Risk-Taking Behaviors in Huntington's Disease

Forensic neurology: a distinct subspecialty at the intersection of neurology, neuroscience and law

Neurological evidence is increasingly used in criminal cases to argue that a defendant is less responsible for their behaviour, is not competent to stand trial or should receive a reduced punishment for the crime. Unfortunately, neurologists are rarely involved in such cases despite having the expertise to help to inform these decisions in court. In this Perspective, we advocate for the development of 'forensic neurology', a subspecialty of neurology focused on using neurological clinical and scientific expertise to address legal questions for the criminal justice system. We review literature suggesting that the incidence of criminal behaviour is higher in people with certain neurological disorders than the general public and that undiagnosed neurological abnormalities are common in people who commit crimes. We discuss the need for forensic neurologists in criminal cases to provide an opinion on what neurological diagnoses are present, the resulting symptoms and ultimately whether the symptoms affect legal determinations such as criminal responsibility or competency.

Measuring Antisocial Behaviors in Behavioral Variant Frontotemporal Dementia With a Novel Informant-Based Questionnaire

OBJECTIVE

Antisocial behaviors are common and problematic among patients with behavioral variant frontotemporal dementia (bvFTD). In the present study, the investigators aimed to validate an informant-based questionnaire developed to measure the extent and severity of antisocial behaviors among patients with dementia.

METHODS

The Social Behavior Questionnaire (SBQ) was developed to measure 26 antisocial behaviors on a scale from absent (0) to very severe (5). It was administered to 23 patients with bvFTD, 19 patients with Alzheimer's disease, and 14 patients with other frontotemporal lobar degeneration syndromes. Group-level differences in the presence and severity of antisocial behaviors were measured. Psychometric properties of the SBQ were assessed by using Cronbach's alpha, exploratory factor analysis, and comparisons with a psychopathy questionnaire. Cluster analysis was used to determine whether the SBQ identifies different subgroups of patients.

RESULTS

Antisocial behaviors identified by using the SBQ were common and severe among patients with bvFTD, with at least one such behavior endorsed for 21 of 23 (91%) patients. Antisocial behaviors were more severe among patients with bvFTD, including the subsets of patients with milder cognitive impairment and milder disease severity, than among patients in the other groups. The SBQ was internally consistent (Cronbach's α=0.81). Exploratory factor analysis supported separate factors for aggressive and nonaggressive behaviors. Among the patients with bvFTD, the factor scores for aggressive behavior on the SBQ were correlated with those for antisocial behavior measured on the psychopathy scale, but the nonaggressive scores were not correlated with psychopathy scale measures. The k-means clustering analysis identified a subset of patients with severe antisocial behaviors.

CONCLUSIONS

The SBQ is a useful tool to identify, characterize, and measure the severity of antisocial behaviors among patients with dementia.

"Ten euros now" temporal discounting in Huntington disease

BACKGROUND

When making decisions, one often faces a trade-off between immediate and long-term rewards. In these situations, people may prefer immediate over later rewards, even if immediate rewards are smaller than later ones; a phenomenon known as temporal discounting. In this study, we, for the first time, assessed temporal discounting in three populations: participants with manifest Huntington disease (HD), participants with premanifest HD, and control participants.

METHODS

Using the temporal discounting task, we invited participants to choose between small immediate amount of money vs. delayed, but larger amount of money (e.g., "Which do you prefer: you get 10 euros right now or 50 euros in a month?"). We also measured inhibition in order to test if it impacts discounting performance.

RESULTS

Analysis demonstrated higher temporal discounting (i.e., a preference for the immediate rewards) in participants with manifest HD compared to those with premanifest HD or control participants, but no significant differences were observed in participants with premanifest HD and control participants. Analysis also demonstrated significant correlations between temporal discounting and scores on an inhibition test in participants with manifest HD, but not in those with premanifest HD or in control participants.

DISCUSSION

We suggest that, when making decisions, patients with manifest HD may have difficulties with suppressing the temptation of smaller, but immediate, rewards.

Impairments to executive function in emerging adults with Huntington disease

BACKGROUND AND OBJECTIVES

The clinical diagnosis of Huntington disease (HD) is typically made once motor symptoms and chorea are evident. Recent reports highlight the onset of cognitive and psychiatric symptoms before motor manifestations. These findings support further investigations of cognitive function across the lifespan of HD sufferers.

METHODS

To assess cognitive symptoms in the developing brain, we administered assessments from the National Institutes of Health Toolbox Cognitive Battery, an age-appropriate cognitive assessment with population norms, to a cohort of children, adolescents and young adults with (gene-expanded; GE) and without (gene-not-expanded; GNE) the trinucleotide cytosine, adenine, guanine (CAG) expansion in the Huntingtin gene. These five assessments that focus on executive function are well validated and form a composite score, with population norms. We modelled these scores across age, and CAP score to estimate the slope of progression, comparing these results to motor symptoms.

