Pure Tones Of Different Frequencies Research Articles

Absence of the Fragile X messenger ribonucleoprotein alters response patterns to sounds in the auditory midbrain.

Among the different autism spectrum disorders, Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability. Sensory and especially auditory hypersensitivity is a key symptom in patients, which is well mimicked in the Fmr1 -/- mouse model. However, the physiological mechanisms underlying FXS’s acoustic hypersensitivity in particular remain poorly understood. Here, we categorized spike response patterns to pure tones of different frequencies and intensities from neurons in the inferior colliculus (IC), a central integrator in the ascending auditory pathway. Based on this categorization we analyzed differences in response patterns between IC neurons of wild-type (WT) and Fmr1 -/- mice. Our results report broadening of frequency tuning, an increased firing in response to monaural as well as binaural stimuli, an altered balance of excitation-inhibition, and reduced response latencies, all expected features of acoustic hypersensitivity. Furthermore, we noticed that all neuronal response types in Fmr1 -/- mice displayed enhanced offset-rebound activity outside their excitatory frequency response area. These results provide evidence that the loss of Fmr1 not only increases spike responses in IC neurons similar to auditory brainstem neurons, but also changes response patterns such as offset spiking. One can speculate this to be an underlying aspect of the receptive language problems associated with Fragile X syndrome.

The effects of age and sex on the detection of pure tones by adult CBA/CaJ mice (Mus musculus).

Age-related hearing loss (ARHL) is a neurodegenerative disorder characterized by a gradual decrease in hearing sensitivity. Previous electrophysiological and behavioral studies have demonstrated that the CBA/CaJ mouse strain is an appropriate model for the late-onset hearing loss found in humans. However, few studies have characterized hearing in these mice behaviorally using longitudinal methodologies. The goal of this research was to utilize a longitudinal design and operant conditioning procedures with positive reinforcement to construct audiograms and temporal integration functions in aging CBA/CaJ mice. In the first experiment, thresholds were collected for 8, 16, 24, 42, and 64kHz pure tones in 30 male and 35 female CBA/CaJ mice. Similar to humans, mice had higher thresholds for high frequency tones than for low frequency pure tones across the lifespan. Female mice had better hearing acuity than males after 645days of age. In the second experiment, temporal integration functions were constructed for 18 male and 18 female mice for 16 and 64kHz tones varying in duration. Mice showed an increase in thresholds for tones shorter than 200ms, reaching peak performance at shorter durations than other rodent species. Overall, CBA/CaJ mice experience ARHL for pure tones of different frequencies and durations, making them a good model for studies on hearing loss. These findings highlight the importance of using a wide range of stimuli and a longitudinal design when comparing presbycusis across different species.

Neuromagnetic signatures of syllable processing in fetuses and infants provide no evidence for habituation

BackgroundHabituation, as a basic form of learning, is characterized by decreasing amplitudes of neuronal reaction following repeated stimuli. Recent studies indicate that habituation to pure tones of different frequencies occurs in fetuses and infants. AimsNeural processing of different syllables in fetuses and infants was investigated. Study designAn auditory habituation paradigm including two different sequences of syllables was presented to each subject. Each sequence consisted of eight syllables (sequence /ba/: 5× /ba/, 1× /bi/ (dishabituator), 2× /ba/; sequence /bi/: 5× /bi/, 1× /ba/ (dishabituator), 2× /bi/). Each subject was stimulated with 140 sequences. Neuromagnetic signatures of auditory-evoked responses (AER) were recorded by fetal magnetoencephalography (fMEG). SubjectsMagnetic brain signals of N=30 fetuses (age: 28–39weeks of gestation) and N=28 infants (age: 0–3months) were recorded. Forty-two of the 60 fetal recordings and 29 of the 58 infant recordings were included in the final analysis. Outcome measuresAERs were recorded and amplitudes were normalized to the amplitude of the first stimulus. ResultsIn both fetuses and infants, the amplitudes of AERs were found not to decrease with repeated stimulation. In infants, however, amplitude of syllable 6 (dishabituator) was significantly increased compared to syllable 5 (p=0.026). ConclusionsFetuses and infants showed AERs to syllables. Unlike fetuses, infants showed a discriminative neural response to syllables. Habituation was not observed in either fetuses or infants. These findings could be important for the investigation of early cognitive competencies and may help to gain a better understanding of language acquisition during child development.

Across-ear stimulus-specific adaptation in the auditory cortex.

