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At least 1,153 records · Page 64Linked to original sources
PubMed2000

Characteristics of reliable tone-evoked oscillations in the rat thalamo-cortical auditory system.

Tone-evoked oscillations were studied from simultaneous recordings collected in the auditory cortex, auditory thalamus and auditory sector of the reticular nucleus in urethane anesthetized rats. These oscillations were precisely time-locked to tone onset and were easily observed on peristimulus time histograms (PSTHs). Visual inspection of PSTHs and rasters led us to distinguish between 'reliable' oscillations (which exhibited oscillatory patterns in more than 50% of the trials) and 'labile' oscillations (which exhibited oscillations in less than 50% of the trials). Systematic quantification of oscillations based on several indices derived from power spectra confirmed this distinction. 'Reliable' stimulus-locked oscillations were observed in 51/184 (28%) of the recordings from auditory cortex, 9/55 (17%) of the recordings from auditory thalamus and 11/26 (42%) of the recordings from the auditory sector of the reticular nucleus. The frequency range of these oscillations was the same in the three structures (5-14 Hz). Within the same animal, when one electrode exhibited oscillations, there was a high probability of detecting similar oscillations from electrodes located in the same structure, but not from electrodes located in the other structures. These oscillations were observed for pure tone frequency (or for clicks) whatever the tone duration (1 s, 100 ms, 10 ms). The inter-tone interval (ITI) was found to be the critical factor controlling the occurrence of these oscillations: they were present for ITIs of 2 s or longer, but were absent for ITIs of 1 s or less. In contrast, the occurrence of the oscillations was a function neither of the strength of the 'on' evoked response nor of the animal's temperature. However, lowering the animal's temperature from 37-38 degrees C to 35-36 degrees C systematically led to a decrease in the frequency and an increase in the duration of the tone-evoked oscillations. These results suggest that, even in well defined conditions (temperature, EEG, ITI, level of anesthesia), the oscillations triggered by presentation of the same stimulus can be stable or unstable. This temporal instability of stimulus-evoked oscillations has to be taken into account before stating percentages of oscillations in a given brain structure. They also suggest that some general factors such as the animals temperature or the inter-stimulus interval can considerably affect their characteristics and/or their occurrence.

Acoustic Stimulation↗
PubMed2001

Plasticity in the adult human central auditory system: evidence from late-onset profound unilateral deafness.

Experience-related changes in central nervous system (CNS) activity have been observed in the adult brain of many mammalian species, including humans. In humans, late-onset profound unilateral deafness creates an opportunity to study plasticity in the adult CNS consequent to monaural auditory deprivation. CNS activity was assessed by measuring long-latency auditory evoked potentials (AEPs) recorded from teens and adults with late-onset (post-childhood) profound unilateral deafness. Compared to monaurally stimulated normal-hearing subjects, the AEPs recorded from central electrode sites located over auditory cortical areas showed significant increases in inter-hemispheric waveform cross-correlation coefficients, and in inter-hemispheric AEP peak amplitude correlations. These increases provide evidence of substantial changes from the normal pattern of asymmetrical (contralateral > ipsilateral amplitude) and asynchronous (contralateral earlier than ipsilateral) central auditory system activation in the normal-hearing population to a much more symmetrical and synchronous activation in the unilaterally deaf. These cross-sectional analyses of AEP data recorded from the unilaterally deaf also suggest that the changes in cortical activity occur gradually and continue for at least 2 years after the onset of hearing loss. Analyses of peak amplitude correlations suggest that the increased inter-hemispheric symmetry may be a consequence of changes in the generators producing the N (approximately 100 ms peak latency) potential. These experience-related changes in central auditory system activity following late-onset profound unilateral deafness thus provide evidence of the presence and the time course of auditory system plasticity in the adult brain.

Adolescent↗
PubMed2001

Auditory nerve fiber differences in the normal and neurofilament deficient Japanese quail.

