Original Research ARTICLE
Cortical Regions Encoding Hardness Perception Modulated by Visual Information Identified by Functional Magnetic Resonance Imaging with Multivoxel Pattern Analysis
- 1Cognitive Neuroscience Section, Primate Research Institute, Kyoto University, Japan
- 2Tokyo Medical and Dental University, Japan
- 3Center for Brain Integration Research, Tokyo Medical and Dental University, Japan
- 4Brain Science Institute, Tamagawa University, Japan
Recent studies have revealed that hardness perception is determined by visual information along with the haptic input. This study investigated the cortical regions involved in hardness perception modulated by visual information using functional magnetic resonance imaging and multivoxel pattern analysis (MVPA). Twenty-two healthy participants were enrolled. They were required to place their left and right hands at the front and back, respectively, of a mirror attached to a platform placed above them while lying in a magnetic resonance scanner. In conditions SFT, MED, and HRD, one of three polyurethane foam pads of varying hardness (soft, medium, and hard, respectively) was presented to the left hand in a given trial, while only the medium pad was presented to the right hand in all trials. MED was defined as the control condition, because the visual and haptic information was congruent. During the scan, the participants were required to push the pad with the both hands while observing the reflection of the left hand and estimate the hardness of the pad perceived by the right (hidden) hand based on magnitude estimation. Behavioral results showed that the perceived hardness was significantly biased toward softer or harder in > 73% of the trials in conditions SFT and HRD; we designated these trials as visually modulated (SFTvm and HRDvm, respectively). The accuracy map was calculated individually for each of the pair-wise comparisons of [SFTvm vs. MED], [HRDvm vs. MED], and [SFTvm vs. HRDvm] by a searchlight MVPA, and the cortical regions encoding the perceived hardness with visual modulation were identified by conjunction of the three accuracy maps in group analysis. The cluster was observed in the right sensory motor cortex, left anterior intraparietal sulcus (aIPS), bilateral parietal operculum (PO), and occipito-temporal cortex (OTC). Together with previous findings on such cortical regions, we conclude that the visual information of finger movements processed in the OTC may be integrated with haptic input in the left aIPS, and the subjective hardness perceived by the right hand with visual modulation may be processed in the cortical network between the left PO and aIPS.
Keywords: somatic sensation, multimodal integration, active touch, Mirror visual feedback (MVF), Intraparietal sulcus (IPS), Posterior parietal cortex (PPC), Sensory motor cortex
Received: 08 Feb 2019;
Accepted: 11 Sep 2019.
Copyright: © 2019 Kim, Usui, Miyazaki, Haji, Matsumoto, Taira, Nakamura and Katsuyama. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Dr. Narumi Katsuyama, Tokyo Medical and Dental University, Bunkyo, Japan, email@example.com