The ability to detect unexpected or deviant events in natural scenes is critical for survival. In the auditory system, neurons from the midbrain to cortex adapt quickly to repeated stimuli but this adaptation does not fully generalize to other rare stimuli, a phenomenon called stimulus-specific adaptation (SSA). Most studies of SSA were conducted with pure tones of different frequencies, and it is by now well-established that SSA to tone frequency is strong and robust in auditory cortex. Here we tested SSA in the auditory cortex to the ear of stimulation using broadband noise. We show that cortical neurons adapt specifically to the ear of stimulation, and that the contrast between the responses to stimulation of the same ear when rare and when common depends on the binaural interaction class of the neurons.

Interactions between “What” and “When” in the Auditory System: Temporal Predictability Enhances Repetition Suppression

Neural activity in the auditory system decreases with repeated stimulation, matching stimulus probability in multiple timescales. This phenomenon, known as stimulus-specific adaptation, is interpreted as a neural mechanism of regularity encoding aiding auditory object formation. However, despite the overwhelming literature covering recordings from single-cell to scalp auditory-evoked potential (AEP), stimulation timing has received little interest. Here we investigated whether timing predictability enhances the experience-dependent modulation of neural activity associated with stimulus probability encoding. We used human electrophysiological recordings in healthy participants who were exposed to passive listening of sound sequences. Pure tones of different frequencies were delivered in successive trains of a variable number of repetitions, enabling the study of sequential repetition effects in the AEP. In the predictable timing condition, tones were delivered with isochronous interstimulus intervals; in the unpredictable timing condition, interstimulus intervals varied randomly. Our results show that unpredictable stimulus timing abolishes the early part of the repetition positivity, an AEP indexing auditory sensory memory trace formation, while leaving the later part (≈ >200 ms) unaffected. This suggests that timing predictability aids the propagation of repetition effects upstream the auditory pathway, most likely from association auditory cortex (including the planum temporale) toward primary auditory cortex (Heschl's gyrus) and beyond, as judged by the timing of AEP latencies. This outcome calls for attention to stimulation timing in future experiments regarding sensory memory trace formation in AEP measures and stimulus probability encoding in animal models.

Across-Channel Timing Differences as a Potential Code for the Frequency of Pure Tones

When a pure tone or low-numbered harmonic is presented to a listener, the resulting travelling wave in the cochlea slows down at the portion of the basilar membrane (BM) tuned to the input frequency due to the filtering properties of the BM. This slowing is reflected in the phase of the response of neurons across the auditory nerve (AN) array. It has been suggested that the auditory system exploits these across-channel timing differences to encode the pitch of both pure tones and resolved harmonics in complex tones. Here, we report a quantitative analysis of previously published data on the response of guinea pig AN fibres, of a range of characteristic frequencies, to pure tones of different frequencies and levels. We conclude that although the use of across-channel timing cues provides an a priori attractive and plausible means of encoding pitch, many of the most obvious metrics for using that cue produce pitch estimates that are strongly influenced by the overall level and therefore are unlikely to provide a straightforward means for encoding the pitch of pure tones.

Auditory discrimination learning and knowledge transfer in mice depends on task difficulty

Mice reproduce interesting effects in auditory discrimination learning and knowledge transfer discussed in human studies: (i) the advantage in the transfer from a hard to an easy task by benefits from transfer of procedural knowledge and information-integration learning, and (ii) the disadvantage in the transfer from easy to hard tasks by inability to generalize across perceptually different classes of stimuli together with initially unsuccessful attempts to transfer cognitive skills from one task to the other. House mice (NMRI strain) were trained in a shuttle-box stimulus discrimination task. They had to discriminate either between two pure tones of different frequencies (PT) or between two different modulation frequencies of an amplitude-modulated tone (AM). Then transfer of knowledge between these two tasks was tested. Mice rapidly learned PT discrimination within two to three training sessions (easy task). AM discrimination learning took longer and did not reach the high performance level of PT discrimination (hard task). No knowledge transfer was detected in animals first trained with the easy (PT) followed by the hard (AM) discrimination task. Mice benefited, however, from knowledge transfer when the AM discrimination was followed by the PT discrimination. When the task changed, confusion of conditioned stimuli occurred if the carrier frequency of the AM was the same as one of the frequencies in the PT task. These results show a hard-to-easy effect when possible knowledge transfer is tested between qualitatively different stimulus classes. The data establish mice as promising animal model for research on genetics of auditory perception and learning.

