|New Scientist, 22-06-2005, door Anna Gosline ||
Why your brain has a ‘Jennifer Aniston cell'
Obsessed with reruns of the TV sitcom Friends? Well then you probably have at
least one "Jennifer Aniston cell" in your brain, suggests research on the
activity patterns of single neurons in memory-linked areas of the brain. The
results point to a decades-old and dismissed theory tying single neurons to
individual concepts and could help neuroscientists understand the elusive human
"For things that you see over and over again, your family,
your boyfriend, or celebrities, your brain wires up and fires very specifically
to them. These neurons are very, very specific, much more than people think,"
says Christof Koch at the California Institute of Technology in Pasadena, US,
one of the researchers.
In the 1960s, neuroscientist Jerry Lettvin suggested that
people have neurons that respond to a single concept such as, for example, their
grandmother. The notion of these hyper-specific neurons, coined "grandmother
cells" was quickly rejected by psychologists as laughably simplistic.
But Rodrigo Quiroga, at the University of Leicester, UK, who
led the new study, and his colleagues have found some very grandmother-like
cells. Previous unpublished findings from the team showed tantalising results: a
neuron that fired only in response to pictures of former US president Bill
Clinton, or another to images of the Beatles. But for such "grandmother cells"
to exist, they must invariably respond to the "concept" of Bill Clinton, not
just similar pictures.
Wired up, fired up
To investigate further, the team turned to eight patients currently undergoing
treatment for epilepsy. In an attempt to locate the brain areas responsible for
their seizures, each patient had around 100 tiny electrodes implanted in their
brain. Many of the wires were placed in the hippocampus - an area of the brain
vital to long-term memory formation.
They first gave each subject a screening test, showing them
between 71 and 114 images of famous people, places, and even food items. For
each subject, the researchers measured the electrical activity or "firing" of
the neurons connected to the electrodes. Of the 993 neurons sampled, 132 fired
to at least one image.
The team then went back for a testing phase, this time
showing participants three to seven different pictures of the initial 132 photo
subjects that hit. For example, one woman saw seven different photos of the
Jennifer Aniston alongside 80 other photos of animals, buildings or additional
famous people such as Julia Roberts. The neuron almost ignored all other photos,
but fired steadily each time Aniston appeared on screen.
The team found similar results with another woman who had a neuron for pictures
of Halle Berry, including a drawing of her face and an image of just the words
of her name. "This neuron is responding to the concept, the abstract entity, of
Halle Berry," says Quiroga. "If you show a line drawing or a profile, it's the
same response. We also showed pictures of her as Catwoman, and you can hardly
see her because of the mask. But if you know it is Halle Berry then the neurons
Given more time and an exhaustive list of images, the team
may well have landed upon other images that spiked the activity of the "Halle
Berry" neuron. In one participant, the "Jen" neuron also fired in response to a
picture of her former Friends cast-mate, Lisa Kudrow. The pattern suggests that
the actresses are tied together in the memory associations of this particular
woman, says Charles Connor, a neuroscientist at Johns Hopkins University in
These object-specific neurons may be at the core of how we
make memories, say Connor. "I think that's the excitement to these results," he
says. "You are looking at the far end of the transformation from metric, visual
shapes to conceptual memory-related information. It is that transformation that
underlies our ability to understand the world. It's not enough to see something
familiar and match it. It's the fact that you plug visual information into the
rich tapestry of memory that brings it to life."
Journal reference: Nature (vol 435 p 1102)
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