Robert S. Schmidt

Frog Labyrinthine Efferent Impulses

Efferent impulses were recorded from the free ends of nerves detached from the ampullae, sacculus, utriculus, and lagena in the leopard frog (Rana pipiens). These impulses were found to be initiated by stimulation of any ampulla or a variety of unidentified extralabyrinthine proprioceptors. None were evoked in response to stimulation of the auditory or otolith organs. There was no spontaneous resting activity in the efferent fibers. Surgical difficulties have so far prevented adequate study of possible efferent input to the pars basilaris and pars neglecta.

SODIUM AND POTASSIUM IN VERTEBRATE COCHLEAR ENDOLYMPH AS DETERMINED BY FLAME MICROSPECTROPHOTOMETRY.

Abstract 1. 1. Concentrations of 1·8 mM/1 Na and 151 mM/1 K (K/Na quotient 84) were measured in cochlear endolymph of guinea pigs, using a simplified flame microspectrophotometer which is described. 2. 2. This sodium concentration is low enough to admit of the possibility that the positive endocochlear potential is a sodium diffusion potential. 3. 3. K/Na quotients were measured in other species, the highest values obtained for each being 42 (turtle), 30 (frog) and 20 (lizard).

STUDIES ON HABITUATION OF VESTIBULAR REFLEXES. EFFECT OF CALORIC STIMULATION IN DECORTICATED CATS

Abstract : Habituation of nystagmus elicited by repetitive caloric stimulation was studied in seven decorticated cats. The histopathologic studies revealed total ablation of neocortex, excepting small remnants in two cases, and extensive damage to basal ganglia and diencephalon. All animals exhibited response decline of nystagmus, demonstrating that neocortex and probably basal ganglia and diencephalon are not essential for inducing habituation. There was no conclusive data regarding transfer and long-lasting retention of the response decline. The locus and neurophysiologic basis of the phenomenon are discussed. (Author)

Types of endolymphatic potentials

Abstract 1. 1. The potential difference between the endolymph and perilymph was recorded in a lizard, snake, turtle and bird. 2. 2. The level of this potential in the lizards and snakes is essentially the same as in other coldblooded groups. 3. 3. Only slight differences were found between the cochlear and vestibular parts of the labyrinth in the reptiles. 4. 4. A small, but definite, difference was found between the cochlear and vestibular parts of the pigeon labyrinth. 5. 5. Three types of endolymphatic potentials (Poikilotherm, Avian and Mammalian) are characterized.

Termite (Apicotermes) Nests-Important Ethological Material

The subterranean nests of the African genus of termites, Apicotermes, present unique material for the study of the evolution of behavior. The nests are species-specific and show phylogenetic relationships much more clearly than do the morphological characteristics of the termites building them. Unusually complete phylogenetic series are found. The phylogeny of Apicotermes, although based largely upon nest characteristics, is also corroborated by taxonomic, zoogeographical, and ecological data. The evolution of nest-building behavior in Apicotermes illustrates particularly well several similarities to the evolution of structural characteristics. Circular galleries seem to have evolved independently four times within the genus. Wall perforations, the most characteristic feature of the genus, seem to have the function of permitting gas exchange across the nest wall. The circular galleries apparently serve to protect these perforations (probably from ground water). The nest of one species has lost the wall perforations through regressive evolution, while the nest of another species seems to be at an earlier stage of this regression. The ontogeny of galleries seems to recapitulate the evolutionary stages of this structure. The nest-building behavior of termites is instinctive, or innate. Behavioral characteristics evolve by the same processess as do structural characteristics.

HEARING AND RESPONSES TO CALLS IN ANURANS

1. Nerve responses evoked by tone pips of known frequency were recorded from the medulla of Bufo americanus, Rana pipiens, Rana clamitans, Pseudacris triseriata, and Hyla crucifer. 2. Nerve responses were obtained between 20 cps and 4000 cps in Bufo and Rana, and between 100 cps and 6000 cps in Pseudacris and Hyla. 3. In all species, the best frequency for nerve responses was 1000 cps. In Pseudacris and Hyla there was a second low threshold area at 2000-3000 cps. It is suggested that the lower frequency dip in the response curve may represent responses from the pars amphibiorum and that the higher frequency dip may represent responses from the pars basilaris. 4. The threshold at the best frequency in Rana is similar to the sensitivity of human hearing. 5. Three Pseudacris and one Hyla were induced to answer tone pips. 6. These answered pips of frequencies between 700 cps and 4600 cps. Since this conforms to the high frequency dip in the nerve response curve, it is suggested that the Hylids might have been hearing pips with the pars basilaris only. 7. Pseudacris answered pips of a great variety of durations and intervals. 8. The data suggest that responses of Pseudacris males to frog calls may be, to a great extent, non-specific. 9. Alternating of calls in duets is controlled by at least two factors. There is a constant latency between a call and the stimulus eliciting it. A stimulus following a call too closely inhibits calling. 10. The data obtained here and by others suggest that even for location of males by females, the repetitive nature and frequency of calls may be of only minor importance. Rather, trill rate is implicated as an important call parameter.

Crossed Vestibular Connections in the Froc

The crossed vestibular root to the area statica and reticular formation was investigated in frogs by the electrophysiological method. The area statica formed by the nucleus magnocellularis and ventral nucleus presented spontaneous activity, which increased in frequency and amplitude with both clockwise and counter-clockwise rotatory stimulation. In addition, the nucleus magnocellularis responded to acoustic stimuli. Labyrinthectomy carried out in several ways demonstrated that signals arising in one semicircular canal were transmitted to the area statica of both sides. An extensive area of the reticular formation of both sides exhibited spontaneous activity, which also increased in frequency and amplitude with both clockwise and counter-clockwise rotatory stimulation. The results showed that the signals from one lateral semicircular canal are transmitted to the reticular formation of both sides. The lateral ampullary nerve at rest exhibited spontaneous activity, which increased in frequency and amplitude ...