Differential association of HIV-related neuropsychological impairment with semantic versus repetition priming.

There is evidence that the facilitating effects of stimulus repetition (repetition or identity priming) are mediated by visuoperceptual functions local to extrastriate cortex. Semantic or verbal-associative priming, on the other hand, is believed to be a function of more anterior brain systems. The present study finds evidence for disrupted semantic priming with intact repetition priming in a cognitively impaired HIV+ sample. These results are consistent with recent brain-imaging evidence for a subcortical and white-matter locus for HIV associated neuropathology resulting in effects on subcortical-frontal systems.

Effects of hypnotizability on performance of a Stroop task and event-related potentials.

The effect of hypnotizability on verbal reaction times and event-related potentials during performance of a Stroop color-naming task was studied. The Stroop stimuli (colored words) were randomly presented to 5 high and 5 low hypnotizable subjects in the right and left peripheral visual fields during both waking state and hypnotic induction conditions. Unlike studies in which the Stroop stimuli were foveally presented to the subjects, the highly hypnotizable subjects did not show prolonged verbal reaction times in either waking or hypnotic conditions. There was a marked deterioration in performance accuracy, however, for highly hypnotizable subjects during hypnosis. Event-related potentials indicated that the highly hypnotizable subjects showed a reduced P3a amplitude and a decreased N2b latency to the visual stimuli in both waking and hypnotic conditions, suggesting a lack of orienting to or disengagement from peripherally occurring stimuli.

Intact visual word priming in cocaine dependent subjects with and without cognitive deficit.

1. The effects of semantic and repetition priming on reaction time were assessed in 27 recently abstinent cocaine and cocaine/alcohol dependent volunteers and 12 controls without substance abuse history. 2. The 27 cocaine dependent subjects were further divided into cognitively intact (N = 13) and moderate-to-severe cognitively impaired (N = 14) groups on the basis of neuropsychological testing. 3. Both cognitively intact and cognitively impaired cocaine dependent groups showed motor-response facilitation by semantic and repetition priming not significantly different from that of non-abusing controls. 4. It is proposed that both semantic and perceptually mediated visual word priming are implicit cognitive processes resilient to the sequelae of cocaine dependence which impact upon explicit cognitive systems.

Imagery and hypnotizability revisited.

The objective of this study was to correlate computer-generated imagery tasks and a self-report measure of imagery ability with hypnotizability, hypothesizing that computer-generated imagery tasks would be better predictors of hypnotizability than will the self-report measure. Hypnotizability of 43 subjects was assessed using the Hypnotic Induction Profile and the Stanford Hypnotic Susceptibility Scale, Form C. Imagery ability was assessed by the Visual Vividness Imagery Questionnaire (VVIQ) and by computer-generated imagery tasks measuring the ability to generate, maintain, and transform images. Although there was no correlation between the VVIQ and hypnotizability, the less hypnotizable subjects made twice as many mistakes in the spatial imagery tasks than did the more hypnotizables, but this difference was not statistically significant. The relationships among hypnotic performance, hypnotizability, and imagery functions are complex.

Relateralizing hypnosis: or, have we been barking up the wrong hemisphere?

Research and theory over the past couple decades have suggested that the right cerebral hemisphere might be the focus of brain activity during hypnosis. Recent evidence from electrodermal responding, visual event-related potentials, and Stroop interference, however, can make a case for a role of the left hemisphere in some hypnotic phenomena. Although hemispheric activation on hypnotic challenge may depend in large part on the kind of task the challenge might involve, several general aspects of hypnosis might be more appropriately seen as left-rather than right-hemisphere brain functions. Among these are concentrated attentional focus and the role of language in the establishment of hypnotic reality. A left-hemisphere theory of hypnosis is discussed in light of recent findings and theories about a left-hemisphere basis for synthetic or generational capabilities (Corballis, 1991) and a neuro-evolutionary model of a left-hemisphere dopaminergic activation system for the implementation of predetermined motor programs (Tucker & Williamson, 1984).

