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Abstract:
Several lines of evidence suggest that accurate episodic
memory depends on the evaluation of retrieved perceptual details.
We investigated the role of prefrontal cortex in this metamemory
function by comparing brain potentials during tests of recognition
memory for line drawings of objects, while manipulating retrieval
demands. In Experiment 1, subjects were tested with new objects,
objects that were identical to those studied, and studied objects
with an altered aspect ratio. Instructions were to judge objects
old only if they were not modified (specific test) or to disregard
modifications (general test). In Experiment 2, subjects were tested
with new objects and objects that were either larger or smaller
versions of studied objects. Instructions were to determine whether
objects were new or old (general test) or to additionally determine
whether old objects were larger or smaller than at study (specific
test). In both experiments, brain potentials after 200 ms were more
positive during the specific than general test, and this effect
showed a left frontal scalp topography. Because this differential
response was similar for old and new objects, it was interpreted as
a neural correlate of an evaluation process in which specific
perceptual attributes of recognition cues and information retrieved
from memory were compared. This retrieval evaluation process
appears to depend on left prefrontal cortex and to occur whether or
not retrieval is successful. Contrary to the HERA model, these
results highlight the importance of left prefrontal cortex in
accurate episodic retrieval.
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