Stimulus-Timing-Dependent Plasticity of Cortical Frequency Representation

Adult cortical circuits possess considerable plasticity, which can be induced by modifying their inputs. One mechanism proposed to underlie changes in neuronal responses is spike-timing-dependent plasticity (STDP), an up- or downregulation of synaptic efficacy contingent upon the order and timing of presynaptic and postsynaptic activity. The repetitive and asynchronous pairing of a sensory stimulus with either another sensory stimulus or current injection can alter the response properties of visual and somatosensory neurons in a manner consistent with STDP. To examine whether such plasticity also exists in the auditory system, we recorded from neurons in the primary auditory cortex of anesthetized and awake adult ferrets. The repetitive pairing of pure tones of different frequencies induced shifts in neuronal frequency selectivity, which exhibited a temporal specificity akin to STDP. Only pairs with stimulus onset asynchronies of 8 or 12 ms were effective and the direction of the shifts depended upon the order in which the tones within a pair were presented. Six hundred stimulus pairs (lasting approximately 70 s) were enough to produce a significant shift in frequency tuning and the changes persisted for several minutes. The magnitude of the observed shifts was largest when the frequency separation of the conditioning stimuli was < approximately 1 octave. Moreover, significant shifts were found only in the upper cortical layers. Our findings highlight the importance of millisecond-scale timing of sensory input in shaping neural function and strongly suggest STDP as a relevant mechanism for plasticity in the mature auditory system.

Effects of redundant auditory stimuli on reaction time

Auditory redundancy gains were assessed in two experiments in which a simple reaction time task was used. In each trial, an auditory stimulus was presented to the left ear, to the right ear, or simultaneously to both ears. The physical difference between auditory stimuli presented to the two ears was systematically increased across experiments. No redundancy gains were observed when the stimuli were identical pure tones or pure tones of different frequencies (Experiment 1). A clear redundancy gain and evidence of coactivation were obtained, however, when one stimulus was a pure tone and the other was white noise (Experiment 2). Experiment 3 employed a two-alternative forced choice localization task and provided evidence that dichotically presented pure tones of different frequencies are apparently integrated into a single percept, whereas a pure tone and white noise are not fused. The results extend previous findings of redundancy gains and coactivation with visual and bimodal stimuli to the auditory modality. Furthermore, at least within this modality, the results indicate that redundancy gains do not emerge when redundant stimuli are integrated into a single percept.

High-resolution mapping of neuronal activity by thallium autometallography

Different methods are available for imaging neuronal activity in the mammalian brain with a spatial resolution sufficiently high to detect activation patterns at the level of individual functional modules such as cortical columns. Severe difficulties exist, however, in visualizing the different degree of activity of each individual neuron within such a module, and mapping neuronal activity with a spatial resolution of single axons has remained impossible thus far. Here, we present a novel method for mapping neuronal activity that is able to visualize activation patterns with light and electron microscopical resolution. The method is based on the tight coupling of neuronal activity and potassium (K +) uptake. We have injected Mongolian gerbils with the K + analogue thallium (Tl +), stimulated the animals with pure tones of different frequencies and analyzed, by an autometallographic method, the Tl + distribution in the auditory cortex (AC). We find tonotopically organized columns of increased Tl +-uptake in AC. Within columns, the spatial patterns of neuronal activity as revealed by thallium autometallography are highly elaborated. Tl +-uptake differs in different layers, sublayers, and cell types, being especially high in large multipolar inhibitory interneurons in layer IV. A prominent feature of the columnar activation pattern is the presence of vertical modules of minicolumnar dimensions. Clusters of layer Vb pyramidal cells and their apical dendrite bundles are clearly visible in the center of the columns.

Effect of temporal separation on tone-sequence discrimination in monkeys

Perception of auditory spectral–temporal patterns was examined in two Japanese monkeys. The stimuli used were pairs of pure tones of different frequencies that were presented sequentially. The monkeys were required to discriminate whether the frequency of the second tone was higher or lower than the first tone. The performances of the monkeys deteriorated when a temporal gap (i.e., silence) was inserted between the component tones. A comparison experiment did not show such effects in human participants. The results suggested that monkeys use frequency transitions for tone-sequence discrimination, and that local characters are more dominant discrimination cues in monkeys than in humans.

Developmental stability of the tonotopic organization of the chick's basilar papilla.

In the past, the damage patterns produced on the papilla of the chick by loud pure tones of different frequencies have been used to study the development of sound analysis by the hair cells of the basilar papilla. One conclusion from these data was that the best response frequency of individual hair cells changes substantially with age. However, this method has been criticized as unreliable. Now experiments have been performed in which single characterized nerve fibers were stained with horseradish peroxidase to permit the unequivocal localization of specific frequency responses in the papillae of chicks of different ages (2 and 21 days after hatching). There was no statistically significant change in the tonotopic organization of the papilla between the two groups of animals.

