Somesthesis and the Chemical Senses

Abstract

Experimental work in the fields of somesthesis and the chemical senses has been and is still [Adrian (1)] dominated by certain concepts which have proved so convenient that they have come to be accepted without serious question by the majority of physiologists and by many psychologists. These concepts are Muller's so-called "law" of specific nervous energies, and von Frey's extrapolation of this law into the theory of punctate representation of primary sensory modalities. In other words, it is commonly accepted that there are mo ; phologically specific pain, warmth, cold, and touch nerve end ings, specific nerve fibres, and specific nerve pathways.It is for this reason that so much emphasis has been laid on the analysis of somesthesis and the chemical senses in terms of the activity of single nerve fibres, which has resulted in reviews that consist of collations of literature reporting the results of e1ectrophysiological experiments.Recent anatomical and psycho-physiological work, however, has seri ously challenged the validity of Muller's law and von Frey's theory with re gard to cutaneous sensibility, and has made it necessary to re-examine all the experimental observations on the sensory nervous system from a wholly different point of view. This revieJ.V will, therefore, take a somewhat unconventional form. In the first place, we shall examine and collate the evidence which seeks to refute the accepted concepts and then, in the light of these new observations, ex amine some of the literature in the field of somesthesis which has appeared in the course of the past year. The literature on the chemical senses was ably reviewed in Volume 5 of the Annual Review of Psychology and for this reason has been dealt with less exhaustively on this occasion. The review is intended to be provocative and critical, and necessarily reflects the author's personal opinion of the evidence before him. SOMESTHESISRecent observations on the mechanism of cutaneous sensibility.-The state ments which follow are based on a series of publications by Weddell and his co-workers (2 to 21) , some of which appeared before 1953. Reference should be made to all of these publications if exhaustive examination of the evi dence is desired.Neurohistological observations have shown that in the skin of the human ear and in hairy skin from elsewhere, i.e., abdomen and forearm, there are but two morphologically separable types of nerve termination: unencapsu lated (free) nerve endings and nerves ending in hair follicles of different

Theories of pain: from specificity to gate control

“…To support this claim, they cited work that had shown that distorting a nerve fiber would cause action potentials to discharge in any nerve fiber, whether encapsulated or not. Furthermore, intense stimulation of any of these nerve fibers would cause the percept of pain (Sinclair 1955;Weddell 1955).…”

Pain mechanisms: A commentary on concepts and issues

“…These histological explorations also tested predictions by von Frey relating defined neural structures in the skin to the mode of sensory experience (Woollard et al ., 1940). The morphological surveys did not yield evidence in favor of a special cutaneous neural network or of a correlation between morphologically recognizable structures and specific sensation (Sinclair, 1955; Sinclair et al ., 1952; Weddell, 1955; Woollard et al ., 1940). The absence of findings relating particular sensory structures of the skin to modes of sensation led to vigorous proposals for mechanoreceptive cutaneous sensation and pain to represent the product of special patterns of nerve activity, concepts similar to those postulated by Nafe (1934) several decades earlier.…”

Scientific Discoveries: What Is Required for Lasting Impact

“…The idea that multiple types of sensory receptors rather than specific nociceptors generate impulse patterns that lead to pain (pattern theory, gate control theory) is one example (123)(124)(125). Medicine is full of failed ideas, as indicated by the many surgical or pharmacological interventions that were abandoned when it became clear that the side effects far outweighed any benefits or that the benefits turned out to be placebo effects (126).…”