Time dilates after spontaneous blinking.

Accumulating evidence from pharmacology, neuroimaging, and genetics indicates that striatal dopamine influences time perception [1-5]. Despite these converging results, it is not known whether endogenous variations in dopamine underlie transient fluctuations in our perception of time. Here, we exploited the finding that striatal dopamine release is associated with an increase in spontaneous eye blink rate [6-8] to examine the relationship between intra-individual fluctuations in dopamine and interval timing. In two studies, participants overestimated visual subsecond and suprasecond and auditory subsecond intervals if they had blinked on the previous trial. These results are consistent with the hypothesis that transient fluctuations in striatal dopamine contribute to intra-individual variability in time perception.

Daydreaming style moderates the relation between working memory and mind wandering: Integrating two hypotheses.

Mind wandering-mentation unrelated to one's current activity and surroundings-is a ubiquitous phenomenon, but seemingly competing ideas have been proposed regarding its relation to executive cognitive processes. The control-failure hypothesis postulates that executive processes prevent mind wandering, whereas the global availability hypothesis proposes that mind wandering requires executive resources, and thus an excess of such resources enables mind wandering. Here, we examined whether these hypotheses could be reconciled by considering the moderating influence of daydreaming style. We expected that executive resources would be positively related to mind wandering in those who typically experience positive mind wandering mentation, but negatively related in those who typically experience negative mentation. One hundred eleven participants reported mind wandering over 4 days using experience sampling and completed the sustained attention to response task (SART), the symmetry span task, and the Stroop task. There was a significant interaction between working memory and negative, but not positive, daydreaming style on mind wandering: Working memory related positively to mind wandering in those with a low negative style, but negatively in those with a high negative style. In contrast, poor Stroop performance significantly predicted increased mind wandering, but only in those with a low positive style. SART responses did not predict mind wandering although the relation was suggestively enhanced as the difficulty of daily life activities increased, indicating that the SART is more generalizable to high-demanding than low-demanding activities. These results suggest that the content and context of mind wandering episodes play important roles in the relation between executive processes and mind wandering.

Discrete response patterns in the upper range of hypnotic suggestibility: A latent profile analysis.

High hypnotic suggestibility is a heterogeneous condition and there is accumulating evidence that highly suggestible individuals may be comprised of discrete subtypes with dissimilar cognitive and phenomenological profiles. This study applied latent profile analysis to response patterns on a diverse battery of difficult hypnotic suggestions in a sample of individuals in the upper range of hypnotic suggestibility. Comparisons among models indicated that a four-class model was optimal. One class was comprised of very highly suggestible (virtuoso) participants, two classes included highly suggestible participants who were alternately more responsive to inhibitory cognitive suggestions or posthypnotic amnesia suggestions, and the fourth class consisted primarily of medium suggestible participants. These results indicate that there are discrete response profiles in high hypnotic suggestibility. They further provide a number of insights regarding the optimization of hypnotic suggestibility measurement and have implications for the instrumental use of hypnosis for the modeling of different psychological conditions.

Enhanced dimension-specific visual working memory in grapheme-color synesthesia.

There is emerging evidence that the encoding of visual information and the maintenance of this information in a temporarily accessible state in working memory rely on the same neural mechanisms. A consequence of this overlap is that atypical forms of perception should influence working memory. We examined this by investigating whether having grapheme-color synesthesia, a condition characterized by the involuntary experience of color photisms when reading or representing graphemes, would confer benefits on working memory. Two competing hypotheses propose that superior memory in synesthesia results from information being coded in two information channels (dual-coding) or from superior dimension-specific visual processing (enhanced processing). We discriminated between these hypotheses in three n-back experiments in which controls and synesthetes viewed inducer and non-inducer graphemes and maintained color or grapheme information in working memory. Synesthetes displayed superior color working memory than controls for both grapheme types, whereas the two groups did not differ in grapheme working memory. Further analyses excluded the possibilities of enhanced working memory among synesthetes being due to greater color discrimination, stimulus color familiarity, or bidirectionality. These results reveal enhanced dimension-specific visual working memory in this population and supply further evidence for a close relationship between sensory processing and the maintenance of sensory information in working memory.

Guilt by dissociation: guilt primes augment the relationship between dissociative tendencies and state dissociation.

We examined the influence of guilt on the relationship between dissociative tendencies and state dissociation during mirror-gazing in a non-clinical sample. Dissociative tendencies correlated with state dissociation following guilt primes, but not after negative or neutral primes. This suggests that guilt augments the relationship between dissociative tendencies and state dissociation.

Exceptional abilities in the spatial representation of numbers and time: insights from synesthesia.

