Investigating the interaction between schizotypy, divergent thinking and cannabis use

Cannabis acutely increases schizotypy and chronic use is associated with elevated rates of psychosis. Creative individuals have higher levels of schizotypy, however links between cannabis use, schizotypy and creativity have not been investigated. We investigated the effects of cannabis smoked naturalistically on schizotypy and divergent thinking, a measure of creativity. One hundred and sixty cannabis users were tested on 1 day when sober and another day when intoxicated with cannabis. State and trait measures of both schizotypy and creativity were administered. Quartile splits compared those lowest (n=47) and highest (n=43) in trait creativity. Cannabis increased verbal fluency in low creatives to the same level as that of high creatives. Cannabis increased state psychosis-like symptoms in both groups and the high creativity group were significantly higher in trait schizotypy, but this does not appear to be linked to the verbal fluency change. Acute cannabis use increases divergent thinking as indexed by verbal fluency in low creatives.     

The relationship between retrieval-induced forgetting, anxiety, and personality

Abstract Retrieval-induced forgetting (RIF) refers to the finding that the retrieval of a memory trace suppresses the retrieval of rival memory traces, and there is evidence that RIF reflects the effects of cognitive inhibition. The Attentional Control Theory (ACT) postulates that cognitive inhibition will be impaired by a high level of state anxiety, but the effect of anxiety on RIF has not previously been investigated. A sample of 116 participants were tested on the RIF procedure, and were also administered the Spielberger State Anxiety Inventory and the Big Five Personality Inventory. The results indicated a significant negative correlation between RIF scores and state anxiety, and a significant positive correlation between RIF scores and extraversion. However, a multiple regression analysis identified extraversion as the main predictor of RIF performance. None of the other personality factors correlated with RIF scores. These findings are consistent with the predictions of the ACT.     

Retrieval per se is not sufficient to trigger reconsolidation of human fear memory

Ample evidence suggests that consolidated memories, upon their retrieval, enter a labile state, in which they might be susceptible to change. It has been proposed that memory labilization allows for the integration of relevant information in the established memory trace (memory updating). Memory labilization and reconsolidation do not necessarily occur when a memory is being reactivated, but only when there is something to be learned during memory retrieval (prediction error). Thus, updating of a fear memory trace should not occur under retrieval conditions in which the outcome is fully predictable (no prediction error). Here, we addressed this issue, using a human differential fear conditioning procedure, by eliminating the very possibility of reinforcement of the reminder cue. A previously established fear memory (picture-shock pairings) was reactivated with shock-electrodes attached (Propranolol group, n=18) or unattached (Propranolol No-Shock Expectation group, n=19). We additionally tested a placebo-control group with the shock-electrodes attached (Placebo group, n=18). Reconsolidation was not triggered when nothing could be learned during the reminder trial, as noradrenergic blockade did not affect expression of the fear memory 24h later in the Propranolol No-Shock Expectation group. Only when the outcome of the retrieval cue was not fully predictable, propranolol, contrary to placebo, reduced the startle fear response and prevented the return of fear (reinstatement) the following day. In line with previous studies, skin conductance response and shock expectancies were not affected by propranolol. Remarkably, a double dissociation emerged between the emotional (startle response) and more cognitive expression (expectancies, SCR) of the fear memory. Our findings have important implications for reconsolidation blockade as treatment strategy for emotional disorders. First, fear reducing procedures that target the emotional component of fear memory do not necessarily affect the cognitive component and vice versa. Second, mere retrieval of the fear memory is not sufficient to induce its labilization and reconsolidation.     

Selective interference with verbal short-term memory for serial order information: A new paradigm and tests of a timing-signal hypothesis

Many recent computational models of verbal short-term memory postulate a separation between processes supporting memory for the identity of items and processes supporting memory for their serial order. Furthermore, some of these models assume that memory for serial order is supported by a timing signal. We report an attempt to find evidence for such a timing signal by comparing an “item probe” task, requiring memory for items, with a “list probe” task, requiring memory for serial order. Four experiments investigated effects of irrelevant speech, articulatory suppression, temporal grouping, and paced finger tapping on these two tasks. In Experiments 1 and 2, irrelevant speech and articulatory suppression had a greater detrimental effect on the list probe task than on the item probe task. Reaction time data indicated that the list probe task, but not the item probe task, induced serial rehearsal of items. Phonological similarity effects confirmed that both probe tasks induced phonological recoding of visual inputs. Experiment 3 showed that temporal grouping of items during list presentation improved performance on the list probe task more than on the item probe task. In Experiment 4, paced tapping had a greater detrimental effect on the list probe task than on the item probe task. However, there was no differential effect of whether tapping was to a simple or a complex rhythm. Overall, the data illustrate the utility of the item probe/list probe paradigm and provide support for models that assume memory for serial order and memory for items involve separate processes. Results are generally consistent with the timing-signal hypothesis but suggest further factors that need to be explored to distinguish it from other accounts.     

Invariant reversible QEEG effects of anesthetics.

Continuous recordings of brain electrical activity were obtained from a group of 176 patients throughout surgical procedures using general anesthesia. Artifact-free data from the 19 electrodes of the International 10/20 System were subjected to quantitative analysis of the electroencephalogram (QEEG). Induction was variously accomplished with etomidate, propofol or thiopental. Anesthesia was maintained throughout the procedures by isoflurane, desflurane or sevoflurane (N = 68), total intravenous anesthesia using propofol (N = 49), or nitrous oxide plus narcotics (N = 59). A set of QEEG measures were found which reversibly displayed high heterogeneity of variance between four states as follows: (1) during induction; (2) just after loss of consciousness (LOC); (3) just before return of consciousness (ROC); (4) just after ROC. Homogeneity of variance across all agents within states was found. Topographic statistical probability images were compared between states. At LOC, power increased in all frequency bands in the power spectrum with the exception of a decrease in gamma activity, and there was a marked anteriorization of power. Additionally, a significant change occurred in hemispheric relationships, with prefrontal and frontal regions of each hemisphere becoming more closely coupled, and anterior and posterior regions on each hemisphere, as well as homologous regions between the two hemispheres, uncoupling. All of these changes reversed upon ROC. Variable resolution electromagnetic tomography (VARETA) was performed to localize salient features of power anteriorization in three dimensions. A common set of neuroanatomical regions appeared to be the locus of the most probable generators of the observed EEG changes.