We have previously demonstrated that neuronal responses in primary auditory cortex of halothane-anesthetized cats depend strongly on the natural background. 
In order do this we have reviewed our past studies on auditory cortical plasticity based on longlatency evoked potential recordings in humans following cochlear implantation, and multiple single-unit recordings from cat auditory cortex following noise trauma and exposure to a non-deafening acoustic environment. The results of these studies, and those of other investigators highlighted here, show that the auditory cortex shows plastic changes throughout life. This review provides evidence that in adults, long-lasting plastic changes in auditory cortex occur even in the absence of behaviorally relevant acoustic stimulation.
Age-related changes in GAD65 and GAD67 levels were investigated using immunohistochemistry and Western blotting in the inferior colliculus (IC), the auditory cortex (AC) and the visual cortex in Long-Evans rats.
Selective auditory attention powerfully modulates neural activity in the human auditory cortex (AC).
Abstract At the level of the auditory cortex, musicians discriminate pitch changes more accurately than nonmusicians.
Using recordings in the primary auditory cortex of anesthetized cats, we show that presentation of narrowband stimuli not including the best frequency of neurons provokes the appearance of residual peaks and increased firing rate at some specific spectral edges of stimuli compared with classical STRFs obtained from broadband stimuli.
Auditory evoked brainstem responses (ABR) is a non-invasive electrical potential registration which evaluates the auditory tract from the middle ear to the auditory cortex in the first 12 milliseconds (ms).
Neurons in the auditory cortex can lock to the fine timing of acoustic stimuli with millisecond precision, but it is not known whether this precise spike timing can be used to guide decisions. We used chronically implanted microelectrode pairs to stimulate neurons in the rat auditory cortex directly and found that rats can exploit differences in the timing of cortical activity that are as short as 3 ms to guide decisions..
Real-time optical imaging was conducted in the guinea pig auditory cortex to study spatiotemporal interrelations of excitation and inhibition in response to tone stimulation. Tone stimulation elicited responses consisting of three phases in the anterior field (the primary auditory cortex of guinea pig) and in the dorsocaudal field of the auditory cortex. These results show that inhibition is dynamic, both in time and in space, in the auditory cortex..
Seven regions of interest in language-correlated areas, namely Broca's area, Wernicke's area, the arcuate fasciculus, and the angular gyrus, as well as their right hemisphere homologous regions, and the auditory cortex, the motor cortex, and the visual cortex were examined. On the basis of scatter plot results, we put these areas into three groups: Group A, which included the motor cortex, the auditory cortex, and the visual cortex, myelinated faster than Group B, which included Broca's area, Wernicke's area, and the angular gyrus before 1.5 years old; Group C, consisting of the arcuate fasciculus, has similar degree of myelination as Group B before 1.5 years but then myelinated more slowly after 3 years of age.
The spatiotemporal dynamics of the neurovascular response to brief acoustic stimuli were investigated in guinea pig primary auditory cortex. The acoustic stimulus was given as a wide band sound (click), which induced global activation or as one of two pure tones (1 kHz and 12 kHz), which induced distinct localizations in the auditory cortex. The findings can be explained by the methodological limitations of LDF and/or neurovascular regulatory systems in the auditory cortex..
To explore the effects of acoustic and behavioral context on neuronal responses in the core of auditory cortex (fields A1 and R), two monkeys were trained on a go/no-go discrimination task in which they learned to respond selectively to a four-note target (S+) melody and withhold response to a variety of other non-target (S-) sounds.
Effects of center frequency on the binaural auditory filter in the human auditory cortex were examined using auditory-evoked magnetic fields.
Age-related changes in the effects of nitric oxide (NO) on neurons of the auditory cortex have not been determined.
Furthermore, when males were exposed to other males' songs, local estradiol levels also increased and testosterone levels dropped in a cortical/pallial auditory region that is analogous to mammalian auditory cortex.
Some neurons in auditory cortex respond to recent stimulus history by adapting their response functions to track stimulus statistics directly, as might be expected. In marmoset monkey auditory cortex, the latter type of adaptation appears to exist only in neurons tuned to stimulus intensity..
The superior temporal gyrus, which contains the auditory cortex, including the planum temporale, is the most consistently altered neocortical structure in schizophrenia (Shenton ME, Dickey CC, Frumin M, McCarley RW. These age-associated differences are reported in an adult population (age range 29-90 years) and were not found in the primary auditory cortex of Heschl's gyrus, indicating that they are selective to the more plastic regions of association cortex involved in cognition.
Facilitatory interactions were found in 46 of 264 (17%) neurons tuned in the echolocation range (25-60 kHz) in the auditory cortex of the pallid bat.
Specifically, the SA group showed significant enlargement of MMNm after training compared with the A group, reflecting greater enhancement of musical representations in auditory cortex after sensorimotor-auditory training compared with after mere auditory training. Thus, we have experimentally demonstrated that not only are sensorimotor and auditory systems connected, but also that sensorimotor-auditory training causes plastic reorganizational changes in the auditory cortex over and above changes introduced by auditory training alone..
Between the early and late auditory system, the role of primary auditory cortex (A1) is still debated.
