Kenneth O. Johnson
Steven S. Hsiao
Dept. Neurosci., Johns Hopkins School of Medicine, 725 N. Wolfe St., Baltimore, MD 21205
Data from a variety of sources suggest complementary roles for the SAI, RA, and PC afferent systems. The following is a working hypotheses: The SAI system is the primary spatial system and is responsible for tactual form and rough perception when the fingers contact a surface directly and for the perception of external events through the distribution of forces across the skin surface. The PC system is responsible for the perception of external events that are manifested through transmitted high-frequency vibrations. The RA system has a lower spatial acuity than the SAI system but a higher sensitivity to local vibration and is responsible for the detection and representation of localized movement between skin and a surface as well as for surface form and texture when surface variation is too small to engage the SAI system. The evidence for these hypotheses will be reviewed. The issue for haptic interfaces is how to drive these systems in order to simulate real contact between the hand and objects in the environment. That will be the subject of the remainder of the talk [Johnson and Hsiao, Ann. Rev. Neurosci. 15, 227--250 (1992)]. [Work supported by NIH.]