RESULTS

We find significant deficits in the composite measure of executive function in GE compared with GNE participants. GE participant performance on working memory was significantly lower compared with GNE participants. Modelling these results over age suggests that these deficits occur as early as 18 years of age, long before motor manifestations of HD.

CONCLUSIONS

This work provides strong evidence that impairments in executive function occur as early as the second decade of life, well before anticipated motor onset. Future investigations should delineate whether these impairments in executive function are due to abnormalities in neurodevelopment or early sequelae of a neurodegenerative process.

Network localization of antisocial behavior in neurological patients: Evidence and implications

Antisocial behavior may develop in otherwise normal persons as a result of neurological diseases, including patients with focal brain lesions, frontotemporal dementia, and Parkinson Disease patients taking dopamine agonist medications. Evidence from these neurological patients demonstrates that antisocial behaviors relate to dysfunction in several different brain regions that form a specific brain network, rather than any single location alone. This network associated with acquired antisocial behavior is involved in social decision-making (measured using moral decision-making tasks) and value-based decision-making (measured using neuroeconomic and reward-based tasks). Collectively, this work supports the hypothesis that antisocial behavior across different neurological diseases results from dysfunction within a common network of brain regions associated with social valuation and decision-making, providing insight into the neural mechanisms leading to acquired antisocial behavior. These findings have important implications, but also important limitations, for understanding criminal behavior in patients with psychopathy, for rehabilitation in criminals, for ethical discussions regarding moral and legal responsibility, and for forensic neurological evaluations in persons accused of crimes.

Targeting the Nrf2 signaling pathway using phytochemical ingredients: A novel therapeutic road map to combat neurodegenerative diseases

BACKGROUND

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a classical nuclear transcription factor that regulates the system's anti-oxidative stress response. The activation of Nrf2 induces the expression of antioxidant proteins and improves the system's anti-oxidative stress ability. Accumulating evidence suggests that Nrf2-centered signaling pathways may be a key pharmacological target for the treatment of neurodegenerative diseases (NDDs). However, phytochemicals as new therapeutic agents against NDDs have not been clearly delineated.

PURPOSE

To review the therapeutic effects of phytochemical ingredients on NDDs by activating Nrf2 and reducing oxidative stress injury.

METHODS

A comprehensive search of published articles was performed using various literature databases including PubMed, Google Scholar, and China National Knowledge Infrastructure. The search terms included "Nrf2", "phytochemical ingredients", "natural bioactive agents", "neurodegenerative diseases", "Antioxidant", "Alzheimer's disease", "Parkinson's disease", "Huntington's disease", "amyotrophic lateral sclerosis" "multiple sclerosis", "toxicity", and combinations of these keywords. A total of 769 preclinical studies were retrieved until August 2022, and we included 39 of these articless on phytochemistry, pharmacology, toxicology and other fields.

RESULTS

Numerous in vivo and in vitro studies showed that phytochemical ingredients could act as an Nrf2 activator in the treatment of NDDs through the antioxidant defense mechanism. These phytochemical ingredients, such as salidroside, naringenin, resveratrol, sesaminol, ellagic acid, ginsenoside Re, tanshinone I, sulforaphane, curcumin, naringin, tetramethylpyrazine, withametelin, magnolol, piperine, and myricetin, had the potential to improve Nrf2 signaling, thereby combatting NDDs.

CONCLUSION

As Nrf2 activators, phytochemical ingredients may provide a novel potential strategy for the treatment of NDDs. Here, we reviewed the interaction between phytochemical ingredients, Nrf2, and its antioxidant damaging pathway in NDDs and explored the advantages of phytochemical ingredients in anti-oxidative stress, which provides a reliable basis for improving the treatment of NDDs. However, further clinical trials are needed to determine the safety and efficacy of Nrf2 activators for NDDs.

Excessive response to provocation rather than disinhibition mediates irritable behaviour in Huntington's disease

Background

Irritable and impulsive behaviour are common in Huntington's disease (HD: an autosomal dominant disorder causing degeneration in cortico-striatal networks). However, the cognitive mechanisms underlying these symptoms remain unclear, and previous research has not determined if common mechanisms underpin both symptoms. Here we used established and novel tasks to probe different aspects of irritable and impulsive behaviour to determine the neural mechanisms involved.

Methods

We recruited a cohort of 53 gene positive HD participants and 26 controls from non-affected family members and local volunteers. We used established questionnaire measures of irritability in HD (Snaith Irritability Scale, Problem Behaviours Assessment) and impulsivity [Urgency, Premeditation Perseverance, Sensation-seeking, Positive urgency scale (UPPSP), Barratt Impulsivity Scale], in addition to cognitive tasks of provocation, motor inhibition, delay discounting and decision making under uncertainty. We used generalised linear models to determine differences between cases and controls, and associations with irritability in the HD group.

