Effects of deep brain stimulation of the nucleus basalis of Meynert in EEG resting-state oscillatory power and phase synchronization

Abstract

s / Brain Stimulation 8 (2015) 360e377 376 pulse TMS over the right superior cerebellum (lobule 6) [3] and verified the necessity of the left superior (with visual and motor control) and inferior cerebellum during visual working memory with a double-pulse (1s interval) stimulation using fMRI-guided TMS [4]. In the current follow-up study, involvement of the right inferior cerebellum during visual working memory is further investigated. Methods: 9 healthy, right-handed young-adults performed 2 tasks: (1) Visual Memory TMS (VM-TMS) and (2) Verbal Memory TMS (VERM-TMS) while a double-pulse (1s interval) stimulation sequence was applied over the right inferior cerebellum (lobule 8A/ 7B) specific to VM activation during fMRI-guided (BrainSight Ver2) TMS (Magstim Rapid2 systemwith a 110mm double cone coil). Each task comprised of two runs of 18 stimulation (Stim) and 18 nonstimulation (non-Stim) trials per run (Fig. 1). Task order was counterbalanced across all subjects. Results: Paired t-tests showed, TMS administered to the right inferior cerebellum, decreased accuracy only in the VM-TMS task (t [8]1⁄44.64;p1⁄40.0017), but had no effects on RT or the VERM-TMS conditions (Fig. 2). Discussion: Our findings verified the contributions of the right inferior cerebellum during VM-TMS and possible topographic specificity for visual and verbal WM within this lobule. Kirschen et al. [5] showed the right lobule 8 to be activated specifically for auditory input and lobule 7B for visual processes during VERM. It is plausible that our lack of significant effect during VERM-TMS is explained by the TMS target to be within lobule 7B and not 8, hence disrupting the visual processes essential for VM but not VERM. Further investigations using VERM fMRIguided targets in the right inferior cerebellum are needed to ascertain this.