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PubMed1995

Neural responses to free-field auditory stimulation in the superior colliculus of the wallaby (Macropus eugenii).

Auditory responses to free-field broad band stimulation from different directions were recorded from clusters of neurones in the superior colliculus (SC) of the anaesthetized tammar wallaby. The auditory responses were found approximately 2 mm beneath the first recording of visually evoked responses in the superficial layers, the vast majority being solely auditory in nature; only one recording responded to both auditory and visual stimulation. Responses to suprathreshold intensities displayed sharp spatial tuning to sound in the contralateral hemifield. Those from the rostral pole of the SC disclosed a preference for auditory stimuli in the azimuthal anterior field, whereas those in the caudal SC preferentially responded to sounds in the posterior field. A continuum of directionally tuned responses was seen along the rostrocaudal axis of the SC so that the entire azimuthal contralateral auditory hemifield was represented in the SC. Furthermore, tight spatial alignment was evident between the best position of the visual responses in the superficial layers in azimuth and the peak angle of the auditory response in the deeper layers.

Acoustic Stimulation↗
PubMed1988

Unusual discharge patterns of single fibers in the pigeon's auditory nerve.

Extracellular recording from single auditory nerve fibers in the pigeon, Columba livia, revealed some unusual discharge patterns of spontaneous and evoked activity. Time interval histograms (TIHs) of spontaneous activity showed a random interval distribution in 73% of the auditory fibers (Fig. 1a). The remaining 27% revealed periodicity in the TIHs (Fig. 1b-e), determined by the characteristic frequency (CF) of a given fiber. Normally, those fibers had a CF less than 2.2 kHz. In both cases spontaneous activity was irregular. The time pattern of quasiperiodic spontaneous firing in different auditory fibers is described by three main types of autocorrelation histograms (ACHs; decaying, nondecaying, and modulated), reflecting the spontaneous oscillations of the hair cell membrane potential (Fig. 1b-d). Single-tone suppression in auditory fibers with quasi-periodic spontaneous activity was found (Figs. 2, 10) and it could be observed if the eighth nerve was cut. There was no suppressive effect in fibres with random spontaneous firing. The frequency selectivity properties of auditory fibers were studied by means of an automatic method. Both 'simple' (Fig. 4) and 'complex' (Figs. 7, 8) response maps were found. Apart from the usual excitatory area, complex response maps were characterized by suppressive areas lying either above (Fig. 7), below (Fig. 8e), or on both sides of the CF (Fig. 8a-c). Generally, complex response maps were observed for fibers showing quasiperiodic spontaneous activity (Figs. 7, 8). Input-output functions at frequencies evoking single-tone suppression were nonmonotonic, while they were always monotonic at frequencies near the CF (Fig. 12). No difference in sharpness was observed between normal frequency threshold curves (FTCs) and excitatory areas of 'complex' response maps (Fig. 9). 'On-off' responses evoked by suppressive stimuli were found (Figs. 2, 3). They had a periodic pattern determined by the CF and did not depend on the stimulus frequency (Fig. 3). Low-CF fibers were observed which changed their time discharge structure to tone levels about 45 dB lower than their thresholds at the CF (Fig. 6). The observed features of the discharge patterns of the pigeon's auditory fibers reflect the distinctive nature of the fundamental mechanisms of auditory analysis in birds that are connected with electrical tuning of the hair cells and probably with the micromechanics of the bird's cochlea.

Acoustic Stimulation↗
PubMed2002

Histochemical identification of cortical areas in the auditory region of the human brain.

Despite numerous studies stretching over the last 100 years there is still no general agreement on the number of auditory areas in the human cortex or even how to define them by histological methods. Full definition of these areas will require a combination of functional and histological methods but, by using six complementary histological methods, of which most have been used in the monkey, we provide a clearer description of these areas. The primary auditory area was located on the posteromedial two-thirds of the first transverse temporal (Heschl's) gyrus and was distinguished by a dense band of cytochrome oxidase activity in layer IV and the base of layer III, as well as a relatively thick, pale layer V and VI. Layers V and VI together made up 40% of the cortical thickness. Acetylcholinesterase (AChE)-containing pyramidal cells were sparsely distributed within the primary auditory area. The anterolateral third of Heschl's gyrus did not have a clear band of high cytochrome oxidase activity but contained a moderately high density of AChE-containing pyramidal cells and thus appeared to be part of the auditory belt. Within Heschl's sulcus there was a third area, which had a band of high cytochrome oxidase activity and bands of high parvalbumin immunoreactivity and AChE activity in layer IV. This area appeared to be part of the auditory core. Thus the use of staining methods for cytochrome oxidase, AChE and parvalbumin provided additional information which allowed a clearer definition of auditory areas than Nissl or myelin staining alone. Our results suggest that there are two core areas surrounded by at least six belt areas in the human auditory region.