In the study of basic and high-level cognitive functions, neuroscientists, psychologists, and philosophers have tended to focus on normal psychological processes and on deficits in these processes, whereas the study of exceptional abilities has been largely neglected. Here the authors emphasize the value of researching exceptional abilities. They make the case that studies of exceptional representations, such as of time, number, and space in synesthesia, can provide us with insights regarding the nature of the neurocognitive mechanisms of these dimensions, as well as their developmental, evolutionary, and cultural origins.

Doing better by getting worse: posthypnotic amnesia improves random number generation.

Although forgetting is often regarded as a deficit that we need to control to optimize cognitive functioning, it can have beneficial effects in a number of contexts. We examined whether disrupting memory for previous numerical responses would attenuate repetition avoidance (the tendency to avoid repeating the same number) during random number generation and thereby improve the randomness of responses. Low suggestible and low dissociative and high dissociative highly suggestible individuals completed a random number generation task in a control condition, following a posthypnotic amnesia suggestion to forget previous numerical responses, and in a second control condition following the cancellation of the suggestion. High dissociative highly suggestible participants displayed a selective increase in repetitions during posthypnotic amnesia, with equivalent repetition frequency to a random system, whereas the other two groups exhibited repetition avoidance across conditions. Our results demonstrate that temporarily disrupting memory for previous numerical responses improves random number generation.

Enhanced cortical excitability in grapheme-color synesthesia and its modulation.

Synesthesia is an unusual condition characterized by the over-binding of two or more features and the concomitant automatic and conscious experience of atypical, ancillary images or perceptions. Previous research suggests that synesthetes display enhanced modality-specific perceptual processing, but it remains unclear whether enhanced processing contributes to conscious awareness of color photisms. In three experiments, we investigated whether grapheme-color synesthesia is characterized by enhanced cortical excitability in primary visual cortex and the role played by this hyperexcitability in the expression of synesthesia. Using transcranial magnetic stimulation, we show that synesthetes display 3-fold lower phosphene thresholds than controls during stimulation of the primary visual cortex. We next used transcranial direct current stimulation to discriminate between two competing hypotheses of the role of hyperexcitability in the expression of synesthesia. We demonstrate that synesthesia can be selectively augmented with cathodal stimulation and attenuated with anodal stimulation of primary visual cortex. A control task revealed that the effect of the brain stimulation was specific to the experience of synesthesia. These results indicate that hyperexcitability acts as a source of noise in visual cortex that influences the availability of the neuronal signals underlying conscious awareness of synesthetic photisms.

Differential frontal-parietal phase synchrony during hypnosis as a function of hypnotic suggestibility.

Spontaneous dissociative alterations in awareness and perception among highly suggestible individuals following a hypnotic induction may result from disruptions in the functional coordination of the frontal-parietal network. We recorded EEG and self-reported state dissociation in control and hypnosis conditions in two sessions with low and highly suggestible participants. Highly suggestible participants reliably experienced greater state dissociation and exhibited lower frontal-parietal phase synchrony in the alpha2 frequency band during hypnosis than low suggestible participants. These findings suggest that highly suggestible individuals exhibit a disruption of the frontal-parietal network that is only observable following a hypnotic induction.

Dissociative tendencies and individual differences in high hypnotic suggestibility.

INTRODUCTION: Inconsistencies in the relationship between dissociation and hypnosis may result from heterogeneity among highly suggestible individuals, in particular the existence of distinct highly suggestible subtypes that are of relevance to models of psychopathology and the consequences of trauma. This study contrasted highly suggestible subtypes high or low in dissociation on measures of hypnotic responding, cognitive functioning, and psychopathology. METHODS: Twenty-one low suggestible (LS), 19 low dissociative highly suggestible (LDHS), and 11 high dissociative highly suggestible (HDHS) participants were administered hypnotic suggestibility scales and completed measures of free recall, working memory capacity, imagery, fantasy-proneness, psychopathology, and exposure to stressful life events. RESULTS: HDHS participants were more responsive to positive and negative hallucination suggestions and experienced greater involuntariness during hypnotic responding. They also exhibited impaired working memory capacity, elevated pathological fantasy and dissociative symptomatology, and a greater incidence of exposure to stressful life events. In contrast, LDHS participants displayed superior object visual imagery. CONCLUSIONS: These results provide further evidence for two highly suggestible subtypes: a dissociative subtype characterised by deficits in executive functioning and a predisposition to psychopathology, and a subtype that exhibits superior imagery and no observable deficits in functioning.

Dissociated control as a signature of typological variability in high hypnotic suggestibility.

This study tested the prediction that dissociative tendencies modulate the impact of a hypnotic induction on cognitive control in different subtypes of highly suggestible individuals. Low suggestible (LS), low dissociative highly suggestible (LDHS), and high dissociative highly suggestible (HDHS) participants completed the Stroop color-naming task in control and hypnosis conditions. The magnitude of conflict adaptation (faster response times on incongruent trials preceded by an incongruent trial than those preceded by a congruent trial) was used as a measure of cognitive control. LS and LDHS participants displayed marginally superior up-regulation of cognitive control following a hypnotic induction, whereas HDHS participants' performance declined. These findings indicate that dissociative tendencies modulate the influence of a hypnotic induction on cognitive control in high hypnotic suggestibility and suggest that HS individuals are comprised of distinct subtypes with dissimilar cognitive profiles.

