Abstract

Objective To investigate test-retest reliability of contact heat evoked potentials (CHEPs) from lower extremities using two different stimulation protocols, i.e., normal and increased baseline temperature. Methods A total of 32 able-bodied subjects were included and a subset (N = 22) was retested. CHEPs were recorded from three different dermatomes of the lower extremity (i.e., L2, L5, and S2). Test-retest reliability of CHEPs acquisition after simulation in various lower limb dermatomes using different stimulation protocols was analyzed. Results The study revealed an improved acquisition of CHEPS employing the increased baseline protocol, particularly when stimulating more distal sites, i.e., dermatome L5 and S2. Based on repeatability coefficients, CHEP latency (N2 potential) emerged as the most robust CHEP parameter. Although CHEP amplitudes (N2P2 complex) and pain ratings were decreased in the retest, amplitudes still showed fair to excellent intraclass correlation coefficients using normal baseline or increased baseline temperature, respectively. Conclusions This is the first study to demonstrate that CHEPs acquisition from the lower extremities is improved by increasing the baseline temperature of the thermode. Significance This study highlights the usability of CHEPs as a viable diagnostic method to study small fiber integrity.

Abstract

Much of our knowledge of the course of animal and plant evolution is based on shape. Recognition, description, arrangement, rearrangement, organization, reorganization, and interpretation of shape are the prime working tools of the paleontologist, the life blood of the systematist, the raw material of the evolutionist, and the dilemma of the developmental biologist. Keith Thomson's book, Morphogenesis and Evolution, deals with how shape changes both in ontogeny and in phylogeny. Morphogenesis is the study of the development of shape over an individual lifetime; evolution includes changes in shape throughout phylogeny. The development of form has been treated as a separate discipline since the German Naturphilosophie of Oken (1779-1851) and His (183 1-1904) and has been linked to phylogeny since von Baer (1792-1876). For Darwin, morphology was the soul of natural history (Darwin, 1910 p. 358), development and embryology, "one of the most important subjects in the whole round of natural history" (Darwin, 1910 p. 363). Mayr (1982 p. 468) believes that "evolutionary morphology" did not arise until the 1950's, with the distinction between function and role and the exploration of preadaptation, multiple functions, and multiple pathways. An integrated treatment of"morphogenesis and evolution" or, better, of morphogenesis as an evolutionary process therefore addresses, or should address, key questions in development, in evolution, and in the consequences of the one for the other. In developmental biology, and certainly in general treatises on animal development (of which the second edition of Scott Gilbert's [19881 Developmental Biology is the best currently available), morphogenesis is normally treated alongside differentiation (specialization of the parts of the embryo). This is not because morphogenesis and differentiation always proceed handin-hand, for even when they occur contemporaneously in space and time, each may be under separate and independent developmental control (see Maclean and Hall, 1987), but because the two, along with growth, constitute the triad of developmental processes. Morphogenesis normally occurs alongside cellular differentiation in growing tissues or organs. Differentiating cells often change shape as they grow (either by