Acetylcholinesterase↗
PubMed2001

Neuroarchitecture of the auditory cortex in the rufous horseshoe bat (Rhinolophus rouxi).

This study describes the location and anatomical subdivisions of the auditory cortex of the horseshoe bat, Rhinolophus rouxi. The basic cyto- and myeloarchitectural features and cytochrome oxidase reactivity patterns are evaluated in brains where auditory fields have been previously established neurophysiologically (Radtke-Schuller and Schuller 1995). Thus, the neuroanatomical findings from these brains and additional analyzed material are related to neurophysiological characteristics. The neocortex of Rhinolophus shows a typical mammalian six-layered organization. It is poorly laminated, has a low density of granular elements, a wide layer I, and a phylogenetically old pyramidal cell type in a sharply accentuated layer II. These features are generally considered 'primitive' or conservative. Frontal, parietal, temporal and occipital regions can be distinguished. In the temporal cortex, layers III and IV are found to be markedly thicker than layer V, in contrast to the parietal region, where a prominent layer V, containing a high concentration of large pyramidal cells is the most outstanding feature. The entire temporal region, most of the parietal and parts of the occipital region are responsive to auditory stimuli. The primary auditory field corresponds to most of the temporal region. The fields of the parietal region almost completely coincide with the dorsal fields of the auditory cortex. Border zones between the temporal, parietal, and occipital regions correspond to the posterior auditory field. The non-primary fields of the auditory cortex occupy a larger area of the bat's neocortex than the primary field. The accentuated neuroarchitectural features, like cortical thickness and staining intensity, are shown to coincide with the physiological representation of biologically significant parameters.

Animals↗
PubMed1989

Learning-related activation in the auditory system of the rat produced by long-term habituation: a 2-deoxyglucose study.

Autoradiography with [14C]2-deoxyglucose (2-DG) was used to examine the functional activity of the rat auditory system during long- and short-term habituation of the acoustic startle reflex. The data showed that presentation of the acoustic stimulus to long-term habituated rats resulted in a learning-related metabolic enhancement that was significantly greater than the response evoked by the same acoustic stimulus in the inexperienced rats. This enhancement was localized to brainstem and midbrain auditory nuclei and no significant changes occurred at thalamocortical levels of the auditory pathway. The largest difference in 2-DG uptake between long- and short-term habituated rats was in the lateral superior olivary nucleus (LSO). The LSO activation suggests that olivocochlear efferents may operate in a central feedback control of peripheral auditory input during long-term habituation. Findings of enhanced metabolism from the cochlear nuclei to the central nucleus of the inferior colliculus indicated that active processes of neuronal plasticity take place in the lower auditory system during long-term habituation. The results provide the first demonstration of how a nonassociative learning experience such as long-term habituation modifies the metabolic activity of the auditory system. The findings support the conclusion that auditory responses of behaving animals to acoustic stimuli are dependent not only on the physical parameters of a stimulus, but also on its learned behavioral significance.

Acoustic Stimulation↗
PubMed1990

Investigation of central auditory nuclei in the budgerigar with cytochrome oxidase histochemistry.

Cytochrome oxidase (CO) histochemistry was used to study the organization of central auditory structures in the budgerigar (Melopsittacus undulatus). In contrast to prior studies in birds showing that acetylcholinesterase staining is most intense within hindbrain auditory structures CO staining was prominent at all levels of the auditory pathway including the thalamus (i.e. nucleus ovoidalis) and primary telencephalic auditory area (Field 'L'). Furthermore, CO staining clearly distinguishes the boundaries of Field 'L' from adjacent portions of the neostriatum intermedium pars dorsolateralis which do not receive input from the auditory thalamus. Thus CO staining can be used as a marker for distinguishing auditory and non-auditory portions of the avian telencephalon.

