Charles A. Warren’s research while affiliated with University of Illinois Chicago and other places

A cigarette smoker's reactivity to smoking cues, or cue-reactivity, traditionally has been indexed by self-report and/or measures of autonomic nervous system activity. Recent evidence suggests that measures of central nervous system activity in the form of event-related brain potentials (ERPs) may also index cue-reactivity in smokers. The present study sought to confirm the sensitivity of ERPs to smoking cues and to investigate the question of whether 12 h of smoking deprivation would enhance ERP cue-reactivity to such stimuli. Scalp ERPs were recorded to 80 smoking-related pictures and 80 neutral pictures, i.e., similar pictures with a nonsmoking theme, in 19 tobacco-deprived smokers, 17 nondeprived smokers, and 19 nonsmokers. Smokers' N300 amplitudes over fronto-central scalp were larger to neutral than to smoking-related stimuli, thus reflecting N300 smoking cue-reactivity. N300 cue-reactivity was greater for deprived than for nondeprived smokers. Smokers' P300 values were greater to smoking-related than to neutral stimuli, particularly over the centro-parietal area; however, nonsmokers also showed a P300 main effect to smoking cues. Smoking deprivation did not affect P300 cue-reactivity, nor did deprivation affect self-reported urges to smoking relative to neutral cues. These data confirm the sensitivity of ERPs to tobacco cues in smokers and suggest, additionally, that the cue-reactivity of the N300 component is modulated by smoking deprivation. N300 cue-reactivity may reflect an internally generated priming of the semantic network related to the smokers' need states. Stimulus-category differences in P300 may reflect cue-reactivity in smokers and/or nonaddiction-specific factors in both smokers and nonsmokers.

Rationale: A cigarette smoker's reactivity to smoking cues, or cue-reactivity, traditionally has been indexed by self-report and/or measures of autonomic nervous system activity. Recent evidence suggests that measures of central nervous system activity in the form of event-related brain potentials (ERPs) may also index cue-reactivity in smokers. Objective: The present study sought to confirm the sensitivity of ERPs to smoking cues and to investigate the question of whether 12h of smoking deprivation would enhance ERP cue-reactivity to such stimuli. Methods: Scalp ERPs were recorded to 80 smoking-related pictures and 80 neutral pictures, i.e., similar pictures with a nonsmoking theme, in 19 tobacco-deprived smokers, 17 nondeprived smokers, and 19 nonsmokers. Results: Smokers' N300 amplitudes over fronto-central scalp were larger to neutral than to smoking-related stimuli, thus reflecting N300 smoking cue-reactivity. N300 cue-reactivity was greater for deprived than for nondeprived smokers. Smokers' P300 values were greater to smoking-related than to neutral stimuli, particularly over the centro-parietal area; however, nonsmokers also showed a P300 main effect to smoking cues. Smoking deprivation did not affect P300 cue-reactivity, nor did deprivation affect self-reported urges to smoking relative to neutral cues. Conclusions: These data confirm the sensitivity of ERPs to tobacco cues in smokers and suggest, additionally, that the cue-reactivity of the N300 component is modulated by smoking deprivation. N300 cue-reactivity may reflect an internally generated priming of the semantic network related to the smokers' need states. Stimulus-category differences in P300 may reflect cue-reactivity in smokers and/or nonaddiction-specific factors in both smokers and nonsmokers.

Reactivity to smoking cues, shown previously by autonomic and self-report variables, was investigated in smokers and nonsmokers using event-related brain potentials (ERPs). Average ERPs to 20 color pictures of people smoking and 20 neutral pictures depicting nonsmoking themes, randomly mixed with 4 repetitions/stimulus, were measured from 20 light-moderate smokers and 18 nonsmokers, following a stressor. Smoker status and stimulus type effects on ERPs and principal components factor scores (FS) were tested by repeated-measures ANOVAs. Smokers' N268 showed significant medial and midline smoking cue-reactivity (ERP to smoking-related minus neutral stimuli); while a P300-like, P412, showed significant smoking cue-reactivity over medial and left hemisphere scalp. FS analyses confirmed most of the foregoing. P412 smoking cue-reactivity was correlated with unpleasantness-pleasantness cue-reactivity but not with urge-to-smoke cue-reactivity. Nonsmokers' N268 stimulus differences were not significant, but significant P412 stimulus effects (unconfirmed by FS analyses) were found in central-to-posterior and in left parietal-temporal areas. Smokers' N268 is identified with a process detecting stimuli incongruent with tobacco-addicted states; and P412 smoking cue-reactivity is discussed in terms of an automatic, perceptual-categorization system, consistent with Tiffany's drug-use and Johnson's P300 models. Implications of ERP smoking cue-reactivity for study of tobacco and other addictions are discussed.