A primary axonal disease affecting the central and peripheral nervous system was discovered in a mutant strain of the Japanese quail, named quiver (Quv). We have previously demonstrated altered auditory evoked potentials in the neurofilament (NF) deficient quail. In this current study we attempt to find relationships between the auditory evoked potential results and the histo-pathological abnormalities of the auditory neurons. No abnormalities in the external auditory meatus and tympanic cavity were observed in either Quv or control quails and the ganglion cell bodies and their nuclei appeared normal by light microscopy. The myelin staining pattern was found to be similar in both strains with hematoxylin and eosin and Klüver-Barrera staining. The frequency histograms of fiber and axonal diameters of myelinated fibers showed an unimodal pattern in both strains. In Quv quails myelinated fibers and their axoplasm were smaller in diameter than in controls resulting in smaller neural tissue mass. In electron microscopic observation the axons of the Quv quail were composed of mitochondria and microtubules and smooth endoplasmic reticuli. In Quv quail electron micrographs of cochlear nerve myelinated fibers NFs were not seen in the axons and the neuronal cell bodies. Our current findings indicate that the previously reported reduction of conduction velocity of auditory evoked potentials may be due to smaller fiber and/or axonal diameter. The g-ratio, myelin thickness and fiber circularity were found to be the same for both strains. In conclusion, loss of axonal cytoskeletal elements (NFs) correlates well with our electrophysiological findings. Reduced conduction velocity and severely distorted auditory evoked potentials in NF deficient quails seem to be primarily due to axonal hypotrophy.

Animals↗
PubMed2004

Immunocytochemical distribution of Met-enkephalin-Arg6-Gly7-Leu8 (Met-8) in the auditory system of the rat.

Methionine-enkephalin-Arg(6)-Gly(7)-Leu(8) (Met(8)) is known to act as a neurotransmitter or neuromodulator and it has been implicated in pain, cardiovascular and motor mechanisms, but its role in audition is currently unknown. In the present study we have applied an immunocytochemical technique and describe the distribution of cell bodies and fibers containing Met(8) in the auditory pathway of the rat. The main finding is that we found either Met(8)-immunoreactive fibers or cell bodies or both in virtually all nuclei of the rat auditory system except for the medial superior olive and the ventral division of the medial geniculate body in which we did not find any immunoreactivity for Met(8). This suggests that the neuropeptide Met(8) is widely distributed throughout the auditory system of the rat. Our results suggest that Met(8) could play at least two roles in hearing. It seems to be involved in the processing of the descending auditory pathway, and it may be implicated in the multisensory integration of auditory information that takes place in the non-lemniscal auditory pathway.

Animals↗
PubMed1997

Histological and physiological effects of the central auditory prosthesis: surface versus penetrating electrodes.

To rehabilitate profoundly deaf patients who are not suitable for cochlear implants, central auditory prostheses have been implanted. To compare two possible electrode configurations - penetrating and surface ones - electrical stimulation of the cochlear nucleus with both types of arrays was tested on guinea pigs and cats. Electrophysiological, autoradiographic and histological measures were used to study effects of the central auditory prostheses on the auditory pathway. The results showed that a successful electrically evoked auditory brainstem response could be recorded with both surface and penetrating electrodes in cats and guinea pigs. In guinea pigs the penetrating electrodes had advantages over surface arrays in the sense of lower thresholds and wider dynamic ranges. In cats penetrating electrodes showed lower thresholds than surface ones. In cats and guinea pigs stimulated with either surface or penetrating electrodes, evoked 2-deoxyglucose (2-DG) label was found in the auditory pathway from the cochlear nucleus to the inferior colliculus. No non-auditory tissues were found with evoked 2-DG label. Histological results showed that in subdivisions of the guinea pig cochlear nucleus stimulated with penetrating electrodes the neurone density was decreased, and the mean soma area was increased compared with the control side. In the cat, penetrating electrodes were associated only with increased mean soma area in parts of the stimulated cochlear nucleus. These results suggest that the physiological advantages of penetrating electrodes over surface ones were achieved with some trade-off in safety, especially in the guinea pig.