Animals↗
PubMed1994

Quantitative mapping of cytochrome oxidase activity in the central auditory system of the gerbil: a study with calibrated activity standards and metal-intensified histochemistry.

The objective was to obtain detailed topographic determinations of cytochrome oxidase activity in the gerbil central auditory system at the light microscopic level. Quantitative techniques were developed using (1) tissue standards calibrated to express histochemical measures as actual enzyme activity units, (2) densitometry and image analysis of histochemical reaction product formation, (3) spectrophotometry of cytochrome oxidase activity, and (4) a cobalt-intensified staining procedure compatible with autoradiography and other techniques requiring fresh-frozen brains without perfusion-fixation. Linear relationships between incubation time, section thickness, and activity of dissected brain regions, with their reaction product measured densitometrically were determined. Auditory structures with the high activities showed about 8 times the labeling intensity of the white matter or control sections inhibited with cyanide, glutaraldehyde, or heat. This indicated the high sensitivity of the method without loss of specificity. Specific activity for each of the 18 auditory structures measured were all above the units measured for whole brain homogenates, supporting the notion that basal levels of oxidative metabolism are greater for the auditory system. There was a progressive decrement in activity from brain stem to forebrain auditory structures. The more peripheral nuclei also showed a higher proportion of somatic as compared to neuropil reactivity. In contrast, auditory midbrain and thalamocortical regions were characterized primarily by neuropil reactivity. Comparison of intrinsic patterns of activity with morphological schemes to subdivide nuclei, showed a good correspondence with classical subdivisions derived from Golgi studies. The reported activities may provide a base of normative data in the gerbil for subsequent studies of central auditory functions. The method presented fulfilled established quantitative criteria and provided a more sensitive approach for regional mapping studies of brain cytochrome oxidase activity.

Animals↗
PubMed1995

Restoration of sensory gating of auditory evoked response by nicotine in fimbria-fornix lesioned rats.

Recordings of auditory evoked potentials in the CA3 region of the hippocampus reveal a decrement in the N40 wave after the presentation of the second of closely paired auditory stimuli (interstimulus interval of 500 ms), a phenomenon known as sensory gating. Previous experiments have suggested the involvement of nicotinic cholinergic systems in auditory sensory processing. The present study examined the effects of lesioning the fimbria-fornix on auditory sensory processing in the hippocampus. Fimbria-fornix lesions resulted in a failure to decrement the N40 wave in the auditory evoked response to the second tone. When nicotine was administered to rats with fimbria-fornix lesions the drug was able to reinstate the normal suppression of the second auditory evoked response. These data support the involvement of nicotinic cholinergic afferents in auditory sensory modulation in the hippocampus.

Acetyl Coenzyme A↗
PubMed1986

Short-latency auditory evoked potentials in the monkey. II. Intracranial generators.

The generators of the short-latency auditory evoked potentials (SLAEPs) in the monkey have been defined by intracranial mapping from cochlea to auditory cortex. SLAEP components other than 1a and the slow negativity (SN) following wave 7 derive from compound action potentials propagated in subcortical auditory pathways. The component generators are complex due to the presence of two bursts of activity in the eighth nerve, to the fact that the ascending auditory fibers both synapse on and bypass specific relay nuclei, and to the differences in orientation of segments of the auditory pathways. Most SLAEP components recorded at the surface reflect the summation of activity from multiple generators. However, much of the activity seen within subcortical structures cannot be traced to the surface of the brain. Component 1a is identified with the cochlear summating potential, while 1b reflects the initial afferent volley in the distal portion of the eighth nerve. Component 2 represents the initial depolarization of the eighth nerve terminals within the ipsilateral cochlear nucleus. Component 3h reflects the second volley of activity in the distal portion of the eighth nerve and the outflow of the cochlear nucleus which decussates in the trapezoid body. Component 3v represents the initial cochlear nucleus outflow volley ascending the lateral lemniscus. Component 4 principally reflects the second volley of activity within the eighth nerve terminals, and outflow from the ipsilateral superior olivary complex ascending in that lateral lemniscus, with a possible contribution from activity in the contralateral CNC. Component 5 represents the outflow of the contralateral superior olivary complex ascending in that lateral lemniscus. Component 6 reflects another volley from the ipsilateral superior olivary complex ascending in that lateral lemniscus, as well as outflow from both inferior colliculi propagating in their brachii. The generators of component 7 are the most complex encountered, representing volleys in both lateral lemnisci, activity of the contralateral inferior colliculus, and activity in both auditory radiations. A component that follows wave 7, seen best in mastoid-to-mastoid recording linkage, represents outflow from both inferior colliculi propagating in their brachia. Components 8 and 9 principally reflect propagated action potentials in the auditory radiations bilaterally, with an additional contribution from activity of both inferior colliculi. The SN mainly represents volume-conducted postsynaptic potentials from both inferior colliculi and cochlear nuclei.

