Alpha and beta power decrease during enhanced cognitive effort in the basal ganglia: An intracerebral recording study

Abstract

Purpose Cognitive adverse effects may accompany deep brain stimulation (DBS) treatment, as the basal ganglia have influence on widespread neocortical networks. The aim of this study was to investigate how complex motor-cognitive activities are processed in the subthalamic nucleus (STN) and internal globus pallidum (GPi). Methods Dystonia patients implanted with GPi-DBS electrodes ( n = 5), and individuals with Parkinson’s disease (PD) ( n = 4) or essential tremor ( n = 1) with STN-DBS electrodes performed two tasks involving the writing of single letters: 1. copying letters from a monitor; and 2. writing of any letter other than that appearing on the monitor. The cognitive load of the second task was increased relative to the first. Intracranial recordings of task-related oscillatory changes were assessed and compared. Results Local event-related alpha and beta desynchronization (ERD) were more expressed during the second task while the lower gamma synchronization (ERS) decreased regardless of the basal ganglia structure from which recordings were obtained or the clinical diagnosis. Task-related ERD differences recorded from the language-dominant left hemisphere correlated with a behavioural (RT) measure of cognitive effort. ERD changes declined after levodopa intake in PD patients. Conclusions The STN and Gpi participate in cognitive networks. Alpha and beta ERD seems to be essential during processing complex motor-cognitive tasks and increase with enhanced cognitive effort.