Animals↗
PubMedDate not supplied

The effects of early lead exposure on auditory function in rhesus monkeys.

Thirty-one female rhesus monkeys were randomly assigned to three lead exposure conditions (none, birth to 1 year, and birth to 2 years). Blood lead levels were maintained at 35-40 microg/dl beginning shortly after birth and continuing for 1 or 2 years postnatally. Auditory function was assessed in these monkeys at least 1 year after exposure to lead. The outcome measures included tympanometry to assess middle ear function, otoacoustic emissions (OAEs) to assess cochlear function, and auditory brainstem-evoked responses (ABRs) to assess the auditory nerve and brainstem pathways. There were no significant differences among the three experimental groups for any of the tympanometric variables measured suggesting no effect of lead exposure on middle ear function. Suprathreshold and threshold distortion product OAEs (DPOAEs) were comparable among the three groups. Finally, the auditory-evoked response at levels from the auditory nerve to the cerebral cortex did not significantly differ as a function of lead exposure. The lead exposure in this study had little effect on auditory function.

Acoustic Impedance Tests↗
PubMed2002

The effects of noise on the auditory sensitivity of the bluegill sunfish, Lepomis macrochirus.

As concerns about the effects of underwater anthropogenic noises on the auditory function of organisms increases, it is imperative to assess if all organisms are equally affected by the same noise source. Consequently, auditory capabilities of an organism need to be evaluated and compared interspecifically. Teleost fishes provide excellent models to examine these issues due to their diversity of hearing capabilities. Broadly, fishes can be categorized as hearing specialists (broad hearing frequency range with low auditory thresholds) or hearing generalists (narrower frequency range with higher auditory thresholds). The goal of this study was to examine the immediate effects of white noise exposure (0.3-2.0 kHz, 142 dB re: 1 microPa) and recovery after exposure (1-6 days) on a hearing generalist fish, bluegill sunfish (Lepomis macrochirus). Noise exposure resulted in only a slight, but not statistically significant, elevation in auditory threshold compared to fish not exposed to noise. In combination with results from our previous studies examining effects of noise on a hearing specialist fish, the fathead minnow (Pimephales promelas), this study provides evidence supporting the hypothesis that fish's auditory thresholds can be differentially affected by noise exposure.

Animals↗
PubMed2002

Temporal integration: intentional sound discrimination does not modulate stimulus-driven processes in auditory event synthesis.

OBJECTIVE: Our previous study showed that the auditory context could influence whether two successive acoustic changes occurring within the temporal integration window (approximately 200ms) were pre-attentively encoded as a single auditory event or as two discrete events (Cogn Brain Res 12 (2001) 431). The aim of the current study was to assess whether top-down processes could influence the stimulus-driven processes in determining what constitutes an auditory event. METHODS: Electroencepholagram (EEG) was recorded from 11 scalp electrodes to frequently occurring standard and infrequently occurring deviant sounds. Within the stimulus blocks, deviants either occurred only in pairs (successive feature changes) or both singly and in pairs. Event-related potential indices of change and target detection, the mismatch negativity (MMN) and the N2b component, respectively, were compared with the simultaneously measured performance in discriminating the deviants. RESULTS: Even though subjects could voluntarily distinguish the two successive auditory feature changes from each other, which was also indicated by the elicitation of the N2b target-detection response, top-down processes did not modify the event organization reflected by the MMN response. CONCLUSIONS: Top-down processes can extract elemental auditory information from a single integrated acoustic event, but the extraction occurs at a later processing stage than the one whose outcome is indexed by MMN. SIGNIFICANCE: Initial processes of auditory event-formation are fully governed by the context within which the sounds occur. Perception of the deviants as two separate sound events (the top-down effects) did not change the initial neural representation of the same deviants as one event (indexed by the MMN), without a corresponding change in the stimulus-driven sound organization.

