Toru Hashimoto

Frequency discrimination in the central nerve cords of locusts

Abstract The auditory mechanism in locusts, especially the central mechanism of frequency analysis, was examined electrophysiologically. The central auditory response had a sharp rise of threshold at a certain frequency range, and it showed a remarkable change when all peripheral fibres except the tympanic nerve were cut off. The response pattern was also changed by this procedure. These results indicate the presence of an inhibitory interaction mechanism of various auditory inputs. It can be concluded that locusts are able to discriminate sound frequency to some degree by this interactive mechanism.

Efferent system of lateral-line organ of fish

Abstract 1. 1. The efferent feedback system of the lateral-line organ of a fish, Japanese sea eel, was confirmed electrophysiologically by the following observations. 2. 2. An inhibitory effect to the afferent neural activity is caused by the descending electrical stimulation of the lateral-line nerve. 3. 3. The descending spontaneous activity of the lateral-line nerve is responsive to the mechanical stimulation of the contra-lateral or ipsilateral intact end organs. 4. 4. The efferent system might adjust the sensitivity of the receptor to various environmental conditions. 5. 5. The crosed efferent might also play an important role in identifying the stimulus location in the environmental free space.

Shark Pit Organs: Enhancement of Mechanosensitivity by Potassium Ions

The mandibular pit organs of pelagic sharks, which respond sensitively to monovalent cations, often show neural discharges synchronized with respiratory gill movement. The mechanosensitivity of the organs is remarkably enhanced by application of potassium ions on the same end organ, respiratory movement remaining constant. In view of their michanosensitivity to an incr-ease of potassium ions in the cell environment, as well as their chemosensitivity,the pit organs of sarks, rather than the canal organs which have no chemosensitivity, may be designated as a better model of the inner ear of higher animals.

Enhancement of the Mechanosensivity of Hair Cells of the Lateral‐Line Organs by Environmental Potassium Ions

The cochlear hair cell has a remarkably high sensitivity to the displacement of the basilar membrane of the inner ear. However, the detailed mechanism of the receptor process, especially for the high sensitivity, has not been fully established. The present article is concerned with the enhancement of the mechanosensitivity of the receptor hair cells of the lateral‐line organ of aquatic animals by the environmental potassium ions. The potassium ion on the receptor surface of the lateral‐line organ, the free standing neuromast, modified the receptor sensitivity to vibratory mechanostimuli. Studies on the free neuromast rather than on the canal neuromast may better contribute to the understanding of the excitation mechanism of the cochlear hair cell.

Chapter 35 Measurement of intracochlear current flow

Publisher Summary This chapter focuses on the measurement of intracochlear current flow. The chapter attempted to measure the intracochlear current flow by applying the voltage clamp technique to the scala media of the cochlea of a guinea-pig. The cochlear microphonic (CM) current flow, which should be associated with the sound stimulus, was recorded indirectly by the feedback technique. The CM current was modified with command signal for the potential control. The sound-induced conductance change could be estimated by DC command. The sound-induced current should be the spatial summation of the transduction current of ionic channels on the stereocilia of the cochlear hair cell. For a simple method of impedance measurement, the present chapter developed a single electrode technique with the aid of an active bridge circuit. The validity of the model could be confirmed at the lower level of sound stimulation and injected current.