Animals↗
PubMed1985

The effectiveness of imagery and sentence strategy instructions as a function of visual and auditory processing in young school-age children.

The relationship between auditory and visual processing modality and strategy instructions was examined in first- and second-grade children. A Pictograph Sentence Memory Test was used to determine dominant processing modality as well as to assess instructional effects. The pictograph task was given first followed by auditory or visual interference. Children who were disrupted more by visual interference were classed as visual processors and those more disrupted by auditory interference were classed as auditory processors. Auditory and visual processors were then assigned to one of three conditions: interactive imagery strategy, sentence strategy, or a control group. Children in the imagery and sentence strategy groups were briefly taught to integrate the pictographs in order to remember them better. The sentence strategy was found to be effective for both auditory and visual processors, whereas the interactive imagery strategy was effective only for auditory processors.

Attention↗
PubMedDate not supplied

The descending auditory pathway and acousticomotor systems: connections with the inferior colliculus.

In this review the following major points are emphasized. First, the descending auditory system includes 3 separate, but parallel pathways connecting the AC, MGB and IC. Each pathway makes a strong set of connections with a distinctive area from each of 3 auditory centers. The three sets of connections are mutually exclusive, such that the pathways describe 3 separate corticocolliculo-geniculate systems. Thus, multiple feedback loops between the AC and the IC are formed which create a great capacity for parallel processing of auditory information. Second, the IC projects to the SOC and, in particular, to the source of olivocochlear efferent neurons. The connections of the IC with the AC rostrally, and with the olivocochlear neurons caudally, imply a descending trisynaptic pathway from the cortex to the cochlea whose travel time could better that of the ascending pathway and thus provide an efficient feedback mechanism. It is probable that the IC influences cochlear signal processing. The reciprocal connectivity between any two of either the IC, SOC or the CN, again, affords to the auditory system remarkable parallel processing capabilities. Finally, the descending auditory, and 'extra-auditory' connections of the IC bestow a functional separateness to the 3 nuclei of the IC, a view that is best illustrated by description of the ICX as an acousticomotor nucleus, having connections with the SC, cerebellum and somatosensory and vocalization systems. More sophisticated questions about the descending auditory system will incorporate these present observations and test functional implications to which they allude.

Animals↗
PubMed1995

Mapping of stimulus features and meaning in gerbil auditory cortex with 2-deoxyglucose and c-Fos antibodies.

The basic functional organization of gerbil auditory cortex was previously mapped with unit recording of best frequency and with the fluoro-2-deoxyglucose mapping (FDG) technique. Among at least seven subfields in this cortex the primary auditory cortex (AI) and the anterior auditory field (AAF) showed prominent tonotopic organization with parallel dorsoventral iso-frequency contours (electrophysiology) in correspondence to FDG labelling of frequency band laminae. In an approach to mechanisms of learning aversive tone conditioning paradigms were found to reshape frequency receptive fields of single units in AI and also produced spatial shifts of tone representation in the tonotopic maps of AI and AAF. Both results suggest that spectral features as well as aspects of behavioural meaning of sounds may be represented even in primary auditory cortex. General meaningfulness in terms of occurrence of novel and salient stimuli may be reflected by expression of immediate early genes. Mapping with an antibody against the immediate early gene product c-Fos was performed in order to identify the spatial distribution of neurons in auditory cortex which change metabolism as a result of stimulation with auditory signals in a new environment. Very short e.g. less than 3 min repetitive stimulation with a tone led to frequency-specific columnar expression of c-Fos in AI and to spare non-tonotopic expression in other fields. Longer stimulation or longer aversive conditioning with the same tone led to spreading of expression, i.e. to accessory non-tonotopic labelling in AI and other fields, particularly pronounced in the output layers V and VI. It is assumed that this spreading relates to the formation of output schemes from auditory cortex in terms of implicit behavioural meaning of stimuli.

