Carnegie Mellon University
August 25, 2014

Press Release: "Haven't I Seen This Before?" Researchers Show How Neurons Respond to Sequences of Familiar Objects

Contact: Jocelyn Duffy / 412-268-9982 /

Training ImagesPITTSBURGH—The world grows increasingly more chaotic year after year, and our brains are constantly bombarded with images. A new study from Center for the Neural Basis of Cognition (CNBC), a joint project between Carnegie Mellon University and the University of Pittsburgh, reveals how neurons in the part of the brain responsible for recognizing objects respond to being shown a barrage of images. The study is published online by Nature Neuroscience.

The CNBC researchers showed animal subjects a rapid succession of images, some that were new, and some that the subjects had seen more than 100 times. The researchers measured the electrical response of individual neurons in the inferotemporal cortex, an essential part of the visual system and the part of the brain responsible for object recognition.

In previous studies, researchers found that when subjects were shown a single, familiar image, their neurons responded less strongly than when they were shown an unfamiliar image. However, in the current study, the CNBC researchers found that when subjects were exposed to familiar and unfamiliar images in a rapid succession, their neurons — especially the inhibitory neurons — fired much more strongly and selectively to images the subject had seen many times before.

"It was such a dramatic effect, it leapt out at us," said Carl Olson, a professor at Carnegie Mellon. "You wouldn't expect there to be such deep changes in the brain from simply making things familiar. We think this may be a mechanism the brain uses to track a rapidly changing visual environment."

The researchers then ran a similar experiment in which they used themselves as subjects, recording their brain activity using EEG. They found that the humans' brains responded similarly to the animal subjects' brains when presented with familiar or unfamiliar images in rapid succession. In future studies, they hope to link these changes in the brain to improvements in perception and cognition.

Co-authors of the study include Travis Meyer of Carnegie Mellon and the CNBC, and Christopher Walker and Raymond Cho of the Department of Psychiatry at Pitt. The research was funded by the National Institutes of Health's National Eye Institute and National Institute of Mental Health (R01 EY018620, P50 MH084053, K08 MH080329), and the Pennsylvania Department of Health's Commonwealth Universal Research Enhancement Program.

A new study from CMU and Pitt researchers at the Center for the Neural Basis of Cognition shows how neurons react to a stream of images. Test subjects were trained to look at images of items (pictured above) until those images became familiar.