In a first-ever demonstration, UCLA School of Medicine and Caltech researchers have shed new light on how the "mind's eye" works, uncovering evidence that single neurons -- individual cells in the brain -- are involved in recalling specific visual images to mind.
The study, published in the Nov. 16 issue of the journal Nature, further defines the role that individual neurons play in the brain during imagery and builds upon previous UCLA findings.
"Our research helps clarify how the mind's eye works," said lead author and UCLA neurosurgeon Dr. Itzhak Fried. "Visual images can be generated in our mind's eye in the absence of actually looking at the image. Our study reveals that the same brain cells that fire when a person looks at a picture of the Mona Lisa are, in fact, the same neurons that excite when that person is asked to imagine the Mona Lisa."
To investigate neuronal activity related to encoding and retrieval of visual images, the researchers recorded the activity of 276 single neurons during several patient sessions. In this study, researchers recorded the electrical activity of several brain cells in nine patients with severe epilepsy who had tiny microelectrodes implanted in their brains to find the focus of their seizures.
Researchers implanted the electrodes in areas of the brain involved in memory and social behavior. They recorded impulses from single neurons in the human medial temporal lobe while the subjects were asked to imagine previously viewed images. They found that single neurons in certain areas of the brain - the hippocampus, amygdala, entorhinal cortex and parahippocampal gyrus - selectively altered their firing rates depending on the stimulus the subjects imagined.
A series of images was shown on a monitor and each picture was repeated several times. Subjects viewed images of faces, household objects, spatial layouts, cars, animals, food, drawings and photos of famous people and complex patterns
Contact: Roxanne Yamaguchi Moster
University of California - Los Angeles