Animals↗
PubMed1986

Neural generators of the brain-stem auditory evoked potentials (BAEPs) in the rhesus monkey.

Brain-stem auditory evoked potentials (BAEPs) were recorded from rhesus monkeys in response to click stimuli. The BAEPs in the monkey have only 4 major peaks, while 5 major peaks can be identified in the human BAEP. The responses from electrodes placed at the vertex and the mastoid recorded either differentially or separately using non-cephalic references were compared to concomitant recordings from the auditory nerve, the cochlear nucleus, and the inferior colliculus, including the lateral lemniscus and the brachium of the inferior colliculus. It was found that the response from the intracranial portion of the auditory nerve lags behind the far-field response recorded from the mastoid by about 0.2 msec. The major component of the potentials recorded from the lateral lemniscus appeared with a latency that was close to that of the fourth peak in the BAEP. Deafferentation of the inferior colliculus resulted in only small changes in the BAEP, indicating that the contributions to the BAEP from the inferior colliculus and more central structures of the ascending auditory pathway are insignificant. It is concluded that the main reason for the difference between the human BAEP and the BAEP in the rhesus monkey is the smaller size of the monkey's head and the resulting shorter auditory nerve. The result is that the auditory nerve in the monkey only generates one peak in the far-field response, while in man the auditory nerve gives rise to both of the two earliest peaks in the BAEP; thus, the BAEP in man has 5 peaks while that in the monkey has only 4 peaks.

Animals↗
PubMed1989

Disruption of auditory function by acute administration of a "room odorizer" containing butyl nitrite in rats.

Butyl nitrite is the predominant and presumed active ingredient in a variety of commercial preparations sold as "room odorizers." These compounds have significant abuse potential, giving the user the sensation of a "rush", which may be related to their intense cardiovascular effects. The pharmacological properties of butyl nitrites are similar to those of amyl nitrite which is also abused for its psychological effects, but whose availability is limited by prescription for treatment of angina. A significant body of literature suggests that the inner ear is vulnerable to acute hypoxic exposure. Since butyl nitrite induces high levels of methemoglobin and also reduces blood pressure due to peripheral vasodilation, we hypothesized that this compound might produce auditory dysfunction. We studied the effect of acute exposure to a butyl nitrite "room odorizer" on 10- and 40-kHz auditory function in rats. A loss in auditory sensitivity was found at both frequencies on the day following administration of the compound. Auditory dysfunction tended to subside over the next several days at 40 kHz, although a significant loss of sensitivity for tones of 10 kHz was observed over a 6-day period after administration of the agent. Methemoglobin levels measured in rats of the same age were elevated significantly 30 and 60 min after butyl nitrite to levels of 30-45%. Methemoglobin levels were found to be normal 18 hr after administration when the first audiometric tests were conducted. The data suggest that auditory function in the middle of the rats' auditory range, 10 kHz, was disrupted for a longer period than was high-frequency (40 kHz) auditory function.

Air Pollutants↗
PubMed1996

Electrically induced fos-like immunoreactivity in the auditory pathway of the rat: effects of survival time, duration, and intensity of stimulation.