Acoustic sensitivity and bimodal properties of cells in the anterior suprasylvian gyrus of the cat.

The properties of acoustically responsive neurons were studied in the anterior part of the gyrus suprasylvius (ASG) of the cat. The most important features of the responses given to pure tones of different frequencies were: short latency, sharp tuning curves with well definable best frequency (BF). In these respects the cells showed a close resemblance to those of primary acoustic area (AI), and at the same time they proved to be true bimodal cells (responding to somatosensory stimuli, too) like those of the associative areas.

Cochlear partition displacement patterns to frequency varying signals

Cochlear microphonic recordings from 10 guinea pig cochleas were used to infer cochlear partition displacement patterns to frequency varying signals. Rate‐dependent differences between rising and falling sweeps were predicted on the basis of delay‐line characteristics of the cochlear partition. The frequency responses of three basal turn locations were assessed using puretones of different frequencies. Tone sweeps with different frequency change rates (i.e., frequency endpoints were kept constant and duration was varied) were generated near the “best‐frequencies” of these regions. Responses to sweeps obtained from each electrode location were summed and the time of occurrence of cochlear microphonic maxima and minima from each location was measured relative to the other locations. The results indicate that inferred cochlear partition displacements to falling frequency sweeps occur sequentially at different points along the partition. Corresponding rising‐frequency sweeps cause displacements more closely spaced in time. Displacement pattern differences occurred only at high rates of change. At low rates, cochlear partition displacements for the rising sweep disperse in time, showing the sequential pattern obtained with falling sweeps. [Work supported by NIH.]

Identification of temporal order in three-tone sequences

Well-trained subjects identified with remarkable accuracy the temporal order of three contiguous pure tones of different frequencies, presented as a single sequence. For a given set of three frequencies covering a one-octave span, the minimum duration of each component tone necessary for absolute identification of a sequence was 2–7 msec on the average. A total frequency range narrower than 1/3–2/3 octave depressed the identifiability of temporal order, whereas increasing the frequency range beyond this limit had no appreciable effect. Simple harmonic relation between the three components was associated with higher identification performace than was a complex harmonic relation. In general, those temporal orders in which the frequency change was unidirectional were more easily identified than the others. Also, the highest and the lowest of the three tones in final position were recognized more often than any of the sequences and were, most probably, used by the observers as cues for the identification of sequences.

Dependence of inhibitory zones of inferior collicular unit responses on temporal parameters of acoustic stimuli

Single unit activity was studied in the inferior colliculi of anesthetized albino rats in response to pure tones of different frequencies. The dependence of inhibitory interaction between neurons on temporal parameters of the acoustic stimuli (duration, time interval between tones) was investigated. Quantitative characteristics of the lateral inhibitory zones, defined as ranges of frequencies inhibiting spike generation in response to the optimal or near-optimal frequency, were examined. The inhibitory zones were found to depend essentially on the interval between application of the conditioning and testing stimuli. With an increase in the interval the inhibitory interaction decreased. If the duration of the acoustic stimuli was shortened, interaction was reduced as regards both the width of the frequency band and the intensity evoking the inhibitory effect.

Programmed presentation of pure tones of different frequencies using a single oscillator

A simple and inexpensive method is described for the programmed presentation of pure tones of different frequencies using a single oscillator.

Acoustic threshold in goldfish and its relation to the sound source distance

1. 1. Acoustic threshold levels have been obtained for goldfish in classical conditioning experiments, stimulating the fish with pure tones of different frequencies (50–5000 c/s). The threshold intensity for response has been established for different distances (0·1–2·0 m) between the fish and the underwater loudspeaker. 2. 2. Sound pressure thresholds (given in decibels re 1 μBar) for frequencies below 600–700 c/s are strongly dependent upon distance to the sound source, while no significant threshold differences were found for higher frequencies. Tests with an air loudspeaker gave thresholds similar to those obtained with the underwater loudspeaker at 2 m distance. 3. 3. Lowest threshold (−42 to −45 db) are in the 100–1500 c/s range, increasing to −10 db for 5000 c/s and to −6 db (at 2 m distance) or −38 db (at 0·1 m distance) for 50 c/s. 4. 4. The variation in threshold with distance is probably due to the physical characteristics of the sound stimulus. Close to the sound source, i.e. within a distance equal to the wavelength divided by 2π, the near-field water displacement amplitude is considerable. Calculated particle displacement at threshold is roughly the same for all distances for any given frequency and particle acceleration is the same for all distance and frequencies.