7 No. 1
science and art of memory
of emotional events, especially aversive ones, tend to attach themselves
to anything around them.
Ressler Assistant Professor of Psychiatry, Center for Behavioral
in a weird way is about the future. . . . It's the sense that it's
probably going to happen again.
Bammer, Associate Professor, Graduate Institute of the Liberal Arts
My Return to the Chair
Identity and academic sacred
space in Middle Eastern and South Asian studies
Gordon D. Newby, Professor and Chair, Middle Eastern and South
for Bird Brains
An unconventioal frontier
for understanding social behavior
Donna Maney, Assistant Professor of Psychology
Politics of Advice
Biased scientific information
in government agencies
Mike Kuhar, Charles Howard Candler Professor of Neuropharmacology
How intellectual initiatives
form and flourish
Paul Jean, Associate Director of New Research Initiatives, Emory
College Office of Research, and Daniel Teodorescu, Director of Institutional
Research, Office of the Provost
Exchange: Describe your research.
Kerry Ressler: The main question I’ve been
interested in is how the environment shapes the brain. How can we
use hard science to understand the actual mechanisms of learning
and memory, as far as that shapes who we are? My lab focuses on
using molecular biology in combination with behavioral neurobiology
to try to understand the molecular and cellular mechanisms of fear
learning. In animal models, fear learning is a process of classical
conditioning [the kind of learning Pavlov and his dogs made famous]
in which a previously neutral cue, such as a light, tone, or odor,
becomes paired with an aversive cue, such as a mild foot shock.
After this pairing, which creates a memory that lasts for months
to years, the previously neutral cue now elicits a fear reaction.
We can then measure the physiological and behavioral fear response
in these animals. The basic tenet that brings the two together is
that we can understand in a concrete way how new learning occurs
behaviorally. By doing that in a simple way in animals, we can eventually
understand the structural and molecular mechanisms of learning.
Many mental disorders relate to learning and memory. At one level
for example, Posttraumatic Stress Disorder (PTSD) is a disorder
of negative memories that are either overlearned or difficult to
diminish through extinction, or are a combination of both.
One day a week, I work at Grady Hospital, mostly with people from
the inner city with ptsd, which is an under-recognized phenomenon.
In our clinic, the Trauma Clinic at Fulton County Community Mental
Health Center, the prevalence of ptsd is as high as it is among
Vietnam veterans. Interpersonal violence, gun violence, and neglect
lead to a level of trauma in the inner city that can be as high
as it is for people in war. And that contributes to cycles of violence.
AE: When someone is frightened, does emotion
distort the process of creating the memory of that moment?
KR: The term “distortion” has implications
that I would not want to evoke. But human behavioral data and animal
data show that emotionally charged events lead to much stronger
memory retention and memory encoding than those without emotional
contexts. There’s decades of data on that. And that’s
probably for positive as well as negative emotions. What we know
now is that the amygdala and the hippocampus are probably acting
as the hubs of memory, and they are telling the rest of the brain
what’s important and what’s not.
AE: Why are you hesitant to use the word “distorted”
to describe the way emotionally laden memories are recorded?
KR: Because of the political ramifications of that
word: “distortion” implies it’s stretched from
truth. The animal data, if anything, would argue that in these models
it’s not stretched from truth, but may instead represent a
hyper-aware memory that is learned in a more vivid or enduring way.
Such data also suggest that emotionally laden memories may be discriminated
differently than non-emotional memories.
Discriminated in what way?
KR: Discrimination versus generalization refers
to the ability of an organism to discriminate between any two different
cues. The level at which it can distinguish between the two shows
discriminative learning. If it responds to both cues, even though
only one was paired with the fear stimulus, then the learning is
Having something emotionally laden makes it encoded in a way that
is more clearly discriminated. But memories also are constantly
being reactivated. Simply remembering a memory is probably making
it in some ways plastic again. And the memories of emotional events,
especially aversive ones, tend to attach themselves to anything
around them. Thus some memories tend to generalize a lot quicker
if they contain negative emotional contexts. Think of someone with
ptsd—say, someone who is raped in an evening somewhere in
an alley. Initially, they may avoid that part of town, then going
out at night, then perhaps all men, or even leaving the house. The
negative event has become more and more broadly associated or generalized.
AE: What’s most interesting about what’s
happening broadly in this field now?
KR: With the genome sequencing, we know that 50
percent of the genes in the body are more or less specific to the
brain. And the primary function of the brain is probably to allow
for adaptability to the environment. Almost everything that needs
to happen for us to interact with the environment requires some
level of memory.
Sophistication in behavioral research is converging with sophistication
in molecular biology. We can manipulate genes in specific cells,
pathways, and circuits into behavioral paradigms in ways that I
think will allow us in the next decade to dissect out some complex
processes. Understanding how a memory that occurs in a simple animal
model, like a mouse, is the first step.