Acting with the future in mind is impaired in long-term opiate users

Episodic foresight is impaired following acute alcohol intoxication

BACKGROUND

Alcohol intoxication disrupts many aspects of cognition, including the generation of phenomenological characteristics of future events (a component of episodic foresight), and the execution of directed preparatory behaviours (a component of prospective memory). However, no study has tested whether alcohol intoxication is also associated with deficits engaging episodic foresight to guide future-directed behaviour.

AIMS

This study was designed to provide the first test of how alcohol intoxication influences the functional application of episodic foresight. The secondary aim was to establish the degree to which any observed episodic foresight difficulties associated with alcohol use might reflect broader problems in retrospective memory and executive control. Sex differences were also examined.

METHODS

Healthy adult social drinkers randomly received either a moderate dose of 0.6 g/kg alcohol (n = 61) or a matched placebo drink (n = 63) and then completed a validated measure that met strict criteria for assessing the functional application of episodic foresight as well as a broader cognitive test battery.

RESULTS

Relative to the placebo condition, episodic foresight was impaired by acute alcohol consumption, with this impairment related to poorer retrospective memory, but not executive control. The negative effects of alcohol intoxication on episodic foresight did not differ as a function of sex.

CONCLUSIONS

Even a moderate level of intoxication impairs the ability to use episodic foresight in a functionally adaptive way. These findings have implications for understanding many of the maladaptive behaviours that are often associated with acute alcohol use.

Parkinson's disease disrupts the ability to initiate and apply episodic foresight

OBJECTIVE

While Parkinson's disease is associated with impairments in many aspects of prospective cognition, no study to date has tested whether these difficulties extend to problems using episodic foresight to guide future-directed behavior. To provide the first examination of whether people with Parkinson's disease are impaired in their capacity to initiate and apply episodic foresight.

METHOD

People with Parkinson's disease (n = 42), and a demographically matched neurotypical comparison group (n = 42) completed a validated behavioral assessment that met strict criteria for assessing episodic foresight (Virtual Week-Foresight), as well as a broader neurocognitive and clinical test battery.

RESULTS

People with Parkinson's disease were significantly less likely than the comparison group to acquire items that would later allow a problem to be solved and were also less likely to subsequently use these items for problem resolution. These deficits were largely unrelated to performance on other cognitive measures or clinical characteristics of the disorder.

CONCLUSIONS

The ability to engage in episodic foresight in an adaptive way is compromised in Parkinson's disease. This appears to be a stable feature of the disorder, and one that is distinct from other clinical symptoms and neurocognitive deficits. It is now critical to establish exactly why these difficulties exist and how they impact on real-life functional capacity.

How do cannabis users mentally travel in time? Evidence from an fMRI study of episodic future thinking

RATIONALE

Episodic future thinking (EFT) is a cognitive function that allows individuals to imagine novel experiences that may happen in the future. Prior studies show that EFT is impaired in different groups of substance users. However, there is no evidence regarding the neurobiological mechanisms of EFT in cannabis users.

OBJECTIVES

We aimed to compare brain activations of regular cannabis users and non-using controls during an EFT fMRI task. Exploratory analyses were also conducted to investigate the association between EFT and cannabis use variables (e.g., duration of use, age onset, frequency of use).

METHODS

Twenty current cannabis users and 22 drug-naïve controls underwent an fMRI scanning session while completing a task involving envisioning future-related events and retrieval of past memories as a control condition. The EFT fMRI task was adapted from the autobiographical interview and composed of 20 auditory cue sentences (10 cues for past and 10 cues for future events). Participants were asked to recall a past or generate a future event, in response to the cues, and then rate their vividness after each response.

RESULTS

We found that cannabis users compared to non-user controls had lower activation within the cerebellum, medial and superior temporal gyrus, lateral occipital cortex, and occipital fusiform gyrus while envisioning future events. Cannabis users rated the vividness of past events significantly lower than non-users (P < 0.005). There were marginal group differences for rating the vividness of future events (P = 0.052). Significant correlations were also found between the medial and superior temporal gyrus activities and behavioral measures of EFT and episodic memory.

