Progressive changes in a recognition memory network in Parkinson's disease

Abstract

In a previous functional MRI (fMRI) study, we found that Parkinson's disease (PD) patients presented dysfunctions in the recruitment of recognition memory networks. We aimed to investigate the changes in these networks over time. We studied 17 PD patients and 13 age and sex-matched healthy subjects. In both groups fMRI (recognition memory paradigm) and neuropsychological assessments were obtained at baseline and follow-up. In order to analyze changes over time in functional networks, modelfree (independent component analysis) analyses of the fMRI data were carried out. After that, a cross-correlation approach was used to assess the changes in the strength of functional connectivity. At follow-up, patients showed reduced recruitment of one network, including decreased activations in orbitofrontal cortices, middle frontal gyri, frontal poles, anterior paracingulate cortex, superior parietal lobes and left middle temporal gyrus, as well as decreased deactivation in anterior paracingulate gyrus and precuneus. Cross-correlation analyses over time showed a decrease in the strength of functional connectivity between middle frontal gyrus and superior parietal lobe in PD patients. Model-free fMRI and cross-correlation connectivity analyses were able to detect progressive changes in functional networks involved in recognition memory in PD patients at early disease stages and without overt clinical deterioration. Functional connectivity analyses could be useful to monitor changes in brain networks underlying neuropsychological deficits in PD.