Non-invasive brain stimulation to treat disorders of human verticality

Abstract

Brain lesions frequently cause verticality misperception and result in poor postural control and functionality. Although the mechanism of verticality misperception remains incompletely understood, available evidence indicates that a cortical hub at the temporo-parietal junction is implicated. A relatively recent tool for investigating and influencing cortical activity is non-invasive electromagnetic brain stimulation (NIBS), that could plausibly be used to understand and treat disorders of verticality. NIBS can target the temporo-parietal junction, or other cortical areas related to verticality perception, such as parietal cortex, superior and middle temporal gyri, and the post-central gyrus. Here we present an overview of the elementary concepts of NIBS and studies aiming to investigate the underlying mechanisms, and develop treatment strategies for verticality misperception using NIBS. Top-down neuromodulatory effects on verticality perception have been demonstrated, using repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), with promising clinical impact. We further discuss the rationale and necessary features for developing future rTMS and tDCS protocols to treat disorders of human verticality.