CONCLUSIONS

Cannabis users, compared to drug-naïve controls, have lower brain activation in EFT relevant regions. Thus, any attempts to improve aberrant EFT performance in cannabis users may benefit from EFT training.

A meta-analytic review of prospection deficits in Parkinson's disease

Parkinson's disease (PD) is one of the most common neurodegenerative disorders, and is associated with prominent motor deficits. However, neurocognitive impairment is also a common clinical feature that can contribute greatly to the overall disease burden. In the current study, a meta-analysis was conducted to gain a clearer understanding of how PD affects one of the most functionally important domains of cognition: prospection. The results indicate that, relative to controls, PD is associated with a large deficit in the capacity to engage in planning (g = -0.81, K = 25) and a moderate-sized deficit in prospective memory (g = -0.57, K = 16). Sub-analyses indicated that these deficits are evident for both time and event-based prospective memory, as well as for prospective memory tasks that have relatively limited ecological validity. Significant impairment was also evident for both medicated and non-medicated PD sub-groups, but for planning, these deficits were substantially greater in the unmedicated sub-group. The theoretical and practical implications of these findings are discussed.

Measuring mental time travel: Is the hippocampus really critical for episodic memory and episodic foresight?

Mental time travel is an adaptive capacity that enables humans to engage in deliberate, prudent action on the basis of remembering past episodes (episodic memory) and simulating future scenarios (episodic foresight). This capacity has become a popular and rapidly growing topic of interdisciplinary research. Perhaps the most influential and frequently tested neuroscientific hypothesis in this domain is that the hippocampus is a hub in a critical neural network for mental time travel, support for which is now commonly assumed by most researchers in the area. In light of recent findings revealing limitations with existing measures of episodic foresight, we critically evaluate the available evidence for this hypothesis and find that it is inconclusive. We suggest that this is due in significant part to the exclusive and widespread reliance on noisy verbal measures and discuss this case as an example of a more general issue pertaining to the measurement of episodic foresight. Accordingly, we suggest that an essential focus of future research should concern the development of objective measures that capture capacity differences by requiring people to put foresight not just into words, but into action.

Research with Older Adult Methadone Clients: The Importance of Monitoring Suicide Ideation

This study reports on the importance of monitoring suicide ideation among older adult research participants. A recently completed randomized controlled trial of older adults who are current clients in methadone maintenance treatment (MMT) served as a case study to elucidate a suicide protocol that was designed to account for the potential instances of suicide ideation within the research project structure. As the numbers of older adult heroin users increases, this study's findings seek to influence research protocols that involve older adults with addictions who may be particularly vulnerable to suicide risk due to comorbid psychiatric conditions and psychosocial adversities.

Predictive mechanisms linking brain opioids to chronic pain vulnerability and resilience

Chronic pain is a major global healthcare problem that is currently inadequately treated. In addition, the current use of opioids for treatment has reached far beyond the paucity of evidence for long-term benefits relative to risks. Benefit-risk models for opioid and non-opioid treatments would benefit from a rational, mechanism-based understanding of neuroplastic and neurochemical contributions to chronic pain. Here, we evaluate the findings and limitations of representative research investigating brain neuroplasticity and neurochemistry in chronic pain. In sum, the mechanisms of pain-related neuroplasticity in the brain remain poorly understood because neuroimaging studies have been largely descriptive. We argue that definition is needed of optimal (pain-resilient) and suboptimal (pain-vulnerable) functioning of the endogenous opioid system in order to identify neurochemical contributions to aberrant neuroplasticity in chronic pain. We outline the potential benefits of computational approaches that utilize evolutionary and statistical optimality principles, illustrating this approach with mechanistic hypotheses on opioid function. In particular, we discuss the role of predictive mechanisms in perceptual and associative plasticity and evidence for their modulation by endogenous opioids. Future research should attempt to utilize formal computational models to provide evidence for the clinical validity of this approach, thereby providing a rational basis for future treatment and, ideally, prevention.

LINKED ARTICLES

This article is part of a themed section on Emerging Areas of Opioid Pharmacology. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.14/issuetoc.