Perception of surface stickiness in different sensory modalities: an functional MRI study

Surface texture can be perceived not only from tactile, but also from auditory and visual sensory cues. In our previous psychophysical study, we demonstrated that humans can recognize surface stickiness using only one kind of sensory modality without any difficulty. However, the brain regions that would be activated by non-corresponding sensory cues, for example, auditory and visual cues, remain unknown. In this human functional MRI study, we explored brain regions associated with surface stickiness perception in each of three different sensory modalities, and sought for common neural activities across modalities. In the tactile condition, participants actually touched a sticky surface with their right index finger. In the auditory and visual conditions, audio and video clips of tactile explorations of a sticky surface were presented and participants were asked to recall the perceived stickiness as vividly as possible. Our results, based on a general linear model analysis, showed that somatosensory cortices including postcentral gyrus, anterior insula, and anterior intraparietal sulcus were significantly activated across all modalities. Moreover, we observed significant activation of primary sensory regions of each modality. A follow-up conjunction analysis identified that postcentral gyrus, anterior intraparietal sulcus, precentral gyrus, and supplementary motor area were activated in common. These findings could deepen our understanding of the surface stickiness perception in the human brain.