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PubMed1976

Auditory pathways to the cortex in Tupaia glis.

The auditory system of the tree shrew, Tupaia glis, was investigated by identifying axonal degeneration after lesions of the lateral lemniscus, the inferior colliculus, the medial geniculate nucleus and the auditory cortex. The results show that the lateral lemniscus projects to the central nucleus of the inferior colliculus which in turn projects principally to the ventral division of the medial geniculate nucleus but to a lesser extent to the magnocellular division of the medial geniculate nucleus. The final step in the pathway to the cortex is achieved by a projection from the ventral division to the fourth layer of auditory koniocortex. There appear to be several auditory pathways parallel to this primary path. The lateral lemniscus projects to the dorsal division of the medial geniculate nucleus; the deeper layers of the superior colliculus project to the posterior nucleus; and both the dorsal division and the posterior nucleus project to the belt caudal to auditory koniocortex. The caudal division of the medial geniculate nucleus may constitute a relay in still another path from the pericentral division of the inferior colliculus. Finally, the magnocellular division also appears to be distinct insofar as its cortical projections are confined chiefly to the deeper layers. A comparison between the tree shrew and the cat reveals a similar organization in the two species. In the cat the starting point for understanding the organization of the several auditory pathways is the distinction between a core cortical zone which corresponds to konicortex and to AI and a peripheral belt. The core receives essential projections from the ventral division; the belt receives sustaining projections from the cell groups which surround the ventral division. It is reasonable to hypothesize that this difference between the core and the belt is characteristic of all mammals.

Animals↗
PubMed1988

Neonatal deafening alters nonpyramidal dendrite orientation in auditory cortex: a computer microscope study in the rabbit.

In order to examine the influence of afferent input on nonpyramidal dendrite development in the auditory cortex, unilateral deafening was carried out in neonatal rabbits at birth, approximately 6 days prior to the onset of hearing. Deafening was produced by surgical removal of the incus and stapes ossicles, aspiration of the cochlear perilymph, and kanamycin injection into the oval window. At 60 days of age, acoustic stimulation of the deafened ear was unable to evoke auditory brainstem responses. The brains of experimental and littermate control rabbits were processed according to the Golgi-Cox Nissl method. The dendritic systems of lamina III/IV spine-free nonpyramidal cells in the auditory cortex contralateral to the deafened ear were digitized from 340-micron-thick coronal sections with the aid of a computer microscope. Three-dimensional spatial and statistical analyses revealed that nonpyramidal dendrite length in neonatally deafened rabbits increased 27% relative to littermate controls. A fan-in projection analysis revealed that the increased dendrite length in the deafened animals was maximum in the tangential direction and toward the white matter. Computer rotation of digitized neurons from neonatally deafened rabbits also revealed evidence of abnormal dendritic growth in the form of recurved dendrites. We interpret our results to indicate that unilateral cochlear destruction early in development causes a reorganization of the ascending auditory pathway which extends to the contralateral cerebral cortex. Because the auditory cortex contralateral to the deafened ear still receives acoustic input from the undamaged ipsilateral ear, normal nonpyramidal dendritic growth in the auditory cortex is, in part, dependent upon afferent activity arising from both ears.

Animals↗
PubMed2005

Auditory and speech processing and reading development in Chinese school children: behavioural and ERP evidence.

By measuring behavioural performance and event-related potentials (ERPs) this study investigated the extent to which Chinese school children's reading development is influenced by their skills in auditory, speech, and temporal processing. In Experiment 1, 102 normal school children's performance in pure tone temporal order judgment, tone frequency discrimination, temporal interval discrimination and composite tone pattern discrimination was measured. Results showed that children's auditory processing skills correlated significantly with their reading fluency, phonological awareness, word naming latency, and the number of Chinese characters learned. Regression analyses found that tone temporal order judgment, temporal interval discrimination and composite tone pattern discrimination could account for 32% of variance in phonological awareness. Controlling for the effect of phonological awareness, auditory processing measures still contributed significantly to variance in reading fluency and character naming. In Experiment 2, mismatch negativities (MMN) in event-related brain potentials were recorded from dyslexic children and the matched normal children, while these children listened passively to Chinese syllables and auditory stimuli composed of pure tones. The two groups of children did not differ in MMN to stimuli deviated in pure tone frequency and Chinese lexical tones. But dyslexic children showed smaller MMN to stimuli deviated in initial consonants or vowels of Chinese syllables and to stimuli deviated in temporal information of composite tone patterns. These results suggested that Chinese dyslexic children have deficits in auditory temporal processing as well as in linguistic processing and that auditory and temporal processing is possibly as important to reading development of children in a logographic writing system as in an alphabetic system.

