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At least 343 records · Page 19Linked to original sources
PubMed1998

Effect of environmental sound familiarity on dynamic neural activation/inhibition patterns: an ERD mapping study.

The aim of this study was to analyze the timing and topography of brain activity in relation to the cognitive processing of different types of auditory information. We specifically investigated the effects of familiarity on environmental sound identification, an issue which has been little studied with respect to cognitive processes, neural substrates, and time course of brain activity. To address this issue, we implemented and applied an electroencephalographic mapping method named event-related desynchronization, which allows one to assess the dynamics of neuronal activity with high temporal resolution (here, 125 ms); we used 19 recording electrodes with standard positioning. We designed an activation paradigm in which healthy subjects were asked to discriminate binaurally heard sounds belonging to one of two distinct categories, "familiar" (i.e., natural environmental sounds) or "unfamiliar" (i.e., altered environmental sounds). The sounds were selected according to strict preexperimental tests so that the former should engage greater semantic, and the latter greater structural, analysis, which we predicted to preferentially implicate left posterior and right brain regions, respectively. During the stimulations, significant desynchronizations (thought to reflect neuronal activations) were recorded over left hemisphere regions for familiar sounds and right temporofrontal regions for unfamiliar sounds, but with only few significant differences between the two sound categories and a common bilateral activation in the frontal regions. However, strongly significant differences between familiar and unfamiliar sounds occurred near the end of and following the stimulations, due to synchronizations (though to reflect deactivations) which appeared over the left posterior regions, as well as the vertex and bilateral frontal cortex, only after unfamiliar sounds. These unexpected synchronizations after the unfamiliar stimuli may reflect an awareness of the unfamiliarity of such sounds, which may have induced an inhibition of semantic and episodic representations because the latter could not be associated with meaningless sounds.

Arousal↗
PubMed1996

Auditory responsive cortex in the squirrel monkey: neural responses to amplitude-modulated sounds.

The neural response to amplitude-modulated sinus sounds (AM sound) was investigated in the auditory cortex and insula of the awake squirrel monkey. It was found that 78.1% of all acoustically driven neurons encoded the envelope of the AM sound; the remaining 21.9% displayed simple On, On/Off or Off responses at the beginning or the end of the stimulus sound. Those neurons with AM coding were able to encode the AM sound frequency in two different ways: (1) the spikes followed the amplitude modulation envelopes in a phase locked manner; (2) the spike rate changed significantly with changing modulation frequencies. As reported in other species, the modulation transfer functions for rate showed higher modulation frequencies than the phase-locked response. Both AM codings exhibited a filter characteristic for AM sound. Whereas 46.6% of all neurons had the same filter characteristic for both the spike discharge and the phase-locked response, the remaining neurons displayed combinations of different filter types. The discharge pattern of a neuron to simple tone or noise bursts suggests the behaviour of this neuron when AM sound is used as the stimulus. Neurons with strong onset responses to tone/noise bursts tended to have higher phase-locked AM responses than neurons with weak onset responses. The spike rate maxima for AM sound showed no relation to the tone/noise burst discharge patterns. Varying modulation depth was encoded by the neuron's ability to follow the envelope cycles and not by the non-phase-locked spike rate frequency. The organization of the squirrel monkey's auditory cortex has previously been established by an anatomical study. We have added two new fields using physiological parameters. All fields investigated showed a clear functional separation for time-critical information processing. The best temporal resolution was shown by the primary auditory field (AI), the first-temporal field (T1) and the parainsular auditory field (Pi). The neural data in these fields and the amplitude modulation frequency range of squirrel monkey calls suggest a similar correlation between vocalization and perception as in human psychophysical data for speech and hearing sensation. The anterior fields in particular failed to follow the AM envelopes. For the first time in a primate, the insula was tested with different sound parameters ranging from simple tone bursts to AM sound. It is suggested that this cortical region plays a role in time-critical aspects of acoustic information processing. The observed best frequencies covered the same spectrum as AI. As in the auditory fields, most neurons in the insula encoded AM sound with different filter types. The high proportion of neurons unable to encode AM sound (40.6%) and the low mean best modulation frequency (9.9 Hz) do not support a prominent role of the insula in temporal information processing.

Acoustic Stimulation↗
PubMed2005

The role of GABAergic inhibition in shaping the response size and duration selectivity of bat inferior collicular neurons to sound pulses in rapid sequences.