Although animal and invasive human studies have consistently implicated the auditory cortex, prefrontal cortex and hippocampus in mediating the sensory gating response, localized activation in these structures has not always been reported during non-invasive imaging modalities. Results also indicated that the left auditory cortex may play a preferential role in determining the stimuli that should be inhibited (gated) or receive further processing due to novelty of information.
PURPOSE OF REVIEW: From the cochlea to associative auditory cortex, incoming acoustic data undergo a series of transformations that allow us to build up representations of the various sound sources present in the environment.
The results revealed that different temporal patterns of auditory stimuli were represented in different temporal features of BOLD responses in the bilateral auditory cortex, whereas different temporal patterns of tapping were reflected in contralateral primary motor cortex and the ipsilateral anterior cerebellum.
The frequency-intensity receptive fields (RF) of neurons in primary auditory cortex (AI) are heterogeneous.
We therefore investigated neuronal properties in slices of the auditory cortex (AC) of normal hearing mice using whole-cell patch-clamp recordings of pyramidal neurons in layers II/III, IV, V, and VI in the current- and voltage clamp mode.
High-density EEG and source modeling revealed principal activity from auditory cortex in normal hearing and early implanted children.
The MPL has afferent neuronal connections distinct from adjacent brain regions including major inputs from the auditory cortex, medial part of the medial geniculate body, superior colliculus, external and dorsal cortices of the inferior colliculus, periolivary area, lateral preoptic area, hypothalamic ventromedial nucleus, lateral and dorsal hypothalamic areas, subparafascicular and posterior intralaminar thalamic nuclei, periaqueductal gray, and cuneiform nucleus. In addition, injection of the anterograde tracer biotinylated dextran amine into the auditory cortex and the hypothalamic ventromedial nucleus confirmed projections from these areas to the distinct MPL.
STRFs for different stimulus densities were derived from multiple single-unit activity (MUA) and local field potentials (LFPs), simultaneously recorded in primary auditory cortex of cats. Plausibly, the over-representation may be a functional correlate of the periodic pattern of corticocortical connections observed along the tonotopic axis of cat auditory cortex..
Neurons in the Doppler-Shifted Constant Frequency processing (DSCF) area in the primary auditory cortex of mustached bats, Pteronotus parnellii, are multifunctional, responding both to echolocation and communication sounds.
Given that neural correlates of AVHs involve the auditory cortex, it is likely that those brain regions responsible for recognition of voice identity are invoked during AVHs.
Our results support the role of the right temporal lobe in musicogenic epilepsy and demonstrate that the cerebral areas activated during the period of strong emotion leading to the seizures encompass the auditory cortex activated by neutral music..
In the Attend Conjunction condition when the auditory but not the visual feature was a target there was an SN over auditory cortex, when the visual but not auditory stimulus was a target there was an SN over visual cortex, and when both auditory and visual stimuli were targets (i.e.
Functional magnetic resonance imaging has been used to investigate the signal representation in human auditory cortex for a sinusoidal signal in the presence of a noise masker. This interaction between S/N, overall level and perception is reflected by a spatial dissociation of the respective activation in auditory cortex. Brain regions mainly sensitive to level changes were found in various parts of the superior temporal lobes, including primary auditory cortex and Planum temporale, while those regions mainly sensitive to S/N changes were located at or close to lateral Heschl's gyrus.
These results suggest that pitch is processed differently in auditory cortex by 2-month-olds and 4-month-olds, and that a cortical change-detection mechanism for pitch discrimination similar to that of adults emerges between 2 and 4 months of age..
To identify the most stable reference gene in the auditory cortex and cochlea of young and old rats. mRNA levels of some common reference genes such as beta-actin, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), ubiquitin C, hypoxanthine phosphoribosyl-transferase and eukaryotic translation elongation factor (EF) were quantified in the auditory cortex and cochlea of young and old rats by quantitative RT-PCR, and then their stability was evaluated using GeNorm and Normfinder software. There were some variations in the expression of reference genes found in the auditory cortex and cochlea of rats, wherein EF and GAPDH were identified as the most stable reference genes in auditory cortex and cochlea, respectively. mRNA levels of Cu/Zn-superoxide dismutase (SOD), Mn-SOD, catalase and glutathione peroxidase in the auditory cortex and cochlea do not vary significantly in young and old rats, when they are normalized with EF or GAPDH, the valid reference genes, respectively. However, Cu/Zn-SOD and catalase levels differ significantly in the auditory cortex when they are normalized with beta-actin, an invalid reference gene, resulting in the misinterpretation of the target gene expression levels..
Given that serotonin (5-HT) is one such system, the present study was designed to specifically evaluate 5-HT tissue content as well as 5-HT(2A) receptor protein levels within the developing auditory cortex (AC).
The pathologies that affect higher levels of the auditory pathway, from the brainstem to the auditory cortex, might be the main sites of lesion in cases with only wave I developed.
To address these issues, neurophysiological recordings were made from the auditory cortex (AC) of awake rats using chronically implanted electrodes before and after acoustic overstimulation.
Animals exposed to noise trauma show augmented synchronous neural activity in tonotopically reorganized primary auditory cortex consequent on hearing loss.
In parallel, a significant increase was noted in NMDA receptor subunit NR2B protein expression in the auditory cortex. Furthermore, we found that auditory enrichment with music starting from PND 28 or 56 did not influence NR2B expression in the auditory cortex.