Asian People↗
PubMed2004

The effect of MR scanner noise on auditory cortex activity using fMRI.

Auditory functional magnetic resonance imaging (fMRI) studies are limited by the presence of noise produced by echo planar imaging (EPI). The current study quantifies the effect of MR scanner noise on psychophysical measures of the perception of loudness and on measures of tonotopy, the representation of auditory frequencies within the auditory cortex. Seven normal hearing adults were examined using tones of 5 different auditory frequencies (250, 500, 1,000, 2,000, 4,000 Hz) of equal loudness. Using an imaging protocol with peak MR scanner noise at 1,460 Hz, the perception of loudness and detectable fMRI activity in response to a 1-kHz tone was less compared to other frequencies. When the imaging protocol was changed such that peak MR scanner noise occurred at 2,080 Hz, the perception of loudness and detectable fMRI activity in response to a 2-kHz tone was less compared to other frequencies. The reduction in the measured fMRI activity for tones near scanner frequencies may be due to an inflated scanner-induced baseline at those frequencies. In addition, fMRI activity decreased with increasing frequency, possibly due to the upward spread of masking of low-frequency, high-intensity tonal stimuli or the proximity of low-frequency core and belt areas of the auditory cortex. These results demonstrate the direct effect of scanner noise and high-intensity tonal stimuli on measurements of auditory cortex tonotopy.

Acoustic Stimulation↗
PubMed2002

Frontal and temporal dysfunction of auditory stimulus processing in schizophrenia.

Attention deficits have been consistently described in schizophrenia. Functional neuroimaging and electrophysiological studies have focused on anterior cingulate cortex (ACC) dysfunction as a possible mediator. However, recent basic research has suggested that the effect of attention is also observed as a relative amplification of activity in modality-associated cortical areas. In the present study, the question was addressed whether an amplification deficit is seen in the auditory cortex of schizophrenic patients during an attention-requiring choice reaction task. Twenty-one drug-free schizophrenic patients and 21 age- and sex-matched healthy controls were studied (32-channel EEG). The underlying generators of the event-related N1 component were separated in neuroanatomic space using a minimum-norm (LORETA) and a multiple dipole (BESA) approach. Both methods revealed activation in the primary auditory cortex (peak latency approximately 100 ms) and in the area of the ACC (peak latency approximately 130 ms). In addition, the adapted multiple dipole model also showed a temporal-radial source activation in nonprimary auditory areas (peak latency approximately 140 ms). In schizophrenic patients, significant activation deficits were found in the ACC as well as in the left nonprimary auditory areas that differentially correlated with negative and positive symptoms. The results suggest that (1) the source in the nonprimary auditory cortex is detected only with a multiple dipole approach and (2) that the N1 generators in the ACC and in the nonprimary auditory cortex are dysfunctional in schizophrenia. This would be in line with the notion that attention deficits in schizophrenia involve an extended cortical network.

Acoustic Stimulation↗
PubMed1997

Metabolic effects of blocking tone conditioning on the rat auditory system.

The Kamin blocking phenomenon occurs when behavioral expression of conditioning to a novel stimulus fails in the presence of a previously conditioned stimulus (CS). Neural metabolic effects of a tone conditioned as an excitor were compared to the effects of the same physical tone when excitatory conditioning was blocked by previous conditioning with a light. We examined the metabolic activity of the auditory system to test the hypothesis that auditory processing of a tone CS changes during blocking. Quantitative histochemistry of cytochrome oxidase (C.O.), the final mitochondrial enzyme for oxidative metabolism, was used to evaluate cumulative changes in the metabolic capacity of the auditory system resulting from blocking. Rats (Long-Evans) in the Blocking group received pairings of a light CS with a mild footshock unconditioned stimulus (US) during Phase 1 training. Rats in the Control group received random presentations of the same stimuli during Phase 1. Both groups then received the same Phase 2 training consisting of simultaneous tone and light presentations paired with footshock. The Control group exhibited significant suppression of drinking to tone alone presentations after training, whereas the Blocking group did not. Metabolic mapping results demonstrated that blocking effects were localized to auditory regions receiving direct US somatosensory projections. Significantly greater C.O. activity in the inferior colliculus and the dorsal cochlear nucleus was found for the Blocking group relative to the Control group. Input cell layers of secondary auditory cortex also demonstrated a group difference, in that layers II/III and IV had lower levels of C.O. activity in the Blocking group. These specific changes in C.O. activity linked to behavioral training demonstrated that the blocking phenomenon produced distinct neural metabolic changes in CS processing in the auditory system localized to regions with CS-US interactions.

