PubMed · 901606
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R J Van Hattum. 1977. Shaping future shock.. https://pubmed.ncbi.nlm.nih.gov/901606/
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It has been recently demonstrated that some primary otolith afferents and most otolith-related vestibular nuclei neurons encode two spatial dimensions that can be described by two vectors in temporal and spatial quadrature. These cells are called broadly-tuned neurons. They are characterized by a non-zero tuning ratio which is defined as the ratio of the minimum over the maximum sensitivity of the neuron. Broadly-tuned neurons exhibit response gains that do not vary according to the cosine of the angle between the stimulus direction and the cell's maximum sensitivity vector and response phase values that depend on stimulus orientation. These responses were observed during stimulation with pure linear acceleration and can be explained by spatio-temporal convergence (STC) of primary otolith afferents and/or otolith hair cells. Simulations of STC of the inputs to primary otolith afferents and vestibular nuclei neurons have revealed interesting characteristics: First, in the case of two narrowly-tuned input signals, the largest tuning ratio is achieved when the input signals are of equal gain. The smaller the phase difference between the input vectors, the larger the orientation differences that are required to produce a certain tuning ratio. Orientation and temporal phase differences of 30-40 degrees create tuning ratios of approximately 0.10-0.15 in target neurons. Second, in the case of multiple input signals, the larger the number of converging inputs, the smaller the tuning ratio of the target neuron. The tuning ratio depends on the number of input units, as long as there are not more than about 10. For more than 10-20 input vectors, the tuning ratio becomes almost independent of the number of inputs. Further, if the inputs comprise two populations (with different gain and phase values at a given stimulus frequency), the largest tuning ratio is obtained when the larger population has a smaller gain. These findings are discussed in the context of known anatomical and physiological characteristics of innervation patterns of primary otolith afferents and their possible convergence onto vestibular nuclei neurons.
Hearing conservation for divers and swimmers has been overlooked nearly everywhere in the world. Because submerging a listener changes his or her auditory physiology dramatically, the research upon which we base exposure limits for airborne noise is not pertinent under water. Of the research that is necessary for developing a damage-risk standard for underwater noise exposure, only a negligible amount has been done. The value of Poland's marine industries and the motivation of its audiologists make Poland and ideal country in which to accomplish this research and to develop the foundation for national and international standards.
The injuries induced by noise to auditory system affect above all the inner ear. Thus the hair cells forming the most fragile structures of the sensorial neuro-epithelium will suffer from hair disturbances. As a result these lesions will reduce hearing acuity and sensitivity leading to noise induced hearing loss. There are two types of hearing loss. The sudden hearing loss, called acute sonorous trauma, or the insidious one due to industrial-like noises. On the other hand, noisy environments may have some effects on the intelligibility known as effects on the recognition of speech. To conclude, the epidemiological studies carried on all sections of the population, including teen-agers, revealed a worrying yielding of their hearing performances, probably resulting from excessive level of noisy surroundings as supposed some years ago by Glorig.