Such fast timing of multisensory interactions rules out the possibility of an origin in the polymodal areas mediated through back projections, but is rather in favor of heteromodal connections such as the direct projections observed in the monkey, from auditory areas (including the primary auditory cortex AI) directly to the primary visual cortex V1.
Induced oscillatory activity in the auditory cortex peaks at around 40 Hz in humans. In this study, using functional magnetic resonance imaging (fMRI) we estimated the influence of 40-Hz auditory stimulation on the coupling between auditory cortex and superior temporal sulcus (STS) and Crus II, using a dynamic causal model of the interactions between medial geniculate nuclei, auditory superior temporal gyrus (STG)/STS, and the cerebellar Crus II auditory region.
We report MEG evidence that the missing fundamental component of a complex auditory stimulus is recovered in auditory cortex within 100 ms post stimulus onset. CONCLUSIONS: Our findings suggest that listeners are reconstructing the inferred pitch by roughly 100 ms after stimulus onset and are consistent with previous electrophysiological research suggesting that the inferential pitch is perceived in early auditory cortex..
Increases in ECoG gamma power (70-100 Hz) were observed in response to hearing tones (primary auditory cortex), hearing words (posterior temporal and parietal cortex) and repeating words (lateral frontal and anterior parietal cortex).
Despite the fact that the Heschl gyrus (HG) is a crucial brain structure as it contains the primary auditory cortex (PAC), relatively few structural MRI studies have concentrated upon it.
RESULTS: Overt production of single monosyllables activated a network of brain regions, including left ventral premotor cortex, left posterior inferior frontal gyrus, bilateral supplementary motor area, sensorimotor cortex, auditory cortex, thalamus, and cerebellum.
In the superior temporal gyrus (STG), both left and right auditory cortex showed increased activation in the noise conditions relative to quiet, including the middle portion of STG (mSTG).
Several recent studies indicate that perceptual auditory object formation, or "streaming," may be based on neural activity within the auditory cortex and beyond [ 2, 3].
These results therefore demonstrate the presence of sensory gating for auditory inputs of the human voice in the primary auditory cortex and the auditory association area..
The auditory cortical areas examined included the anterior auditory field (AAF), primary auditory cortex (AI), dorsal zone (DZ), secondary auditory cortex (AII), field of the rostral suprasylvian sulcus (FRS), field anterior ectosylvian sulcus (FAES) and the posterior auditory field (PAF).
Both these types of personal information are encoded in characteristic acoustic feature patterns analyzed within the auditory cortex.
In auditory cortex, of the four tonotopically-organized regions, neuronal labeling was identified in the supragranular layers of the posterior auditory field (PAF). Little to no labeling was evident in the primary auditory cortex, the anterior auditory field, the ventral posterior auditory field or in the remaining six non-tonotopically organized regions of auditory cortex. Therefore, direct projections can be identified from tonotopically organized auditory cortex to the earliest stages of visual cortical processing..
Most prior lesion studies have demonstrated that the nodal point for decoding these prosodic emotion cues is mediated by unimodal auditory cortex in the right posterior lateral temporal lobe.
Whole head magnetoencephalographic (MEG) recordings were used to estimate the phase and amplitude behavior of sources in primary auditory cortex in both hemispheres of schizophrenic and comparison subjects. Schizophrenic subjects exhibit significant impairment of generation and phase locking of this activity in auditory cortex, suggesting an impairment of GABA-ergic inhibitory interneuronal modulation of pyramidal cell activity..
Previous studies in anesthetized animals reported that the primary auditory cortex (A1) showed homogenous phasic responses to FM tones, namely a transient response to a particular instantaneous frequency when FM sweeps traversed a neuron's tone-evoked receptive field (TRF).
Differences in 2-DG uptake were found between groups in the ipsilateral auditory cortex, basilar pontine nuclei, and inferior colliculus.
BACKGROUND: The mammalian auditory cortex can be subdivided into various fields characterized by neurophysiological and neuroarchitectural properties and by connections with different nuclei of the thalamus. Besides the primary auditory cortex, echolocating bats have cortical fields for the processing of temporal and spectral features of the echolocation pulses. This paper reports on location, neuroarchitecture and basic functional organization of the auditory cortex of the microchiropteran bat Phyllostomus discolor (family: Phyllostomidae). Cortical units were characterized and classified depending on their response properties such as best frequency, auditory threshold, first spike latency, response duration, width and shape of the frequency response area and binaural interactions.Based on neurophysiological and neuroanatomical criteria, the auditory cortex of P. CONCLUSION: The auditory cortex of P. discolor resembles the auditory cortex of other phyllostomid bats in size and basic functional organization. The tonotopically organized posterior ventral field might represent the primary auditory cortex and the tonotopically organized anterior ventral field seems to be similar to the anterior auditory field of other mammals.
Tinnitus-related activity leads to changes in tonotopic representation in auditory cortex. We also saw changes in the intensity dependence of the auditory N100 in tinnitus patients, supporting the idea that tinnitus reflects a reorganization of tonotopic maps in the auditory cortex.
When raised in a quiet environment, the rat primary auditory cortex (A1) has a well-defined 'critical period', lasting several days, for its representation of sound frequency.