Animals↗
PubMed1995

The auditory pathway in cat corpus callosum.

The cortical auditory fields of the two hemispheres are interconnected via the corpus callosum. We have investigated the topographical arrangement of auditory callosal axons in the cat. Following circumscribed biocytin injections in the primary (AI), secondary (AII), anterior (AAF) and posterior (PAF) auditory fields, labelled axons have been found in the posterior two-thirds of the corpus callosum. Callosal axons labelled by small individual cortical injections did not form a tight bundle at the callosal midsagittal plane but spread over as much as one-third of the corpus callosum. Axons originating from different auditory fields were roughly topographically ordered, reflecting to some extent the rostro-caudal position of the field of origin. Axons from AAF crossed on average more rostrally than axons from AI; the latter crossed more rostrally than axons from PAF and AII. Callosal axons originating in a discrete part of the cortex travelled first in a relatively tight bundle to the telo-diencephalic junction and then dispersed progressively. In conclusion, the cat corpus callosum does not contain a sector reserved for auditory axons, nor a strictly topographically ordered auditory pathway. This observation is of relevance to neuropsychological and neuropathological observations in man.

Animals↗
PubMed2002

Effects of acute hypoglycaemia on auditory information processing in adults with Type I diabetes.

AIMS/HYPOTHESIS: Acute hypoglycaemia in humans causes general impairment of cognitive function, but information about its effects on more specific cognitive processes is limited. METHODS: Basic aspects of auditory function were studied in 15 adults with uncomplicated Type I (insulin-dependent) diabetes mellitus. Two separate hyperinsulinaemic glucose clamp procedures were done on different study days, in a counterbalanced fashion, either maintaining euglycaemia (blood glucose 5.0 mmol x l(-1)) or inducing hypoglycaemia (blood glucose 2.6 mmol x l(-1)). During each study, the subjects performed a battery of auditory and cognitive function tasks. RESULTS: Hypoglycaemia caused deterioration in mental efficiency as assessed by Digit Symbol (p<0.001) and Trail Making B (p=0.004) tasks. Acute hypoglycaemia also caused deterioration in one of three measures of simple auditory processing (single-tone loudness, p=0.001) and in auditory temporal processing (p=0.007). The amplitude and latency of auditory N100, P200 and P300 event-related potentials were not affected, but the amplitude of the N240 potential was reduced during acute hypoglycaemia. CONCLUSION/INTERPRETATION: Our findings are consistent with other recognised disruptive effects of acute hypoglycaemia on sensory information processing in non-diabetic and diabetic adults, including adverse effects on auditory information processing in non-diabetic subjects. These derangements have implications for the everyday activities of people with Type I diabetes who are frequently exposed to acute hypoglycaemia.

Acute Disease↗
PubMed2005

Tropisetron improves deficient inhibitory auditory processing in DBA/2 mice: role of alpha 7 nicotinic acetylcholine receptors.