Left hemisphere superiority for event-related potential effects of hypnotic obstruction.

Twenty-two highly hypnotizable subjects were run in a visual target detection task which compared hypnotic obstruction of the left and right visual fields over separate blocks. The visual event-related potentials (ERPs) to non-target stimuli revealed that hypnotic obstruction reduced the P200 component to stimuli in the right hemifield, but did not affect P200 for stimulation in the left hemifield. The earlier P100 and N100 were also reduced to hypnotic obstruction but not as preferentially for either hemifield, while the P300 was not significantly changed. Right visual field left hemisphere P200 reduction predicted suppression of behavioral response (button press) to hypnotically obstructed targets in both hemifields. The results are discussed in terms of Farah's model of a left hemisphere mechanism for image generation, and how highly hypnotizable subjects might use this mechanism to comply successfully with the suggestion of a hallucinated visually opaque barrier.

Hypnotizability and traumatic experience: a diathesis-stress model of dissociative symptomatology.

OBJECTIVE: The authors propose a diathesis-stress model to describe how pathological dissociation may arise from an interaction between innate hypnotizability and traumatic experience. METHOD: To support the proposition that pathological dissociation may reflect autohypnotic process, the authors highlight clinical and research data indicating parallels between controlled hypnotic dissociative states and uncontrolled pathological dissociative symptoms and summarize evidence of hypnotizability in persons with psychiatric disorders that manifest these symptoms. The authors present this evidence by examining dissociative symptomatology in four psychological domains: perception, behavior and will, affect, and memory and identity. In addition, modern cognitive and neuropsychological models of dissociation are briefly reviewed. RESULTS: Several lines of evidence converge in support of the role of autohypnosis in pathological dissociation. There is considerable evidence that controlled formal hypnosis can produce a variety of dissociations of awareness and control that resemble many of the symptoms in uncontrolled pathological dissociative conditions; and it is possible to discern in dissociative pathology the features of absorption, dissociation, and suggestibility/automaticity that characterize formal hypnotic states. There is also accumulating evidence of high levels of hypnotic capacity in all groups with dissociative symptomatology that have been systematically assessed. In addition, the widespread and successful therapeutic use of hypnosis in the treatment of many dissociative symptoms and conditions (and the potential for hypnosis to induce dissociative symptomatology) also supports the assumption that hypnosis and pathological dissociation share an underlying process. CONCLUSIONS: High hypnotizability may be a diathesis for pathological dissociative states, particularly under conditions of acute traumatic stress.

The effects of magnitude and direction of stimulus change on auditory event-related potentials elicited by deviant signal stimuli.

The present study sought to identify components of the auditory event-related potential (ERP) elicited by stimuli that serve as signals for overt discriminative responses. Sokolov's view of a selective neural filter for deviant stimuli predicts that responses to deviant signal stimuli will be graded in proportion to the amount of change from the standard and independent of the direction of that change. The demonstration of a bi-directional and graded ERP response requires at least two levels of stimulus change in each direction. The present study incorporated two deviants that were lower in pitch (lowest, low) and two that were higher in pitch (high, highest) in order to evaluate the degree (linear, quadratic, etc.) of the function relating ERP response to tonal deviance. Stimulus changes on both the direction and magnitude dimensions were also varied on a trial-by-trial, rather than on a block-by-block, basis which eliminated potential confounds with block or session differences, and discriminative responses were required to both standard and deviant tones, thereby investing both categories of stimuli with signal value. The amplitude of the P3 component associated with deviant stimuli showed close correspondence to the (quadratic) function predicted from the selective filter model. A late negative slow wave (NSW) at Fz and a positive slow wave (PSW) at Pz differentiated deviant tones from the standard but did not distinguish between the deviants themselves. A fronto-central NSW observed at Fz and Cz for initial standard tones was greater than the predominantly frontal NSW elicited by the deviant tones. The topographical differences in NSW elicited by the initial standard tone and by all deviant tones suggest that different processes are reflected in the NSW response to these stimuli.