Locus coeruleus integrity correlates with inhibitory functions of the fronto-subthalamic 'hyperdirect' pathway in Parkinson's disease

Subjective time dilation in abstinent patients with alcohol use disorder

INTRODUCTION

Patients with alcohol use disorder (AUD) may have distortions in time perception. This study investigated subjective time dilation (the tendency to perceive a time interval longer than it is) and its association with craving and impulsivity in AUD.

METHOD

Thirty abstinent male inpatients with AUD (age 29-60 years) and thirty sex-, age-, and education-matched healthy controls completed a temporal generalization task, which assessed the preference (point of subjective equality, PSE) and sensitivity of time perception in the second range. Craving for alcohol was assessed using the Alcohol Urge Questionnaire. Impulsivity was assessed using a delay discounting task and the Barratt Impulsiveness Scale-11. A comprehensive battery of neuropsychological tests was used to measure executive function (flanker task, symbol digit modalities test, trail-making test-A/B), negative emotionality (Beck Depression Inventory-II, Self-rating Anxiety Scale), and incentive salience (monetary incentive delay task) following the Addictions Neuroclinical Assessment (ANA) framework.

RESULTS

AUD patients exhibited a smaller PSE than healthy controls, perceiving a time interval 8% longer than it was. AUD patients with a smaller PSE showed a greater craving for alcohol but not greater impulsivity. Exploratory factor analysis incorporating the PSE and ANA measures revealed four latent factors. The PSE loaded highly onto a factor reflecting time perception but not three other factors reflecting executive function, negative emotionality, and incentive salience.

CONCLUSIONS

AUD patients exhibit a pathological form of subjective time dilation, which is associated with a greater craving for alcohol. Time perception may be an independent functional dimension for understanding addictive behaviors in AUD.

Noradrenergic alterations in Parkinson's disease: a combined 11C-yohimbine PET/neuromelanin MRI study

Degeneration of the noradrenergic system is now considered a pathological hallmark of Parkinson's disease, but little is known about its consequences in terms of parkinsonian manifestations. Here, we evaluated two aspects of the noradrenergic system using multimodal in vivo imaging in patients with Parkinson's disease and healthy controls: the pigmented cell bodies of the locus coeruleus with neuromelanin sensitive MRI; and the density of α2-adrenergic receptors (ARs) with PET using 11C-yohimbine. Thirty patients with Parkinson's disease and 30 age- and sex-matched healthy control subjects were included. The characteristics of the patients' symptoms were assessed using the Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS). Patients showed reduced neuromelanin signal intensity in the locus coeruleus compared with controls and diminished 11C-yohimbine binding in widespread cortical regions, including the motor cortex, as well as in the insula, thalamus and putamen. Clinically, locus coeruleus neuronal loss was correlated with motor (bradykinesia, motor fluctuations, tremor) and non-motor (fatigue, apathy, constipation) symptoms. A reduction of α2-AR availability in the thalamus was associated with tremor, while a reduction in the putamen, the insula and the superior temporal gyrus was associated with anxiety. These results highlight a multifaceted alteration of the noradrenergic system in Parkinson's disease since locus coeruleus and α2-AR degeneration were found to be partly uncoupled. These findings raise important issues about noradrenergic dysfunction that may encourage the search for new drugs targeting this system, including α2-ARs, for the treatment of Parkinson's disease.