The eyes remember
Movement may reveal memories that the brain recalls even when a person isn’t aware of them
Eyewitness testimony is notoriously flaky, but new research suggests that eye movements can accurately reveal what a person remembers, even if the person isn’t aware of the memory.
In a memory test, participants’ eye movements picked the right answer even when the participant failed to, Deborah Hannula and Charan Ranganath, both of the University of California, Davis, report in the Sept. 10 Neuron. The eye movements corresponded to activity in the hippocampus, an important learning and memory center in the brain. The results suggest that eye movements can reveal unconscious memories activated in the hippocampus, the authors say.
Some neuroscientists have believed that the hippocampus is involved only in conscious or “declarative” memories, such as of people, facts or events. People who have damage to the hippocampus aren’t able to form or recall declarative memories. These amnesiac patients can, however, learn new skills that require unconscious “procedural” memories, such as riding a bike — leading to the belief that an intact hippocampus is not needed for unconscious recall.
But the new study suggests that the hippocampus actually is involved in memories of relationships that a person does not consciously recollect. Hannula and Ranganath showed volunteers in a functional MRI scanner pictures of faces paired with an outdoor scene. After presenting about 50 such pairs, the researchers showed the landscape picture followed by three faces. Participants were then asked to choose which face had previously been matched with the landscape.