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Stapedius-reflex measurement and the glycerol-test in combination with pure tone audiogram and speech-audiogram are reliable methods for an exact diagnosis of Menière's disease. For differential diagnosis one should know the so called "tensor tympani syndrome" which is discussed in this paper.
The inner ear of the leopard frog, Rana pipiens, receives sound via two separate pathways: the tympanic-columellar pathway and an extra-tympanic route. The relative efficiency of the two pathways was investigated. Laser interferometry measurements of tympanic vibration induced by free-field acoustic stimulation reveal a broadly tuned response with maximal vibration at 800 and 1500 Hz. Vibrational amplitude falls off rapidly above and below these frequencies so that above 2 kHz and below 300 Hz tympanic vibration is severely reduced. Electrophysiological measurements of the thresholds of single eighth cranial nerve fibers from both the amphibian and basilar papillae in response to pure tones were made in such a way that the relative efficiency of tympanic and extratympanic transmission could be assessed for each fiber. Thresholds for the two routes are very similar up to 1.0 kHz, above which tympanic transmission eventually becomes more efficient by 15-20 dB. By varying the relative phase of the two modes of stimulation, a reduction of the eighth nerve response can be achieved. When considered together, the measurements of tympanic vibration and the measurements of tympanic and extratympanic transmission thresholds suggest that under normal conditions in this species (1) below 300 Hz extratympanic sound transmission is the main source of inner ear stimulation; (2) for most of the basilar papilla frequency range (i.e., above 1.2 kHz) tympanic transmission is more important; and (3) both routes contribute to the stimulation of amphibian papilla fibers tuned between those points. Thus acoustic excitation of the an uran's inner ear depends on a complex interaction between tympanic and extratympanic sound transmission.
Frequency selectivity of hearing was measured in the green treefrog, Hyla cinerea. A psychophysical technique based on reflex modification was used to obtain masked threshold estimates for pure tones (300-5,400 Hz) presented against two levels of broadband masking noise. A pure tone (S-1) presented 200 ms prior to a reflex-eliciting stimulus (S-2) inhibited the motor reflex response to S-2. The magnitude of this reflex modification effect varied systematically with the sound pressure level (SPL) of S-1, and threshold was defined as the SPL of S-1 at which the reflex modification effect disappeared. Masked thresholds were used to calculate critical ratios, an index of the auditory system's frequency selectivity. The frequency selectivity of the treefrog's hearing is greatest and critical ratios are lowest (22-24 dB) at about 900 and 3,000 Hz, the two spectral regions dominant in the male treefrog's species-specific advertisement call. These results suggest that the treefrog's auditory system may be specialized to reject noise at biologically-relevant frequencies. As in other vertebrates, critical ratios remain constant when background noise level is varied; however, the shape of the treefrog's critical ratio function across frequencies differs from the typical vertebrate function that increases with increasing frequency at a slope of about 3 dB/octave. Instead, the treefrog's critical ratio function resembles its pure tone audiogram. Although the shape of the treefrog's critical ratio function is atypical, the critical ratio values themselves are comparable to those of many other vertebrates in the same frequency range. Critical ratio values here measured behaviorally do not match critical ratio values previously measured physiologically in single eighth nerve fibers.(ABSTRACT TRUNCATED AT 250 WORDS)
To investigate the relationship between disease severity, cognitive impairment and depression in progressive supranuclear palsy (PSP) we studied a group of 25 patients who fulfilled strict research criteria and 25 matched controls. Disease severity was judged from the duration of symptoms, level of physical disability using the Columbia Rating Scale (CRS), and the degree of eye movement abnormality. The neuropsychological battery was designed to assess attention and executive function, visual and auditory perception, semantic memory and language production. Although the PSP group were significantly impaired on almost all of these measures, the most profound deficits were on tests of sustained and divided attention. There was no correlation between cognitive impairment and either disease duration or scores on the CRS, but performance on tests of attention correlated significantly with the degree of ocular motor impairment. Depression was found to be common in PSP but did not correlate with any other parameters. It is concluded that the cognitive deficit in PSP is widespread and independent of depression. The association between the severity of eye movement disorder and deficits in sustained and divided attention leads us to postulate that pathology involving the midbrain periaqueductal region may be critical for breakdown in these fundamental processes.
In female choice experiments, Drosophila melanogaster males from a selected photonegative strain show a highly significant mating advantage over males from a photopositive strain. While photonegative behavior is sex linked in this species, the X chromosome is not involved in the mating advantage seen for this strain. The degree of the photonegative male advantage changes when tests are conducted with females mutant for olfaction and auditory perception but not when females are blind.
