P300 correlates of simulated malingered amnesia in a matching-to-sample task: topographic analyses of deception versus truthtelling responses.

Two experiments using a P300-enhanced Forced Choice Procedure (P3FCP) investigated simulated amnesia in a matching-to-sample task. In Experiment 1, successful manipulation of subjects towards different behavioral hit rates (75-80% vs. 85-90%) did not adversely affect the diagnostic sensitivity of match-mismatch Pz-P300 amplitude analyses, allowing detection of 69% of simulators. P300 amplitudes of simulators (Malinger group) were as large as those of truth-tellers (truth group, a control), indicating no dual task-related (Malingering) reduction across different behavioral hit rates. Experiment 2 found no main effect of oddball type, match vs. mismatch, on P300 (P3) amplitude with a mismatch-rare variant of the P3FCP. This study also revealed larger Pz-P3s in the Malingering (vs. Truth-telling) condition. Subsequent topographic analyses suggested different Truth and Malinger scaled P3 amplitude topographies in both these sets of P3FCP data and in those from a previous autobiographical memory paradigm. Further analysis yielded preliminary evidence for a common deception-related P3 amplitude topography across different paradigms/conditions.

The effects of alpha (10-Hz) and beta (22-Hz) "entrainment" stimulation on the alpha and beta EEG bands: individual differences are critical to prediction of effects.

Two different groups of normal college students were formed: One (the alpha group) received 10-Hz audiovisual (AV) stimulation for 8 minutes, and the other (beta) group received 22-Hz AV stimulation for 8 minutes. EEG power in the alpha (8-13 Hz) and beta (13-30 Hz) bands was FFT-extracted before, during, and for 24 minutes after stimulation. It was found that baseline (prestimulation) alpha and beta power predict the effects of stimulation, leading to individual differences in responsivity. High-baseline alpha participants showed either no entrainment or relatively prolonged entrainment with alpha stimulation. Low-baseline participants showed transient entrainment. Baseline alpha also predicted the direction of change in alpha with beta stimulation. Baseline beta and alpha predicted beta band response to beta stimulation, which was transient enhancement in some participants, inhibition in others. Some participants showed relatively prolonged beta enhancement with beta stimulation.