Results

We found differences between cases and controls on the negative urgency subscale of the UPPSP, which was associated with irritability in HD. The frustrative non-reward provocation task also showed differences between cases and controls, in addition to predicting irritability in HD. The stop signal reaction time task showed case-control differences but was not associated with irritability in HD. None of the other measures showed group differences or predicted irritability in HD after correcting for confounding variables.

Discussion

Irritability in HD is mediated by excessive response to provocation, rather than a failure of motor inhibition.

Disordered Decision Making: A Cognitive Framework for Apathy and Impulsivity in Huntington's Disease

A caregiver's all‐too‐familiar narrative ‐ “He doesn't think through what he does, but mostly he does nothing.” Apathy and impulsivity, debilitating and poorly understood, commonly co‐occur in Huntington's disease (HD). HD is a neurodegenerative disease with manifestations bridging clinical neurology and psychiatry. In addition to movement and cognitive symptoms, neurobehavioral disturbances, particularly apathy and impulsivity, are prevalent features of HD, occurring early in the disease course, often worsening with disease progression, and substantially reducing quality of life. Treatments remain limited, in part because of limited mechanistic understanding of these behavioral disturbances. However, emerging work within the field of decision‐making neuroscience and beyond points to common neurobiological mechanisms underpinning these seemingly disparate problems. These insights bridge the gap between underlying disease pathology and clinical phenotype, offering new treatment strategies, novel behavioral and physiological biomarkers of HD, and deeper understanding of human behavior. In this review, we apply the neurobiological framework of cost‐benefit decision making to the problems of apathy and impulsivity in HD. Through this decision‐making lens, we develop a mechanistic model that elucidates the occurrence of these behavioral disturbances and points to potential treatment strategies and crucial research priorities. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson Movement Disorder Society.

Suicidality Risk Factors Across the CARE-HD, 2CARE, and CREST-E Clinical Trials in Huntington Disease

Background and Objectives:

Suicidality is a common concern in the routine care of persons with HD as well as for the many participants in HD clinical trials. In a previous analysis, we identified baseline and time-dependent factors associated with suicidal ideation and attempts from 2CARE, a large, randomized, double-blind clinical trial.

Methods:

The present analysis extends our prior methodology to two other large interventional HD clinical trials, CARE-HD and CREST-E.

Results:

We observed relationships across studies between suicidality events and prior suicidal ideation at baseline, antidepressant/anxiolytic use, chorea, increasing age, and several domains in the UHDRS Behavioral Assessment (depressed mood, low self-esteem, aggression, active suicidality).

Discussion:

These data may form the basis for a subscale of demographic and UHDRS items with the potential for prospectively identifying suicidality risk in HD clinics and clinical trials. (Registry: 2CARE and CREST are registered at clinicaltrials.gov. 2CARE NCT00608881, registered February 6, 2008; first enrollment March 2008. CREST-E NCT00712426, registered July 10, 2008; first enrollment September 2009. CARE-HD not registered; first enrollment July 1997).

Manganese-induced hyperactivity and dopaminergic dysfunction depend on age, sex and YAC128 genotype

Manganese (Mn) is an essential micronutrient but is neurotoxic in excess. Environmental and genetic factors influence vulnerability to Mn toxicity, including sex, age, and the autosomal dominant mutation that causes Huntington disease (HD). To better understand the differential effects of Mn in wild-type (WT) versus YAC128 mice, we examined impacts of Mn exposure across different ages and sexes on disease-relevant behavioral tasks and dopamine dynamics. Young (3-week) and aged (12-month) WT and YAC128 mice received control (70 ppm) or high (2400 ppm) Mn diet for 8 weeks followed by a battery of behavioral tasks. In young female WT mice, high Mn diet induced hyperactivity across two independent behavioral tasks. Changes in the expression of tyrosine hydroxylase (TH) were consistent with the behavioral data in young females such that elevated TH in YAC128 on control diet was decreased by high Mn diet. Aged YAC128 mice showed the expected disease-relevant behavioral impairments in females and decreased TH expression, but we observed no significant effects of Mn diet in either genotype of the aged group. Fast-scan cyclic voltammetry recorded dopamine release and clearance in the nucleus accumbens of eight-month-old WT and YAC128 mice following acute Mn exposure (3×/1 week subcutaneous injections of 50 mg/kg MnCl[2]-tetrahydrate or saline). In WT mice, Mn exposure led to faster dopamine clearance that resembled saline treated YAC128 mice. Mn treatment increased dopamine release only in YAC128 mice, possibly indirectly correcting the faster dopamine clearance observed in saline treated YAC128 mice. The same exposure paradigm led to decreased dopamine and serotonin and metabolites (3-MT, HVA and 5-HIAA) in striatum and increased glutamate in YAC128 mice but not WT mice. These studies confirm an adverse effect of Mn in young, female WT animals and support a role for Mn exposure in stabilizing dopaminergic dysfunction and motivated behavior in early HD.