Acoustic Stimulation↗
PubMed2004

Magnetoencephalographic evidence of abnormal auditory processing in amyotrophic lateral sclerosis with bulbar signs.

OBJECTIVE: Amyotrophic lateral sclerosis (ALS) is characterized by progressive motor neuron damage that gives rise to muscle denervation. Besides motor neuron damage, conscious auditory processing appears to be impaired in ALS, whereas it has remained ambiguous whether preceding automatic auditory processing is abnormal in ALS and specifically in ALS with bulbar signs. METHODS: Auditory evoked fields (AEFs) to monaurally presented frequent and infrequent tones with stimulus intervals of 500 and 2500 ms were recorded with magnetoencephalography (MEG) from 10 ALS patients having bulbar signs and from 10 age-matched healthy subjects. RESULTS: The amplitudes of the P50m and N100m responses, which index automatic auditory processing underlying stimulus detection, were significantly increased and P50m latency was shortened in ALS patients. MMNm, which reflects memory-based auditory comparison process, was increased in amplitude in the patient group, whereas the MMNm latency was similar in both groups. AEF latency and amplitude values failed to correlate with the severity of ALS as measured by ALS Functional Rating Scale (ALSFRS). CONCLUSIONS: The present results suggest that auditory processing underlying stimulus detection, and subsequent memory-based comparison processes are abnormal in ALS patients with severe bulbar signs. This might be due to cortical overactivity of excitatory neurotransmitter glutamate observed in ALS.

Acoustic Stimulation↗
PubMed2005

Auditory abnormalities in autism: toward functional distinctions among findings.

Recently, findings on a wide range of auditory abnormalities among individuals with autism have been reported. To date, functional distinctions among these varied findings are poorly established. Such distinctions should be of interest to clinicians and researchers alike given their potential therapeutic and experimental applications. This review suggests three general trends among these findings as a starting point for future analyses. First, studies of auditory perception of linguistic and social auditory stimuli among individuals with autism generally have found impaired perception versus normal controls. Such findings may correlate with impaired language and communication skills and social isolation observed among individuals with autism. Second, studies of auditory perception of pitch and music among individuals with autism generally have found enhanced perception versus normal controls. These findings may correlate with the restrictive and highly focused behaviors observed among individuals with autism. Third, findings on the auditory perception of non-linguistic, non-musical stimuli among autism patients resist any generalized conclusions. Ultimately, as some researchers have already suggested, the distinction between impaired global processing and enhanced local processing may prove useful in making sense of apparently discordant findings on auditory abnormalities among individuals with autism.

Auditory Perceptual Disorders↗
PubMed2000

Visual behaviour mediated by retinal projections directed to the auditory pathway.

An unresolved issue in cortical development concerns the relative contributions of intrinsic and extrinsic factors to the functional specification of different cortical areas. Ferrets in which retinal projections are redirected neonatally to the auditory thalamus have visually responsive cells in auditory thalamus and cortex, form a retinotopic map in auditory cortex and have visual receptive field properties in auditory cortex that are typical of cells in visual cortex. Here we report that this cross-modal projection and its representation in auditory cortex can mediate visual behaviour. When light stimuli are presented in the portion of the visual field that is 'seen' only by this projection, 'rewired' ferrets respond as though they perceive the stimuli to be visual rather than auditory. Thus the perceptual modality of a neocortical region is instructed to a significant extent by its extrinsic inputs. In addition, gratings of different spatial frequencies can be discriminated by the rewired pathway, although the grating acuity is lower than that of the normal visual pathway.

Animals↗
PubMed2003

Effect of hypoxia on the auditory system of goat fetuses during extrauterine incubation.