EEG data were recorded under field conditions from 11 members of the Santo Daime Doctrine, a Brazilian shamanistic religion, before and after ingesting the psychoactive alkaloid preparation, ayahuasca, or daime, as they term it. Post-ingestion, we observed increases in power in the 36-44 Hz frequency band ("40 Hz") from the left occipital-temporal-parietal scalp electrodes in the eyes-closed condition, which extended to most of the posterior scalp in the eyes-open condition. The results are consistent with many reports that ayahuasca intensifies visual imagery. These results are discussed in terms of a thalamocortical model of the role of 40 Hz activity in brain function and conscious experience. We also noted tendencies toward decreases in the power of slow (theta and alpha) brain rhythms, and increases in the 14-30 Hz beta band, in accord with studies reported 30 years ago with other consciousness-altering compounds. Analysis of four ayahuasca samples yielded an average composition per ingested dose (75 ml) of 55.6 mg harmine, 43.9 mg tetrahydroharmine, 41.3 mg N,N-dimethyltryptamine (DMT), 4.6 mg harmaline, and 3.1 mg harmol. The DMT appeared to be of sufficient concentration to promote psychoactive effects, while the β-carbolines functioned to supply MAO inhibitors necessary to prevent degradation of DMT and to maintain its oral activity.

Event-related brain potentials (ERPs) were recorded from 22 subjects performing a forced-choice guessing task which was part of a larger study of gambling behavior. On each trial, ERPs were elicited by 4 sequentially presented graphic images. After the last stimulus was delivered, subjects guessed which of the 4 images would later be randomly selected as the target for that trial. On the basis of 2 previous studies, we hypothesized that, first, the Late Negative Slow Wave (L-NSW; 400-500 ms poststimulus) and, second, the Early Negative Slow Wave (E-NSW; 150-400 ms) would both have greater negative-going amplitude over 5 prespecified scalp sites for targets than for nontargets on "nonwager" trials. The test of the first hypothesis fell just short of significance (p = .085, one-tailed); the second hypothesis was strongly confirmed (p = .007, one-tailed). The results were interpreted as evidence of unconscious or preconscious psi. That is, although conscious target discrimination did not occur, as indicated by nonsignificant, marginally below-chance guessing accuracy, differential brain responses to target and nontarget stimuli indicated that psi information was detected by the subjects. Importantly, these results represent a replication and confirmation, with a group of subjects unselected for psi, of our earlier findings from a single selected subject.

Event-related Potentials (ERPs) were recorded to feedback during a cognitively demanding, arithmetic rule-learning task and a relatively simple, skill-oriented, perceptuomotor task. For both tasks, a compound feedback display was employed. It consisted of numeric feedback information presented simultaneously with a red or green light (50% each) which indicated whether the numeric information was real (valid) or dummy (invalid). The task and feedback-validity manipulations showed a functional dissociation between the P3b (350-450 msec.) and a Positive Slow Wave (600-900-msec.). P3b was larger for real than for dummy feedback; Positive Slow Wave was larger for rule-learning than for perceptuomotor tasks.

