Alfred Finck

Hibernation: An opioid-dependent state?☆

Hibernation reduces substantially the heart rate of hamsters as well as the respiratory rate, the body temperature and the arousal level. The heart rate is reversed dramatically by the injection of low doses of Naloxone and in some cases the hamster arouses prematurely from hibernation. The effect is not due to the pain of the injection because saline injections do not produce such changes. The effect requires a pre-existing state of hibernation because Naloxone has no cardioacceleratory or arousal effect in non-hibernating hamsters that have had their heart rate and body temperature decreased substantially during hypothermia. These results suggest that endogenous opioids may contribute specifically to the state of hibernation. Moreover, a physiological role may exist for an anti-opioid system in the promotion of arousal from hibernation.

Physiological Correlate of Tonal Masking

A gross, slow potential that is differentially sensitive to the frequency of a tone burst was recorded from the region of the auditory nerve in the hamster. An experimental paradigm similar to that employed in psychological studies of tonal masking was used to measure neural‐response amplitude change in the presence of a second tone. The influence of one tone upon the other, as evidenced by the neural response, yielded functions similar to the masking curves generated by human listeners. Increases in the level of the signal required increases in the level of the masker in order to maintain the masking criterion. High‐tone maskers were seen to be less effective than low‐tone maskers. Masking was viewed as a preempting of neural activity by the secondary tone.

Monaural Double Click Interactions at the Round Window, Eighth Nerve, and Inferior Colliculus of Cat

These experiments study the interactions between successive, supra‐threshold stimuli in the auditory nervous system of the anesthetized cat. Experiments have been carried out using two clicks to stimulate the ear of the anesthetized cat. The clicks were varied as to intensity and intra‐click interval (delta interval). The effect of the first click upon the response to the second click was studied by measuring the electrophysiological response at the round window, eighth nerve, and inferior colliculus. The results obtained at the round window were different for the two components of the potential observed there. A smooth, monotonic recovery was found for the N1, whereas the recovery of the N2 between cats showed a depression for low‐intensity click‐pairs for delta intervals of 5 to 20 msec. Measurement of recovery at the inferior colliculus demonstrated three characteristics. An oscillatory component was observed. There was a difference in the relative recovery amplitudes of the evoked potentials which was...

Auditory Sensitivity of the Mongolian Gerbil (Meriones unguiculatus)

The Mongolian gerbil is native to the region of the Gobi Desert. The gerbil cochlear and vestibular elements are unusually well exposed for study and experimental investigation. This report depicts several features of the gross and microscopic anatomy of the gerbil and describes its auditory sensitivity by the cochlear‐potential method. Criterion cochlear potentials (0.5 μV) range from 50 dB at 200 Hz to 60 dB at 30 000 Hz. In the regions of 1000 and 4000 Hz cochlear sensitivity is seen at 15 and 0 dB SPL, respectively. Comparisons are made between gerbil cochlear responses and responses from other small rodents. [Research supported by the National Institutes of Neurological Diseases and Blindness, U. S. Department of Health, Education and Welfare.]

The lyriform organ of the orb‐weaving spider Araneoussericatus: Vibration sensitivity is altered by bending the leg

The patella of the spider A. sericatus contains a lyriform organ which responds to vibrations applied to the tip of the leg. Single unit activity indicates that this sense organ has an elevated threshold when the leg is bent toward the cepalothorax. The leg appears to function like a mechanical attenuator in which its position determines the efficiency of stimulating the lyriform organ. This system would allow spiders to exert control over the vibrational input by merely varying the position of their legs.

The orb−web as an acoustic detector

Movement response of the web of Araneus diadematus Cl. exhibits resonance from 20 to 30 Hz when placed in a sound field of at least 60 dB SPL. Virtually no movement of the web occurred for frequencies above 50 Hz (up to 20000 Hz). Hence it is unlikely that the orb−web serves an an acoustic detector for the approach of flying insects.Subject Classification: 80.45, 80.50.

Low‐Frequency Pure Tone Masking

Binaural masked thresholds from 50 cps to 4800 cps were measured using low‐frequency (10, 15, 25, 30, and 50 cps), high‐intensity (100, 115, and 130 db SPL) pure tones. The results obtained for 5 listeners demonstrate a broad masking spread with masking peaks for 130‐db SPL pure tones.

Development of Auditory Function in the Mongolian Gerbil

The gerbil ear is not mature at birth. The sound‐conducting apparatus as well as inner‐ear structures continue to develop over a period of at least 16 to 20 days postparturition. This circumstance allows a unique opportunity to examine relationships between morphology and function in the auditory apparatus. Mongolian gerbils were vitally perfused at various ages ranging from 20 min to more than 23 days. Serial sections were done and observations made on the developmental status of the external, middle, and inner parts of the ear. Cochlear potentials were recorded from some animals. The presence of reflex activity to sound was noted. Our observations indicate that the earliest reflex response to sound (whole body) occurred at 16 days. Electrical activity could be recorded from the round window niche by day 14. Maturation of the organ of Corti was questionable by day 10, and the limbus and spiral sulci were not well differentiated. By day 16, all parts of the organ of Corti appeared well developed. Ossicula...

Analysis of Response Areas from Single Units of the Auditory Nerve

This study approaches the problem of how responses from single auditory neurons may represent the configuration of auditory threshold. Response areas of 164 single units were obtained from the acoustic nerve of the golden hamster. These data were analyzed with respect to the threshold SPL for each of 31 frequencies. The results indicate that the likelihood of obtaining fiber activity in the acoustic nerve differs for different frequency tones. In those regions where the frequency of occurrence of response areas is high, absolute threshold values are typically low. It is suggested that innervation density, as well as absolute sensitivity, may be important features in the representation of the hearing curve at the level of the acoustic nerve. [Research supported by the National Institutes of Neurological Diseases and Blindness, U. S. Department of Health, Education and Welfare.]

Temporal Patterns of Response in Single Neural Units of the Auditory Nerve

Responses were taken by microelectrode from single elements in the auditory nerve of the golden hamster. The activity evoked by tones of various frequencies and intensities was analyzed according to the interval histogram. Temporal aspects of the spike responses were studied for units having different best frequencies. The results of these analyses indicated that the frequency of occurrence of particular time intervals between successive action potentials was constant over a wide range of stimulus intensities. The constant pattern of spike intervals was observed for units having low as well as high best frequencies. The data suggest that the density of intervals generated by a particular unit may be linearly related to the absolute value of the interval (in milliseconds). [Work supported by a grant from the National Institute of Neurological Diseases and Blindness, National Institutes of Health, U. S. Department of Health, Education, and Welfare.]