Functional hierarchy for tactile processing in the visual cortex of sighted adults

• Published in: NeuroImage (Orlando, Fla.) Vol. 202; p. 116084
• Main Authors: Bola, Łukasz, Matuszewski, Jacek, Szczepanik, Michał, Droździel, Dawid, Sliwinska, Magdalena W., Paplińska, Małgorzata, Jednoróg, Katarzyna, Szwed, Marcin, Marchewka, Artur
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.11.2019; Elsevier Limited
• Subjects: Braille; Brain architecture; Brain research; Cross-modal interactions; Information processing; Magnetic fields; Perception; Reading; Somatosensory cortex; Spatial discrimination; Studies; Tactile perception; Tactile stimuli; TMS; Transcranial magnetic stimulation; Visual cortex; Visual perception; Poland; Braille; Somatosensory cortex; Perception; Visual cortex; Cross-modal interactions; TMS
• ISSN: 1053-8119; 1095-9572; 1095-9572
• DOI: 10.1016/j.neuroimage.2019.116084

Perception via different sensory modalities was traditionally believed to be supported by largely separate brain systems. However, a growing number of studies demonstrate that the visual cortices of typical, sighted adults are involved in tactile and auditory perceptual processing. Here, we investigated the spatiotemporal dynamics of the visual cortex’s involvement in a complex tactile task: Braille letter recognition. Sighted subjects underwent Braille training and then participated in a transcranial magnetic stimulation (TMS) study in which they tactually identified single Braille letters. During this task, TMS was applied to their left early visual cortex, visual word form area (VWFA), and left early somatosensory cortex at five time windows from 20 to 520 ms following the Braille letter presentation’s onset. The subjects’ response accuracy decreased when TMS was applied to the early visual cortex at the 120–220 ms time window and when TMS was applied to the VWFA at the 320–420 ms time window. Stimulation of the early somatosensory cortex did not have a time-specific effect on the accuracy of the subjects’ Braille letter recognition, but rather caused a general slowdown during this task. Our results indicate that the involvement of sighted people’s visual cortices in tactile perception respects the canonical visual hierarchy—the early tactile processing stages involve the early visual cortex, whereas more advanced tactile computations involve high-level visual areas. Our findings are compatible with the metamodal account of brain organization and suggest that the whole visual cortex may potentially support spatial perception in a task-specific, sensory-independent manner. •TMS of early and ventral visual areas disrupted tactile recognition in sighted adults.•TMS of the early visual cortex had an effect when applied 120–220 ms post-stimulus.•TMS of the ventral visual cortex had an effect when applied 320–420 ms post-stimulus.