Saturday, September 12, 2009

Eye Movements Give Away Memories

September 10, 2009 
Your eye movements can show that the elements of a memory are in place 
even when you cannot consciously recall it or when you get it wrong, according 
to a new study from the UC Davis Center for Neuroscience. The findings, 
published Sept. 10 in the journal Neuron, could have several practical 
It has been known for some time that a part of the brain called the 
hippocampus is necessary for the conscious recall of memories, but Debbie 
Hannula, a postdoctoral researcher at UC Davis, and Charan Ranganath, 
associate professor of psychology, addressed the controversial question of 
whether the hippocampus can support memories even when people are 
unaware of them. 
Hannula and Ranganath tracked the eye movements and scanned brain activity 
of volunteers using a functional MRI (fMRI) machine while they performed a 
simple memory test. The volunteers were briefly shown a scene, then a face 
superimposed on the scene. To test their recall, they were shown the same 
scene again, but with three faces on it, and asked which one they associated 
with the scene. 
Previous work conducted by Hannula and her colleagues had shown that the 
eyes move to the correct face before the volunteer is aware of recalling the 
memory. In the new experiments, the hippocampus lit up with activity seconds 
before the eyes fixated on the correct face, even when participants failed to 
explicitly recall it. 
"The signal in the hippocampus was closely tied to how long people spent 
looking at the right face," Ranganath said. “So even when your conscious 
memory is wrong, the eyes (and the hippocampus) may have it.” Ranganath 
The fMRI images also showed more activity in another part of the brain, the 
prefrontal cortex, when memories were correctly recalled. The scans showed 
that communication between the hippocampus and the prefrontal cortex was 
increased when people accurately recalled the face. 
"We think that conscious memory comes from communication between the 
hippocampus, prefrontal cortex, and other parts of the brain," Ranganath said. 
"But the hippocampus may be able to support memories, even when you can't 
recall them." 
The eye-movement technique could have a range of uses. For example, it could 
be used to look for evidence of memories in people who are unable or unwilling 
to consciously recall them, to study hippocampal function in patients or young 
children, and in studies aimed at developing new drugs to improve memory 
function, Ranganath said.
9/12/09 8:52 AMUC Davis News & Information :: Printable news 
Page 2 of 2 
The work is funded by grants from the National Institutes of Health. 
About UC Davis 
For 100 years, UC Davis has engaged in teaching, research and public service 
that matter to California and transform the world. Located close to the state 
capital, UC Davis has 31,000 students, an annual research budget that exceeds 
$500 million, a comprehensive health system and 13 specialized research 
centers. The university offers interdisciplinary graduate study and more than 
100 undergraduate majors in four colleges — Agricultural and Environmental 
Sciences, Biological Sciences, Engineering, and Letters and Science — and 
advanced degrees from six professional schools — Education, Law, 
Management, Medicine, Veterinary Medicine and the Betty Irene Moore School 
of Nursing. 
Media contact(s): 
• Charan Ranganath, Center for Neuroscience, (530) 757-8750, 
• Andy Fell, UC Davis News Service, (530) 752-4533, 
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