify potential threats and danger.
Because it is highly interconnected with
the senses, the amygdala can take in danger signals — the sight of a snake or the
sound of a gunshot — and flash messages
almost instantly through the nervous
1. as the brain’s command center, the
prefrontal cortex is responsible for
making social choices, predicting
future events, planning behavior and
controlling emotions.
2. a part of the prefrontal cortex, the
orbitofrontal cortex appears to be
active during sensory integration
and decision making.
3. the anterior cingulate cortex
plays a role in attention, motivation
and error detection.
4. the amygdala’s central nucleus is
involved in fear responses, including
freezing in place, rapid heartbeat
and increased respiration. it is also
linked with stress-hormone release.
5. after receiving information from the
senses, the lateral nucleus forms
associations with memories.
6. Clusters of nerve cells, the basal
nuclei and accessory basal nuclei
are responsible for body movement
and coordination.
7. the intercalated masses are cell
groups thought to play a role in
emotional learning and memory.
8. the hippocampus plays an impor-
tant part in learning and memory.
handle positive and negative events.
In a follow-up experiment with a
slightly different setup, Salzman’s group
found that a set of nerve cells is specifically tuned for processing surprise.
Some among those nerve cells were dedicated solely to the rewarding surprise,
the water sip.
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February 26, 2011 | science news | 23