RATIONALE: Deficient inhibitory processing of the P50 auditory evoked potential is a pathophysiological feature of schizophrenia. Several lines of evidence suggest that alpha 7 nicotinic receptors play a critical role in this phenomenon. Similar to schizophrenic patients, DBA/2 mice spontaneously exhibit a deficit in inhibitory processing of the P20-N40 auditory evoked potential, which is thought to be a rodent analog of the human P50 auditory evoked potential. OBJECTIVE: The present study was undertaken to examine whether tropisetron, a partial agonist at alpha 7 nicotinic receptors and an antagonist at 5-hydroxytryptamine-3 receptors, improves this deficit in DBA/2 mice. RESULTS: Administration of tropisetron (1 mg/kg i.p.) significantly improved the deficient inhibitory processing of the P20-N40 auditory evoked potential in DBA/2 mice. Coadministration of methyllycaconitine (MLA; 3 mg/kg i.p.), a partially selective antagonist at alpha 7 nicotinic receptors, significantly blocked the normalizing effect of tropisetron. Furthermore, MLA alone did not alter the deficient inhibitory processing of the P20-N40 auditory evoked potential in DBA/2 mice. CONCLUSIONS: The data suggest that tropisetron improves the deficient inhibitory processing of the P20-N40 auditory evoked potential in DBA/2 mice by effects on alpha 7 and perhaps alpha 4 beta 2 nicotinic receptors. Tropisetron may be useful for the treatment of deficient inhibitory processing in schizophrenia.

Aconitine↗
PubMed2003

CNS somatosensory-auditory interactions elicit or modulate tinnitus.

Evidence has accumulated linking clinical tinnitus to the somatosensory system. Most clinical tinnitus patients can change the psychoacoustic attributes of their tinnitus with forceful head and neck contractions. The significance of such somatic modulation of tinnitus was assessed by testing non-clinical subjects. Like clinical tinnitus patients, about 80% of non-clinical subjects who had ongoing tinnitus at the time of testing (whether or not they had been previously aware of it) could modulate their tinnitus with head and neck contractions. Almost 60% of those with no tinnitus at the time of testing could elicit a tinnitus-like auditory percept with head and neck contractions. Because similar results were found in the profoundly deaf, we conclude that somatosensory-auditory interactions within the central nervous system account for most, if not all, somatic modulation of tinnitus as well as the development of auditory percepts with somatic testing. Other observations implicate the muscle spindle as initiating the neural activation that ultimately modulates the central auditory pathway, including the dorsal cochlear nucleus. Somatic influences upon auditory perception are not limited to tinnitus subjects but are a fundamental property of the auditory system.

Adolescent↗
PubMed2007

Auditory evoked visual awareness following sudden ocular blindness: an EEG and TMS investigation.

Neurophysiological and neuroanatomical studies have provoked controversy about whether the visual cortex may be more modifiable than previously believed. Auditory processing is enhanced in blind compared to sighted people, and the enhancement might reflect encroachment of auditory transmission onto visual cortex. To address this issue, we recorded the auditory event-related potentials (ERPs) correlated with auditory related paradoxical visual awareness in a subject with traumatic total late-onset blindness. We found that (1) there was auditory related brain activity over the occipital visual scalp regions starting from a very early stage (< 80 ms) and (2) this occipital activity was significantly different between "visually aware" and "visually unaware" responses in the P1 (40-80 ms) component following meaningful stimuli. There was also a significant difference between responses with and without visual awareness in the N1 (100-120 ms) component following either tones or meaningful stimuli. The phosphenes accompanying auditory stimuli in the ERP experiment were always perceived to be directly in front of the subject and this was reproduced by transcranial magnetic stimulation over the blind primary visual cortex and by sudden sounds delivered to the side or behind the subject. The TMS induced phosphenes were restricted to the central part of the space and were, at least qualitatively, the same as those induced by sounds. The results are clear evidence that human perceptual functions can be reorganized after sudden, late-onset, total ocular blindness.

Acoustic Stimulation↗
PubMed1997

Deoxyglucose uptake in the ferret auditory cortex.

Histological methods and 2-deoxyglucose autoradiography were used in an attempt at finding distinguishing characteristics that would permit the clear definition of different auditory areas on the ectosylvian gyrus. This region was studied in both coronal and flattened tangential sections. In tangential sections a crescent-shaped region of high deoxyglucose uptake was identified. The centre of this crescent was in the position of the primary auditory area on the middle ectosylvian gyrus. The ventro-anterior arm of the crescent was on the surface of the anterior ectosylvian gyrus and the ventro-posterior arm on the posterior ectosylvian gyrus. All three parts of the crescent appear to have an auditory function, because ablating the inferior colliculus or inserting a contralateral earplug reduced their deoxyglucose uptake. This was shown by using two separately distinguishable forms of 2-deoxyglucose, incorporating the 18F and 14C isotopes. In addition, another area of high deoxyglucose activity was identified in the ventral wall of the suprasylvian sulcus, which seems to correspond to the anterior auditory field. These four areas with high deoxyglucose uptake also have high levels of succinate dehydrogenase activity and moderately high densities of myelinated fibres. Succinate dehydrogenase histochemistry provides a simple method for identifying auditory cortical areas and should be of use in future physiological studies. These results provide evidence that the ferret has four separate auditory areas with relatively high metabolic and functional activity.

