Willem A. van Bergeijk

Evidence that the Lateral‐Line Organ Responds to Near‐Field Displacements of Sound Sources in Water

The lateral‐line organ of killifish is shown to be sensitive to a linear function of water displacements associated with the near‐field of sound sources, with the displacement probably being the most important factor rather than velocity or acceleration. The near‐field effect is discussed and is shown to be important not only for the lateral‐line organs but also for the acoustical and vestibular organs. It is emphasized that the near‐field effect introduces considerable complications into the study of the acoustico‐lateralis system, and is of conceptual importance for the theory of hearing and the study of schooling fish.

Variation on a Theme of Békésy: A Model of Binaural Interaction

The model of binaural interaction proposed by Bekesy in 1930 which has received very little attention in modern theories is re‐examined the light of recent anatomical and physiological findings. A modified model is proposed in which time and intensity are mapped independent of each other in the accessory nuclei of the superior olive; excitatory and inhibitory neural signals interact at the accessory nucleus neurons, giving rise to time‐intensity trade. The behavior of the model is in qualitative accord with psychophysical and physiological observations.

Studies with artificial neurons. II. Analog of the external spiral innervation of the cochlea.

Summary1.Artificial neurons (neuromimes) are used to simulate the external spiral innervation of the cochlea.2.On the basis of the experimental observations the proposition is advanced that the spiral innervation serves to extend the dynamic range of the ear. Dynamic range extension follows from elementary considerations of the refractory and summing properties of nerve fibers.3.Experiments with different neuromime densities, supported with psychophysical observations reported in the literature, lead to the hypothesis that dynamic range and growth of sensation are related to the innervation density in the area of sensory tissue under consideration (e.g., skin). The spiral nerves are considered as a special case of a more general sensory nerve, branching in binary fashion.4.The pathological phenomenon of “loudness recruitment” is explained as a “thinning” of cochlear innervation density, giving rise to smaller dynamic range and faster growth of loudness.

Nomenclature of Devices Which Simulate Biological Functions

The suffix -mime is proposed to create generic names for the general class of man-made devices which simulate biological functions. The suffix is used after the stem of the word that describes the organ or cell being simulated; for instance, artificial neurons are described as neuromimes.

Evidence that the Lateral Line Organ Responds to Water Displacements

In recent years, there has been controversy whether the lateral line is sensitive to water displacements or to sound. Sound in this context has usually been understood to be pressure variations due to compressional waves. These waves produce displacements too small to stimulate the lateral‐line organ. The near‐field effects of acoustical sources in water, however, often produce displacements which can stimulate the lateral line organ. Depending on the type of source used, the amplitudes of these water motions decrease as the square or cube of the distance from the source. The magnitude of microphonics from the lateral‐line organ on the head of killifish decreases with distance from the acoustical source in a way which proves that they are sensitive to the near‐field effects and, thus, to some function of water displacement.

Studies with Artificial Neurons, IV: Binaural Temporal Resolution of Clicks

A psychophysical experiment performed by Guttman, van Bergeijk, and David in 1960 showed that binaural auditory resolution of repetitively presented, closely spaced clicks improves as repetition rate is increased. We propose a model in which the action of a single neuron can account for the phenomenon; it depends on a self‐inhibition function that serves to vary temporal resolution with stimulus rate. Single‐spike (click) stimuli elicit output bursts of variable duration; burst lengths are controlled by an output‐derived feedback whose level depends on stimulus repetition rate. An electronic model of a neuron, simulating a cochlear‐nucleus unit, accurately replicates the essential features of the psychophysical data. Two time constants, estimated by extrapolation, are postulated for single units in the human auditory system.

Evolution of Vertebrate Hearing

The morphological kinship of the lateral‐line organ and the various maculae of the inner ear has long been recognized. Recent investigations of the ultrastructure of the sensory cells in the organs and maculae have strongly reinforced the belief that the acoustico‐lateralis system should be considered a unitary sensory system. Its several subsystems have special peripheral adaptations to deal with particular forms of mechanical stimulation, but use the same fundamental sense cell, the hair cell. Since the lateral line has been shown to be a displacement detector that responds to acoustic stimulation in the near field only, the question arises how the farfield, pressure‐sensitive ear has evolved. It is proposed that the middle ear be regarded as a pressure‐to‐displacement transformer. Its earliest evolutionary form is the fishs swimbladder, which generates a local near field inside the fish in response to pressure waves. This local near field is then transmitted to the inner ear, through the body tissues ...

Lateral Line Organ of Fish: A Possible Key to the Hair Cell Problem

The mechanics and physiology of the hair cells of the cochlea are very difficult to investigate for obvious technical reasons. The hair cells of the lateral line of fish are embryologically and morphologically very similar to the hair cells of the inner ear. The morphological similarity is so close, in fact, that it seems warranted to investigate the hypothesis that all these different hair cells behave physiologically in a similar way. The ear can be thought of as an invaginated lateral line organ with a middle ear of some kind attached to transform pressure waves into volume displacements. We find, however, differences as well as similarities. Morphologically, the lateral‐line organ of the killifish shows a curious polarization: in an oval patch of supporting cells, a strip of hair cells is embedded along the major axis. Physiologically, the organ is directionally sensitive along this axis, too. One remarkable difference is that, although the cochlear microphonic over a wide intensity range is proportio...

Sound Localization by Fishes

Fishes have two sound‐sensitive organ‐systems—the lateral line, which is sensitive to the near‐field water motions of a sound source, and the swimbladder‐ear system, which is sensitive to pressure waves. Since the lateral line is spread out over the fishs body, spatially sampling the strong intensity gradient of the near‐field motions, it should be possible for a fish to localize a source of motion with this system. The swimbladder, however, is a solitary organ that samples only one point in the far field. The fish, therefore, should not be able to localize a source of pressure waves with the swimbladder‐ear system. Experimental evidence, though spotty, confirms these notions.

Origin of the Middle Ear

The evolution of the middle ear, especially the eardrum, has been shrouded in uncertainty for many years. It is first found in the primitive Stegocephalian amphibians. In these animals, it was already quite highly developed, but there has been no hint of a transitional stage between fish and amphibian. Among the extinct Rhipidistian fishes, from which, for many comparative‐anatomical reasons, the amphibians are believed to have arisen, were a few species that appear to represent this “missing link.” These fishes, notably Eusthenopteron and Osteolepis, had a diverticulum of the first pharyngeal pouch that probably developed in the first instance as an auxiliary respiratory organ. The diverticulum came to the surface of the fish in close association with a superficial ligament, with which it formed a narrow drum membrane. The endothelium of the drum was intimately attached to the hyomandibular bone, which is the homolog of the stapes and articulates with the otic capsule. It can be shown that the entire sys...