Delay discounting in mild cognitive impairment

In a circuit necessary for cognition and emotional affect, Alzheimer's-like pathology associates with neuroinflammation, cognitive and motivational deficits in the young adult TgF344-AD rat

In addition to extracellular amyloid plaques, intracellular neurofibrillary tau tangles, and inflammation, cognitive and emotional affect perturbations are characteristic of Alzheimer's disease (AD). The cognitive and emotional domains impaired by AD include several forms of decision making (such as intertemporal choice), blunted motivation (increased apathy), and impaired executive function (such as working memory and cognitive flexibility). However, the interaction between these domains of the mind and their supporting neurobiological substrates at prodromal stages of AD, or whether these interactions can be predictive of AD severity (individual variability), remain unclear. In this study, we employed a battery of cognitive and emotional tests in the young adult (5-7 mo) transgenic Fisher-344 AD (TgF344-AD; TgAD) rat model of AD. We also assessed whether markers of inflammation or AD-like pathology in the prelimbic cortex (PrL) of the medial prefrontal cortex (mPFC), basolateral amygdala (BLA), or nucleus accumbens (NAc), all structures that directly support the aforementioned behaviors, were predictive of behavioral deficits. We found TgAD rats displayed maladaptive decision making, greater apathy, and impaired working memory that was indeed predicted by AD-like pathology in the relevant brain structures, even at an early age. Moreover, we report that the BLA is an early epicenter of inflammation, and notably, AD-like pathology in the PrL, BLA, and NAc was predictive of BLA inflammation. These results suggest that operant-based battery testing may be sensitive enough to determine pathology trajectories, including neuroinflammation, from early stages of AD.

Dorsal and ventral fronto-amygdala networks underlie risky decision-making in age-related cognitive decline

Older adults often have difficulty in making decisions under uncertainty, increasing the risk of financial exploitation. However, it is still under investigation about the extent to which cognitive decline influences risky decision-making and the underlying neural correlates. We hypothesized that the individual differences of risk-taking behavior depend on cognitive integrity, in which the dorsal and ventral fronto-amygdala connectivity would play dissociable roles. In the current study, thirty-six young and 51 older adults were tested with the Iowa gambling task combing resting-state and task-related functional magnetic resonance imaging. The results showed significant changes in behaviors and the fronto-amygdala network in older adults relative to young adults. More importantly, age-effect on risk-taking behaviors was remarkably different in cognitively normal and impaired older adults. In resting-state analysis, task performance was positively correlated with the ventral fronto-amygdala connectivity and negatively correlated with the dorsal fronto-amygdala connectivity in cognitively impaired older adults, compared with cognitively normal individuals. Furthermore, task-related analysis confirmed the relationships between dorsal/ventral fronto-amygdala network and risk-taking behaviors depending on cognitive integrity. These findings indicate that the fronto-amygdala network is crucial for understanding altered risky decision-making in aging, suggesting dissociable contributions of the dorsal and ventral pathways in the context of cognitive decline.

Enhanced putamen functional connectivity underlies altered risky decision-making in age-related cognitive decline

Risky decision-making is critical to survival and development, which has been compromised in elderly populations. However, the neural substrates of altered financial risk-taking behavior in aging are still under-investigated. Here we examined the intrinsic putamen network in modulating risk-taking behaviors of Balloon Analogue Risk Task in healthy young and older adults using resting-state fMRI. Compared with the young group, the elderly group showed significantly different task performance. Based on the task performance, older adults were further subdivided into two subgroups, showing young-like and over-conservative risk behaviors, regardless of cognitive decline. Compared with young adults, the intrinsic pattern of putamen connectivity was significantly different in over-conservative older adults, but not in young-like older adults. Notably, age-effects on risk behaviors were mediated via the putamen functional connectivity. In addition, the putamen gray matter volume showed significantly different relationships with risk behaviors and functional connectivity in over-conservative older adults. Our findings suggest that reward-based risky behaviors might be a sensitive indicator of brain aging, highlighting the critical role of the putamen network in maintaining optimal risky decision-making in age-related cognitive decline.

