Brain activation related to the tactile perception of touching ridged texture using fingers

Humans can recognize the physical properties of objects by touching them, even when vision is unavailable. Tactile perception is important for humans in interacting with the environment. The triangular ridged textures are usually added to surface to improve the grip reliability of products, but the sharp edge of triangular ridge induces sharp and uncomfortable feeling.

To study the effect of the edge shape of triangular ridged texture on brain activity, functional magnetic resonance imaging technique was used to obtain the blood oxygen level-dependent (BOLD) signal of subjects during the touching of textured surfaces. Samples with sharp, round, and flat shape ridged textures were chosen as the tactile stimulus.

The contralateral postcentral gyrus, the precentral gyrus, the inferior parietal lobule, and the supramarginal gyrus, corresponding with the functional regions of the primary somatosensory cortex (SI), the secondary somatosensory cortex (SII), and the primary motor cortex (MI) were related to the perception of three shape ridged textures. The main brain activation located in the postcentral gyrus and the SI. The tactile information of three shape ridged textures was received by Brodmann area (BA) 3 of the SI, and then inputted to BA 2 of the SI, the further tactile discrimination of shape of ridged textures was involved in BA40 of the SII. The intensity, the areas, and the percent signal change (PSC) of brain activation that were evoked by different shape ridged textures were related to the geometric structures of the ridged textures. The more complex the geometric structures of texture are, the larger the intensity, the area, and the PSC in brain activation are. The negative BOLD responses of the ipsilateral sensory cortex that were evoked by the flat ridged texture indicated the ipsilateral neuronal inhibition within the sensory systems. The bilateral precuneus, the superior parietal gyrus, and the inferior parietal gyrus, corresponding with the functional areas of the SII (BA40) and the SSA(BA7), were involved in the tactile discriminate of the differences in shapes of ridged textures. The differences in brain activation were related to the differences in geometric structures of the ridged texture. The larger the differences in geometric structure of texture are, the larger the differences in brain activation are. This study revealed the activated location of brain related to the tactile stimulation of different edge shape of ridged textures and the relationship between the geometric structures of ridged texture and brain activities. This research contributes to optimize surface tactile characteristics on products, especially effective surface textures design for good grip.