In vivo cholinergic basal forebrain degeneration and cognition in Parkinson's disease: Imaging results from the COPPADIS study

INTRODUCTION

We aimed to assess associations between multimodal neuroimaging measures of cholinergic basal forebrain (CBF) integrity and cognition in Parkinson's disease (PD) without dementia.

METHODS

The study included a total of 180 non-demented PD patients and 45 healthy controls, who underwent structural MRI acquisitions and standardized neurocognitive assessment through the PD-Cognitive Rating Scale (PD-CRS) within the multicentric COPPADIS-2015 study. A subset of 73 patients also had Diffusion Tensor Imaging (DTI) acquisitions. Volumetric and microstructural (mean diffusivity, MD) indices of CBF degeneration were automatically extracted using a stereotactic CBF atlas. For comparison, we also assessed multimodal indices of hippocampal degeneration. Associations between imaging measures and cognitive performance were assessed using linear models.

RESULTS

Compared to controls, CBF volume was not significantly reduced in PD patients as a group. However, across PD patients lower CBF volume was significantly associated with lower global cognition (PD-CRS_total: r = 0.37, p < 0.001), and this association remained significant after controlling for several potential confounding variables (p = 0.004). Analysis of individual item scores showed that this association spanned executive and memory domains. No analogue cognition associations were observed for CBF MD. In covariate-controlled models, hippocampal volume was not associated with cognition in PD, but there was a significant association for hippocampal MD (p = 0.02).

CONCLUSIONS

Early cognitive deficits in PD without dementia are more closely related to structural MRI measures of CBF degeneration than hippocampal degeneration. In our multicentric imaging acquisitions, DTI-based diffusion measures in the CBF were inferior to standard volumetric assessments for capturing cognition-relevant changes in non-demented PD.

Subregional volume reduction of the cholinergic forebrain in subjective cognitive decline (SCD)

Subjective cognitive decline (SCD) patients are considered as a risk population for preclinical Alzheimer's Disease (AD). Supporting this idea, previous studies in SCD populations report subtle alterations in various cognitive and neuroimaging biomarkers that are typically affected during AD progression. To extend these observations, the present study examined whether SCD patients show atrophy of cholinergic basal forebrain nuclei (chBFN), analogous with recent findings in prodromal and clinical AD patients. We assessed volume reductions of the chBFN in 24 SCD subjects compared to 49 matched controls on 3D-T1-weighted MR images based on a postmortem derived atlas. Furthermore, we assessed whether chBFN atrophy was linked with cognitive, structural and metabolic biomarker alterations we previously reported in this SCD cohort: Using correlation analyses we tested for associations between the volumes of the chBFN with the hippocampal gray matter volume, and posterior medial glucose consumption, and the trajectory of verbal memory performance. The SCD cases showed a significant total volume reduction of the chBFN, with largest effect sizes in the Ch1/2 and Ch4p subdivisions of the chBFN. The latter was associated with a reduced glucose metabolism in the precuneus for the SCD group only. These data show an early involvement of the cholinergic basal forebrain nuclei in SCD predominantly in Ch1/2 and Ch4p which supports the conceptual link between SCD and preclinical AD.

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Cholinergic forebrain shows atrophy in SCD.

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Ch12 and posterior part of Nucl. Basalis Meynert (Ch4p) show largest effect size.

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Atrophy of the Ch4p correlates with reduced glucose metabolism in precuneus.

Stress alters asenapine-induced Fos expression in the Meynert's nucleus: response of adjacent hypocretin and melanin-concentrating hormone neurons in rat

OBJECTIVE

Asenapine (ASE), an atypical antipsychotic drug used in the treatment of schizophrenia, induces Fos expression in forebrain. Effect of ASE on activity of basal nucleus of Meynert (NBM) cells, a part of the striatal-cortical circuits, was studied. We were also interested to reveal whether a chronic unpredictable variable mild stress (CMS) preconditioning might affect the ASE impact.

