Stanley J. Bolanowski
Lisa M. Maxfield
Karen L. Hall
James C. Makous
Dept. of Bioeng. and Neurosci., Inst. for Sensory Res., Syracuse Univ., Syracuse, NY 13244
The parallel processing of tactile information by independent channels as defined psychophysically, physiologically and anatomically has been amply described in the literature. For a unified percept to occur, however, information carried by these separate channels must be combined centrally. Furthermore, the unified percepts are affected by submodality interactions, such as the gate theory of pain whereby tactile stimulation suppresses pain, and cognitive factors (e.g., attention). Several series of experiments are presented showing that painfully hot and cold stimuli can substantially diminish vibrotactile sensation, but only when co-localized with the tactile stimuli. The effect occurs regardless of the tactile channel activated. This tough-gate acts oppositely to the pain gate and indicates centrally located touch--pain interactions. The results of additional experiments show that training of observers in an intensity-discrimination task can significantly affect the ability to distinguish differences in vibrotactile intensity. This learning effect appears to be bilateral and affects intensity as well as spatio-temporal perceptions of tactile stimuli. The effect indicates that high-level cognitive functions can influence tactile perceptions; the neural basis for these perceptions are presumably located at the cortical level.