Natural sounds, such as vocal communication sounds of many animal species typically occur as sequential sound pulses. Therefore, the response size of auditory neurons to a sound pulse would be inevitably affected when the sound pulse is preceded and succeeded by another sound pulse (i.e., forward and backward masking). The present study presents data to show that increasing strength of GABAergic inhibition relative to excitation contributes to decreasing response size and sharpening of duration selectivity of bat inferior collicular (IC) neurons to sound pulses in rapid sequences. The response size in number of impulses and duration selectivity of IC neurons were studied with a pulse train containing 9 sound pulses. A family of duration tuning curves was plotted for IC neurons using the number of impulses discharged to each presented sound pulse against pulse duration. Our data show that the response size of IC neurons progressively decreased and duration selectivity increased when determined with sequentially presented sound pulses. This variation in the response size and duration selectivity of IC neurons with sequentially presented sound pulses was abolished or reduced during bicuculline and GABA application. Bicuculline application increased the response size and broadened the duration tuning curve of IC neurons while GABA application produced opposite results. Possible mechanisms underlying increasing strength of GABAergic inhibition with sequentially presented sound pulses are presented. Biological significance of these findings in relation to acoustic signal processing is also discussed.

Acoustic Stimulation↗
PubMed2000

Patients' perception of sound levels in the surgical suite.

STUDY OBJECTIVES: To measure sound levels that our patients are exposed to in the surgical suite and their perception of these sound levels. DESIGN: Sound levels experienced by 100 patients undergoing general anesthesia for elective surgery during three phases: induction and maintenance of anesthesia in the operating room (OR), and recovery from anesthesia in the recovery room, were measured using a Type 4436 Noise Dose Meter. The equivalent continuous sound levels (Leq), maximum sound levels (Lmax), and the sources of sounds were noted. Patients were interviewed 24 hours after anesthesia about their perception of the sound levels they had experienced in the OR and recovery rooms. MEASUREMENTS AND MAIN RESULTS: The Leq during the induction, maintenance, and recovery phases were 70.3 +/- 16.8 dB(A), 66.2 +/- 4.1 dB(A) and 71.8 +/- 6.1 dB(A), respectively. These sound levels are much higher than international recommendations for hospital acute care areas and exceed the thresholds to produce noise-induced cardiovascular and endocrine effects. Sound levels were significantly higher during the induction and recovery phases compared to the maintenance phase. Thirty-two patients found the induction phase noisy and 33 patients found the recovery phase noisy. The sound levels distressed 16 patients and 52 patients would have preferred a quieter environment. There was no difference in the sound levels experienced by those who expressed dissatisfaction with the sound levels and those who did not. Much of the noise, particularly staff conversations, unnecessary alarms, and preparation of equipment, could have been prevented by simple measures. CONCLUSION: Noise prevention in the OR and recovery room needs more attention and should be a routine part of patient care.

Anesthesia↗
PubMed2004

Characterization of the Korotkoff sounds using joint time-frequency analysis.

The sounds associated with the five classical Korotkoff phases are clinically important for measuring systolic and diastolic blood pressures. The frequency ranges of the sounds have already been described simply using the overall peak frequencies within each phase by Fourier methods. However, such analysis may be missing potentially useful clinical information. The aim of this study was to compare features associated with the different phases of the Korotkoff sounds obtained during blood pressure measurement using a joint time-frequency analysis (JTFA) technique. A single operator recorded Korotkoff sounds from 25 healthy subjects using a measurement system comprising cardiology stethoscope, microphone, amplifier and recording system for computer sound digitization, and a MiniDisc system for playback to the cardiologist for Korotkoff phase classification. We have shown that using this system the phase classification by the cardiologist is repeatable, with no significant differences found in the number of sounds allocated to phases on two separate recording assessments. The digitized sounds were processed using a MATLAB-based short-time Fourier transform JTFA technique and differences in time, frequency and amplitude characteristics between the phases compared. It was found that on average, phase III had the largest overall amplitude and high frequency energy. Phase II had the greatest high frequency component and longest murmur, and was visibly the most complex phase in terms of time and frequency content. In contrast, phases IV and V had the lowest amplitude and frequency components. Overall, the statistically significant transitions between phases were: phase I to II with increases in high frequency (224 to 275 Hz) (p < 0.01) and sound duration (49 to 98 ms) (p < 0.0001), II to III with a significant decrease in sound duration (to 37 ms) (p < 0.0001), III to IV with decreases in maximum amplitude (0.95 to 0.25), highest frequency (262 to 95 Hz), and relative high frequency energy of the sounds (0.61 to 0.10) (all p < 0.0001), and IV to V with decreases in the maximum amplitude (0.25 to 0.13) (p < 0.0002) and high frequency energy (0.10 to 0.03) (p < 0.005). This study has demonstrated that joint time-frequency analysis of Korotkoff sounds was able to identify characteristic differences associated with the different phases classified by the expert cardiologist. Ultimately, exploiting the joint time and frequency characteristics of the sounds may improve blood pressure measurement and help to assess the stiffness of the peripheral arteries.