METHODS

Rats were divided into as follows: controls-vehicle, controls-ASE, stressed-vehicle and stressed-ASE groups. CMS included restrain, social isolation, crowding, swimming and cold applied for 21 days. On the 22nd day, rats were subcutaneously injected with ASE (0.3 mg/kg) or vehicle (saline 300 μl/rat), 90 min prior euthanizing. After transcardial fixation, brains were cut into 30 μm thick coronal sections. Fos protein presence, as indicator of cell activity, was detected by ABC immunohistochemistry. Hypocretin (Hcrt) and melanin-concentrating hormone (MCH) containing cells were visualized with fluorescent dyes.

RESULTS

ASE induced significant increase in Fos expression in NBM in both controls and CMS preconditioned rats in comparison with the related vehicle-treated controls. CMS preconditioning, however, significantly lowered the Fos response to ASE in NBM. From Hrct and MCH cells, only Hcrt ones displayed Fos presence in response to ASE.

DISCUSSION

This study demonstrates for the first time that ASE may target a special group of cells occupying NBM, which effect can be modulated by CMS preconditioning. This finding extends a view that ASE impact may extend beyond the classical forebrain target areas common for the action of all antipsychotics and might be helpful in the identification of sites and side effects of its therapeutic actions.

Basal forebrain atrophy and cortical amyloid deposition in nondemented elderly subjects

BACKGROUND

Both neurodegeneration of the cholinergic basal forebrain (BF) and deposition of β-amyloid are early events in the course of Alzheimer's disease (AD). Associations between increased amyloid pathology and cholinergic atrophy have been described in autopsy studies.

METHODS

We used structural MRI and AV45-PET amyloid imaging data of 225 cognitively normal or mildly impaired elderly subjects from the Alzheimer's Disease Neuroimaging Initiative to assess in vivo associations between BF atrophy and cortical amyloid deposition. Associations were examined using region-of-interest (ROI) and voxel-based approaches with reference to cytoarchitectonic mappings of the cholinergic BF nuclei.

RESULTS

ROI- and voxel-based approaches yielded complementary evidence for an association between BF volume and cortical amyloid deposition in presymptomatic and predementia stages of AD, irrespective of age, gender, and APOE genotype.

CONCLUSIONS

The observed correlations between BF atrophy and cortical amyloid load likely reflect associations between cholinergic degeneration and amyloid pathology as reported in neuropathologic examination studies.

Stimulate or degenerate: deep brain stimulation of the nucleus basalis Meynert in Alzheimer dementia

OBJECTIVE

Deep brain stimulation (DBS) is a therapeutically effective neurosurgical method originally applied in movement disorders. Over time, the application of DBS has increasingly been considered as a therapeutic option for several neuropsychiatric disorders, including Gilles de la Tourette syndrome, obsessive compulsive disorder, major depression and addiction. Latest research suggests beneficial effects of DBS in Alzheimer dementia (AD). Because of the high prevalence and the considerable burden of the disease, we endeavored to discuss and reveal the challenges of DBS in AD.

METHODS

Recent literature on the pathophysiology of AD, including translational data and human studies, has been studied to generate a fundamental hypothesis regarding the effects of electrical stimulation on cognition and to facilitate our ongoing pilot study regarding DBS of the nucleus basalis Meynert (NBM) in patients with AD.

RESULTS

It is hypothesized that DBS in the nucleus basalis Meynert could probably improve or at least stabilize memory and cognitive functioning in patients with AD by facilitating neural oscillations and by enhancing the synthesis of nerve growth factors.

CONCLUSIONS

Considering the large number of patients suffering from AD, there is a great need for novel and effective treatment methods. Our research provides insights into the theoretical background of DBS in AD. Providing that our hypothesis will be validated by our ongoing pilot study, DBS could be an opportunity in the treatment of AD.