This is interesting, too:
May 27, 2009

Mapping of brain acetylcholinesterase alterations in Lewy body disease by PET

H. Shimada, MD, S. Hirano, MD, PhD, H. Shinotoh, MD, PhD,

Objective: To characterize brain cholinergic deficits in Parkinson disease (PD), PD with dementia (PDD), and dementia with Lewy bodies (DLB).

Methods: Participants included 18 patients with PD, 21 patients with PDD/DLB, and 26 healthy controls. The PD group consisted of nine patients with early PD, each with a disease duration of less than 3 years, five of whom were de novo PD patients, and nine patients with advanced PD, each with a disease duration greater than or equal to 3 years. The PDD/DLB group consisted of 10 patients with PDD and 11 patients with DLB. All subjects underwent PET scans with N-[11C]-methyl-4-piperidyl acetate to measure brain acetylcholinesterase (AChE) activity. Brain AChE activity levels were estimated voxel-by-voxel in a three-compartment analysis using the arterial input function, and compared among our subject groups through both voxel-based analysis using the statistical parametric mapping software SPM5 and volume-of-interest analysis.

Results: Among patients with PD, AChE activity was significantly decreased in the cerebral cortex and especially in the medial occipital cortex (% reduction compared with the normal mean = –12%) (false discovery rate–corrected p value <0.01). Patients with PDD/DLB, however, had even lower AChE activity in the cerebral cortex (% reduction = –27%) (p < 0.01). There was no significant difference between early PD and advanced PD groups or between DLB and PDD groups in the amount by which regional AChE activity in the brain was reduced.

Conclusions: Brain cholinergic dysfunction occurs in the cerebral cortex, especially in the medial occipital cortex. It begins in early Parkinson disease, and is more widespread and profound in both Parkinson disease with dementia and dementia with Lewy bodies.
**********************

Cholinergic denervation occurs early in Parkinson disease
Nicolaas I. Bohnen and Roger L. Albin

Published online before print June 17, 2009
There's no abstract. An earlier article:

Cognitive correlates of cortical cholinergic denervation in Parkinson’s disease and parkinsonian dementia
Journal Journal of Neurology
Publisher Steinkopff
ISSN 0340-5354 (Print) 1432-1459 (Online)
Issue Volume 253, Number 2 / February, 2006

Abstract

We recently reported findings that loss of cortical acetylcholinesterase (AChE) activity is greater in parkinsonian dementia than in Alzheimer’s disease (AD). In this study we determined cognitive correlates of in vivo cortical AChE activity in patients with parkinsonian dementia (PDem, n = 11), Parkinson’s disease without dementia (PD, n = 13), and in normal controls (NC, n = 14) using N–[11C]methyl–piperidin–4–yl propionate ([11C]PMP) AChE positron emission tomography (PET). Cortical AChE activity was significantly reduced in the PDem (–20.9%) and PD (–12.7 %) subjects (P < 0.001) when compared with the control subjects. Analysis of the cognitive data within the patient groups demonstrated that scores on the WAIS-III Digit Span, a test of working memory and attention, had most robust correlation with cortical AChE activity (R = 0.61, p < 0.005).

There were also significant correlations between cortical AChE activity and other tests of attentional and executive functions, such as the Trail Making and Stroop Color Word tests. There was no significant correlation between cortical AChE activity and duration of motor disease (R = –0.01, ns) or severity of parkinsonian motor symptoms (R = 0.14, ns).

We conclude that cortical cholinergic denervation in PD and parkinsonian dementia is associated with decreased performance on tests of attentional and executive functioning.