The role of single touch domes in tactile perception.

Detection thresholds to step indentations applied to touch domes were measured and compared with threshold values obtained on adjacent areas of hairy skin. The mean of the detection thresholds determined on touch domes for five subjects was 504 +/- 27 microns (SEM). The detection thresholds found off the touch domes (2-3 mm away) were somewhat higher in all ten cases (two studies per subject), with a mean value of 587 +/- 28 microns, which was significant at the 0.01 level. These thresholds are an order of magnitude greater than those that elicit responses in touch-dome-associated slowly adapting type I (SAI) fibres in cats, and, together with the small difference between the detection thresholds determined on and off touch domes, indicate that the activity of single touch dome SAI fibres does not mediate the detection of steady indentation in the hairy skin.