Single-Cell Recognition: A Halle Berry Brain Cell
Embargoed for release at 10 a.m., PDT, June 22, 2005
PASADENA, Calif. - World travelers can instantly identify the architectural
sails of the Sydney Opera House, while movie aficionados can immediately
I.D. Oscar-winning actress Halle Berry beneath her Catwoman costume or even
in an artist's caricature. But how does the human brain instantly translate
varied and abstract visual images into a single and consistently recognizable
Now a research team of neuroscientists from the California Institute of
Technology and UCLA has found that a single neuron can recognize people,
landmarks, and objects--even letter strings of names ("H-A-L-L-E-B-E-R-R-Y").
The findings, reported in the current issue of the journal Nature, suggest
that a consistent, sparse, and explicit code may play a role in transforming
complex visual representations into long-term and more abstract memories.
"This new understanding of individual neurons as 'thinking cells' is an
important step toward cracking the brain's cognition code," says co-senior
investigator Itzhak Fried, a professor of neurosurgery at the David Geffen
School of Medicine at UCLA, and a professor of psychiatry and biobehavioral
sciences at the Semel Institute for Neuroscience and Human Behavior, also
at UCLA. "As our understanding grows, we one day may be able to build cognitive
prostheses to replace functions lost due to brain injury or disease, perhaps
even for memory."
"Our findings fly in the face of conventional thinking about how brain cells
function," adds Christof Koch, the Lois and Victor Troendle Professor of
Cognitive and Behavioral Biology and professor of computation and neural
systems at Caltech, and the other co-senior investigator. "Conventional wisdom
views individual brain cells as simple switches or relays. In fact, we are
finding that neurons are able to function more like a sophisticated computer."
The study is an example of the power of neurobiological research using data
drawn directly from inside a living human brain. Most neurobiological research
involves animals, postmortem tissue, or functional brain imaging in magnetic
scanners. In contrast, these researchers draw data directly from the brains
of eight consenting clinical patients with epilepsy at the UCLA Medical Center,
wiring them with intracranial electrodes to identify the seizure origin for
potential surgical treatment.
The team recorded responses from the medial temporal lobe, which plays a
major role in human memory and is one of the first regions affected in patients
with Alzheimer's disease. Responses by individual neurons appeared on a computer
screen as spikes on a graph.
In the initial recording session, subjects viewed a large number of images
of famous people, landmark buildings, animals, objects, and other images
chosen after an interview. To keep the subjects focused, researchers asked
them to push a computer key to indicate whether the image was a person. After
determining which images prompted a significant response in at least one
neuron, additional sessions tested response to three to eight variations
of each of those images.
Responses varied with the person and stimulus. For example, a single neuron
in the left posterior hippocampus of one subject responded to 30 out of 87
images. It fired in response to all pictures of actress Jennifer Aniston,
but not at all, or only very weakly, to other famous and non-famous faces,
landmarks, animals, or objects. The neuron also (and wisely, it turns out)
did not respond to pictures of Jennifer Aniston together with actor Brad
In another patient, pictures of Halle Berry activated a neuron in the right
anterior hippocampus, as did a caricature of the actress, images of her in
the lead role of the film Catwoman, and a letter sequence spelling her name.
In a third subject, a neuron in the left anterior hippocampus responded to
pictures of the landmark Sydney Opera House and Baha'í Temple, and also to
the letter string "Sydney Opera," but not to other letter strings, such as
In addition to Koch and Fried, the research team included Rodrigo Quian-Quiroga
of Caltech and UCLA, Leila Reddy of Caltech, and Gabriel Kreiman of the Massachusetts
Institute of Technology.
The research was funded by grants from the National Institute of Neurological
Disorders and Stroke, National Institute of Mental Health, the National Science
Foundation, the Defense Advanced Research Projects Agency, the Office of
Naval Research, the W. M. Keck Foundation Fund for Discovery in Basic Medical
Research, a Whiteman fellowship, the Gordon Moore Foundation, the Sloan Foundation,
and the Swartz Foundation for Computational Neuroscience.
MEDIA CONTACTS: Mark Wheeler, Caltech
Dan Page, UCLA