Animals↗
PubMed2005

A model for the mechanism of generating the auditory evoked field.

The auditory evoked potentials and fields, recorded with electro- and magneto-encephalography, respectively, have the prominent peak at the latency of about 100 ms, named N100(m). The mechanism for generating the peak is not yet fully elucidated, however. Firstly, this study reviewed empirical results on the mechanism that had been previously published by the same author. The results showed that phases of the ongoing oscillations at around 6 Hz above the auditory cortex are locked with respect to onsets of the auditory stimuli during the period of N100 m, and also that powers of the oscillations are increased during the same period. Taking into account these results as well as another evidence that the peak arises from multiple sources within the auditory cortex, a model for the mechanism of generating the auditory N100 m was proposed. The model assumed several oscillators in the auditory cortex, whose phases were locked during the period of N100 m, but not locked at other periods. Computer simulation validated the model. The model could represent a starting point for further experiment and simulation.

Acoustic Stimulation↗
PubMed1975

Single cell activity in the auditory cortex of the unanesthetized, behaving monkey: correlation with stimulus controlled behavior.

The neural activity of 60 cells in the auditory cortices of two rhesus monkeys was examined in relation to systematic variations in cued reinforcement conditions. Subjects were trained on a variant of the auditory reaction time (RT) task. In the final behavioral paradigm monkeys were rewarded for rapid key releases to all tonal stimuli in one reinforcement condition (frequency irrelevant = FI), while in the other stimulus-cued condition (frequency discrimination = FD) releases to certain tonal test frequencies were unrewarded. Upon completion of behavioral training, RTs to identical tonal test stimuli were longer and more variable when presented in the unrewarded (FD) condition. Following neurosurgery it was possible to observe the effects of reinforcement condition on auditory RT performance and the activity of single auditory cortical cells simultaneously. Of the auditory cortical cells sampled, 25% showed definite and repeatable alterations in evoked activity to the same tonal stimulus which were correlated with reinforcement condition. For nearly all cells examined the influence of reinforcement condition was much the same: on excitatory responses were increased in the FD condition. A few of the cells also showed alterations in latency and/or pattern of evoked discharge. Importantly, none of the units examined showed changes in their spontaneous discharge rates as a function of reinforcement condition. both peripheral mechanical and central neural theories were considered as a basis for the observed neural alterations. The specificity and latency of the alterations as well as the absence of tonic effects seemed to indicate that the neural changes observed were mediated by central mechanisms. Our results strongly suggest that the activity of a sample of auditory cortical neurons depends on the behavioral state of the preparation. We propose that 'behavioral state", appropriately defined, can be a useful concept for neurophysiologists.

Action Potentials↗
PubMed1983

Thalamic and callosal connections of the rat auditory cortex.

This study was designed to assess the relative distributions of two extrinsic afferent fiber systems in the rat auditory cortex as indicated by the patterns of specific lesion-induced degeneration evident in Fink-Heimer preparations. The auditory cortex consists of cytoarchitectural areas 41, 20 and 36. Lesions were made in the medial geniculate body (MGB) or the corpus callosum in some rats, while in other rats, lesions were made in both the MGB and the corpus callosum. Following the thalamic lesions, degenerating terminals occur throughout the auditory region of cortex, principally in layer IV and deep layer III, but also in layer VI and in the superficial part of layer I. With the exception of the band of degeneration in layer I, the density of the thalamic degeneration is uneven, such that patches of increased density of degeneration are separated by regions with few degenerating terminals. Following lesions of the corpus callosum, degenerating callosal terminals are also evident throughout the auditory region of cortex and they occur in deep layer I through layer III, superficial layer V and in layer VI. The density of the degenerating callosal terminals is not uniform throughout most of area 41, to the extent that there are radially-oriented bands of increased density which appear within the continuous callosal projection. Following the double lesions, degenerating terminals throughout the auditory region are distributed homogeneously within all cortical layers with the exception of deep layer V which is relatively free of degeneration. The results indicate that all regions within the rat auditory cortex are subject to both thalamic and callosal influence, although the input is not completely uniform, for the zones in layers IV and VI which have decreased thalamic input appear to have increased callosal input.

