Brain degeneration in Parkinson’s disease patients with cognitive decline: a coordinate-based meta-analysis

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Abstract

<p class="first" id="d1579310e184">Cognitive decline in Parkinson's disease (PD) is a common sequela of the disease, with its severity increasing as the neurodegenerative process advances. The present meta-analysis used anisotropic effect size seed-based d mapping software to perform analyses using both functional and structural brain imaging data. The analyses were between PD patients with mild cognitive impairment (PD-MCI) and PD patients with dementia (PDD) compared to PD cognitively unimpaired patients (PD-CU) and PD patients without dementia (PD-ND) respectively. Thirty-four studies were found and split into three analyses: 405 PD-MCI patients compared to 559 PD-CU patients from 1) 15 studies with structural imaging modalities and 2) eight studies with functional imaging modalities, as well as 178 PDD patients compared to 278 PD-ND patients (which includes both PD-CU and PD-MCI) in 3) 11 studies with structural imaging modalities. Statistical threshold was set to uncorrected p < 0.001. We found several brain regions that differed between PD-MCI and PD-CU patients: the left insula, bilateral dorsolateral prefrontal cortex, left angular gyrus, midcingulate cortex, and right supramarginal gyrus. The brain regions identified in the PD-MCI analyses are associated with the somatosensory network and executive processing. In PDD patients, the bilateral insula and right hippocampus were found as regions of structural atrophy. The insula was found in both structural analyses of PD-MCI and PDD, with unilateral insula involvement in PD-MCI extending to bilateral insula involvement in PDD. The results found both a spectrum of increasing brain atrophy in PD cognitive impairment and supports the existence of sub-typing in PD-MCI. </p>

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A cortical-hippocampal system for declarative memory.

H. Eichenbaum (2000)

Recent neurobiological studies have begun to reveal the cognitive and neural coding mechanisms that underlie declarative memory--our ability to recollect everyday events and factual knowledge. These studies indicate that the critical circuitry involves bidirectional connections between the neocortex, the parahippocampal region and the hippocampus. Each of these areas makes a unique contribution to memory processing. Widespread high-order neocortical areas provide dedicated processors for perceptual, motor or cognitive information that is influenced by other components of the system. The parahippocampal region mediates convergence of this information and extends the persistence of neocortical memory representations. The hippocampus encodes the sequences of places and events that compose episodic memories, and links them together through their common elements. Here I describe how these mechanisms work together to create and re-create fully networked representations of previous experiences and knowledge about the world.

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The distinct cognitive syndromes of Parkinson's disease: 5 year follow-up of the CamPaIGN cohort.

Caroline Williams-Gray, Jonathan Evans, An Goris … (2009)

Cognitive abnormalities are common in Parkinson's disease, with important social and economic implications. Factors influencing their evolution remain unclear but are crucial to the development of targeted therapeutic strategies. We have investigated the development of cognitive impairment and dementia in Parkinson's disease using a longitudinal approach in a population-representative incident cohort (CamPaIGN study, n = 126) and here present the 5-year follow-up data from this study. Our previous work has implicated two genetic factors in the development of cognitive dysfunction in Parkinson's disease, namely the genes for catechol-O-methyltransferase (COMT Val(158)Met) and microtubule-associated protein tau (MAPT) H1/H2. Here, we have explored the influence of these genes in our incident cohort and an additional cross-sectional prevalent cohort (n = 386), and investigated the effect of MAPT H1/H2 haplotypes on tau transcription in post-mortem brain samples from patients with Lewy body disease and controls. Seventeen percent of incident patients developed dementia over 5 years [incidence 38.7 (23.9-59.3) per 1000 person-years]. We have demonstrated that three baseline measures, namely, age >or=72 years, semantic fluency less than 20 words in 90 s and inability to copy an intersecting pentagons figure, are significant predictors of dementia risk, thus validating our previous findings. In combination, these factors had an odds ratio of 88 for dementia within the first 5 years from diagnosis and may reflect the syndrome of mild cognitive impairment of Parkinson's disease. Phonemic fluency and other frontally based tasks were not associated with dementia risk. MAPT H1/H1 genotype was an independent predictor of dementia risk (odds ratio = 12.1) and the H1 versus H2 haplotype was associated with a 20% increase in transcription of 4-repeat tau in Lewy body disease brains. In contrast, COMT genotype had no effect on dementia, but a significant impact on Tower of London performance, a frontostriatally based executive task, which was dynamic, such that the ability to solve this task changed with disease progression. Hence, we have identified three highly informative predictors of dementia in Parkinson's disease, which can be easily translated into the clinic, and established that MAPT H1/H1 genotype is an important risk factor with functional effects on tau transcription. Our work suggests that the dementing process in Parkinson's disease is predictable and related to tau while frontal-executive dysfunction evolves independently with a more dopaminergic basis and better prognosis.

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Voxel-wise meta-analysis of grey matter changes in obsessive-compulsive disorder.

Joaquim Radua, David Mataix-Cols (2009)

Specific cortico-striato-thalamic circuits are hypothesised to mediate the symptoms of obsessive-compulsive disorder (OCD), but structural neuroimaging studies have been inconsistent. To conduct a meta-analysis of published and unpublished voxel-based morphometry studies in OCD. Twelve data-sets comprising 401 people with OCD and 376 healthy controls met inclusion criteria. A new improved voxel-based meta-analytic method, signed differential mapping (SDM), was developed to examine regions of increased and decreased grey matter volume in the OCD group v. control group. Results No between-group differences were found in global grey matter volumes. People with OCD had increased regional grey matter volumes in bilateral lenticular nuclei, extending to the caudate nuclei, as well as decreased volumes in bilateral dorsal medial frontal/anterior cingulate gyri. A descriptive analysis of quartiles, a sensitivity analysis as well as analyses of subgroups further confirmed these findings. Meta-regression analyses showed that studies that included individuals with more severe OCD were significantly more likely to report increased grey matter volumes in the basal ganglia. No effect of current antidepressant treatment was observed. Conclusions The results support a dorsal prefrontal-striatal model of the disorder and raise the question of whether functional alterations in other brain regions commonly associated with OCD, such as the orbitofrontal cortex, may reflect secondary compensatory strategies. Whether the reported differences between participants with OCD and controls precede the onset of the symptoms and whether they are specific to OCD remains to be established.