Methodological and interpretative issues regarding the Phenomenology of consciousness inventory--hypnotic assessment procedure: a comment on pekala et al. (2010a, 2010b).

In two papers, Pekala et al. (2010a, 2010b) reviewed and empirically assessed the relationships among response expectancies, hypnotic suggestibility, spontaneous alterations in consciousness following a hypnotic induction, and hypnotic depth. We appreciate their attempt to integrate diverse facets of hypnotic responding and reconcile seemingly competing accounts of hypnosis. In addition, we applaud their complementary use of phenomenological and hypnotic suggestibility measures. However, in their attempt to develop a clinically-viable measure of hypnotic responsiveness, we believe that they have sacrificed too much, resulting in a measure with a number of important shortcomings whose empirical utility is questionable. Furthermore, their review and study gloss over a number of important distinctions. Finally, we believe that they over-interpret the relationships between their selected measures and ones previously used in the extant literature. A closer examination of variability among highly suggestible individuals, from the purview of the approach that Pekala et al. have adopted, but with a greater diversity of methods, is likely to yield a number of insights into the characteristics and determinants of hypnotic suggestibility and self-perceived hypnotic depth.

Disruption of synaesthesia by posthypnotic suggestion: an ERP study.

This study examined whether the behavioral and electrophysiological correlates of synaesthetic response conflict could be disrupted by posthypnotic suggestion. We recorded event-related brain potentials while a highly suggestible face-color synaesthete and matched controls viewed congruently and incongruently colored faces in a color-naming task. The synaesthete, but not the controls, displayed slower response times, and greater P1 and sustained N400 ERP components over frontal-midline electrodes for incongruent than congruent faces. The behavioral and N400 markers of response conflict, but not the P1, were abolished following a posthypnotic suggestion for the termination of the participant's synaesthesia and reinstated following the cancellation of the suggestion. These findings demonstrate that the conscious experience of synaesthesia can be temporarily abolished by cognitive control.

Differential patterns of spontaneous experiential response to a hypnotic induction: a latent profile analysis.

A hypnotic induction produces different patterns of spontaneous experiences across individuals. The magnitude and characteristics of these responses covary moderately with hypnotic suggestibility, but also differ within levels of hypnotic suggestibility. This study sought to identify discrete phenomenological profiles in response to a hypnotic induction and assess whether experiential variability among highly suggestible individuals matches the phenomenological profiles predicted by dissociative typological models of high hypnotic suggestibility. Phenomenological state scores indexed in reference to a resting epoch during hypnosis were submitted to a latent profile analysis. The profiles in the derived four-class solution differed in multiple experiential dimensions and hypnotic suggestibility. Highly suggestible individuals were distributed across two classes that exhibited response patterns suggesting an inward attention subtype and a dissociative subtype. These results provide support for dissociative typological models of high hypnotic suggestibility and indicate that highly suggestible individuals do not display a uniform response to a hypnotic induction.

Dissociative alterations in body image among individuals reporting out-of-body experiences: a conceptual replication.

A conceptual replication of the link between self-reported dissociative alterations in body-image under experimental conditions and the reporting of prior out-of-body experiences in a recent data set was undertaken. Also examined was whether this relationship would hold for experiences reported during the experimental context and whether it is independent of self-reported New Age belief. Data from mostly undergraduates (N= 40; M age = 33.5, SD = 12.5; 27 women) in a mirror-gazing study were retrospectively analyzed. The 9 individuals who reported prior out-of-body experiences, relative to those 31 who did not, exhibited significantly greater self-reported dissociative alterations in body-image during the mirror-gazing task, even when the influence of scores on New Age belief was controlled for statistically. The same differential relationship was not found between 6 individuals who did and 34 who did not report out-of-body experiences during the task.

The induction of anomalous experiences in a mirror-gazing facility: suggestion, cognitive perceptual personality traits and phenomenological state effects.

Previous research suggests that mirror-gazing is efficacious for the facilitation of anomalous experiences. The present experiment tested the hypothesis that the incidence of such experiences is a function of the demand characteristics of the procedure. Participants were randomly allocated to one of two conditions and completed a battery of trait and state measures. Individuals who were given suggestions for anomalous experiences, relative to those who were not, reported a greater number of visual, and a suggestively greater number of vocal, hallucinations. The experience of a descriptively dissociative phenomenological state was the strongest predictor of the reporting of anomalous experiences, but only correlated with the experience of anomalous perceptions in the suggestion condition. Experients of visual apparitions were found to significantly differ from nonexperients in their preference for a visual cognitive style independently of condition.