Feedback does not influence the recognition-related P300 in a novel concealed information test while feedback-evoked P300 shows promising diagnostic accuracy.

The feedback concealed information test (fCIT) is a novel variant of a CIT, which provides participants with feedback regarding their memory concealment performance during the CIT. Previous studies have found that feedback-related ERPs associated with feedback processing in the fCIT can accurately identify concealed information. However, it is still unknown whether the feedback influences the process and ERP signs of recognition during memory concealment, such as the recognition P300. To address this issue, the present study directly compared the recognition-based P300 in CITs with and without feedback. Results showed that the probe elicited a larger recognition P300 than irrelevants in both CITs with and without feedback, and there were no significant differences in recognition P300 between those two CITs. Moreover, the detection rate for recognition-based P300 in both CITs also had no significant difference. The feedback-related ERPs, especially feedback P300, continued to discriminate guilty and innocent subjects with AUCs well above the chance.

Single versus multiple probe blocks of P300-based concealed information tests for self-referring versus incidentally obtained information.

UNLABELLED: The aim of the present study was to compare two protocols and two information types on detection of concealed knowledge. Four independent groups of subjects were run. Two were tested on probe stimuli of a self-referring (AUTO) nature and two were tested on incidentally acquired details of a mock crime (MOCK). Each pair of groups was run either in a one-probe (1PB) or multiple probe (6PB) block. In the single probe block, which was repeated three times with a different probe on each block, one probe item was randomly repeated multiple times in a Bernoulli series with frequently presented, meaningless or irrelevant items. There was also a rare target item designed to force attention to the stimulus screen. All stimulus types were of the same category within each block. In contrast, in the multiple probe (and category) block, rare probes, rare targets and frequent irrelevant items were repeatedly presented in a Bernoulli series within one block. MAJOR RESULTS: There was a difference in task demand as measured by reaction time between the two protocols (the multiple probe protocol was more demanding), and a difference trend in P300 detection sensitivity between protocols for both information types combined in favor of the 1PB (p<.07). With both protocols combined, there was a trend (p<.07) favoring detection of familiar versus incidentally learned information. In terms of P300 amplitudes, both protocols showed the usual result that P300 to probes was greater than that to irrelevants. Also, as with detection rates, self-referring information was better detected in terms of Probe-Irrelevant P300 amplitude differences than mock crime information, regardless of protocol. There was no effect of time passage across the repeated blocks of the one-probe protocol. Methodological problems with the multiple probe protocol as utilized in most recent publications are discussed.

P300 latency, but not amplitude or topography, distinguishes between true and false recognition.

Two experiments are described in which the P300 component of the event-related potential was recorded during a modification of the Deese-Roediger-McDermott false-memory paradigm. P300 amplitudes and topographies were evaluated in both true recognition of previously presented (studied) words and in false recognition of associatively related, never presented (critical lure) words. P300 topography and amplitude did not appear to differ between true and false recognition. However, false recognition of critical lures produced substantially shorter P300 latencies than did the true recognition of studied words.

Peak-to-peak measurement of P300 recorded at 0.3 Hz high pass filter settings in intraindividual diagnosis: complex vs. simple paradigms.

We compared effects of 0.3 Hz with 0.01 Hz settings of the high pass amplifier filter, and baseline-to-peak with peak-to-peak measurements of the P300 event-related potential. The key dependent variable of interest was intraindividual rate of accuracy in discrimination of oddball vs. frequent evoked P300 responses, in various paradigms. In Experiment 1 (a lab deception paradigm), we found that the combination of the 0.3 Hz filter setting and the peak-peak measurement of P300 correctly diagnosed oddball vs. frequent in 26 of 26 (100%) cases. This parameter combination outperformed all others. In a second, more field-like experiment (in that the participant knew that the experimenter was blind to ground truth), the peak-peak index again outperformed the base-peak index. It was also observed that the pre-stimulus EEG baseline variability exceeded that of the negative peak (NEG) following P300, i.e. the peak to which the peak-peak index refers P300 for computation. We also observed that the base-peak measurement of P300 is uncorrelated with NEG, and that NEG, seen only in 0.3 Hz channels, correlates highly (-0.67) with the duration of recovery of P300 to the pre-stimulus baseline EEG level as seen in the 0.01-Hz channel. However, in a final experiment using two simple visual and auditory oddball tasks, the base-peak measurement was as diagnostic as the peak-peak measurement.

