Reduced neuronal efficacy in progressive mild cognitive impairment: A prospective fMRI study on visuospatial processing

Vannini, Patrizia; Almkvist, Ove; Dierks, Thomas; Lehmann, Christoph; Wahlund, Lars-Olof

doi:10.1016/j.pscychresns.2007.02.003

« Previous Next »Psychiatry Research: Neuroimaging
Volume 156, Issue 1 , Pages 43-57, 15 October 2007

Reduced neuronal efficacy in progressive mild cognitive impairment: A prospective fMRI study on visuospatial processing

Patrizia Vannini
- Department of Neurobiology, Care Sciences and Society, Division of Clinical Geriatrics, Karolinska Institutet, Karolinska University Hospital, Huddinge, 141 86 Stockholm, Sweden
- Corresponding author. Karolinska Institutet, Department of Neurobiology, Care Sciences and Society, Division of Clinical Geriatrics, Novum, level 5 / Karolinska University Hospital Huddinge, 14186 Stockholm, Sweden. Tel.: +46 8 585 828 89; fax: +46 8 585 854 70.
Ove Almkvist
- Department of Neurobiology, Care Sciences and Society, Division of Clinical Geriatrics, Karolinska Institutet, Karolinska University Hospital, Huddinge, 141 86 Stockholm, Sweden
- Department of Psychology, Stockholm University, 106 91 Stockholm, Sweden
Thomas Dierks
- Department of Neurobiology, Care Sciences and Society, Division of Clinical Geriatrics, Karolinska Institutet, Karolinska University Hospital, Huddinge, 141 86 Stockholm, Sweden
- Department of Psychiatric Neurophysiology, University Hospital of Psychiatry, CH-3000 Bern, Switzerland
Christoph Lehmann
- Department of Psychiatric Neurophysiology, University Hospital of Psychiatry, CH-3000 Bern, Switzerland
Lars-Olof Wahlund
- Department of Neurobiology, Care Sciences and Society, Division of Clinical Geriatrics, Karolinska Institutet, Karolinska University Hospital, Huddinge, 141 86 Stockholm, Sweden

Received 3 October 2006; received in revised form 19 January 2007; accepted 12 February 2007.

Abstract

Mild cognitive impairment (MCI) often refers to the preclinical stage of dementia, where the majority develop Alzheimer's disease (AD). Given that neurodegenerative burden and compensatory mechanisms might exist before accepted clinical symptoms of AD are noticeable, the current prospective study aimed to investigate the functioning of brain regions in the visuospatial networks responsible for preclinical symptoms in AD using event-related functional magnetic resonance imaging (fMRI). Eighteen MCI patients were evaluated and clinically followed for approximately 3 years. Five progressed to AD (PMCI) and eight remained stable (SMCI). Thirteen age-, gender- and education-matched controls also participated. An angle discrimination task with varying task demands was used. Brain activation patterns as well as task demand-dependent and -independent signal changes between the groups were investigated by using an extended general linear model including individual performance (reaction time [RT]) of each single trial. Similar behavioral (RT and accuracy) responses were observed between MCI patients and controls. A network of bilateral activations, e.g. dorsal pathway, which increased linearly with increasing task demand, was engaged in all subjects. Compared with SMCI patients and controls, PMCI patients showed a stronger relation between task demand and brain activity in left superior parietal lobules (SPL) as well as a general task demand-independent increased activation in left precuneus. Altered brain function can be detected at a group level in individuals that progress to AD before changes occur at the behavioral level. Increased parietal activation in PMCI could reflect a reduced neuronal efficacy due to accumulating AD pathology and might predict future clinical decline in patients with MCI.

Keywords: Preclinical Alzheimer's disease, Angle discrimination, Reaction time