Everyday and prospective memory deficits in ecstasy/polydrug users

The impact of ecstasy/polydrug use on real-world memory (i.e. everyday memory, cognitive failures and prospective memory [PM]) was investigated in a sample of 42 ecstasy/polydrug users and 31 non-ecstasy users. Laboratory-based PM tasks were administered along with self-reported measures of PM to test whether any ecstasy/polydrug-related impairment on the different aspects of PM was present. Self-reported measures of everyday memory and cognitive failures were also administered. Ecstasy/polydrug associated deficits were observed on both laboratory and self-reported measures of PM and everyday memory. The present study extends previous research by demonstrating that deficits in PM are real and cannot be simply attributed to self-misperceptions. The deficits observed reflect some general capacity underpinning both time- and event-based PM contexts and are not task specific. Among this group of ecstasy/polydrug users recreational use of cocaine was also prominently associated with PM deficits. Further research might explore the differential effects of individual illicit drugs on real-world memory

Neuropsychological Sequelae of Brain Tumors

Investigation of the neuropsychological sequelae of brain tumors is extremely complex largely because the neurobehavioral consequences of brain tumors depend upon complex interactions among disease and treatment variables as well as patient characteristics. To illustrate some of these complexities, we present case studies of two patients in whom the behavioral outcome was not easily predictable on the basis of our current understanding of brain-behavior relationships in tumor patients. The case studies do illustrate how neuropsychological evaluation aids in identifying cognitive deficits which have implications for subsequent quality of life. Recommendations for future experiments and statistical analyses of neurobehavioral data of this population are given

Prospective memory deficits in illicit polydrug users are associated with the average long term typical dose of ecstasy typically consumed in a single session

Rationale Neuroimaging evidence suggests that ecstasy-related reductions in SERT densities relate more closely to the number of tablets typically consumed per session rather than estimated total lifetime use. In order to better understand the basis of drug related deficits in prospective memory (PM) we explored the association between PM and average long-term typical dose and long-term frequency of use. Method Study 1: Sixty five ecstasy/polydrug users and 85 non-ecstasy users completed an event based, a short-term and a long-term time based PM task. Study 2: Study 1 data were merged with outcomes on the same PM measures from a previous study creating a combined sample of 103 ecstasy/polydrug users, 38 cannabis-only users and 65 nonusers of illicit drugs. Results Study 1: Ecstasy/polydrug users had significant impairments on all PM outcomes compared to non-ecstasy users. Study 2: Ecstasy/polydrug users were impaired in event based PM compared to both other groups and in long-term time based PM compared to non illicit drug users. Both drug using groups did worse on the short-term time based PM task compared to nonusers. Higher long-term average typical dose of ecstasy was associated with poorer performance on the event and short-term time based PM tasks and accounted for unique variance in the two PM measures over and above the variance associated with cannabis and cocaine use. Conclusions The typical ecstasy dose consumed in a single session is an important predictor of PM impairments with higher doses reflecting increasing tolerance giving rise to greater PM impairment

Assessing the functional significance of ecstasy-related memory deficits using a virtual paradigm

Rationale/Objectives: Previous research shows that the use of ecstasy results in working memory and executive impairments in some users. The present study sought to assess the functional significance of such deficits using a virtual reality task. Methods: Twenty-three ecstasy-polydrug users and 26 nonusers were recruited. Individuals completed a drug use questionnaire measures of sleep quality and fluid intelligence. Participants also completed a virtual reality executive function task in which they play the role of an office worker for the day completing predefined tasks such as prioritising different activities according to their importance, organising the physical office environment and managing the outgoing mail in accordance with a delivery schedule. Results: MANOVA revealed that ecstasy users performed worse on the virtual reality task overall, and this was due to poorer performance on the planning and selection subscales. Contrary to expectations, ecstasy-polydrug users performed better on the time-based prospective memory subscale. Indices of ecstasy use were correlated with the planning subscale of the virtual task. Conclusions: The present study provides further support for ecstasy/polydrug related deficits in executive functioning. As it is possible that this task is more ecologically valid and relevant to day-to-day activities of many users, previous research finding null results on executive function tasks may have underestimated the impact of ecstasy-polydrug use on executive functioning

