Neural correlates of lexical decisions in Parkinson's disease revealed with multivariate extraction of cortico-subthalamic interactions. Issue 4 (April 2017) - Hohlefeld, F.U.
Highlights: Parkinsonian patients with subthalamic electrodes for deep brain stimulation. Maximized cortico-subthalamic i-coherency (MIC) in 14–35 Hz oscillations. Positive correlation between MIC and accuracy in lexical decisions. Abstract: Objective: Neural interactions between cortex and basal ganglia are pivotal for sensorimotor processing. Specifically, coherency between cortex and subthalamic structures is a frequently studied phenomenon in patients with Parkinson's disease. However, it is unknown whether cortico-subthalamic coherency might also relate to cognitive aspects of task performance, e.g., language processing. Furthermore, standard coherency studies are challenged by how to efficiently handle multi-channel recordings. Methods: In eight patients with Parkinson's disease treated with deep brain stimulation, simultaneous recordings of surface electroencephalography and deep local field potentials were obtained from bilateral subthalamic nuclei, during performing a lexical decision task. A recent multivariate coherency measure (maximized imaginary part of coherency, MIC) was applied, simultaneously accounting for multi-channel recordings. Results: Cortico-subthalamic synchronization (MIC) in 14–35 Hz oscillations positively correlated with accuracy in lexical decisions across patients, but not in 7–13 Hz oscillations. In contrast to multivariate MIC, no significant correlation was obtained when extracting cortico-subthalamic synchronization by "standard" bivariate coherency. Conclusions: Cortico-subthalamic synchronization may relate to non-motor aspects of task performance, here reflected in lexical accuracy. Significance: The results tentatively suggest the relevance of cortico-subthalamic interactions for lexical decisions. Multivariate coherency might be effective to extract neural synchronization from multi-channel recordings.