Further investigation of traumatic brain injury versus insufficient effort with the California Verbal Learning Test.

The present study replicates and attempts to extend previous research using the California Verbal Learning Test (CVLT) to identify malingerers. Documented moderate and severe traumatic brain injury patients (n = 42) were compared with clinical malingerers identified by criteria other than the CVLT (n = 21), malingering simulators instructed in realistic potential injury sequelae (n = 25), and normal controls (n = 21). Results of discriminant function analyses for high and low base rates are reported, showing similar results. Also, the four individual cutoff scores (Recognition Hits, Discriminability, Total Words Recalled, Long Delay Cued Recall) from Millis, Putnam, Adams, and Ricker (1995) were evaluated with these groups. Similar specificity rates were found with all four variables, while sensitivity rates were slightly lower than that of Millis. Adjusted cutoffs derived from the new samples resulted in slightly improved overall classification rates. Overall, present findings support those of Millis et al. (1995) with regard to the use of the CVLT in detection of malingering. Exploratory use of Total Intrusions and Recognition Hits Compared to Long Delay Free Recall was not promising. Simulators were found to be fairly comparable in performance to actual malingerers, affirming their use in malingering research.

Applied psychophysiology: exclusions and inclusions.

Mark Schwartz has done a fine job in a systematic attempt to define applied psychophysiology. The present author disagrees on a few points concerning what areas will be included and what areas excluded from Schwatz's definition of this term.

P300 scalp amplitude distribution as an index of deception in a simulated cognitive deficit model.

Truth-telling (Truth) and simulated malingering (Malinger) groups were tested in a matching-to-sample procedure in which each sample three-digit number was followed by a series of nine test numbers, only one of which matched the sample. P300 was recorded during test-number presentation. Group analyses revealed differences between the P300s of the groups in unscaled amplitude, but not latency, in response to match and mismatch stimuli. P300 amplitudes at Fz, Cz, and Pz were scaled to remove possible confounding effects of amplitude in tests of the interactions of site with other variables. Significant interactions of both stimulus-type (match vs. mismatch) and group (Truth vs. Malinger) with site were obtained. Within the Malinger group, a significant interaction was obtained (scaled data) between site and response type (honest vs. dishonest). These interactions suggest that deceptive and honest responding are associated with different neurogenerator sets or different sets of P300-overlapping components. In within-individual analyses, 100% of the Truth participants and 87% of the Malinger participants were found to have larger P300 responses at Pz to match stimuli than to mismatch stimuli on the basis of intra-individual bootstrap tests. This represents an improvement in comparison with our related, previous report on a matching-to-sample test using only one test stimulus per sample.

P300 as an index of recognition in a standard and difficult match-to-sample test: a model of amnesia in normal adults.

Earlier research has supported the use of a P300 (P3)-based procedure to detect simulated amnesia. In the present experiment, an attempt was made to model the behavior and event-related potentials (ERPs) that amnestic patients might demonstrate with relatively easy recognition memory tests, by increasing the difficulty of a match-to-sample recognition memory test taken by 18 memory-unimpaired undergraduates. None of the participants in the modeled amnesic condition were classified as having intact recognition memory as the result of P3-based intra-individual tests (specificity = 100%). The results support the utility of a P3 procedure for the detection of malingering by demonstrating the procedure to be a valid measure of impaired recognition with this model of amnesia.

Identifying simulators of cognitive deficit through combined use of neuropsychological test performance and event-related potentials.

Event-related potential (ERP) methods for identifying malingering of cognitive deficit assume that elements of brain/cognitive functioning are not under a person's direct control, whereas neuropsychological methods assume that malingered cognitive deficit will present differently than true impairment in terms of level or pattern of errors on tests of cognitive function. Two studies were conducted to examine the combined use of neuropsychological and ERP methods for identifying malingering because of the potential independence of these approaches. All normal control participants performing at their best level (n = 25) were correctly classified by both ERP and neuropsychological methods. All participants simulating cognitive deficit (n = 35) were correctly classified on the basis of a positive outcome on either the neuropsychological or the ERP method. Results suggest that the neuropsychological and psychophysiological measures of malingering that were studied contribute non-redundant information in the classification of simulators.