AIM: To investigate the effect of hypoxia on the auditory system in fetuses, we attempted to analyze the auditory brainstem response, the middle latency response, and changes of several physiological parameters of goat fetuses during extrauterine incubation. METHODS: We conducted extrauterine incubation of five goat fetuses at around 127days of gestation (term = 148 days). Their physiological parameters, such as fetal heart rate, mean blood pressure, flow rate of carotid artery, as well as the auditory brainstem response and middle latency response, were recorded prior to and during hypoxia, and the two sets of data were compared with each other. RESULTS: In all five cases, the fetal heart rate decreased from 178 +/- 12.2 b.p.m. to 144 +/- 15.2 b.p.m. during hypoxia, while mean blood pressure and flow rate of carotid artery increased from 37.3 +/- 3.7 mmHg to 43.2 +/- 5.1 mmHg, and from 38.5 +/- 5.5mL/min to 47.0 +/- 5.1 mL/min, respectively. The latency of the auditory brainstem response's wave V and of the middle latency response's Pa wave elongated from 5.24 +/- 0.24 ms to 5.69 +/- 0.20 ms, and from 19.2 +/- 1.6 ms to 20.9 +/- 1.4 ms, respectively. CONCLUSIONS: Although fetal compensatory reactions, such as increases in mean blood pressure and flow rate of carotid artery during hypoxia were recognized, elongation of latency, and decrement of amplitude were observed in the auditory brainstem response and middle latency response. These results suggest that hypoxia itself influences the auditory system of the fetus.

Animals↗
PubMed2000

Functional organization of auditory cortex in the Mongolian gerbil (Meriones unguiculatus). III. Anatomical subdivisions and corticocortical connections.

The auditory cortex of the Mongolian gerbil comprises several physiologically identified fields, including the primary (AI), anterior (AAF), dorsal (D), ventral (V), dorsoposterior (DP) and ventroposterior (VP) fields, as established previously with electrophysiological [Thomas et al. (1993) Eur. J. Neurosci., 5, 882] and functional metabolic techniques [Scheich et al. (1993) Eur. J. Neurosci., 5, 898]. Here we describe the cyto-, myelo- and chemoarchitecture and the corticocortical connections of the auditory cortex in this species. A central area of temporal cortex corresponding to AI and the rostrally adjacent AAF is distinguished from surrounding cortical areas by its koniocortical cytoarchitecture, by a higher density of myelinated fibres, predominantly in granular and infragranular layers, and by characteristic patterns of immunoreactivity for the calcium-binding protein parvalbumin (most intense staining in layers III/IV and VIa) and for the cytoskeletal neurofilament protein (antibody SMI-32; most intense staining in layers III, V and VI). Concerning the cortical connections, injections of the predominantly anterograde tracer biocytin into the four tonotopically organized fields AI, AAF, DP and VP yielded the following labelling patterns. (i) Labelled axons and terminals were seen within each injected field itself. (ii) Following injections into AI, labelled axons and terminals were also seen in the ipsilateral AAF, DP, VP, D and V, and in a hitherto undescribed possible auditory field, termed the ventromedial field (VM). Similarly, following injections into AAF, DP and VP, labelling was also seen in each of the noninjected fields, except in VM. (iii) Each field projects to its homotopic counterpart in the contralateral hemisphere. In addition, field AI projects to contralateral AAF, DP and VP, field DP to contralateral AI and VP, and field VP to contralateral AI and DP. (iv) Some retrogradely filled pyramidal neurons within the areas of terminal labelling indicate reciprocal connections between most fields, both ipsilateral and contralateral. (v) The labelled fibres within the injected and the target fields, both ipsilateral and contralateral, were arranged in continuous dorsoventral bands parallel to isofrequency contours. The more caudal the injection site in AI the more rostral was the label in AAF. This suggests divergent but frequency-specific connections within and, at least for AI and AAF, also across fields, both ipsilateral and contralateral. (vi) Projections to associative cortices (perirhinal, entorhinal, cingulate) and to other sensory cortices (olfactory, somatosensory, visual) from AAF, DP and VP appeared stronger than those from AI. These data support the differentiation of auditory cortical fields in the gerbil into at least 'core' (AI and AAF) and 'noncore' fields. They further reveal a complex pattern of interconnections within and between auditory cortical fields and other cortical areas, such that each field of auditory cortex has its unique set of connections.