The effects of single-gene albino (c/c) mutations on auditory behavior and physiology were examined in congenic C57BL/6J mice. At 16 days of age, the c gene was additively associated with both reduced auditory functioning and lower body weight: 16-day-old c/c mice had higher auditory evoked potential (AEP) thresholds than +/c mice, which, in turn, had higher thresholds than +/+ mice; +/c mice were also intermediate with regard to body weight. Since these differences had nearly disappeared by 21 days of age, it was concluded that the c genes worked in an additive fashion to delay development during the period previously (Henry, 1967) found critical for inducing susceptibility to audiogenic seizures. At 16 days of age, albino mice (c/c) displayed susceptibility to audiogenic seizures, but nonalbino genotypes (+/c and +/+) were immune to the convulsive effects of sound. This behavior appeared to be a recessive trait at this age. But 5 days later, the behavioral phenotype exhibited incomplete dominance, with the +/c genotype displaying audiogenic seizures intermediate to those seen in the susceptible c/c and the nonsusceptible +/+ genotypes. These behaviors were compared to the thresholds and peak-to-peak amplitudes of the AEP, as seen in the input-output functions. It is suggested that differential development of the auditory systems in these genotypes is causally related to susceptibility to audiogenic seizures.
Subjects detected a brief near-threshold tone while encoding two-clause sentences for later report. The objective tone locations were at the end of the first clause, at the beginning of the second clause, or in the clause boundary. The effects of intensity variations of the speech signal were assessed by having subjects detect the tones in the same speech stimuli played backward. Tones at the end of a clause are relatively harder to detect than in other positions, comparing forward and backward speech. This supports the view that listeners are preoccupied with internal processes at the end of a clause.
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The investigators carried out threshold determinations on 16 children and 6 adults in wakefulness, under general anaesthesia (we used chloral hydrate anaesthesia) and in sleep (stage II-III and stage REM). Falling asleep (stage I and initial stage of anaesthesia respectively) the latencies of the individual components of the acoustically evoked potentials are prolonged in mean of 30 msec. Simultaneously the amplitude of N1 significantly decreases and N2 becomes a prominent point (Fig. 1). The generation mechanisms of wave N2 are obviously different from those of wave N1. Its input-output curve takes a very steep course (Fig. 5) and the shortening of latencies increases with growing intensity of stimulus too (Fig. 4). Amplitude histogrammes demonstrated the dependency of the form of the acoustically evoked potential on the degree of synchronisation of EEG activity. While in the case of desynchronisation N1 appears more markedly, N2 does in the case of synchronisation. The mean deviation of the ERA threshold totals plus 3.8 +/- 6.9 dB (n = 41) under chloral hydrate anaesthesia, plus 4.9 +/- 6.7 dB (n = 37) in natural sleep in contrast to the wakefulness. With a 99% confidence there occur confidence intervals ranging from + 1 to + 7 dB and from +2 to +8 dB respectively. In identifying the threshold potentials error I (existing potential not recognized) occurred in 15-20%, error II (random wave seen as potential) in 20% of these studies. All these experiments showed significant lower variances for the latencies compared with variancies of amplitudes. The variance of amplitudes is smallest in children (Table 1) under general anaesthesia as well as in adults in wakefulness (Table 2). For the practical performance of ERA chloral hydrate is recommended for studies on children. A uniform EEG-state as well as a uniform depth of sleep are basic conditions for ERA during sleep, sedation or under anaesthesia. These conditions must constantly be controlled by EEG, EOG and EMG.
1. The maximum acoustic gain of the external ear in Macroderma gigas was found to be 25-30 dB between 5-8 kHz and in Nyctophilus gouldi it reached 15-23 dB between 7-22 kHz. Pinna gain reached a peak of 16 dB near 4.5-6 kHz in M. gigas and 12-17 dB between 7-12 kHz in N. gouldi, with average gain of 6-10 dB up to 100 kHz. Pinna gain curves resemble that of a finite conical horn, including resonance. 2. The directional properties of the external ear in both species result from sound diffraction at the pinna face, as it approximates a circular aperture. The frequency dependent movement of the acoustic axis in azimuth and elevation is attributed to the asymmetrical structure of the pinnae. 3. Evoked potentials and neuronal responses were studied in the inferior colliculus. In M. gigas, the neural audiogram has sensitivity peaks at 10-20 kHz and 35-43 kHz, with extremely low thresholds (-18 dB SPL) in the low frequency region. In N. gouldi, the neural audiogram has sensitivity peaks at 8-14 kHz (lowest threshold 5 dB SPL) and 22-45 kHz. Removal of the contralateral pinna causes a frequency dependent loss in neural threshold sensitivity of up to 10-15 dB in both species. 4. The high frequency peak in the audiogram coincides with the sonar energy band in both species, whereas the low frequency region is used for social communication. Highly sensitive low frequency hearing is discussed in relation to hunting in bats by passive listening.
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The introduction of the variable-pitch feature on pulse oximeters in 1983 by the Nellcor Corporation (Hayward, CA) allowed users to rapidly detect changes in oxygen saturation by listening for changes in the pitch of the tones emitted by the pulse oximeter. A few individuals have reported that they have been unable to detect a change in pitch when oxygen saturation changes. To these individuals, the variable-pitch feature of these pulse oximeters has not been beneficial. Using the pitches from one manufacturer of oximeters, we created a computer program to simulate the pitches that accompanied various oxygen saturations. The pitches were recorded onto a tape player and played for 75 volunteer subjects unfamiliar with the pitches of a variable-pitch pulse oximeter. Of our sample, 67% were able to detect a single change in pitch corresponding to a 1% fall in oxygen saturation, and 11% of the population could not detect a change in pitch until there was a change in pitch with every beat. We suggested four alternative designs that may prove beneficial to this group of individuals.