Lateral Heschl's gyrus (HG), a subdivision of the human auditory cortex, is commonly believed to represent a general "pitch center," responding selectively to the pitch of sounds, irrespective of their spectral characteristics.
The primary auditory cortex is now known to be involved in learning and memory, as well as auditory perception. As previous research has focused on tonal frequency, less is known about how learning might alter temporal parameters of response in the auditory cortex. Following training, neuronal responses to white noise and a broad spectrum of tones were determined across the primary auditory cortex in a terminal experiment with subjects under general anesthesia. The facilitation of temporal processing suggests that avoidance learning may increase synaptic strength either within the auditory cortex, in the subcortical auditory system, or both..
Frequency change detection in human auditory cortex. Human posterior auditory cortex gates novel sounds to consciousness.
In this study, we show that long-term adaptation with a time course of tens of minutes is detectable in anesthetized adult cat auditory cortex after a few minutes of listening to random-frequency tone pips. Our findings suggest that low stimulus rates may produce a specific acoustic environment that shapes the primary auditory cortex through very different processing than for spectro-temporally more dense and complex sounds..
The development of the nonspecific changes was scarcely affected by atropine (a muscarinic cholinergic receptor antagonist) and mecamylamine (a nicotinic cholinergic receptor antagonist) applied to the auditory cortex and by muscimol (a GABAA-receptor agonist) applied to the somatosensory cortex.
OBJECTIVES: In general, auditory cortex on the left side of the brain is specialized for processing of acoustic stimuli with complex temporal structure including speech, and the right hemisphere is primary for spectral processing and favors tonal stimuli and music.
OBJECTIVE: To evaluate the response of the human auditory cortex to the temporal amplitude-envelope of speech. Human event-related potentials were recorded to six different sentences and the sources of these potentials in the auditory cortex were determined. CONCLUSIONS: These results show that the human auditory cortex either directly follows the speech envelope or consistently reacts to changes in this envelope.
In three MEG experiments, we characterize the properties of MIS by examining the M100 response from the auditory cortex to a simple tone triggered by a button press.
Scientific evidence has proved reorganisation processes in the auditory cortex after sensorineural hearing loss and overstimulation of certain tonotopic cortical areas, as we see in auditory conditioning techniques.
We show here that multisensory integration of auditory and visual looming signals may be mediated by functional interactions between auditory cortex and the superior temporal sulcus, two areas involved in integrating behaviorally relevant auditory-visual signals.
While it is essential to determine a neuron's receptive field, it remains unclear which features of the acoustic environment are specifically represented by neurons in the primary auditory cortex (AI).
and Nagel and Doupe adapt new computational methods to map the spectrotemporal response fields of neurons in the auditory cortex. The papers take different but complementary approaches to apply theoretical techniques to classical methods of receptive field mapping and, in doing so, provide exciting new insights into the way in which sounds are processed in the auditory cortex..
tones), adults diagnosed with dyslexia showed greater primary auditory cortex activity (BA 42; tones > pseudowords) than normal readers.
Functional imaging studies showed the auditory cortex, the limbic system and language areas, both motor and sensory, to be active during auditory hallucinations. The activity of language areas during hallucinations would conform to such a model while the activity in auditory cortex might explain why auditory hallucinations are often so vivid and real for the patients suffering from them. While the neurophysiological models of hallucination are thus already rather refined, the attempt at suppressing auditory cortex activity with repetitive transcranial magnetic stimulation in order to alleviate treatment-resistant acoustic hallucinations, which is based on the functional imaging findings, still needs further study.
We have developed a preparation for chronic, multi-electrode recordings in the auditory cortex of marmoset monkeys, small primates, as well as techniques for neurophysiological recordings when the animals are free-roaming while singly caged in the environment of the monkey colony.
The staining densities of NADPH-d-positive neurons in the inferior colliculus, the auditory cortex, and the visual cortex were significantly greater in aged compared with younger rats (p<0.05)..
Here we report on the responses of neurons in field L, the primary auditory cortex homolog in songbirds, which allow for accurate discrimination of birdsongs that is invariant to intensity changes over a large range.
This article synthesizes recent studies from our laboratory regarding neural representations of time-varying signals in auditory cortex and thalamus in awake marmoset monkeys. Findings from these studies show that 1) the primary auditory cortex (A1) uses a temporal representation to encode slowly varying acoustic signals and a firing rate-based representation to encode rapidly changing acoustic signals, 2) the dual temporal-rate representations in A1 represent a progressive transformation from the auditory thalamus, 3) firing rate-based representations in the form of monotonic rate-code are also found to encode slow temporal repetitions in the range of acoustic flutter in A1 and more prevalently in the cortical fields rostral to A1 in the core region of marmoset auditory cortex, suggesting further temporal-to-rate transformations in higher cortical areas. These findings indicate that the auditory cortex forms internal representations of temporal characteristics of sounds that are no longer faithful replicas of their acoustic structures. We suggest that such transformations are necessary for the auditory cortex to perform a wide range of functions including sound segmentation, object processing and multi-sensory integration..
We also found attentional modulation of the putative primary auditory cortex (A1) activity at 30-50 ms.