Animals↗
PubMed2000

Functional organization of auditory cortex in the Mongolian gerbil (Meriones unguiculatus). IV. Connections with anatomically characterized subcortical structures.

The subcortical connections of the four tonotopically organized fields of the auditory cortex of the Mongolian gerbil, namely the primary (AI), the anterior (AAF), the dorsoposterior (DP) and the ventroposterior field (VP), were studied predominantly by anterograde transport of biocytin injected into these fields. In order to allow the localization of connections with respect to subdivisions of subcortical auditory structures, their cyto-, fibre- and chemoarchitecture was characterized using staining methods for cell bodies, myelin and the calcium-binding protein parvalbumin. Each injected auditory cortical field has substantial and reciprocal connections with each of the three subdivision of the medial geniculate body (MGB), namely the ventral (MGv), dorsal (MGd) and medial division (MGm). However, the relative strengths of these connections vary: AI is predominantly connected with MGv, AAF with MGm and MGv, and DP and VP with MGd and MGv. The connections of at least AI and MGv are topographic: injections into caudal low-frequency AI label laterorostral portions of MGv, whereas injections into rostral high-frequency AI label mediocaudal portions of MGv. All investigated auditory fields send axons to the suprageniculate, posterior limitans, laterodorsal and lateral posterior thalamic nuclei, with strongest projections from DP and VP, as well as to the reticular and subgeniculate thalamic nuclei. AI, AAF, DP and VP project to all three subdivisions of the inferior colliculus, namely the dorsal cortex, external cortex and central nucleus ipsilaterally and to the dorsal and external cortex contralaterally. They also project to the deep and intermediate layers of the ipsilateral superior colliculus, with strongest projections from DP and VP to the lateral and basolateral amygdaloid nuclei, the caudate putamen, globus pallidus and the pontine nuclei. In addition, AAF and particularly DP and VP project to paralemniscal regions around the dorsal nucleus of the lateral lemniscus (DNLL), to the DNLL itself and to the rostroventral aspect of the superior olivary complex. Moreover, DP and VP send axons to the dorsal lateral geniculate nucleus. The differences with respect to the existence and/or relative strengths of subcortical connections of the examined auditory cortical fields suggest a somewhat different function of each of these fields in auditory processing.

Amygdala↗
PubMed2003

Patterns of calcium-binding proteins support parallel and hierarchical organization of human auditory areas.

The human primary auditory cortex (AI) is surrounded by several other auditory areas, which can be identified by cyto-, myelo- and chemoarchitectonic criteria. We report here on the pattern of calcium-binding protein immunoreactivity within these areas. The supratemporal regions of four normal human brains (eight hemispheres) were processed histologically, and serial sections were stained for parvalbumin, calretinin or calbindin. Each calcium-binding protein yielded a specific pattern of labelling, which differed between auditory areas. In AI, defined as area TC [see C. von Economo and L. Horn (1930) Z. Ges. Neurol. Psychiatr.,130, 678-757], parvalbumin labelling was dark in layer IV; several parvalbumin-positive multipolar neurons were distributed in layers III and IV. Calbindin yielded dark labelling in layers I-III and V; it revealed numerous multipolar and pyramidal neurons in layers II and III. Calretinin labelling was lighter than that of parvalbumin or calbindin in AI; calretinin-positive bipolar and bitufted neurons were present in supragranular layers. In non-primary auditory areas, the intensity of labelling tended to become progressively lighter while moving away from AI, with qualitative differences between the cytoarchitectonically defined areas. In analogy to non-human primates, our results suggest differences in intrinsic organization between auditory areas that are compatible with parallel and hierarchical processing of auditory information.