Altered delay discounting in neurodegeneration: insight into the underlying mechanisms and perspectives for clinical applications

Steeper delay discounting (i.e., the extent to which future rewards are perceived as less valuable than immediate ones) has been proposed as a transdiagnostic process across different health conditions, in particular psychiatric disorders. Impulsive decision-making is a hallmark of different neurodegenerative conditions but little is known about delay discounting in the domain of neurodegenerative conditions. We reviewed studies on delay discounting in patients with Parkinson's disease (PD) and in patients with dementia (Alzheimer's disease / AD or frontotemporal dementia / FTD). We proposed that delay discounting could be an early marker of the neurodegenerative process. We developed the idea that altered delay discounting is associated with overlapping but distinct neurocognitive mechanisms across neurodegenerative diseases: dopaminergic-related disorders of reward processing in PD, memory/projection deficits due to medial temporal atrophy in AD, modified reward processing due to orbitofrontal atrophy in FTD. Neurodegeneration could provide a framework to decipher the neuropsychological mechanisms of value-based decision-making. Further, delay discounting could become a marker of interest in clinical practice, in particular for differential diagnosis.

Aging-related changes in reward-based decision-making depend on punishment frequency: An fMRI study

Introduction

Aging is often accompanied by significant cognitive decline and altered decision making. Previous studies have found that older adults have difficulty in processing reward/risk information, leading to suboptimal decision strategy. However, it is still under investigated about the neural substrates of risky decision-making under ambiguity in aging.

Methods

Using the Iowa Gambling Task, the current study investigated inter-individual differences of risk-taking behaviors in healthy older adults with task-related functional magnetic resonance imaging.

Results

It was found that participants were able to improve their decisions in advantageous decks, but failed to avoid disadvantageous decks during task performance. The task-related activations within multiple brain regions were observed significantly different across the four decks, and showed negative correlations with age in disadvantageous decks but not in advantageous decks. Consistently, age-related whole brain analyses confirmed the negative age-effect on brain activations in disadvantageous decks, especially in high punishment frequency. In addition, the relationship between age and task performance in high punishment frequency was mediated by activation in the frontal subregions such as the middle frontal cortex and superior medial frontal cortex.

Discussion

Our findings shed light on the neural substrates of altered risk-taking behaviors in aging, suggesting a greater sensitivity to high punishment frequency in older adults.

Subjective Time in Dementia: A Critical Review

The capacity for subjective time in humans encompasses the perception of time's unfolding from moment to moment, as well as the ability to traverse larger temporal expanses of past- and future-oriented thought via mental time travel. Disruption in time perception can result in maladaptive outcomes-from the innocuous lapse in timing that leads to a burnt piece of toast, to the grievous miscalculation that produces a traffic accident-while disruption to mental time travel can impact core functions from planning appointments to making long-term decisions. Mounting evidence suggests that disturbances to both time perception and mental time travel are prominent in dementia syndromes. Given that such disruptions can have severe consequences for independent functioning in everyday life, here we aim to provide a comprehensive exposition of subjective timing dysfunction in dementia, with a view to informing the management of such disturbances. We consider the neurocognitive mechanisms underpinning changes to both time perception and mental time travel across different dementia disorders. Moreover, we explicate the functional implications of altered subjective timing by reference to two key and representative adaptive capacities: prospective memory and intertemporal decision-making. Overall, our review sheds light on the transdiagnostic implications of subjective timing disturbances in dementia and highlights the high variability in performance across clinical syndromes and functional domains.

Search for solutions, learning, simulation, and choice processes in suicidal behavior