Under high effort conditions we were able to detect circumscribed BOLD activations specific to the N1 potential in the ACC (t=4.7) and the auditory cortex (t=6.1).
A neural correlate of the psychophysical roughness sensitivity has been described in the auditory cortex of the bat Phyllostomus discolor. In contrast to the auditory cortex experiments, the responses of many units in the inferior colliculus decreased with increasing echo roughness.
We combined magnetoencephalography with simultaneous behavioral measures in humans to investigate neural correlates of informational masking and auditory perceptual awareness in the auditory cortex. In contrast, both detected and undetected targets produced equally robust auditory middle-latency, steady-state responses, presumably from the primary auditory cortex. These findings indicate that neural correlates of auditory awareness in informational masking emerge between early and late stages of processing within the auditory cortex..
Comparison between the statistical maps obtained from MRI scans of the fetuses with those obtained from adults, made it possible to confirm our hypothesis, that there is brain activation in the primary auditory cortex in response to sound.
We used whole-head magnetoencephalograpy (MEG) to record changes in neuromagnetic N100m responses generated in the left and right auditory cortex as a function of the match between visual and auditory speech signals.
It was reported earlier that specific alterations of this activity in the domain of seconds (0.1-0.5 Hz) occurred in the medial geniculate nucleus (MGN) and primary auditory cortex (A1) in response to acoustic stimuli.
Experiment 2 sought correlates of harmonic fusion in single neurons of primary auditory cortex and anterior auditory field, by comparing responses to harmonic tones with those to inharmonic tones in the awake alert ferret.
The core region of primate auditory cortex contains a primary and two primary-like fields (AI, primary auditory cortex; R, rostral field; RT, rostrotemporal field).
Regardless of the mode of salicylate application, a common pattern became evident: 1) BDNF mRNA expression was increased in the spiral ganglion neurons of the cochlea; and 2) Arg3.1 expression was significantly reduced in the auditory cortex. These findings support Arg3.1 and BDNF as markers for activity changes in the auditory system and suggest a role of GABAergic inhibition of cochlear neurons in the modulation of Arg3.1 plasticity changes in the auditory cortex and tinnitus perception..
The present study addresses this issue by simultaneous extracellular action potential and local field potential (LFP) recordings from primary auditory cortex of ketamine-anesthetized cats during spindling activity.
Recent neuroimaging and behavioural evidence suggest a reciprocal relationship between auditory cortex response to external sounds versus that induced by AHs. METHODS: The mismatch negativity (MMN), a well established event-related potential (ERP) index of auditory cortex function, was assessed in 12 hallucinating patients (HP), 12 non-hallucinating patients (NP) and 12 healthy controls (HC).
(a) Both speech and nonspeech motion yielded a consistent attenuation of the auditory M50 field, suggesting a visually induced "preparatory baseline shift" at the level of the auditory cortex.
The auditory center in the cerebrum, the auditory cortex, consists of multiple interconnected areas. The auditory cortex of the mustached bat consists of at least nine areas, including the frequency modulation-frequency modulation (FF) and dorsal fringe (DF) areas.
Moreover, an avian brain nucleus that is analogous to the mammalian secondary auditory cortex (the caudo-medial nidopallium, or NCM) has recently emerged as a plausible site for sensory representation of birdsong, and appears as a well positioned brain region for categorization of songs.
Age-related postsynaptic GABA(A)R changes in IC and primary auditory cortex (A1) involve changes in the subunit makeup of GABA(A)Rs.
Age-related changes in parvalbumin immunoreactivity were investigated in the inferior colliculus (IC), medial geniculate body (MGB) and auditory cortex (AC) in two rat strains, normally aging Long-Evans (LE) and fast aging Fischer 344 (F344). The results demonstrate that the changes in PV-immunoreactivity are strain-dependent with an increase in the number of PV-immunoreactive (PV-ir) neurons occurring in the inferior colliculus of old LE rats and a pronounced decline in the number of PV-ir neurons appearing in the auditory cortex of aged F344 animals. The loss of PV-ir neurons in the auditory cortex of Fischer 344 rats with aging may contribute to the substantial deterioration of hearing function in this strain..
In this article the neuronal mechanisms underlying the processing of communication signals in the higher centers of the auditory system - inferior colliculus (IC), medial geniculate body (MGB) and auditory cortex (AC) - are reviewed, with particular attention to the guinea pig.
We focused on caudomedial nidopallium (NCM), an area analogous to parts of the mammalian auditory cortex with selective responses to birdsong.
The aim of this study was to reveal the existence of similar neuronal properties within the human auditory cortex. Our findings highlight for the first time the existence of long-term spoken word memory traces within the human auditory cortex.
Topographic and tomographic analyses reveal the involvement of the auditory cortex in the processing of contingency violations.
Auditory-evoked potentials were recorded from the primary auditory cortex and vertex location (AI/Vx-AEPs).
Besides the intensity and frequency of an auditory stimulus, the length of time that precedes the stimulation is an important factor that determines the magnitude of early evoked neural responses in the auditory cortex. Here we used chinchillas to demonstrate that the length of the silent period before the presentation of an auditory stimulus is a critical factor that modifies late oscillatory responses in the auditory cortex. We used tetrodes to record local-field potential (LFP) signals from the left auditory cortex of ten animals while they were stimulated with clicks, tones or noise bursts delivered at different rates and intensity levels. We found that the incidence of oscillatory activity in the auditory cortex of anesthetized chinchillas is dependent on the period of silence before stimulation and on the intensity of the auditory stimulus.
