2008 Woodie Awards
Imaging study shows how brain remembers details of life
Issue date: 4/3/08
Figuring out where in the hippocampus a computational process like pattern separation takes place will further our understanding of how memory works in general.
And that's exactly what Stark and his colleagues set out to do. As with most neuropsychological studies, their experiment's design was the secret behind its novel results.
Though the scientists undeniably wanted to study the neural basis of memory, they were obliged, in their choice of stimuli, to take memory out of the equation.
This is because memory capacities vary from person to person, so, in order to balance one subject's particularly good memory or another's particularly lousy one, the study's stimuli had to avoid being overtly memory-based.
In each round of testing, subjects were presented with one of three pictures, which Stark and his colleagues termed "novel," "repeated" or "lure." Novel indicated the first time the subject saw a given picture - for example, a light switch - while repeated corresponded to the presentation of an identical picture.
However, lure, as its name suggests, was a little trickier. It involved presenting subjects with a slight variation on the previous picture. In the case of the light switch, for instance, the switch was up in the novel and repeated pictures but down in the lure picture.
In all three situations, the researchers measured their subjects' brain activity using functional magnetic resonance imaging (fMRI), a technique that uses changes in how blood is supplied to the brain to pinpoint areas of increased neural activity.
Since the brain areas Stark and his colleagues were interested in were quite small, they took very detailed snapshots of activity, each of which consisted of cubes only 1.5 millimeters on each side.
If pattern completion was taking place in a certain area, the researchers hypothesized that there should be no difference in brain activity elicited by the novel picture and the lure.
In other words, if the hippocampus is completing a pattern, it should dismiss any small differences and "see" an identical picture.
And that's exactly what Stark and his colleagues set out to do. As with most neuropsychological studies, their experiment's design was the secret behind its novel results.
Though the scientists undeniably wanted to study the neural basis of memory, they were obliged, in their choice of stimuli, to take memory out of the equation.
This is because memory capacities vary from person to person, so, in order to balance one subject's particularly good memory or another's particularly lousy one, the study's stimuli had to avoid being overtly memory-based.
In each round of testing, subjects were presented with one of three pictures, which Stark and his colleagues termed "novel," "repeated" or "lure." Novel indicated the first time the subject saw a given picture - for example, a light switch - while repeated corresponded to the presentation of an identical picture.
However, lure, as its name suggests, was a little trickier. It involved presenting subjects with a slight variation on the previous picture. In the case of the light switch, for instance, the switch was up in the novel and repeated pictures but down in the lure picture.
In all three situations, the researchers measured their subjects' brain activity using functional magnetic resonance imaging (fMRI), a technique that uses changes in how blood is supplied to the brain to pinpoint areas of increased neural activity.
Since the brain areas Stark and his colleagues were interested in were quite small, they took very detailed snapshots of activity, each of which consisted of cubes only 1.5 millimeters on each side.
If pattern completion was taking place in a certain area, the researchers hypothesized that there should be no difference in brain activity elicited by the novel picture and the lure.
In other words, if the hippocampus is completing a pattern, it should dismiss any small differences and "see" an identical picture.
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