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.

Comparison of two EEG asymmetry indices in depressed patients vs. normal controls.

In 11 non-depressed, age-matched controls, and in 13 depressed patients, we compared the frontal alpha asymmetry mean for a baseline session with the percentage of the time in the session when the asymmetry score > 0. It was found that the percent index was a better discriminator of the two groups than was the asymmetry score.

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.

Detecting simulated amnesia for autobiographical and recently learned information using the P300 event-related potential.

To investigate whether the P300 (P3) event-related potential (ERP) can be used as an index of the intactness of recognition memory in subjects trying to simulate amnesia, two groups of subjects (n = 12 and n = 15) were instructed to simulate amnesia and one group of control subjects (n = 14) did not simulate amnesia while taking three recognition tests, during which ERPs were recorded. The three tests consisted of three different types of memory items: (1) the subject's birthday (birth), (2) the experimenter's name (name), (3) a word list of 14 nouns (words). The memory item was presented in a random series with other, similar in type, non-memory items. In group tests, memory items evoked larger amplitude P3s than non-memory items (p < 0.001). Within-subjects tests were used to determine whether the P3 amplitude in response to memory items was larger than the P3 amplitude in response to non-memory items for each individual. There was no difference between the sensitivity of the best within-subjects tests for amnesia simulators (birth = 0.9, name = 0.85, words = 0.53) versus non-simulators (birth = 1.0, name = 0.81, words = 0.5) averaged across the three test types. This suggests that P3 used as an index of the intactness of recognition memory may be useful in cases of suspected malingering.

Preliminary evidence that daily changes in frontal alpha asymmetry correlate with changes in affect in therapy sessions.

Frontal EEG alpha asymmetry was recorded from five depressed outpatients during early EEG biofeedback sessions. Mood was assessed prior to and after each session, and affect change scores were also derived by subtracting pre-session from post-session scores. Alpha magnitude was obtained via Fast Fourier Transforms. All scores (EEG alpha asymmetry and affect) were converted to deviation scores by subtracting each patient's daily score from that patient's mean across all available sessions for that patient. Pearson correlations were then computed between asymmetry and affect scores using the deviation scores combined over patients. There was little evidence of correlation between day-to-day asymmetry score and any single affect score. Strong correlations were obtained, however, between asymmetry score and affect change score and, in particular, between asymmetry score and change in positive affect.

Operant (biofeedback) control of left-right frontal alpha power differences: potential neurotherapy for affective disorders.

Two experiments were done with subjects from a paid pool of undergraduates. In each study, there were five 1-hour sessions on each of 5 days: (1) Baseline: Rewards given for randomly selected 20% of the 700-ms sequential epochs; mean and SD of baseline power differences determined. 2) Exploration: Subjects were rewarded when right minus left alpha differences in an epoch were greater than the baseline mean plus about .85 SD (p = .20); subjects told to discover how to generate rewards. (3)-(5). Training: Subjects were paid (over and above the $8/h flat rate) in proportion to their hit rates. In the first study (in which active filters passed 8-12 Hz activity, and the rectified, integrated amplitude was utilized), 6 of 8 subjects met learning criteria (a significant difference between baseline and training scores). In the second study (in which on-line FFTs were used to extract alpha power), 3 of 5 subjects met learning criteria.

Detecting simulated amnesia with event-related brain potentials.

Two experiments were done in which groups of normal college undergraduate subjects were instructed to simulate autobiographical amnesia related to head injury. The subjects were tested for autobiographical knowledge with pencil-and-paper recall and recognition tasks, and on another day, with recognition tasks in which event-related potentials were recorded in response to the same autobiographical items, this time presented on a display screen. In the first study, three Event-Related Potential (ERP) block types were utilized: 1) a block in which the subject's birthdate was an oddball with p = 0.11 and other dates (not relevant to the subject) had p = 0.89, 2) a block in which phone numbers were used as stimuli, and 3) a block in which (mothers' maiden) names were used as stimuli. Only birthdate blocks were used in the second study. A P300 ERP was seen in response to rare, personally relevant items. In both studies, the main effect of stimulus type (personally relevant versus not personally relevant) on P300 amplitude was significant (p < 0.0001) and there was no main effect of block type in the first study. Under a sophisticated malingering instruction set, about 15% of the items were correctly recalled and about 50% were correctly recognized by simulators in pencil-and-paper tests. Under a naive malingering instruction set, most simulating subjects failed to recall and recognize autobiographical items. In the first study, an arbitrarily but a priori derived discrimination criterion based on a subject's average P300 amplitude afforded 92% correct discrimination of simulating individual subjects for birthdates and phone numbers. The value was 77% for mothers' maiden names. The same criterion applied to the single birthdate block in the second study yielded 93% correct discrimination. The results suggest the P300 may be useful in detection of malingered amnesia.

