Memories of events comprise many components--including sights, sounds, smells, and tastes. Somehow the many features of an episodic memory are woven together into a coherent whole, and researchers have had little understanding of how this binding takes place as the memories are processed by the brain's memory center, the hippocampus.
A central question has been whether the hippocampus receives an "episodic packet," or a collection of perceptual strands that it must integrate into a memory.
In an article in the November 9, 2006, issue of the journal Neuron, published by Cell Press, Melina Uncapher and colleagues report experiments with human volunteers that shed important light on this process.
In their experiments, the researchers presented the subjects with series of "study" words on a display screen, as their brains were scanned using functional magnetic resonance imaging (fMRI). This technique involves using harmless radio waves and magnetic fields to measure blood flow to brain regions, which reflects brain activity. As their brains were scanned, the subjects were shown words of different colors and that were located in different quadrants of the display screen.
Later, the subjects were presented a collection of words including both the study words and new words. They were asked to recall whether the words were old or new, and for the old words, their color and location.