Several investigations prove that monaural acoustic deprivation induces detrimental changes in the auditory pathway. So far the major interest focused on degenerative processes on the deprived side, while effects on the contralateral untreated side were not taken into consideration. This ontogenetic study investigates effects of early monaural acoustic deprivation on the functional development of the acoustically evoked auditory brainstem response (ABR) in the Mongolian gerbil. Young gerbils were deafened by a single intracochlear application of neomycin sulfate. The ABR development on the contralateral side differed in a late developmental period from that of normally hearing animals. These changes persisted until adulthood. Between day 55 and day 90 a significant 5 dB decrease of the ABR thresholds and a significant shortening of the interpeak latency II-V occurred. The results confirm that a complete monaural deprivation during the sensible or critical period leads on the contralateral side to plastic or compensatory changes in the auditory brainstem.
A sound that we hear in a natural setting allows us to identify the sound source and localize it in space. The two aspects can be disrupted independently as shown in a study of 15 patients with focal right-hemispheric lesions. Four patients were normal in sound recognition but severely impaired in sound localization, whereas three other patients had difficulties in recognizing sounds but localized them well. The lesions involved the inferior parietal and frontal cortices, and the superior temporal gyrus in patients with selective sound localization deficit; and the temporal pole and anterior part of the fusiform, inferior and middle temporal gyri in patients with selective recognition deficit. These results suggest separate cortical processing pathways for auditory recognition and localization.
Neurophysiological studies have shown in animals that a sudden sound enhanced perceptual processing of subsequent visual stimuli. In the present study, we explored the possibility that such enhancement also exists in humans and can be explained through crossmodal integration effects, whereby the interaction occurs at the level of bimodal neurons. Subjects were required to detect visual stimuli in a unimodal visual condition or in crossmodal audio-visual conditions. The spatial and the temporal proximity of multisensory stimuli were systematically varied. An enhancement of the perceptual sensitivity (d') for luminance detection was found when the audiovisual stimuli followed a rather clear spatial and temporal rule, governing multisensory integration at the neuronal level.
The mammalian auditory system evolved to extract meaningful information from complex acoustic environments. Spectrotemporal selectivity of auditory neurons provides a potential mechanism to represent natural sounds. Experience-dependent plasticity mechanisms can remodel the spectrotemporal selectivity of neurons in primary auditory cortex (A1). Electrical stimulation of the cholinergic nucleus basalis (NB) enables plasticity in A1 that parallels natural learning and is specific to acoustic features associated with NB activity. In this study, we used NB stimulation to explore how cortical networks reorganize after experience with frequency-modulated (FM) sweeps, and how background stimuli contribute to spectrotemporal plasticity in rat auditory cortex. Pairing an 8-4 kHz FM sweep with NB stimulation 300 times per day for 20 days decreased tone thresholds, frequency selectivity, and response latency of A1 neurons in the region of the tonotopic map activated by the sound. In an attempt to modify neuronal response properties across all of A1 the same NB activation was paired in a second group of rats with five downward FM sweeps, each spanning a different octave. No changes in FM selectivity or receptive field (RF) structure were observed when the neural activation was distributed across the cortical surface. However, the addition of unpaired background sweeps of different rates or direction was sufficient to alter RF characteristics across the tonotopic map in a third group of rats. These results extend earlier observations that cortical neurons can develop stimulus specific plasticity and indicate that background conditions can strongly influence cortical plasticity.
How the brain responds to sequences of sounds is a question of great relevance to a variety of auditory perceptual phenomena. We investigated how long the responses of neurons in the primary auditory cortex of awake monkeys are influenced by the previous sound. We found that responses to the second sound of a two-sound sequence were generally attenuated compared to the response that sound evoked when it was presented first. The attenuation remained evident at the population level even out to inter-stimulus intervals (ISIs) of 5 s, although it was of modest size for ISIs >2 s. Behavioral context (performance versus non-performance of a visual fixation task during sound presentation) did not influence the results. The long time course of the first sound's influence suggests that, under natural conditions, neural responses in auditory cortex are rarely governed solely by the current sound.
It is known that the response to binaural clicks is smaller in amplitude than the sum of two monaural responses. The difference is called the binaural interaction component (BIC). Also, an amplitude enlargement occurs in guinea pig middle latency responses (MLRs) to monaural clicks when white noise is applied to the other ear. This study was conducted to find out whether these two signs of binaural interaction result from the same mechanism. White noise enhancement (WNE) and BIC were computed from the evoked potential data simultaneously recorded in different phases of anaesthesia. WNE gradually decreased and disappeared with anaesthesia, but the relative amplitude of the BIC remained unchanged. This differential effect showed that different neural mechanisms must be responsible for BIC and WNE in guinea pig MLR.