The auditory evoked potentials were recorded in the epidura above the primary auditory cortex of male Wistar rats whereas extracellular serotonin levels in the primary auditory cortex were measured by in vivo microdialysis before and after i.p. At baseline, the correlation of coefficients between the LDAEP, especially of the N1 component, and extracellular serotonin levels in the primary auditory cortex was negative.
To address these important issues, we assessed whether intact rats, as well as those with induced developmental cortical disruptions (microgyria) could resolve silent gaps of 20-100 ms in duration when embedded in white noise, during functional deactivation of auditory cortex.
An extensive corticofugal system extends from the auditory cortex toward subcortical nuclei along the auditory pathway.
Microelectrode recordings from the human auditory cortex suggest that the tuning of individual neurons can account for sound frequency discrimination thresholds and that this tuning varies in a context-dependent fashion with the type of sound used to measure it..
This effect was taken as an example for plasticity in the auditory cortex elicited by training. These results indicate that the effect of music expertise, which was traced by current density mapping to the auditory cortex, is not primarily caused by selective attention, and it supports the view that increased AEPs on tones in musicians reflect an enlarged neuronal representation for specific sound features of these tones.
Previous studies have demonstrated the interaction of auditory and visual streams at the auditory cortex level, but the importance of these interactions for the qualitative perception change remained unclear because the change could result from interactions at higher processing levels as well. In our electroencephalogram experiment, we combined the McGurk effect with mismatch negativity (MMN), a response that is elicited in the auditory cortex at a latency of 100-250 msec by any above-threshold change in a sequence of repetitive sounds. Deviant stimuli in the unisensory acoustic stimulus sequence elicited a typical MMN, reflecting discrimination of acoustic features in the auditory cortex. Importantly, such deviants did not elicit MMN, indicating that the auditory cortex failed to discriminate between the acoustic stimuli. Our findings show that visual stream can qualitatively change the auditory percept at the auditory cortex level, profoundly influencing the auditory cortex mechanisms underlying early sound discrimination..
OBJECTIVE: The human auditory cortex codes speech temporally according to sequential acoustico-phonetic cues like the voice onset time (VOT). RESULTS: Controls demonstrated L>R RC source probe amplitude asymmetry in the auditory cortex.
Our data demonstrate that the temporal dynamics and response polarity of the neural temporal-edge-detection processes depend in specific ways on the generalized nature of the edge (the context preceding and following the transition) and suggest that distinct neural substrates in core and non-core auditory cortex are recruited depending on the kind of computation (discovery of a violation of regularity, vs.
Previous work in humans and other animals has demonstrated that the auditory cortex is largely suppressed during speaking or vocalizing. Here we show that neurons in the auditory cortex of marmoset monkeys (Callithrix jacchus) are sensitive to auditory feedback during vocal production, and that changes in the feedback alter the coding properties of these neurons.
Neurons in the auditory cortex of anesthetized guinea pigs phase lock to the envelope of sine-modulated electric pulse trains presented through a cochlear implant. The present study used that animal model to quantify the effects of carrier pulse rate, electrode configuration, current level, and modulator wave shape on transmission of temporal information from a cochlear implant to the auditory cortex.
Group-specific activations were found in the extrastriate cortex and the auditory cortex for congenitally blind humans and in the precuneus and the presupplementary motor area for sighted humans.
BACKGROUND: The superior temporal gyrus (STG), which encompasses the primary auditory cortex, is believed to be a major anatomical substrate for speech, language and communication.
Significant activation of the auditory cortex in the middle temporal gyrus was observed during the maintenance phase, which, together with the inferior frontal gyrus activation might underly the maintenance of phonological information..
We tentatively ascribe the deficit observed in the gap-detection test to a dysfunctioning of the auditory cortex, impairing its ability to track rapid fluctuations in sound intensity.
Hemispheric asymmetries of speech and music processing might arise from more basic specializations of left and right auditory cortex (AC).
This methodology, although validated in the auditory cortex activation, maintains a general applicability to any cortical fMRI study, as the basic concepts on which it relies on are not limited to this cortical region.
To test the hypothesis that multisensory responses in auditory cortex are influenced by visual inputs from the superior temporal sulcus (STS), an association area, we recorded local field potentials and single neurons from both structures concurrently in monkeys. The functional interactions between the auditory cortex and the STS, as measured by spectral analyses, increased in strength during presentations of dynamic faces and voices relative to either communication signal alone. A similar analysis of functional interactions within the auditory cortex revealed no similar interactions as a function of stimulus condition, nor did a control condition in which the dynamic face was replaced with a dynamic disk mimicking mouth movements. Single neuron data revealed that these intercortical interactions were reflected in the spiking output of auditory cortex and that such spiking output was coordinated with oscillations in the STS. Our data suggest that the integration of faces and voices is mediated at least in part by neuronal cooperation between auditory cortex and the STS and that interactions between these structures are a fast and efficient way of dealing with the multisensory communication signals..
