Texture Tactile Perception Based on EEG-fNIRS Technology

Texture features play a crucial role in object recognition. Although texture can be perceived through both visual and tactile perspectives, the sense of touch dominates in perceiving material properties such as texture. Tactile perception of texture is the sensation of spatial changes in object surface features over time that occurs in the brain when the tip rubs against the object. During sliding friction, the microscopic geometry of the textured surface causes small deformations and vibrations in the skin, which are encoded as nerve impulses transmitted to the nerve center, and people use this to distinguish subtle textural features of the surface. In this paper, a multimodal frictional tactile perception test platform was built using simultaneous EEG-fNIRS imaging, and two groups of samples with different texture characteristics were designed, namely, the changing texture spacing group and the changing texture depth group, and then the frictional vibration and the induced physiological brain activity during fingertip contact with the frictional samples were observed to further investigate the human tactile perception of different textures and the formation mechanism of tactile perception of textured surfaces. The results of the friction vibration experiment showed that the fitted curve of the sample friction coefficient roughly passed the zero point, and only slight adhesion occurred between the sample and the finger, which was the tribological behavior dominated by shear force; the power spectrum center of gravity of the sound signal was approximately negatively correlated with the friction coefficient, which can reflect the tribological behavior of the experimental sample; The Mayer frequency cepstrum coefficient (MFCC) can reflect the static characteristics of the sound signal, and the results showed that the statistical features such as gray histogram and fractal dimension of MFCC can reflect the texture characteristics of this experimental sample. The results of the joint EEG-fNIRS synchronization experiment showed that touching different textural features on the surface mainly activated left brain regions, mainly because the body complied with contralateral administration, while right-handed touch was used in this experiment; the co-activated channels were dominated by the postcentral gyrus, with the most significant tactile response in primary somatosensory cortex SI. In the process of finger touch sample induced brain activity, alpha rhythm is the main EEG component, which is related to human cognitive function with about 45% of energy, followed by delta rhythm and theta rhythm with about 25% of energy, and there is no significant difference between left and right brain regions in comparison (P>0.05), which shows that both left and right brain regions are involved in tactile perception. The characteristic parameters such as sample entropy and sorting entropy of EEG signals cannot characterize the variability of the samples in this experiment well, mainly because the samples in this experiment are more finely textured and subtle differences are difficult to be distinguished.