Neural correlates of self-awareness of cognitive deficits in non-demented patients with Parkinson's disease

Background and purpose: The aim was to investigate the neural correlates of impaired self-awareness of cognitive deficits (IACd) in non-demented patients with Parkinson's disease (PD). Methods: This cross-sectional study enrolled 153 drug-naïve and non-demented PD patients who underwent brain magnetic resonance imaging, dopamine transporter (DAT) positron emission tomography, detailed neuropsychological testing, and the Cognitive Complaints Interview at baseline. Based on the presence of mild cognitive impairment and subjective cognitive complaints, patients were grouped into those with IACd (PD-IACd+, n = 33) and those with normal recognition of cognitive function (n = 82) or underestimation of cognitive function (n = 38). Cortical thickness, white matter (WM) integrity, DAT availability and cognitive function were compared between the groups. Results: The prevalence of IACd was 21.6% in drug-naïve patients with PD. The PD-IACd+ group had a lower z-score in the Stroop color reading test than the other groups. Patients in the PD-IACd+ group had WM disintegrity, especially in the genu of the corpus callosum and anterior limb of the internal capsule, compared to those without IACd, whilst cortical thickness or striatal DAT availability was comparable regardless of the presence of IACd. Amongst patients with mild cognitive impairment, those with IACd had more severe WM disintegrity than those without IACd. Conclusion: Structural connectivity between and from the frontal lobes is closely associated with self-awareness of cognitive deficits in PD. Evaluating frontal structural connectivity from the early stages of PD will be important in assessing the actual cognitive and daily life performance of patients with PD.