Effects of ecstasy/polydrug use on memory for associative information

Rationale Associative learning underpins behaviours that are fundamental to the everyday functioning of the individual. Evidence pointing to learning deficits in recreational drug users merits further examination. Objectives A word pair learning task was administered to examine associative learning processes in ecstasy/polydrug users. Methods After assignment to either single or divided attention conditions, 44 ecstasy/polydrug users and 48 non-users were presented with 80 word pairs at encoding. Following this, four types of stimuli were presented at the recognition phase: the words as originally paired (old pairs), previously presented words in different pairings (conjunction pairs), old words paired with new words, and pairs of new words (not presented previously). The task was to identify which of the stimuli were intact old pairs. Results Ecstasy/ploydrug users produced significantly more false-positive responses overall compared to non-users. Increased long-term frequency of ecstasy use was positively associated with the propensity to produce false-positive responses. It was also associated with a more liberal signal detection theory decision criterion value. Measures of long term and recent cannabis use were also associated with these same word pair learning outcome measures. Conjunction word pairs, irrespective of drug use, generated the highest level of false-positive responses and significantly more false-positive responses were made in the divided attention condition compared to the single attention condition. Conclusions Overall, the results suggest that long-term ecstasy exposure may induce a deficit in associative learning and this may be in part a consequence of users adopting a more liberal decision criterion value

A BODIPY-Cyclooctyne for Protein Imaging in Live Cells

Cellular proteins that bear reactive azides can be imaged by fluorescence microscopy following strain-promoted ligation to cyclooctyne dyes. Here we describe BODIPY-cyclooctyne (BDPY), a membrane-permeant fluorophore that can be used to label intracellular proteins in live mammalian cells. Flow cytometry reveals fluorescence signals more than 25-fold above background after labeling of azide-tagged cells with BDPY

Earthworm effects on the incorporation of litter C and N into soil organic matter in a sugar maple forest

To examine the mechanisms of earthworm effects on forest soil C and N, we double-labeled leaf litter with C-13 and N-15, applied it to sugar maple forest plots with and without earthworms, and traced isotopes into soil pools. The experimental design included forest plots with different earthworm community composition (dominated by Lumbricus terrestris or L. rubellus). Soil carbon pools were 37% lower in earthworm-invaded plots largely because of the elimination of the forest floor horizons, and mineral soil C:N was lower in earthworm plots despite the mixing of high C:N organic matter into soil by earthworms. Litter disappearance over the first winter-spring was highest in the L. terrestris (T) plots, but during the warm season, rapid loss of litter was observed in both L. rubellus (R) and T plots. After two years, 22.0% +/- 5.4% of C-13 released from litter was recovered in soil with no significant differences among plots. Total recovery of added C-13 (decaying litter plus soil) was much higher in no-worm (NW) plots (61-68%) than in R and T plots (20-29%) as much of the litter remained in the former whereas it had disappeared in the latter. Much higher percentage recovery of N-15 than C-13 was observed, with significantly lower values for T than R and NW plots. Higher overwinter earthworm activity in T plots contributed to lower soil N recovery. In earthworm-invaded plots isotope enrichment was highest in macroaggregates and microaggregates whereas in NW plots silt plus clay fractions were most enriched. The net effect of litter mixing and priming of recalcitrant soil organic matter (SOM), stabilization of SOM in soil aggregates, and alteration of the soil microbial community by earthworm activity results in loss of SOM and lowering of the C:N ratio. We suggest that earthworm stoichiometry plays a fundamental role in regulating C and N dynamics of forest SOM

Prospective memory functioning among ecstasy/polydrug users: evidence from the Cambridge Prospective Memory Test (CAMPROMPT)

Rationale: Prospective memory (PM) deficits in recreational drug users have been documented in recent years. However, the assessment of PM has largely been restricted to self-reported measures that fail to capture the distinction between event-based and time-based PM. The aim of the present study is to address this limitation. Objectives: Extending our previous research, we augmented the range laboratory measures of PM by employing the CAMPROMPT test battery to investigate the impact of illicit drug use on prospective remembering in a sample of cannabis only, ecstasy/polydrug and non-users of illicit drugs, separating event and time-based PM performance. We also administered measures of executive function and retrospective memory in order to establish whether ecstasy/polydrug deficits in PM were mediated by group differences in these processes. Results: Ecstasy/polydrug users performed significantly worse on both event and time-based prospective memory tasks in comparison to both cannabis only and non-user groups. Furthermore, it was found that across the whole sample, better retrospective memory and executive functioning was associated with superior PM performance. Nevertheless, this association did not mediate the drug-related effects that were observed. Consistent with our previous study, recreational use of cocaine was linked to PM deficits. Conclusions: PM deficits have again been found among ecstasy/polydrug users, which appear to be unrelated to group differences in executive function and retrospective memory. However, the possibility that these are attributable to cocaine use cannot be excluded