Cosyne 2007 Workshops
February 26-27, 2007
The Canyons, Utah
Per Sederberg
Oscillatory activity distinguishes true from false memories
To test whether distinct patterns of electrophysiological activity prior to a response can distinguish true from false memories, we analyzed intracranial electroencephalographic (iEEG) recordings while 52 patients undergoing treatment for epilepsy performed a verbal free-recall task. Here we show that the same pattern of gamma band (28-100 Hz) oscillatory activity that predicts successful memory formation at item encoding, increased gamma power in the hippocampus, prefrontal cortex, and left temporal lobe, reemerges at retrieval to distinguish correct from incorrect responses. The timing of these oscillatory effects suggest that self-cued memory retrieval initiates in the hippocampus and then spreads to the cortex. Thus, retrieval of true as compared with false memories induces a distinct pattern of gamma oscillations, possibly reflecting recollection of contextual information associated with past experience. In a follow-up analysis we explore the oscillatory synchrony between these regions during memory retrieval. Preliminary results indicate that changes in low-frequency (3-4 Hz) synchrony between the hippocampus and left temporal lobe also provide an electrophysiological marker of true versus false memory retrieval.
