Tactile estimation of the roughness of gratings yields a graded response in the human brain: an fMRI study. - Ryo Kitada; Toshihiro Hashimoto; Takanori Kochiyama; Tomonori Kito; Tomohisa Okada; Michikazu Matsumura; Susan J. Lederman; Norihiro Sadato (NeuroImage, 2005)