Arteries↗
PubMed2002

Simultaneous storage of two complex temporal sound patterns in auditory sensory memory.

We wished to determine whether multiple sound patterns can be simultaneously represented in the temporary auditory buffer (auditory sensory memory), when subjects have no task related to the sounds. To this end we used the mismatch negativity (MMN) event-related potential, an electric brain response elicited when a frequent sound is infrequently replaced by a different sound. The MMN response is based on the presence of the auditory sensory memory trace of the frequent sounds, which exists whether or not these sounds are in the focus of the subject's attention. Subjects watching a movie were presented with sound sequences consisting of two frequent sound patterns, each formed of four different tones and an infrequent pattern consisting of the first two tones of one of the frequent sound pattern and the last two tones of the other frequent sound pattern. The infrequent sound pattern elicited an MMN, indicating that multiple sound patterns are formed at an early, largely automatic stage of auditory processing.

Acoustic Stimulation↗
PubMed2000

Inaudible high-frequency sounds affect brain activity: hypersonic effect.

Although it is generally accepted that humans cannot perceive sounds in the frequency range above 20 kHz, the question of whether the existence of such "inaudible" high-frequency components may affect the acoustic perception of audible sounds remains unanswered. In this study, we used noninvasive physiological measurements of brain responses to provide evidence that sounds containing high-frequency components (HFCs) above the audible range significantly affect the brain activity of listeners. We used the gamelan music of Bali, which is extremely rich in HFCs with a nonstationary structure, as a natural sound source, dividing it into two components: an audible low-frequency component (LFC) below 22 kHz and an HFC above 22 kHz. Brain electrical activity and regional cerebral blood flow (rCBF) were measured as markers of neuronal activity while subjects were exposed to sounds with various combinations of LFCs and HFCs. None of the subjects recognized the HFC as sound when it was presented alone. Nevertheless, the power spectra of the alpha frequency range of the spontaneous electroencephalogram (alpha-EEG) recorded from the occipital region increased with statistical significance when the subjects were exposed to sound containing both an HFC and an LFC, compared with an otherwise identical sound from which the HFC was removed (i.e., LFC alone). In contrast, compared with the baseline, no enhancement of alpha-EEG was evident when either an HFC or an LFC was presented separately. Positron emission tomography measurements revealed that, when an HFC and an LFC were presented together, the rCBF in the brain stem and the left thalamus increased significantly compared with a sound lacking the HFC above 22 kHz but that was otherwise identical. Simultaneous EEG measurements showed that the power of occipital alpha-EEGs correlated significantly with the rCBF in the left thalamus. Psychological evaluation indicated that the subjects felt the sound containing an HFC to be more pleasant than the same sound lacking an HFC. These results suggest the existence of a previously unrecognized response to complex sound containing particular types of high frequencies above the audible range. We term this phenomenon the "hypersonic effect."

Acoustic Stimulation↗
PubMed1993

Pleasantness-unpleasantness of environmental sounds and gender difference in evaluation.

The present experiment examined emotional evaluation of 40 environmental sounds which were presented to 388 college students in a lecture room. Students were required to rate pleasantness-unpleasantness, to identify the sounds, and to rate their confidence about their identifications. Analysis showed that the pleasant sounds were natural and musical sounds and that the unpleasant sounds were sounds of a belch, of a dentist's drill, and of scratching on a blackboard. It is interesting that for pleasant sounds confidence was always high, which suggested that emotional evaluation of the environmental sounds was closely related to the confidence of observers in their identifications of the sounds. Gender differences were noted on the ratings on pleasantness-unpleasantness of environmental sounds, that is, women evaluated the pleasant sounds as more pleasant than men, and men evaluated the unpleasant sounds as not so unpleasant as did women.

