TABLE 1.

Summary of physiological characteristics of primate mechanoreceptors and thalamic mechanoreceptor-specific neurons

	Von Frey	Receptive Field	Response to Indentation	Frequency of Maximum Vibration Response	Amplitude of Maximum Vibration Response	Optimal Stimulus
Thalamic SA1	≤0.5 g*	Volar aspect of phalanx*	Thresh < 0.2 mm plateau 0.5 mm,* 0.006–0.2 mm†	NA	NA	Step indentation
SA1 afferent	Half <0.1 and half 0.5 to 1.9 g‡	Regular well-defined† <6 mm2	Thresh 0.06 mm,** linear increment up to 1.5 mm††	Nil	Nil	Edge contours of step indentation‡
SA2 afferent (human only)		<25 mm2, obscure‡ than SAI adjacent to nailbed or skin folds‡‡	Thresh 0.3 mm.** 4 times less sensitive than SAI**	Not well defined	Nil	Skin stretch†
Thalamic RA	≤0.5 g*	Fraction of Volar phalanx*	Plateaus between 0.1 and 0.3 mm	>100 Hz, may respond at <10 Hz*	Thresh <0.01 mm*
RA afferent	<0.1 g‡	Regular distinct 5–30 mm2	Thresh 10−3 mm,** plateaus at 0.1–0.2 mm††	40–60 Hz‡	Threshold ≥2 × 10−5 mm	Vibration 40–60 Hz
Thalamic PC	<0.1 g*	Larger than RA*	NA	>100 Hz*	Thresh ≥0.02 plateau = 0.08 mm*
PC afferent	NA	Large (whole finger or palm), obscure, may involve the whole hand, rarely less than a phalanx	Thresh 10−2 mm,** sensitive to third derivative of displacement, not sustained indent	200–300 Hz	Threshold ≥ 10−5 mm	Vibration 200–300 Hz

^*Zhang et al. 2001;

^†Johnson et al. 2000;

^‡Johnson 2001;

^**Johansson and Vallbo 1983;

^††Gybels and van Hees 1972. SA, slowly adapting; RA, rapidly adapting; PC, Pacinian corpusles; NA, not available; g, grams.