Interaction of oddball probability and primary task type on P300 in the dual-task paradigm.

Using a dual-task paradigm with an oddball secondary task, P300 amplitude and latency were studied as a function of factorially manipulated oddball probability (low = .22, high = .44) and primary task type. In addition to a Baseline condition (oddball task only), three primary tasks were used: (1) Pure Sensory; watching a movie; (2) Pure Motor (manipulating a flashlight); and (3) Sensory/Motor (using the flashlight to trace the outlines of characters in a movie). The findings included the usual significant effects of probability on amplitude. There was also a significant effect of task type on amplitude, and a significant interaction of oddball probability with task type. In the low but not high probability condition, a pure Sensory task depressed P300 amplitude. In both probability conditions, the Sensory/motor task depressed P300 amplitude. Only task type had a significant effect on P300 latency. The results confirm the ability of other labs (using Sensory/motor primary tasks) to demonstrate P300 depression at high oddball probability, in view of the difficulty in our lab of achieving P300 depression with pure sensory tasks and high oddball probabilities. The results are discussed in terms of partial overlap of processing resource pools.

The self-regulation of slow potential shifts and evoked potentials: interrelationships in response to somatosensory stimulation.

Research on the effects of the self-regulation of event-related potentials (ERP) has failed to investigate the possible interactions and contributions of slower cortical events such as contingent negative variations (CNV) and slower DC level changes. The present study attempted to investigate such interactions by independently conditioning the ERP 200 ms poststimulus (P200) and the CNV while recording both potentials simultaneously; DC level measures were also recorded. 30 subjects attempted to increase (uptraining) or decrease (downtraining) either P200 or CNV in response to sub-painful somatosensory stimulation in a biofeedback paradigm. Following the training sessions, P200 downtrainees reported a significant decrease in their detection thresholds for the somatosensory stimuli (i.e., increased sensitivity). These results agree with some prior findings that decreased ERP amplitude in individuals is indicative of greater sensitivity in subjective pain reports. Although uptraining resulted in larger P200 amplitudes than downtraining, the difference in amplitudes between groups was not significant. CNV uptrainees achieved a higher level of pain tolerance following training. The increased CNV negativity may be associated with increased specific attentional processes that facilitate the subjects' control of, or response to, pain. CNV trainers showed a significant interaction of training over blocks of trials. Generally, there was a significant inverse correlation of P200 and CNV; as CNV amplitude became more negative, the P200 amplitude increased. DC negativity level increased over blocks for all conditions. Results indicate a complex relationship between P200, CNV and pain sensitivity. Both P200 and CNV processes are involved in pain perception, but in apparently different ways, i.e., P200 with sensitivity and CNV with tolerance.

Interacting brain stem components of opiate-activated, descending, pain-inhibitory systems.

This is a review of research aimed at elucidating how various opiate analgesia substrates in rat brain stem interact with one another to bring about opiate analgesia. The three substrates studied are the midbrain periaqueductal grey (PAG), the bulbar nucleus raphe magnus (RM), and the bulbar nucleus reticularis paragigantocellularis (PGC). The methods used in the reviewed studies are unique in that behavioral and neuronal responses are assessed in consequence of nanoinjecting opiates (met-enkephalin) into subset pairs of these structures. Responses to single and conjoint injections are compared. Effects on neuronal and behavioral responses in consequence of disruption of these structures with tetracaine block are also discussed. It is seen that PGC cannot serve as an opiate analgesia substrate if the functional integrity PAG is impaired. However PAG does not depend on PGC's functional integrity.