We report on a young woman operated for a ganglioglioma involving the right auditory cortex (AC), presenting with auditory seizures.
In this study, we tested the hypothesis that primary auditory cortex (A1) neurons use temporal precision on the order of 1-10 ms to represent speech sounds shifted into the rat hearing range. This result suggests that spike timing contributes to the auditory cortex representation of consonant sounds..
These findings suggest that the auditory cortex of macaque monkeys encodes temporally modulated sounds similar to the auditory cortex of other mammals.
The whole approach to these alterations needs not only peripheral (cochlear) or brainstem studies but also an analysis of the auditory cortex.
We examined effects of the task of categorizing linear frequency-modulated (FM) sweeps into rising and falling on auditory evoked magnetic fields (AEFs) from the human auditory cortex, recorded by means of whole-head magnetoencephalography. These results add to other imaging and lesion studies which suggest a specific role of the right auditory cortex in identifying FM sweep direction and thus in categorizing FM sweeps into rising and falling..
Electrical stimulation of the auditory cortex (AC) causes both facilitatory and inhibitory effects on the medial geniculate body (MGB).
Validating behavioral evidence that gesture affects speech perception, bilateral nonprimary auditory cortex showed greater activity when speech was accompanied by beat gesture than when speech was presented alone.
We examined the intrinsic functional connectivity (fcMRI) of putative primary auditory cortex in 32 young adults during resting state scanning. fcMRI analysis revealed that although overall coupling between the auditory and visual cortex was significantly reduced when subjects performed a visual perception task, coupling between the anterior calcarine cortex and auditory cortex was not disrupted. These results suggest that primary auditory cortex has a functionally distinct relationship with the anterior visual cortex, which is known to represent the peripheral visual field.
Over all, in the 70 subjects examined, this research's results allow us to conclude that: the use of open fitting ear-moulds improves the quality of the natural sound of one's own voice, the natural quality of sounds, and the hearing of speech in the presence of other noises, while reducing irritation of the auditory cortex..
We used reversible cooling deactivation to investigate whether the individual regions in cat nonprimary auditory cortex that are responsible for processing the pattern of an acoustic stimulus or localizing a sound in space could be doubly dissociated in the same animal. These findings support a model of cortical organization that proposes that identifying an acoustic stimulus ('what') and its spatial location ('where') are processed in separate streams in auditory cortex..
Neurons responsive to visual stimulation have now been described in the auditory cortex of various species, but their functions are largely unknown. These data suggest that visual inputs to auditory cortex can enhance spatial processing in the presence of multisensory cues and could therefore potentially underlie visual influences on auditory localization..
We have shown previously that auditory experience regulates the maturation of excitatory synapses in the auditory cortex (ACx).
These results were obtained using nonspeech stimuli, and it is not known whether right-hemisphere auditory cortex is dominant for coding the slow temporal features in speech known as the speech envelope. Right-hemisphere auditory cortex was 100% more accurate in following contours of the speech envelope and had a 33% larger response magnitude while following the envelope compared with the left hemisphere. Results provide evidence that the right hemisphere plays a specific and important role in speech processing and support the hypothesis that acoustic processing of speech involves the decomposition of the signal into constituent temporal features by rate-specialized neurons in right- and left-hemisphere auditory cortex..
Here, we differentiate them by analyzing the time course of their action potentials (APs) and characterizing their receptive field properties in auditory cortex. To compare these neuronal classes, we stimulated cat primary auditory cortex neurons with a dynamic moving ripple stimulus and constructed single-unit spectrotemporal receptive fields (STRFs) and their associated nonlinearities.
In the auditory pathway, the highest expression of nitric oxide synthase is found in the inferior colliculus (IC), an important center for the convergence of parallel ascending pathways traveling in the brainstem, and descending projections from the auditory cortex.
Here, in vivo whole-cell recordings from neurons in the rat primary auditory cortex revealed that the frequency tuning curve of inhibitory input was broader than that of excitatory input.
Activation of the primary auditory cortex was detected in 9 of 16 cases when auditory sensations during ECS occurred, and tended to be more bilaterally distributed in CI candidates than in normal-hearing controls.
The function of the profuse descending innervation from the auditory cortex is largely unknown; however, recent studies have demonstrated that focal stimulation of auditory cortex effects frequency tuning curves, duration tuning, and other auditory parameters in the inferior colliculus. Here we demonstrate that, in an anesthetized guinea pig, nonfocal deactivation of the auditory cortex alters the sensitivity of populations of neurons in the inferior colliculus (IC) to one of the major cues for the localization of sound in space, interaural level differences (ILDs). Eight percent of the cells became unresponsive after deactivation of the auditory cortex.
Is sound location represented in the auditory cortex of humans and monkeys? Human neuroimaging experiments have had only mixed success at demonstrating sound location sensitivity in primary auditory cortex. This suggests that the weakness of the evidence for spatial sensitivity in human neuroimaging studies of auditory cortex may be attributable to limited lateralization at the population level, despite what may be considerable spatial sensitivity in individual neurons..
To test this possibility, we recorded neuronal activity along the AES, together with a sample of neurons from primary auditory cortex (A1) of cats in response to pure tones and to virtual acoustic space stimuli.
