NEUROSCIENCE:
Magnetic Brain Imaging Traces a Stairway to Memory
James Glanz
LOS ANGELES--In work presented at a meeting of the American Physical Society here 2 weeks ago, researchers monitoring the subtle magnetic fields that sprout from the skull were able to watch how neuronal firing marched along the entire visual pathway--the first time that's been done for the human brain. The result was a motion picture of the neural processing of a visual stimulus--and an unexpected discovery: In every location where there is a response to a visual stimulus, it establishes a memory. The data imply that each site has a distinct "forgetting time," ranging from tenths of a second in the primary visual cortex--the first stage of raw processing--to as long as 30 seconds farther downstream.