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MIND & BRAIN, THE JOURNAL OF PSYCHIATRY


ORIGINAL ARTICLE


Neural Correlates of Cognition Deficits in Mild Cognitive Impairment and Alzheimer’s Disease Oskar Dieter Peter Scho


¨nknecht1,2, Pablo Toro2, Aoife Hunt2, Marcus Henze3, Uwe Haberkorn3, and Johannes Schro ¨der2


Affiliations: 1Department of Psychiatry and Psychotherapy, University Hospital Leipzig, Leipzig; 2Section for Geriatric Psychiatry and 3German Cancer Research Center (DKFZ) Heidelberg, Clinical Cooperation Unit Nuclear Medicine and Department of Nuclear Medicine, Ruprecht-Karls-University Heidelberg, Heidelberg, Germany


ABSTRACT INTRODUCTION


Alzheimer’s disease (AD) and mild cognitive impairment (MCI) as its preclinical syndrome are characterized by a variety of cognitive deficits that can be assessed by using the neuropsychological test battery of the CERAD. The cerebral changes underlying the respective cognitive deficits, however, are only partly understood.


METHODS


In 75 patients with mild AD and MCI, cerebral changes were investigated by positron emission tomography with 18Fluorodeoxyglucose. A regression analysis was performed in order to investigate the respective associations of regional cerebral glucose metabolism with the CERAD test scores by statistical parametric mapping.


RESULTS


Episodic memory scores were significantly correlated with glucose metabolism in temporo-frontal and cingulate cortices. Verbal fluency and naming scores were significantly correlated with glucose metabolism predominantly in left temporo-parietal and frontal cortices whereas constructional praxis test scores correlated significantly with left temporal and right frontal cortices. Both subtests of delayed episodic memory were associated with a network including rather frontal association cortices.


CONCLUSION


Findings of the study demonstrate that neuropsychological deficits as assessed by the CERAD refer to different cerebral sites of both hemispheres, and underline the clinical validity of this clinical instrument. Keywords: neural correlates, AD, MCI, CERAD, PET Correspondence: Dr Oskar Dieter Peter Scho


¨nknecht, Department of Psychiatry, University Hospital Leipzig, Semmelweisstr. 10,04103 Leipzig, Germany. Tel: 49-341-9724506; Fax: 49-341-9724569; e-mail: Peter.Schoenknecht@medizin.uni-leipzig.de


INTRODUCTION Alzheimer’s disease (AD) and mild cognitive impairment (MCI) as its potential preclinical state are characterized by a variety of cognitive deficits that effect different neuropsycho- logical domains.13 The latter can be reliably assessed by using the neuropsychological test battery of the Consortium to Establish a Register for Alzheimer’s Disease (CERAD).46 Moreover, the CERAD does not only facilitate early recogni- tion and diagnosis of MCI and AD but may also be used in differential diagnosis.7


The cerebral changes underlying the respective cognitive deficits are only partly understood.8 Using positron emission tomography (PET) with 18 Fluorodeoxyglucose (FDG) as a tracer, several authors9 found impaired recognition*that is, one of the earliest signs of AD*to be associated with a decreased glucose uptake in right frontal and temporal cortices. These associations do not only correspond with the atrophic changes of mesial temporal lobe structures


www.slm-psychiatry.com 1


confirmed in a wealth of structural magnetic resonance imaging (MRI) studies,10 but also concurs with the model of hemispheric encoding/retrieval asymmetry (HERA),11 which suggests that right frontal and temporal cortical areas are involved in retrieval from episodic memory. Along with this, other studies referred changes in left temporo-parietal regions to deficits in naming and praxia, or left frontal lobe changes to a diminished verbal fluency.12


To date, associations between CERAD subscores and cerebral metabolic changes were only addressed in a small sample of AD patients.13 Surprisingly, significant correlations exclusively arose between cognitive measures and left hemi- spheric glucose metabolism. In contrast, delayed episodic memory performance has recently been demonstrated to be associated with bilateral frontal glucose metabolism in patients with MCI.14


Since most cognitive domains in general and memory in particular should not be conceptualized as reflecting unitary


M&B 2011; 2:(1). July 2011


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