The history of audiology

Introduction The paper presents historical data on development of audiology as a medical specialty. It gives the chronological overview of the most significant discoveries which have contributed to the progress and constant development of the science of hearing. The insights and discoveries encompass the ancient, medieval and contemporary medical science. The term "audiology" and first associations of audiologists The paper reviews the origin of the term ?audiology? and the time of its occurrence. The First World Congress of Audiologists was held in 1948, and the Conference of Audiologists and Phoniatrists of Yugoslavia was established in 1974. Historical overview The ancient scientists and philosophers mentioned in the paper are as follows: Democritus, Hippocrates, Empedocles, Plato, Aristotle, and Galenus. Discoveries of Vesalius, Fallopio, Eustachio, Duverney, Schelhammer, Catugno and Helmholtz marked their epochs and made a great contribution to the development of the entire medical science, including audiology. A significant contribution to audiology was made by Schwartz in 1920 and Fletcher in 1926, constructors of audiometers. Fowler, Weigel and Fletcher promoted an audiogram in 1922. Wever and Bray first introduced the cochlear microphonic potentials. The first modern audiometer with a flat zero line for all pitches was constructed in 1937. In 1947, B?k?sy constructed the automatic audiometer, and the theory of mobile waves was introduced in 1928. Fletcher and Steinberg promoted speech audiometries in 1929. Mendel and Goldstein described medium latency responses in 1969. The first hearing aids worn within the ear appeared in the same year. William House pioneered the cochlear implantation in adults in 1969, and the program of infant cochlear implants. Jewett described the evoked auditory potentials in 1970. James Jerger classified tympanometric curves into three tympanogram types (A, B, C). Portmann and Arran introduced transtympanic electrocochleography in 1971. Kemp introduced otoacoustic emission in 1978. Instead of conclusion Finally, the paper lists the titles of available dissertations and subspecialisations in the field of audiology defended in Novi Sad and Belgrade.

Development of Acetylcholine-Induced Responses in Neonatal Gerbil Outer Hair Cells

Development of acetylcholine-induced responses in neonatal gerbil outer hair cells. Cochlear outer hair cells (OHCs) are dominantly innervated by efferents, with acetylcholine (ACh) being their principal neurotransmitter. ACh activation of the cholinergic receptors on isolated OHCs induces calcium influx through the ionotropic receptors, followed by a large outward K+ current through nearby Ca2+-activated K+ channels. The outward K+ current hyperpolarizes the cell, resulting in the fast inhibitory effects of efferent action. Although the ACh receptors (AChRs) in adult OHCs have been identified and the ACh-induced current responses have been characterized, it is unclear when the ACh-induced current responses occur during development. In this study we attempt to address this question by determining the time of onset of the ACh-induced currents in neonatal gerbil OHCs, using whole cell patch-clamp techniques. Developing gerbils ranging in age from 4 to 12 days were used in these experiments, because efferent synaptogenesis and functional maturation of OHCs occur after birth. Results show that the first detectable ACh-induced current occurred at 6 days after birth (DAB) in 12% of the basal turn cells with a small outward current. The fraction of responsive cells and the size of outward currents increased as development progressed. By 11 DAB, the fraction of responsive cells and the current size were comparable with those of adult OHCs. The results indicate that the maturation of the ACh-induced response begins around 6 DAB. It appears that the development of ACh-induced responses occur during the same time period when OHCs develop motility but before the onset of auditory function, which is around 12 DAB when cochlear microphonic potentials can first be evoked with acoustic stimulation in gerbils.

Delay-tuned combination-sensitive neurons in the auditory cortex of the vocalizing mustached bat

1. FM-FM neurons in the auditory cortex of the mustached bat are sensitive to a pair of frequency-modulated (FM) sounds that simulates an FM component of the orientation sound and an FM component of the echo. These neurons are tuned to particular delays between the two FM components, suggesting an encoding of target range information. The response properties of these FM-FM neurons, however, have previously been studied only with synthesized orientation sounds and echoes delivered from a loud-speaker as substitutes for the bat's own orientation sounds and corresponding echoes. In this study, the combination sensitivity and delay tuning of FM-FM neurons were examined while the bat was actively vocalizing. 2. When the bat produced orientation sounds in an anechoic environment, or synthesized single FM echoes were delivered to a silent bat, the FM-FM neurons showed weak or no response. In contrast, when synthesized FM echoes were delivered with a particular delay from the FM component of the vocalized orientation sounds, the FM-FM neurons exhibited strong facilitative responses. 3. In both the vocalizing bats and the silent bats with substituted synthesized orientation sounds, all FM-FM neurons tested responded preferentially to the same echo harmonic (FM2, FM3, or FM4). 4. In vocalizing bats, FM-FM neurons showed maximum response to an echo FM component delivered with a particular delay (best delay) from an FM component in the orientation sound. Best delays measured with vocalized orientation sounds were nearly the same as those measured with synthesized orientation sounds. 5. The equivalent effect of a vocalized orientation sound and a synthesized FM1 component on the activity of FM-FM neurons indicates that, during echolocation, the FM1 component in the vocalized orientation sound stimulates the auditory system and conditions the FM-FM neurons to be sensitive to echoes with particular delays from the vocalized orientation sounds. 6. The amount of vocal self-stimulation to the inner ear by the bat's own vocalized sounds was measured by recording cochlear microphonic potentials (CMs). Spectral analysis of CM indicated that the amount of vocal self-stimulation by each harmonic of an orientation sound was equivalent to a sound of 70 dB sound pressure level (SPL) for the first harmonic (H1), 91 dB SPL for H2, 83 dB SPL for H3, and 70 dB SPL for H4, when the amplitude of the vocalized sound was 117 dB SPL at 5 cm in front of the bat's mouth.