Adult↗
PubMed1995

Octave waveband analysis to determine sound frequencies and intensities produced by nebulizers and humidifiers used with hoods.

BACKGROUND: health-care practitioners should be aware of how their equipment and practices can increase the patient's risk for noise-induced hearing loss. PURPOSE: We conducted this study to determine the type of noise produced by humidifiers and nebulizers used with hoods in the neonatal intensive care unit (NICU). We performed octave waveband analysis to determine sound intensities and frequencies because degree of hearing loss from noise exposure is related to the intensity of sound, frequency of sound and duration of exposure. METHODS: We studies 4 simple humidifiers, 3 heated humidifiers, and 4 nebulizers. Sound levels were measured at various frequencies, flows, and water levels using Peace and Shiley oxygen hoods. RESULTS: The findings show that sound levels were significantly louder (p.0.001) for nebulizers compared to humidifiers. Aquapak nebulizers pose the greatest risk for hearing loss because they produce sound at the highest frequencies and volumes. The peak sound levels of humidifiers not only were significantly lower but also occurred at the lowest sound frequencies, which are the least damaging to hearing. Sound levels were generally higher across sound frequencies at higher flows and with the Peace Hood. CONCLUSION: We conclude that heated humidifiers produce lowest sound intensities at the lowest sound frequencies and, consequently, are most appropriate for use in the NICU.

Environmental Exposure↗
PubMed1992

Temporomandibular joint sounds and condyle/disk relations on magnetic resonance images.

This study compared the condyle/disk relationships on magnetic resonance images (MRIs) in a group of subjects with completely silent temporomandibular joints (TMJ) when tested clinically with those in subjects with readily discernible TMJ sounds. The sounds were recorded with an accelerometer as the transducer. Selected degrees of jaw separation were electronically determined and recorded with interocclusal wafers for use with the imaging process. Of the "silent joints" 89% were found to have sounds when tested with the accelerometer. These "subclinical" sounds tended to be of shorter duration and occurred at a greater degree of vertical opening than the clinically discernable sounds. The MRIs of the group with clinically discernable sounds tended to show a change in the relationship between the head of the condyle and the intermediate zone of the disk, at the degree of jaw separation of the sound occurrence, whereas no condyle/disk change occurred in the group with "clinically silent joints." It is likely that all joints create sound during function. The different characteristics of the subclinical sounds versus the clinical sounds may indicate differing sound origins.

Adult↗
PubMed2004

The influence of duration and level on human sound localization.

The localization of sounds in the vertical plane (elevation) deteriorates for short-duration wideband sounds at moderate to high intensities. The effect is described by a systematic decrease of the elevation gain (slope of stimulus-response relation) at short sound durations. Two hypotheses have been proposed to explain this finding. Either the sound localization system integrates over a time window that is too short to accurately extract the spectral localization cues (neural integration hypothesis), or the effect results from cochlear saturation at high intensities (adaptation hypothesis). While the neural integration model predicts that elevation gain is independent of sound level, the adaptation hypothesis holds that low elevation gains for short-duration sounds are only obtained at high intensities. Here, these predictions are tested over a larger range of stimulus parameters than has been done so far. Subjects responded with rapid head movements to noise bursts in the two-dimensional frontal space. Stimulus durations ranged from 3 to 100 ms; sound levels from 26 to 73 dB SPL. Results show that the elevation gain decreases for short noise bursts at all sound levels, a finding that supports the integration model. On the other hand, the short-duration gain also decreases at high sound levels, which is in line with the adaptation hypothesis. The finding that elevation gain was a nonmonotonic function of sound level for all sound durations, however, is predicted by neither model. It is concluded that both mechanisms underlie the elevation gain effect and a conceptual model is proposed to reconcile these findings.

Adult↗
PubMed2006

Measurement of abnormal respiratory sounds during over-ground exercise.

