Academic journal article Attention, Perception and Psychophysics

Temperature Perception on the Hand during Static versus Dynamic Contact with a Surface

Academic journal article Attention, Perception and Psychophysics

Temperature Perception on the Hand during Static versus Dynamic Contact with a Surface

Article excerpt

Innocuous cooling or heating of the forearm can evoke nociceptive sensations, such as burning, stinging, and pricking (low-threshold thermal nociception, LTN), that are inhibited by dynamic contact. In the present study, I investigated whether LTN can also be perceived on the hand, and if so, whether it is normally suppressed by active touching. Innocuous cold (28°, 25°, and 18°C) and warm (38°, 40°, and 43°C) temperatures were delivered to the distal metacarpal pads and intermediate and distal phalanges of the fingers via a handgrip thermode that subjects either statically held or actively grasped. The same temperatures were delivered to the forearm via another thermode that either rested on the arm or was touched to the arm. Subjects rated the intensity of thermal (warmth, cold) and nociceptive (e.g., burning) sensations and indicated the qualities of sensation experienced. The results showed that LTN can be perceived on the hand, although less frequently and less intensely than on the forearm. Dynamic contact inhibited nociceptive and thermal sensations on the hand, although less strongly than on the forearm. These findings indicate that temperature perception on the hand is attenuated and its quality is changed when thermal stimulation is accompanied by dynamic tactile stimulation, as it is during haptic exploration.

Thermal stimulation encountered during haptic exploration of surfaces and objects is always accompanied by touch. Despite this spatiotemporal coincidence, only one thermotactile interaction has so far been reported in which touch alters temperature perception on the hand. That interaction, termed thermal referral, was originally observed as a mislocalization of thermal sensation across the fingers (Green, 1977). When subjects touched three thermodes simultaneously with three fingers but only the outer two thermodes were heated or cooled, the center (neutral) thermode was also perceived to be warm or cold. Thermal referral, which was also studied on the forearm (Green, 1979), was hypothesized to result from an integrative mechanism that enables otherwise poorly localized temperature sensations (Cain, 1973; Dimmick, 1915; Taus, Stevens, & Marks, 1975) to be colocalized with tactile sensations. Because prior research had found negligible effects of mechanical pressure on the perception of thermal sensation (Jones, Singer, & Twelker, 1962), it was assumed that touch modified the spatial perception of thermal sensations without altering their perceived intensity or quality.

It was recently discovered, however, that, under some conditions, both the quality and the intensity of temperature perception can be modified by mechanical contact. This discovery followed the observation that heating or cooling the skin of the forearm to mild temperatures (e.g., 28°, 36°C) causes some individuals to feel nociceptive sensations such as burning and stinging (low-threshold thermal nociception, LTN) in addition to warmth and cold (Green & Akirav, 2007; Green & Pope, 2003; Green, Roman, Schoen, & Collins, 2008; Green & Schoen, 2005). LTN is optimally perceived when thermal stimulation occurs as a thermode rests statically against the skin. If thermal stimulation is produced instead by touching an already cooled (or heated) thermode to the skin, LTN is greatly reduced or disappears (contact suppression). Both the occurrence of nociceptive sensations at mild temperatures and their inhibition by mechanical contact coincident with the onset of thermal stimulation were unexpected findings. First, LTN occurs at temperatures that are below the thermal thresholds of recognized nociceptors (Bessou & Perl, 1969; Price & Dubner, 1977; Simone & Kajander, 1996, 1997; Tillman, Treede, Meyer, & Campbell, 1995). Second, although touch is well known to inhibit painful sensations (Bini, Cruccu, Hagbarth, Shady, & Torebjörk, 1984; Inui, Tsuji, & Kakigi, 2006; Longe et al., 2001; Pertovaara, 1979; Wall & Cronly-Dillon, 1960; Yarnitsky, Kunin, Brik, & Sprecher, 1997), no prior studies had indicated that merely making contact with a surface was sufficient to produce inhibition. …

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