Animals↗
PubMed1989

Auditory and visual neurons in the cat's superior colliculus selective for the direction of apparent motion stimuli.

In the cat, cells of the superior colliculus (SC) and the tectofugal pathways of the visual system are highly selective for the direction of a moving visual stimulus. Deep layer units of SC in addition respond to auditory and somatosensory stimuli, but the proportion of such non-visual cells is usually found to be much lower than that of visual cells. We recorded the responses of 174 cells in the SC to sequentially presented, localized visual and/or auditory stimuli that produced the sensation of apparent motion to human observers. Controls using single LED flashes or tone pips or clicks at very long intervals that did not produce apparent motion were also used. We found both visual and auditory units that responded vigorously to the apparent motion stimuli and showed pronounced directional selectivity. However, in the auditory domain such units were rare and thus did not increase the proportion of auditory responses in SC substantially. Varying the interstimulus interval (ISI) of these stimuli, both visual and auditory, indicated that the mechanism of direction selectivity in these cells was suppression of the response in the 'non-preferred' direction rather than facilitation in the 'preferred' direction. With long ISI's of 200 ms or more, every single stimulus gave a discrete response peak of constant amplitude. For ISI's of 50 ms or less the discrete peaks merged to a continuous response. Maximal firing rate in the preferred direction remained the same as for longer ISI's, but was decreased for movement in the non-preferred directions. Very short ISI's (10 ms) produced little response in any direction.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1989

Auditory cortex lesions prevent the extinction of Pavlovian differential heart rate conditioning to tonal stimuli in rabbits.

The present study examined the role of the auditory cortex in the extinction of differentially conditioned heart rate (HR) responses in rabbits. Lesions were placed bilaterally in either the auditory cortex or the visual cortex. Three days after recovery from surgery, the auditory cortex lesion group and the visual cortex lesion control group were habituated to the tonal conditioned stimuli (CSs), and then given 2 days of Pavlovian differential conditioning (60 trials per day) in which one tone (CS+) was always paired with the unconditioned stimulus and another tone (CS-) was never paired with the unconditioned stimulus. Animals that had demonstrated reliable differential conditioning (CS+ response at least 5 beats greater than the CS- response) were placed on an extinction schedule for 7 days. The extinction schedule was identical to the differential conditioning schedule with the exception that shock never followed the CS+. The results of the study indicate that auditory cortex lesions prevent the extinction of differential bradycardia conditioned responses (CRs) to tonal CSs. Whereas the bradycardia responses to the CS+ quickly extinguished in the group that had control lesions in the visual cortex, the auditory cortex lesion group continued to exhibit significantly larger bradycardiac HR CRs to the CS+ relative to the CS- during all 7 days of extinction. These results suggest that the animals in the auditory cortex lesioned group did not inhibit responses to a previously reinforced stimulus (i.e., CS+) as well as animals with control lesions in the visual cortex.

Acoustic Stimulation↗
PubMed1995

Specific tonotopic organizations of different areas of the human auditory cortex revealed by simultaneous magnetic and electric recordings.

This paper presents data concerning auditory evoked responses in the middle latency range (wave Pam/Pa) and slow latency range (wave N1m/N1) recorded from 12 subjects. It is the first group study to report multi-channel data of both MEG and EEG recordings from the human auditory cortex. The experimental procedure involved potential and current density topographical brain mapping as well as magnetic and electric source analysis. Responses were compared for the following 3 stimulus frequencies: 500, 1000 and 4000 Hz. It was found that two areas of the auditory cortex showed mirrored tonotopic organization; one area, the source of N1m/N1 wave, exhibited higher frequencies at progressively deeper locations, while the second area, the source of the Pam/Pa wave, exhibited higher frequencies at progressively more superficial locations. The Pa tonotopic map was located in the primary auditory cortex anterior to the N1m/N1 mirror map. It is likely that N1m/N1 results from activation of secondary auditory areas. The location of the Pa map in A1, and its N1 mirror image in secondary auditory areas is in agreement with observations from animal studies.

Acoustic Stimulation↗