Suicide may be viewed as an unfortunate outcome of failures in decision processes. Such failures occur when the demands of a crisis exceed a person's capacity to (i) search for options, (ii) learn and simulate possible futures, and (iii) make advantageous value‐based choices. Can individual‐level decision deficits and biases drive the progression of the suicidal crisis? Our overview of the evidence on this question is informed by clinical theory and grounded in reinforcement learning and behavioral economics. Cohort and case–control studies provide strong evidence that limited cognitive capacity and particularly impaired cognitive control are associated with suicidal behavior, imposing cognitive constraints on decision‐making. We conceptualize suicidal ideation as an element of impoverished consideration sets resulting from a search for solutions under cognitive constraints and mood‐congruent Pavlovian influences, a view supported by mostly indirect evidence. More compelling is the evidence of impaired learning in people with a history of suicidal behavior. We speculate that an inability to simulate alternative futures using one's model of the world may undermine alternative solutions in a suicidal crisis. The hypothesis supported by the strongest evidence is that the selection of suicide over alternatives is facilitated by a choice process undermined by randomness. Case–control studies using gambling tasks, armed bandits, and delay discounting support this claim. Future experimental studies will need to uncover real‐time dynamics of choice processes in suicidal people. In summary, the decision process framework sheds light on neurocognitive mechanisms that facilitate the progression of the suicidal crisis.

This article is categorized under:

Economics > Individual Decision‐Making

Psychology > Emotion and Motivation

Psychology > Learning

Neuroscience > Behavior

Neural and behavioral correlates of episodic memory are associated with temporal discounting in older adults

When facing decisions involving trade-offs between smaller, sooner and larger, delayed rewards, people tend to discount the value of future rewards. There are substantial individual differences in this tendency toward temporal discounting, however. One neurocognitive system that may underlie these individual differences is episodic memory, given the overlap in the neural circuitry involved in imagining the future and remembering the past. Here we tested this hypothesis in older adults, including both those that were cognitively normal and those with amnestic mild cognitive impairment (MCI). We found that performance on neuropsychological measures of episodic memory retrieval was associated with temporal discounting, such that people with better memory discounted delayed rewards less. This relationship was specific to episodic memory and temporal discounting, since executive function (another cognitive ability) was unrelated to temporal discounting, and episodic memory was unrelated to risk tolerance (another decision-making preference). We also examined cortical thickness and volume in medial temporal lobe regions critical for episodic memory. Entorhinal cortical thickness was associated with reduced temporal discounting, with episodic memory performance partially mediating this association. The inclusion of MCI participants was critical to revealing these associations between episodic memory and entorhinal cortical thickness and temporal discounting. These effects were larger in the MCI group, reduced after controlling for MCI status, and statistically significant only when including MCI participants in analyses. Overall, these findings suggest that individual differences in temporal discounting are driven by episodic memory function, and that a decline in medial temporal lobe structural integrity may impact temporal discounting.

The update of semantic memories in amnestic mild cognitive impairment

It is still controversial to what extent neocortical consolidated memories are susceptible of change by processes of reconsolidation and transformation throughout experience, and whether the medial temporal lobes are necessary for this update of semantic consolidated memories, as they are for episodic remembering. We hypothesize that patients with amnestic mild cognitive impairment (aMCI) who have deficits in episodic memory may also have difficulties in updating information on added new features of objects. Sixteen participants with aMCI and 20 healthy control participants performed a semantic word-to-picture task, in which they were asked to identify as belonging to a given semantic category NEW objects, that have incorporated novel features, as well as OLD items, semantically and visually SIMILAR items and UNRELATED items. Patients with aMCI made a greater percentage of errors than healthy controls. Participants globally made greater percentages of errors in difficult types of items, namely NEW and SIMILAR, as compared to easier ones, OLD and UNRELATED. Importantly, an item by diagnostic group interaction effect was observed, and post hoc analysis showed that patients with aMCI made a higher percentage of errors than controls in NEW items only. In conclusion, patients with aMCI had a particular difficulty in identifying the NEW items of the word-to-picture task as compared to the control participants, supporting the concept of a flexible and dynamic conceptual knowledge system, involving the update of semantic memories and the integration of new attributes in a constant transformation process, which is impaired in these patients.

