Discharges from the sensory organs of the cat's vibrissae and the modification in their activity by ions

Abstract

RECORDS from the cutaneous nerves of the cat, rabbit and guinea-pig [Adrian & Zotterman, 1926;Zotterman, 1939] have given information as to the sensory discharges from the hairs covering the body surface. These discharges are usually of brief duration, occurring only when movement is carried out and ceasing when a steady deflected position is reached. The nerve endings stimulated by hair movement can therefore be described as rapidly adapting, although the short duration of the discharges might be due to mechanical factors, such as the yielding oftissues, rather than to the intrinsic properties of the endings [cf. Dun & Finley, 1938]. But the investigations referred to have been concerned with the covering hairs of the body and limbs; the large vibrissae or tactile hairs of the face have not been specially examined. They might well react differently, since they are supplied by more elaborate nerve endings and have a more definite sensory function than the covering hairs. Indeed, the vibrissae represent a distinct type of organ, absent in man but important in the life of most quadrupeds.The present work deals primarily with the normal sensory activity of the tactile hairs of the face, studied by the usual technique for recording afferent impulses. In the course of the work it became clear that preparations of these organs gave such consistent results that they could be used for the investigation of problems of more general interest, such as the nature of the adaptation process, its modification by ions, etc. The latter is dealt with in the second part of the paper.

Tactual discrimination of size and shape by a California sea lion (Zalophus californianus)

“…Therefore, differences in the deflection angle of the vibrissal shaft result in mechanical stimulations of different intensity inside the follicle, which then lead to a different response of the follicle receptors. It has been repeatedly shown that the discharge rate of impulses in the slowly adapting afferent fibers of the trigeminal nerve rise in proportion to the extent of the vibrissae's deflection angle (Dykes, 1975;Fitzgerald, 1940;Gottschaldt, Iggo, & Young, 1973;Hahn, 1971;Hunt & Mcintyre, 1960). When the neural mechanism underlying the size discriminations of the sea lion is the measurement of impulse rates of afferent fibers, the animal used, according to the definition by Johnson and Phillips (1981), a "purely intensive cue" for its discriminations.…”

The mechanoreceptors of the rabbit mandibular incisor

“…It is of great interest that Boyd (1954) has been able to identify the 'rapidly adapting' receptor of Boyd & Roberts as an elongated lamellated corpuscle and the 'slowly adapting' receptor as a spray (or Ruffini) ending, since Lewinsky & Stewart (1936) illustrate apparently similar endings found in preparations from the periodontal membranes of cat and rabbit. Directionality A relationship between the direction of a mechanical stimulus and the response of a stimulated sensory receptor has been observed in mechanoreceptors of the lateral line organ of fish (Sand, 1937), and of the teeth (Pfaffmann, 1939a), vibrissae (Fitzgerald, 1940), and knee-joint (Boyd & Roberts, 1953) of the cat. The incisor tooth of the rabbit has provided a suitable preparation for examining this relationship in some detail.…”

Vestibular, cochlear and trigeminal projections to the cortex in the anterior suprasylvian sulcus of the cat

“…The mechanoreceptors discharged by movement of the vibrissae are very sensitive and slowly adapting when subjected to a constant stimulus (cf. Fitzgerald, 1940). The vibrissae are often very long and reach in front of the cat's nose.…”