REASONS FOR PERFORMING STUDY: The presence of abnormal respiratory sounds is commonly associated with obstructions of the upper respiratory tract. In order to establish their clinical significance measurements are required of both normal and abnormal respiratory sounds produced by horses exercising over-ground. OBJECTIVES: To determine whether high quality recordings of respiratory sound can be made during over-ground exercise, and to develop a convenient measurement system that can be used to obtain respiratory sounds from horses exercising in field conditions. METHODS: A range of prototypes was evaluated against the requirements that the system must be easy to use under field conditions and produce high-quality recordings of respiratory sound. The chosen design incorporated a miniature microphone and an air-flow direction sensor mounted on a lightweight plastic face mask. The mask was attached to the horse's head using nylon straps secured by velcro fastenings. Sound and flow signals were recorded on a portable minidisc player carried by the jockey. RESULTS: The system fulfilled the design criteria. High quality recordings of respiratory sounds were obtained from Thoroughbred horse exercising on a training gallop under a variety of weather conditions. Intermittently occurring abnormal sounds were readily identified from the data. CONCLUSIONS: High quality measurements of respiratory sounds during over-ground exercise can be made relatively easily. POTENTIAL RELEVANCE: The system enables measurement of respiratory sounds outside a laboratory environment creating new opportunities for scientific research and clinical assessment. The study demonstrated that diagnostic systems based on respiratory sound analysis could potentially be manufactured at relatively low cost and be convenient and simple to use.

Airway Obstruction↗
PubMed1993

Degenerate hearing and sound localization in naked mole rats (Heterocephalus glaber), with an overview of central auditory structures.

Behavioral tests of absolute sensitivity and sound localization in African naked mole rats show that, despite their communal social structure and large vocal repertoire, their hearing has degenerated much like that of other subterranean species. First, their ability to detect sound is limited, with their maximum sensitivity being only 35 dB (occurring at 4 kHz). Second, their high-frequency hearing is severely limited, with their hearing range (at 60 dB sound pressure level [SPL]) extending from 65 Hz to only 12.8 kHz. Third, determination of the effect of duration on noise thresholds indicates that, compared with other animals, mole rats require a sound to be present for a much longer duration before reaching asymptotic threshold. Finally, they are unable consistently to localize sounds shorter than 400 ms and cannot accurately localize sounds of longer duration, raising the possibility that they are unable to use binaural locus cues. Thus, it seems that the essentially one-dimensional burrow system of a subterranean habitat produces severe changes in hearing comparable to the changes in vision that result from the absence of light. To explore the relation between vision and sound-localization acuity, retinal ganglion cell densities were determined. The results indicate that naked mole rats have a broad area of best (albeit poor) vision, with maximum acuity estimated at 44 cycles/degree. That mammals with wide fields of best vision have poorer sound-localization acuity than those with narrower fields is consistent with the thesis that a major function of sound localization is to direct the gaze to the source of a sound. However, the fact that subterranean mammals have little use for vision in a lightless environment suggests that they represent an extreme case in this relationship and may explain the fact that, unlike surface-dwelling mammals, they have virtually lost the ability to localize brief sounds. Finally, despite their very limited auditory abilities, the major brainstem auditory nuclei, although relatively small, appear to be present.

Animals↗
PubMed2005

Aspects of sound communication in the pearlfish Carapus boraborensis and Carapus homei (Carapidae).

Several species of Carapidae are known to have symbiotic relationships with marine invertebrates. The two most common species in Moorea (French Polynesia), Carapus boraborensis and Carapus homei, undergo conspecific and heterospecific encounters in the same holothurian host during which they produce sounds. Another characteristic of these fish lies in their abilities to produce sounds. The objective of this study was dual: (1) to seek if there was a sexual difference in the sounds produced by C. boraborensis; (2) to seek if there was a difference in the sound emissions between heterospecific and conspecific encounters. In each trial, sounds were only recorded when one individual entered the sea cucumber that was already occupied. In encounters, sounds were structured in regular pulse emissions whose pulse lengths and periods allowed to significantly distinguish each species, as well as both sexes in C. boraborensis. In the latter species, results show for the first time that temporal features of the emitted sounds can have a functional importance in sex identification. In heterospecific encounters, sounds were reduced 68% of the time to a single pulse emission and there was a modification in the pulse length of each species: it shortens in C. homei and it lengthens in C. boraborensis. It highlights that both carapids are able to adapt their sounds to the facing species. Because a modification of the sound appears to be done at the first emission, it is supposed that recognition precedes the sound emission.

Air Sacs↗
PubMed1990

Sound environment of the fetal sheep.

The internal sound pressure levels within the intact amnion of pregnant ewes surgically implanted with a hydrophone was determined during conditions of quiet and during sound field exposures to broadband and octave-band noise. Measurements were made of sound pressures outside and inside the ewe, and sound attenuation through maternal tissues and fluids was calculated. Sound pressures generated by low frequencies (less than 0.25 kHz) were 2 to 5 dB greater inside than outside the ewe. Above 0.25 kHz, sound attenuation increased at a rate of 6 dB per octave. For 4.0 kHz, sound attenuation averaged 20 dB. The sound pressure recorded at different locations within the amnion with respect to the sound source varied by up to 6 dB. The internal noise floor in the absence of externally generated sounds was as low as 50 dB (spectrum level) above 0.2 kHz. Thus the fetus is developing in an environment that is rich with internal and external sounds.