Memory of decisions: Relationship between decline of autobiographical memory and temporal discounting in Alzheimer's disease

Temporal discounting refers to the tendency to attribute higher value to a reward received early than to one received later. We evaluated this tendency in patients with Alzheimer's Disease. We also evaluated whether temporal discounting is associated with decline in autobiographical memory (i.e., the ability to remember past personal experiences), with executive dysfunction, and/or with general cognitive decline. We invited patients with AD and control participants to answer binary questions involving the choice between receiving a smaller amount of money earlier or a larger one later (e.g., "Which do you prefer, 10 euros in cash right now or 50 euros in a month?"). Results demonstrated higher temporal discounting in patients with AD than in control participants. Temporal discounting was significantly correlated with decline in AM and general cognitive decline but not with executive dysfunction in patients with AD. The tendency to decide based on immediate rewards (i.e., temporal discounting) in AD is related with difficulty in remembering information about experiences of previous decisions, and/or their consequences (i.e., decline in autobiographical memory).

Hepatitis C Pretreatment Profile and Gender Differences: Cognition and Disease Severity Effects

Background

The hepatitis C virus (HCV) is known to infect the brain, however, the findings based on associated neuropsychiatric syndrome are controversial and the association itself remains unclear. Gender research in HCV infection is limited, failing to integrate the role of gender differences in neurocognitive syndrome. The aim of this study was to characterize psychological and neurocognitive profiles in HCV-infected patients before treatment and to explore gender differences in those profiles, as well as the impact of disease severity.

Methods

A total of 86 patients diagnosed with chronic hepatitis C were included. Depression and anxiety were assessed using Hamilton anxiety scale (HAM-A), Hamilton depression scale (HAM-D), Beck Depression Inventory (BDI). For cognition, a neuropsychological battery to measure attention, concentration and memory was used, and executive function components validated for the Portuguese population was also used before starting treatment. To identify the disease severity, platelet ratio index, and FibroScan^® were used.

Results

A statistically significant gender effect was found on HAM-A (B = 0.64, CI: 0.17–1.11) and HAM-D (B = 0.62, CI: 0.14–1.09), with women scoring higher compared to men. Regarding neuropsychological scores, significant differences between gender were identified in executive functions measured by Trail Making Test (TMT B) (B = 0.48, CI: 0.02–0.97), TMT B-A (B = 0.26, CI: −39.2 to −3.7) and in digit span total (B = −0.52, CI: −1.0 to −0.04), with women performing worse than men. Controlling for years of substance dependence, TMT-B and TMT B-A showed significant gender differences. Regarding the presence or absence of substance dependence, only HAM-A and HAM-D remained significant. For categorical variables, Digit Span Total was also influenced by gender, with women being more likely to be impaired: odds ratio (OR) = 7.07, CI: 2.04–24.45), and a trend was observed for Digit Span Backward (OR = 3.57, CI: 1.31–9.75). No significant differences were found between disease severity and neurocognitive performance.

Conclusion

Data suggest that gender has an influence on depression, anxiety and cognitive functions with women showing greater impairment compared with men. This effect seems to be influenced by substance dependence.

Mental time travel in mild cognitive impairment

Introduction: Mental Time Travel (MTT) is the people's ability to remember themselves in the past and to imagine themselves in the future, and influence important life domains such as making decisions and planning future actions. It is widely recognized that patients with aMCI have deficits in episodic memory, but they also show impairments in semantic memory. It has been controversial whether MTT tasks are disturbed in aMCI mainly in relation to internal details related to episodic information, or external details, representing semantic and other extraneous information. The present study assessed whether patients with aMCI are affected in MTT regarding generation of internal details and external details, in past and future dimensions. Furthermore, it analyzed production in individual detail categories (internal: event details, thought/emotion, place, time, perceptual; external: extraneous events, semantic, other, repetitions). Method: Twenty-nine patients with aMCI and 29 healthy controls underwent a MTT task based on an Autobiographical Interview, where they had to generate past and future events in response to cue words. Transcriptions were segmented and classified into internal detail categories and external detail categories, and composite scores were obtained. Results: Patients with aMCI could globally produce significantly less details than controls. Similar to controls, patients with aMCI produced more internal details than external details, had more difficulty in generating details regarding the future as compared to the past, and scored higher in the detail categories event details and thought/emotion which represent internal detail types. Conclusions: Patients with aMCI showed widespread deficits in MTT, presumably reflecting deficiencies in the complex and multiple cognitive abilities required for MTT tasks.