Suggested visual hallucination without hypnosis enhances activity in visual areas of the brain

This functional Magnetic Resonance Imaging (fMRI) study investigated high and low suggestible people responding to two visual hallucination suggestions with and without a hypnotic induction. Participants in the study were asked to see color while looking at a grey image, and to see shades of grey while looking at a color image. High suggestible participants reported successful alterations in color perception in both tasks, both in and out of hypnosis, and showed a small benefit if hypnosis was induced. Low suggestible people could not perform the tasks successfully with or without the hypnotic induction. The fMRI results supported the self report data, and changes in brain activity were found in a number of visual areas. The results indicate that a hypnotic induction, although having the potential to enhance the ability of high suggestible people, is not necessary for the effective alteration of color perception by suggestion.     

Manipulating cues in involuntary autobiographical memory: Verbal cues are more effective than pictorial cues

In two experiments, pictorial cues were compared with their verbal labels to assess their effectiveness in eliciting involuntary autobiographical memories. Cues were relatively complex in Experiment 1 (e.g., relaxing on a beach) and simple objects in Experiment 2 (e.g., a ball). In both experiments, participants went through a vigilance task in which they were presented with frequent nontarget and rare target visual stimuli. Pictures or their corresponding verbal labels were also displayed on both target and nontarget stimuli, but participants were told that these were irrelevant to the task. They were asked to interrupt the vigilance task whenever they became aware of task-unrelated mental contents and to report them. In both experiments, more involuntary memories were elicited in the verbal cue condition, rather than in the pictorial cue condition. This result is discussed in relation to previous work that highlighted the greater effectiveness of verbal cues in memory tasks.     

"Don't know" responding to answerable and unanswerable questions during misleading and hypnotic interviews

"Don't know" (DK) responses to interview questions are conceptually heterogeneous, and may represent uncertainty or clear statements about the contents of memory. A study examined the subjective intent of DK responses in relation to the objective status of information queried, in the context of memory distorting procedures. Participants viewed a video and responded to answerable and unanswerable questions phrased in misleading or nonmisleading formats, while hypnotized or not hypnotized. Subjective meanings of DK responses were queried, and a recognition measure assessed the contents of memory. Lower DK and accuracy rates were consistently associated with unanswerable and misleading questions. One-third of DK responses were statements that the information had no not presented. When these were recoded, accuracy estimates for answerable questions decreased and more so for hypnotized participants. These results demonstrate that DK responses convey different types of information, thus accuracy estimates in studies that permit DK responses may be misestimated. Robust risks associated with asking unanswerable questions and asking questions at all were observed. Implications for working with DK responses during interviews are discussed.     

Imagination can create false autobiographical memories

Previous studies have shown that imagining an event can alter autobiographical beliefs. The current study examined whether it can also create false memories. One group of participants imagined a relatively frequent event and received information about an event that never occurs. A second group imagined the nonoccurring event and received information about the frequent event. One week before and again 1 week immediately after the manipulation, participants rated the likelihood that they had experienced each of the two critical events and a series of noncritical events, using the Life Events Inventory. During the last phase, participants were also asked to describe any memories they had for the events. For both events, imagination increased the number of memories reported, as well as beliefs about experiencing the event. These results indicate that imagination can induce false autobiographical memories.     

Hypnotic suggestibility,cognitive inhibition,and dissociation

We examined two potential correlates of hypnotic suggestibility: dissociation and cognitive inhibition. Dissociation is the foundation of two of the major theories of hypnosis and other theories commonly postulate that hypnotic responding is a result of attentional abilities (including inhibition). Participants were administered the Waterloo-Stanford Group Scale of Hypnotic Susceptibility, Form C. Under the guise of an unrelated study, 180 of these participants also completed: a version of the Dissociative Experiences Scale that is normally distributed in non-clinical populations; a latent inhibition task, a spatial negative priming task, and a memory task designed to measure negative priming. The data ruled out even moderate correlations between hypnotic suggestibility and all the measures of dissociation and cognitive inhibition overall, though they also indicated gender differences. The results are a challenge for existing theories of hypnosis.     

Hypnotic induction decreases anterior default mode activity

The ‘default mode’ network refers to cortical areas that are active in the absence of goal-directed activity. In previous studies, decreased activity in the ‘default mode’ has always been associated with increased activation in task-relevant areas. We show that the induction of hypnosis can reduce anterior default mode activity during rest without increasing activity in other cortical regions. We assessed brain activation patterns of high and low suggestible people while resting in the fMRI scanner and while engaged in visual tasks, in and out of hypnosis. High suggestible participants in hypnosis showed decreased brain activity in the anterior parts of the default mode circuit. In low suggestible people, hypnotic induction produced no detectable changes in these regions, but instead deactivated areas involved in alertness. The findings indicate that hypnotic induction creates a distinctive and unique pattern of brain activation in highly suggestible subjects.     

Response to an intervening event reverses nonspatial repetition effects in 2AFC tasks: Nonspatial IOR?

The repetition effect in two-alternatiave forced choice (2AFC) tasks is a cornerstone effect in human cognition. Yet the experiments described here show that the customary benefit of repetition reverses to a cost of repetition when participants respond to an irrelevant event between targets. In Experiments 1A-1C, participants made manual 2AFC decisions to both of two consecutive targets on a trial and, on some trials, also made a manual response to an intervening event that appeared between the two targets. A repetition benefit was observed when no intervening event appeared, whereas a repetition cost was observed when a response was required to an intervening event. Experiment 2 ruled out a solely strategic interpretation of the repetition cost effect observed on intervening event trials. In Experiments 3A and 3B, an intervening event that required a simple vocal "go" response also produced a repetition cost. In Experiment 4, a repetition cost was observed when the intervening event was changed to a tone presented aurally. In Experiment 5, the repetition benefit was observed when a response was withheld to an intervening event. A dual-process interpretation of these results is discussed, with one process related to episodic integration, and the other related to processes that produce inhibition of return.     

Both differences in encoding processes and monitoring at retrieval reduce false alarms when distinctive information is studied

ABSTRACT

Recent research has provided evidence for memory modifications when a post-reactivation treatment (e.g., drugs, new learning) interferes with the memory re-stabilisation (reconsolidation) process. This finding contradicts the long-standing consolidation theory and has high practical and theoretical implications. With an object-learning paradigm, it was shown that episodic memory is highly susceptible to interfering material presented after its reactivation [Hupbach, A., Gomez, R., Hardt, O., &; Nadel, L. (2007). Reconsolidation of episodic memories: A subtle reminder triggers integration of new information. Learning &; Memory, 14, 47–53. doi:10.1101/lm.365707]. The reactivation of a learned list (List 1) before a second learned list (List 2) led to intrusion errors from List 2 when trying to recall List 1, but not vice-versa. Their work has been widely cited and their findings have been explained according to reconsolidation theory. For the first time, we systematically explored the role of retrieval context as an alternative explanation for Hupbach’s results. Our results showed that the intrusion effect occurs independently of the retrieval context (Experiment 1). Additionally, even when the intrusion rate probability is increased (i.e., List 1 memory test is performed in the List 2 learning context), the groups that did not reactivate the original list did not commit intrusion errors (Experiment 2). In sum, we found that the intrusion effect critically depends on the presence of reactivation, discarding alternative interpretations of the results.