Volumetric correlates of cognitive functioning in nondemented patients with Parkinson's disease

Abstract

A challenge in Parkinson's disease (PD) is to identify biomarkers of early cognitive change because functioning in some domains may be more prognostic of dementia. Few studies have investigated whether structural magnetic resonance imaging (MRI) correlates in a regionally specific manner with functioning in different cognitive domains. The aim of this study was to identify neuroanatomical correlates of executive functioning, memory, and visual cognition in PD without dementia. 3T MRI was conducted in 51 PD patients and 39 control participants. Brain volumes were measured in structures comprising the frontostriatal cognitive-control system, the medial temporal memory system, the ventral object-based system, and the dorsal spatial-based system. Measures of executive functioning (Stroop Test; Letter Fluency), memory (California Verbal Learning Test), visuospatial cognition (Judgment of Line Orientation), and visuoconstruction (Pentagon Copy) were correlated with volumes comprising each system. Poorer executive functioning largely correlated with decreased frontostriatal volumes. Poorer memory correlated with decreased volumes in all medial temporal regions, but also with frontostriatal volumes. Poorer visuospatial cognition correlated with decreased volumes in the object-based system, whereas poorer visuoconstruction correlated with decreased frontal and object-based system volumes. These relationships were nonsignificant in the control group. This is the first study to demonstrate that subtle changes in multiple cognitive domains in PD without dementia correlate with regional volumes in specific systems implicated in the development of cognitive impairment. The findings suggest that structural MRI holds promise as a marker of early changes in different brain systems, some of which may predict future cognitive deterioration.

Keywords: Parkinson's disease; executive function; magnetic resonance imaging; memory; visual cognition.

Fig. 1

Correlation of regional volumes with cognitive performances in PD. Cortical regions are displayed on lateral and medial surfaces of the left (L)/right (R) hemispheres. Axial views show putamen, amygdala, and hippocampus. Color bar designates the partial correlation coefficient magnitude.

Fig. 2

Scatter plots showing neurocognitive correlations in PD. Residuals from the regression of age and gender onto regional volumes and neuropsychological measures are plotted. L/R, left/right hemisphere; parahippa, parahippocampus; pTrng, pars triangularis; rMFG, rostral middle frontal; SMA, supplementary motor area; STG, superior temporal.