title: Effects of parietal TMS on visual and auditory processing at the primary cortical level -- a concurrent TMS-fMRI study.
abstract: Accumulating evidence suggests that multisensory interactions emerge already at the primary cortical level. Specifically, auditory inputs were shown to suppress activations in visual cortices when presented alone but amplify the blood oxygen level-dependent (BOLD) responses to concurrent visual inputs (and vice versa). This concurrent transcranial magnetic stimulation-functional magnetic resonance imaging (TMS-fMRI) study applied repetitive TMS trains at no, low, and high intensity over right intraparietal sulcus (IPS) and vertex to investigate top-down influences on visual and auditory cortices under 3 sensory contexts: visual, auditory, and no stimulation. IPS-TMS increased activations in auditory cortices irrespective of sensory context as a result of direct and nonspecific auditory TMS side effects. In contrast, IPS-TMS modulated activations in the visual cortex in a state-dependent fashion: it deactivated the visual cortex under no and auditory stimulation but amplified the BOLD response to visual stimulation. However, only the response amplification to visual stimulation was selective for IPS-TMS, while the deactivations observed for IPS- and Vertex-TMS resulted from crossmodal deactivations induced by auditory activity to TMS sounds. TMS to IPS may increase the responses in visual (or auditory) cortices to visual (or auditory) stimulation via a gain control mechanism or crossmodal interactions. Collectively, our results demonstrate that understanding TMS effects on (uni)sensory processing requires a multisensory perspective.
authors.affiliation: Cognitive Neuroimaging Group, Max Planck Institute for Biological Cybernetics, 72076 Tübingen, Germany. joana.leitao@tuebingen.mpg.de
authors.forename: Joana
authors.initials: J
authors.lastname: Leitão
authors.forename: Axel
authors.initials: A
authors.lastname: Thielscher
authors.forename: Sebastian
authors.initials: S
authors.lastname: Werner
authors.forename: Rolf
authors.initials: R
authors.lastname: Pohmann
authors.forename: Uta
authors.initials: U
authors.lastname: Noppeney
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D001931:Brain Mapping; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009434:Neural Pathways / Q000098:blood supply* / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D010296:Parietal Lobe / Q000098:blood supply* / Q000502:physiology*; D010775:Photic Stimulation; D011601:Psychophysics; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
chemical_list: D010100:Oxygen