Apart from its motor symptoms, Parkinson´s disease (PD) is characterized by cognitive deficits; among these, executive functioning (EF) deficits are common. Stroke studies have shown a role of the...Show moreApart from its motor symptoms, Parkinson´s disease (PD) is characterized by cognitive deficits; among these, executive functioning (EF) deficits are common. Stroke studies have shown a role of the whole thalamus, and specifically the medial nuclear group (Mng), in EF. Although in PD studies have shown volume loss in the thalamus and Mng, little is known about the relationship between this phenomenon and EF deficits in PD. We aimed to address this gap and examine the relationship between thalamic and Mng volumes and EF in PD. As the thalamus is difficult to segment due to poor tissue contrast, we also aimed to explore whether using Phase-Sensitive Inversion Recovery MRI scans in addition to T1 MRI scans (T1+PSIR MRI) would optimize automatic thalamic segmentation over using T1 MRI scans alone. A total of 76 PD participants underwent T1 and PSIR MRI scans and completed tests measuring verbal fluency, resistance to cognitive interference and planning abilities, which were used to calculate an EF composite score. We found that using T1+PSIR MRI scans resulted in a more accurate thalamic segmentation as shown by less thalamic overestimation especially in the lateral and anteroventral nuclear groups, and smaller thalamic and nuclear groups volumes. We used the derived volumes to relate to global EF performance. Results showed that total thalamic and total Mng volumes were not significantly related to global EF performance (β = .08, t = 1.24, p = .22; β = .16, t = 1.71, p = .09, respectively). Results of exploratory analyses showed a positive significant relationship between left (β = .16, t = 2.26, p = .02) and right (β = .18, t = 2.67, p = .01) thalamic volumes and left (β = .25, t = 2.84, p = .01) Mng volume and verbal fluency performance. In this thesis project we demonstrated that automatic thalamic segmentation can be optimized by using PSIR MRI scans. Although the association between thalamic and Mng volumes and global EF in PD is not supported in this thesis project, volumes seem to be specifically associated with verbal fluency. We propose that this could be due to the role of the Mng in cognitive flexibility. Supported by future longitudinal studies, our findings could have implications for early diagnosis and effective management of verbal fluency deficits in PD.Show less