Resúmen.- Se obtuvieron los trazos EEG (electroencefalográficos) de 11 miembros de la doctrina del Santo Daimé, una religión shamánica brasilera de Rio de Janeiro, antes y después de ingerir un preparado alcaloide psicoactivo, la "ayahuasca" o "Daimé", como ellos la denominan. Este preparado ha sido utilizado originalmente por shamanes del Amazonas para prácticas de adivinación, sanación y propósitos rituales. Los análisis EEG indicaron un incremento en el potencial cerebral de 36-44 Hz en la banda de frecuencia ("40" Hz) de los electrodos en el pericráneo occipital-temporal-parietal izquierdo en la condición de ojos-cerrados, que se extendió a la mayor parte del pericráneo posterior en la condición de ojos-abiertos. La consistencia de los resultados coincide con muchos informes que indican que la "ayahuasca" intensifica la visión imaginativa, en especial con los ojos cerrados. Estos resultados pueden interpretarse en términos del modelo tálamocortical del rol de la actividad cerebral de 40 Hz y la experiencia consciente. En la Discusión, los autores intentan integrar estos resultados con anteriores hallazgos EEG/ERP relacionándolos con la hipótesis psi. El presente y los anteriores descubrimientos se sintetizan en un modelo de información psi y el cerebro, que propone como este alucinógeno puede facilitar la ampliación de la información inconsciente, de forma tal de hacerlo accesible a la consciencia. Abstract.- EEG data were recorded from 11 members of the Santo Daimé Doctrine, a Brazilian shamanistic religion, in Rio de Janeiro, before and after ingesting the psychoactive alkaloid preparation, "ayahuasca," or "Daime," as they term it. This preparation was originally used by Amazonas shamans for divinatory, healing, and ritual purposes. EEG analyses indicated increases in power in the 36-44 Hz frequency band ("40 Hz") from the left occipital-temporal-parietal scalp electrodes in the eyes-closed condition, which extended to most of the posterior scalp in the eyes- open condition. The results are consistent with many reports that "ayahuasca" intensifies visual imagery, especially with closed eyes. These results are interpreted in terms of a thalamocortical model of the role of 40 Hz activity in brain function and conscious experience. In the Discussion, an attempt is made to intergrate these results with previous EEG/ERP findings relating to the psi hypothesis. The present and previous findings are synthesized into a model of psi information and the brain, which proposes how amplification of unconscious information may be facilitated by this hallucinogen, thereby making it available to consciousness.

Amplitudes of 5 event-related potentials (ERPs) were recorded at 5 sites of 10 males to real (R-) and dummy (D-) feedback (FB) over two difficulty levels of a rule-learning task, with interspersed perceptuomotor (PM) task trials. Rule-learning R-FB for positive slow wave (PSW) and P3b was greater than for D-FB for both mean time-window and principal component factor score measures. FB effects varied by site for P2/P3a (mainly Fz-C4-Pz) and for a late PSW (LPSW; mainly C4-C3-Fz). A new ERP, P508, showed the greatest topographic differentiation, but no FB main effect. The following ERPs may reflect different sources: PSW versus P3b; P2/P3a versus LPSW; R-FB versus D-FB P2/P3a; R-FB versus D-FB LPSW; and P508 versus all others. LPSW was greater to simple than complex task difficulty; while the "P508" factor score trended towards being greater for complex than simple. ERP interpretation is in terms of stimulus recognition classification, comparative evaluation and development elaboration of mental models. Rule-learning D-FB exceeded PM accuracy R-FB for all ERPs but P2/P3a. Strongly implicated in these differences are preparatory acts in the former task as reflected by the PSW and LPSW.

Event-related potentials (ERPs) were recorded from a single subject performing a forced-choice guessing task. On each trial, ERPs were elicited by four, sequential, graphic images; 2 1/2 seconds after the last stimulus was delivered, the subject guessed which of the four images was experimentally (randomly) designated as the target. P200 had greater amplitude over the posterior scalp for stimuli which were guessed by the subject to be targets than for not-guessed stimuli. The amplitude of the P100, N100, and P300 components was unrelated to the subject's guess. A positive displacement evident in the waveforms from about 150-500 ms post-stimulus onset suggested that Slow Wave may have been partially responsible for the observed differences. These results suggest that ERPs may contain predictive information about a subject's subsequent responses in forced-choice guessing tasks. We termed this the "gleam in the eye" effect.