Tactile motion aftereffects produced by appropriate presentation for mechanoreceptors.

Tactile motion perception is one of the most important functions for realizing a delicate appreciation of the tactile world. To explore the neural dynamics of motion processing in the brain, the motion adaptation phenomenon can be a useful probe. Tactile motion aftereffects (MAE), however, have not been reported in a reproducible fashion, and the indistinctive outcomes of the previous studies can be ascribed to the non-optimal choice of adapting and testing stimuli. Considering the features of the stimuli used in the studies, the stimuli activated the different mechanoreceptors in the adapting and testing phase. Consequently, we tested tactile MAE using appropriate combinations of adapting and testing stimuli. We used three pins to generate sensation of apparent motion on the finger cushion. They were sequentially vibrated with the frequency of 30 Hz both in adapting and testing phases. It is expected that this procedure ensured stimulation for the same mechanoreceptor (Rapid-Adapting mechanoreceptor) in both the adaptation and test phases. Using this procedure, we found robust tactile MAEs in the various tactile motions such as the short-distance motion within the fingertip, the long-distance motion from the finger base to the fingertip, and the circular motion on the fingertip. Our development of a protocol that reliably produces tactile MAEs will provide a useful psychophysical probe into the neural mechanisms of tactile motion processing.