Spatial summation effects on lingual vibrotactile thresholds.

Ascending lingual vibrotactile thresholds at 250 Hz were obtained for four groups of normal-speaking adult subjects. Contactor areas were varied for each respective group. Threshold values in microns plotted as a function of the area of vibratory displacement indicated a spatial summation function for the larger contactors (greater than .02 cm2). Findings are discussed in terms of the nature of lingual-tactile mechanoreception and possible implications for neural control mechanisms subserving speech production.