Plastic reorganization of frequency response areas and tonotopic organization does not seem to occur at the midbrain level following acoustic trauma in adult animals in a manner similar to that previously shown in the auditory cortex.
Induced microgyria located in parietal somatosensory cortex have been linked to reduced behavioral detection of rapid sound transitions and altered spectral processing in primary auditory cortex (A1). Here we asked whether belt auditory cortex function would be similarly altered in rats with S1 microgyria (MG+). These data suggest that VAF belt auditory cortex is more vulnerable than A1 to early postnatal induction of microgyria in neighboring somatosensory cortex..
Animals were then anesthetized, and tone-evoked local field potentials (LFPs) recorded in layer 4 of auditory cortex (ACx) before and after a test dose of nicotine (0.7mg/kg, s.c.) or saline.
This review focuses on NCM,an auditory area previously proposed to be analogous to parts of the primary auditory cortex in mammals.Stimulation of songbirds with auditory stimuli drives vigorous electrophysiological responses and the expression of several activity-regulated genes in NCM.Interestingly,NCM neurons are tuned to species-specific songs and undergo some forms of experience-dependent plasticity in-vivo .These activity-dependent changes may underlie long-term modifications in the functional performance of NCM and constitute a potential neural substrate for auditory discrimination.We end this review by discussing evidence that suggests that NCM may be a site of auditory memory formation and/or storage..
As spontaneous activity within all key structures of the central auditory pathway could play an important role in tinnitus generation, the present study investigated direct effects of salicylate superfusion on the spontaneous activity of the deafferented cochlear nucleus (CN), medial geniculate body (MGB), and auditory cortex (AC) in brain slices.
The responses of the inferior colliculus and the auditory cortex to the stimuli were measured.
This study evaluated the central representation of amplitude modulation in the form of phase-locked firing of neurons in the auditory cortex.
Here we show a putative level-invariant representation of sounds by populations of neurons in primary auditory cortex (A1) that may provide a neural basis for the behavioral observations.
Language processing involves multiple neuronal structures in the human auditory cortex. Although a variety of neuroimaging and mapping techniques have been implemented to better understand language processing at the level of the auditory cortex, much is unknown regarding how and by what pathways these structures interact during essential tasks such as sentence comprehension. In this study, the effective and structural connectivity at the level of the auditory cortex were investigated. Once BOLD activation maps were obtained, the effective connectivity between primary auditory cortex and the surrounding auditory regions on the supratemporal plane and superior temporal gyrus (STG) were investigated using Granger causality mapping (GCM). Effective connectivity was observed between the primary auditory cortex and (1) the lateral planum polare and anterior STG, and (2) the lateral planum temporale and posterior STG. The effective and structural connectivity results of the present study provide further insight as to how auditory stimuli (i.e., human language) is processed at the level of the auditory cortex. Furthermore, combining BOLD fMRI-based GCM and DTPM analysis could provide a novel means to study effective and structural connectivity not only in the auditory cortex, but also in other cortical regions..
These patterns suggested different levels of complexity in processing of auditory spatial information, starting with simple left/right discrimination in the regions surrounding the primary auditory cortex, while the integration of information on hemispace and eccentricity of sound may take place at later stages.
In the context of vocal production, a forward model, in which a prediction of action consequence (corollary discharge) is created, has been proposed to explain the dampened activity of the auditory cortex while producing self-generated vocal sounds.
In this experiment, gap-evoked responses in a low-frequency band (0.5-8 kHz) were recorded in the inferior colliculus (IC) and auditory cortex (AC) of guinea pigs through implanted electrodes, before and after a slopping high-frequency hearing loss, which was induced by over-stimulation using a 12-kHz-tone.
Pairing a tone with NB stimulation (NBstm) to alter cortical state induces both associative specific tuning plasticity in the primary auditory cortex (A1) and associative specific auditory behavioral memory.
The primate auditory cortex contains three interconnected regions (core, belt, parabelt), which are further subdivided into discrete areas. The caudomedial area (CM) is one of about seven areas in the belt region that has been the subject of recent anatomical and physiological studies conducted to define the functional organization of auditory cortex. This suggests that CM could be engaged in processing that requires relatively precise temporal envelope discrimination, and supports the hypothesis that CM is positioned at an early stage of processing in the auditory cortex of primates..
Here, we show that altered developmental experience with FM sweeps used in echolocation by the pallid bat leads to either a loss of sideband inhibition or millisecond delays in the timing of inhibitory inputs, both of which lead to a reduction in rate and direction selectivity in auditory cortex.
Here, we show how an early epoch of exposure to structured noise influences temporal processing in the rat primary auditory cortex documented immediately after exposure and again in adulthood.
By means of magnetoencephalography (MEG), we investigated event-related synchronization and desynchronization (ERS/ERD) in auditory cortex activity, recorded from twelve children aged four to six years, while they passively listened to a violin tone and a noise-burst stimulus. The left auditory cortex showed a larger and longer-lasting upper alpha ERD than did the right auditory cortex, likely reflecting hemispheric differences in maturational stages of neural oscillatory mechanisms..
These findings support the prediction that reduced size and asymmetry in temporal lobe auditory cortex and cerebellum may not be specific risk factors for schizophrenia but for cognitive deficits that characterize a broad spectrum of developmental disorders..
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