Lastly, their relative insensitivity to static force and low-frequency vibration may enable
RAI-LTMRs to extract signals related to object movement and Metformin mouse distinguish them from stimuli related to the forces required to grip the object (Johansson and Vallbo, 1979 and LaMotte and Whitehouse, 1986). Like SA-LTMRs, RAI-LTMRs display conduction velocities within the Aβ range (Table 1). Physiological profiles of SAI- and RAI-LTMRs thus suggest that these afferents play complementary roles in discriminating tactile stimuli, analogous to the complementary roles of rods and cones in interpreting visual information. SAI-LTMRs, like cones in the retina, respond with higher spatial resolution but exhibit lower sensitivity. On the other hand, RAI-LTMRs, like rods, exhibit greater sensitivity but poorer spatial resolution (Johnson et al., 2000). It is therefore likely that SAIs and RAIs combine to encode a more complete picture of tactile space. The anatomical structure associated with RAI-LTMRs in glabrous skin is a corpuscle with varied nomenclatures; in primates and rodents, RAI-associated corpuscles are referred to as Meissner
corpuscles. Regardless Sunitinib of slight interspecies variations, all RAI-LTMR-associated corpuscles are thought to be evolutionarily derived from a common ending known to serve the same function in glabrous skin. The Meissner corpuscle of primates and rodents is the best characterized anatomically and it is
made up of flattened lamellar cells arranged as horizontal lamellae embedded in connective tissue. They are localized to dermal papillae in glabrous skin, most notably in fingerprint skin of the human hands and the soles of feet (Figure 1A). Each individual corpuscle can be supplied by up to three large myelinated fibers that are interwoven within the capsular cells of the corpuscle (Cauna and Ross, 1960 and Jänig, 1971). The arrangement of lamellar cells and nerve terminals within the Meissner corpuscle is thought to play a critical role in shaping the physiological properties ADP ribosylation factor of RAI-LTMRs. Upon indentation of glabrous skin, collagen fibers that connect the basal epidermis to lamellar cells of the corpuscle provide the mechanical force that deforms the corpuscle and triggers action potential volleys that quickly ease as a result of the rapidly adapting nature of RAI-LTMRs. When the stimulus is removed, the corpuscle regains its shape, and in doing so it induces another volley of action potentials, generating the distinctive on-off responses of RAI-LTMRs (Table 1). One RA afferent can branch repeatedly to innervate several corpuscles. In primates, 30–80 corpuscles can be innervated by a single RAI afferent fiber (Bolton et al., 1964, Halata, 1975, Paré et al., 2001 and Paré et al., 2002).