Acoustic Stimulation↗
PubMed1985

The effect of low density gas breathing on vesicular lung sounds.

Turbulent airflow (largely gas density dependent) in larger airways is believed by many lung sound researchers to be the mechanism responsible for the generation of vesicular lung sounds. To test the validity of this concept, we measured the amplitude of lung and tracheal sounds of 6 subjects alternately breathing air and a low density gas mixture (80% helium, 20% oxygen: He-O2). Lung sounds were recorded from 3 chest wall sites: Anterior right upper lobe (RUL), posterior and posterolateral right lower lobe (RLL), and a site over the proximal trachea below the larynx. The subjects rebreathed into an electronic spirometer filled with the test gas, and achieved a peak inspiratory and expiratory airflow of 2-2.5 L/sec. Lung sound amplitude was determined by an automated, flow-corrected measurement procedure. The mean decrease in sound amplitude when breathing He-O2 compared to air was: trachea, inspiration 44%; trachea, expiration 45%; RUL, inspiration 13%; RUL, expiration 25%; RLL, inspiration 15% (expiration at the RLL was too quiet to record). Cross-correlation and frequency analyses of the sounds recorded at the two RLL sites on both test gases revealed no consistent change in frequency or time relationships, indicating absence of effect of gas density on sound transmission between the sound generating airways and chest wall. These data suggest that the mechanism of production of the inspiratory vesicular lung sound is not simply turbulent airflow but some other relatively gas density independent mechanism. The tracheal and expiratory lung sounds do appear to be produced by a more density dependent turbulent mechanism.

Adult↗
PubMed2006

Locating the initial stages of speech-sound processing in human temporal cortex.

It is commonly assumed that, in the cochlea and the brainstem, the auditory system processes speech sounds without differentiating them from any other sounds. At some stage, however, it must treat speech sounds and nonspeech sounds differently, since we perceive them as different. The purpose of this study was to delimit the first location in the auditory pathway that makes this distinction using functional MRI, by identifying regions that are differentially sensitive to the internal structure of speech sounds as opposed to closely matched control sounds. We analyzed data from nine right-handed volunteers who were scanned while listening to natural and synthetic vowels, or to nonspeech stimuli matched to the vowel sounds in terms of their long-term energy and both their spectral and temporal profiles. The vowels produced more activation than nonspeech sounds in a bilateral region of the superior temporal sulcus, lateral and inferior to regions of auditory cortex that were activated by both vowels and nonspeech stimuli. The results suggest that the perception of vowel sounds is compatible with a hierarchical model of primate auditory processing in which early cortical stages of processing respond indiscriminately to speech and nonspeech sounds, and only higher regions, beyond anatomically defined auditory cortex, show selectivity for speech sounds.

Adult↗
PubMed2005

Granule cells in the cochlear nucleus sensitive to sound activation detected by Fos protein expression.

Granule cells are the smallest neuronal type in the cochlear nucleus (CN). Due to their small size, it is extremely difficult to record their sound-evoked activity with microelectrodes. Compared with large, non-granule cells, much less is known about their response properties to sound stimulation. Here, we use Fos, the nuclear regulatory protein, as a neuronal activity marker to determine the responsiveness of granule cells to sound in comparison to the larger neurons. The present study determined the threshold sensitivity and activation pattern of neurons in the three subdivisions of the CN with free-field sound stimulation in monaural, awake rats. Immunocytochemical localization of Fos was used as our metric for "sound activation." Neuronal types upregulating Fos expression in response to sound stimulation were further identified with Nissl counterstaining. Our results show that most CN cell types can upregulate Fos expression when sound activated and the number of Fos-expressing neurons is directly related to sound intensity. The threshold for Fos activation in granule cells is lower than that for non-granule cells. The number of Fos activated granule cells saturates at high sound intensity, while the number of Fos activated non-granule cells is a monotonic function. By comparing the patterns of sound-induced Fos expression in different CN cell types, it may be possible to predict features of sound-evoked activity in granule cells.

Acoustic Stimulation↗