Aged↗
PubMed2004

Human posterior auditory cortex gates novel sounds to consciousness.

Life or death in hostile environments depends crucially on one's ability to detect and gate novel sounds to awareness, such as that of a twig cracking under the paw of a stalking predator in a noisy jungle. Two distinct auditory cortex processes have been thought to underlie this phenomenon: (i) attenuation of the so-called N1 response with repeated stimulation and (ii) elicitation of a mismatch negativity response (MMN) by changes in repetitive aspects of auditory stimulation. This division has been based on previous studies suggesting that, unlike for the N1, repetitive "standard" stimuli preceding a physically different "novel" stimulus constitute a prerequisite to MMN elicitation, and that the source loci of MMN and N1 are different. Contradicting these findings, our combined electromagnetic, hemodynamic, and psychophysical data indicate that the MMN is generated as a result of differential adaptation of anterior and posterior auditory cortex N1 sources by preceding auditory stimulation. Early ( approximately 85 ms) neural activity within posterior auditory cortex is adapted as sound novelty decreases. This alters the center of gravity of electromagnetic N1 source activity, creating an illusory difference between N1 and MMN source loci when estimated by using equivalent current dipole fits. Further, our electroencephalography data show a robust MMN after a single standard event when the interval between two consecutive novel sounds is kept invariant. Our converging findings suggest that transient adaptation of feature-specific neurons within human posterior auditory cortex filters superfluous sounds from entering one's awareness.

Adult↗
PubMed2003

A unifying basis of auditory thresholds based on temporal summation.

Thresholds of auditory-nerve (AN) fibers and auditory neurons are commonly specified in terms of sound pressure only, implying that they are independent of time. At the perceptual level, however, the sound pressure required for detection decreases with increasing stimulus duration, suggesting that the auditory system integrates sound over time. The quantity commonly believed to be integrated is sound intensity, implying that the auditory system would have an energy threshold. However, leaky integrators of intensity with time constants of hundreds of milliseconds are required to fit the data. Such time constants are unknown in physiology and are also incompatible with the high temporal resolution of the auditory system, creating the resolution-integration paradox. Here we demonstrate that cortical and perceptual responses are based on integration of the pressure envelope of the sound, as we have previously shown for AN fibers, rather than on intensity. The functions relating the pressure envelope integration thresholds and time for AN fibers, cortical neurons, and perception in the same species (cat), as well as for perception in many different vertebrate species, are remarkably similar. They are well described by a power law that resolves the resolution-integration paradox. The data argue for the integrator to be located in the first synapse in the auditory pathway and we discuss its mode of operation.

Animals↗
PubMed2000

Subdivisions of auditory cortex and processing streams in primates.

The auditory system of monkeys includes a large number of interconnected subcortical nuclei and cortical areas. At subcortical levels, the structural components of the auditory system of monkeys resemble those of nonprimates, but the organization at cortical levels is different. In monkeys, the ventral nucleus of the medial geniculate complex projects in parallel to a core of three primary-like auditory areas, AI, R, and RT, constituting the first stage of cortical processing. These areas interconnect and project to the homotopic and other locations in the opposite cerebral hemisphere and to a surrounding array of eight proposed belt areas as a second stage of cortical processing. The belt areas in turn project in overlapping patterns to a lateral parabelt region with at least rostral and caudal subdivisions as a third stage of cortical processing. The divisions of the parabelt distribute to adjoining auditory and multimodal regions of the temporal lobe and to four functionally distinct regions of the frontal lobe. Histochemically, chimpanzees and humans have an auditory core that closely resembles that of monkeys. The challenge for future researchers is to understand how this complex system in monkeys analyzes and utilizes auditory information.

Animals↗