Multi-channel transcranial current stimulation (mc-tCS): a novel approach to modulate smooth pursuit eye movement control in healthy individuals and patients with psychotic disorders

This is the renewal proposal of the project: "Multi-channel transcranial direct current stimulation (mc-tDCS): a novel approach to modulate smooth pursuit eye movement control in healthy individuals and patients with psychotic disorders" which started in 2021. The project is grounded on the observation that neural networks subserving smooth pursuit eye movements (SPEM) provide an ideal model for investigating the modulation of sensorimotor integration during ongoing movements by transcranial current stimulation (tCS). Notably, SPEM deficits represent a neurophysiological biomarker for sensorimotor processing dysfunction in psychotic disorders being also linked to cognitive dysfunctions. Major nodes within the cortical SPEM network include visual motion processing area V5, and multimodal frontal eye fields (FEF) for SPEM control. In project phase 1 we successfully developed and applied cutting-edge methods for individually targeted and optimized mc-tDCS protocols based on multimodal information from combined electro- (EEG) and magnetoencephalography (MEG) source analysis and structural and functional magnetresonance imaging (sMRI, fMRI) recordings. We found that anodal individually optimized mc-tDCS outperformed normative tDCS, specifically for the modulation of V5 for rightward SPEM initiation in healthy participants. In contrast, exploratory data from patients suggest a modulation of leftward SPEM maintenance including cognitive input to SPEM by anodal individually optimized mc-tDCS over right V5. To further these achievements, the major objectives of this renewal proposal are, (1) to deepen our understanding of structural and functional connectivity within the cortical SPEM network and ist alterations in psychosis by specific multimodal analyses of structural and functional brain-brain connectivity based on MEG, EEG, sMRI, and fMRI data. (2) We will optimize targeting of individual visual areas with respect to location and orientation from combined EEG/MEG/s/fMRI data including sensitivity analysis. (3) We will evaluate the contribution of the work-intensive individual visual mc-tDCS stimulation procedures in comparison to standard bipolar and sham stimulations regarding the processing of visual motion information to V5 to develop more clinically oriented application protocols. (4) To study mechanisms of sustained SPEM maintenance including predictive cognitive input to SPEM and feedforward communication within the cortical SPEM network, we will use individually optimized transcranial alternating current stimulation (tACS) over V5 to modulate the entire SPEM network in healthy participants and psychosis patients. Following a network lesion driven approach, the entire project should pave the way for novel approaches using individually optimized tCS to improve sensorimotor integration and cognitive impairments associated with psychosis.