The goal of the present study was to establish how Fos-like immunoreactivity (FLI) elicited in the rat auditory pathway by unilateral electric stimulation of the cochlea is affected by the following experimental parameters: duration and intensity of stimulation, duration of survival time after offset of stimulation. The dense FLI found in the ipsilateral dorsal cochlear nucleus, as well as the moderate FLI found in the contralateral dorsal cochlear nucleus and in the posteroventral cochlear nucleus on both sides, were consistent after survival times ranging from 0 to 2-3 h, but they significantly decreased after longer survival times (5 and 6 h). In the same nuclei, FLI was increased even by short durations of stimulation (5 and 10 min) as compared to control rats, although FLI progressively increased for longer stimulation (20 and 45 min). In the auditory thalamus, FLI was found mainly in the peripeduncular nucleus, the dorsal and medial divisions of the medial geniculate body, whereas its ventral division was virtually devoid of immunoreactive neurons. This pattern of FLI distribution in the auditory thalamus persisted even after relatively long survival times (5 and 6 h). In both the cochlear nucleus and auditory thalamus, the density of FLI slightly increased in parallel with the intensity of stimulation. In other auditory nuclei, such as the inferior colliculus and the nucleus of the lateral lemniscus, there was no simple relation between the density of FLI and the three tested experimental parameters. Thus, the distribution and density of FLI did not vary in parallel in the various nuclei of the auditory pathway as a function of the tested experimental parameters; different patterns of FLI changes were instead observed in different auditory nuclei.

Action Potentials↗
PubMed1987

Frequency and time domain comparison of low-frequency auditory fiber responses in two anuran amphibians.

A comparative study of the phase-locked response of auditory nerve fibers was performed in two frog species, Eleutherodactylus coqui and Bombina orientalis. From the tuning characteristics and phase response of single auditory nerve fibers to low frequency tones (0.08-1.0 kHz) we attempt to deduce the mechanics of the auditory organ responsible for low-frequency hearing in the frog, the amphibian papilla (a.p.). The phase-locked responses of auditory nerve fibers in B. orientalis were essentially identical to those from cells with similar CFs in E. coqui, despite the presence of a conspicuous caudal extension of the a.p. in E. coqui (an apparently derived morphology), a feature completely absent in B. orientalis. The fine structure of the frequency-dependent phase behavior was examined in both species with a residual phase analysis. The most significant non-linear phase behavior was confined to neurons with CFs less than 0.3 kHz. The intensity dependence of the phase response in E. coqui revealed that the preferred firing phase of an auditory nerve fiber depends upon the relation of test frequency (TF) and CF of the neuron examined. For TFs greater than CF there was a progressive phase lag as stimulus level was increased; the inverse was true for TFs less than CF. Click latencies measured in E. coqui were inversely related to CF and were similar though systematically shorter than the response latencies estimated from the phase-frequency functions. The click response was similar to that documented in other species, showing a significant level dependence and the presence of multiple peaks, with the time between peaks related to the period of the neuron's CF. A 'neurogram' was compiled for a.p. fiber responses in both species in response to several pure tones. Based on the known tonotopy of the a.p. this measure reflects the phase response of the a.p. over the extent of its length. The population phase response in anurans is quite similar to that obtained from mammalian auditory nerve fibers for the same range of test frequencies (0.08-1.0 kHz). The similarity between the responses of auditory fibers in these two anuran species suggests the micromechanics of the a.p. rostral to the tectorial curtain is similar in both species and that it is the likely site for the origin of the CF-dependent time delays.

Acoustic Stimulation↗
PubMedDate not supplied

Chronic in utero alcohol exposure affects auditory function in rats and in humans.

In one experiment, brainstem auditory evoked potentials (BAEPs) were used to study the postnatal development of the peripheral and brainstem auditory pathways in rat pups prenatally exposed to alcohol. The results indicated that prenatal alcohol exposure retards development of the peripheral and brainstem auditory pathways and that prolonged auditory transmission times, despite a "catch-up" trend, persist in maturity. BAEP latency-intensity profiles demonstrated that a significant proportion (19%) of the alcoholized rats had recruitment-type sensorineural hearing loss. In a second study, a group of 12 fetal alcohol syndrome (FAS) children were evaluated for auditory function. These children showed unusually high incidence rates of sensorineural hearing loss (33%) and conductive hearing loss secondary to recurrent serous otitis media (92%). A final study used the cortical auditory evoked potential (CAEP) and found evidence of dysfunctional processing of auditory information at the cortical level in rats prenatally exposed to alcohol. The implications of these findings for the evaluation and treatment of FAS children and for evoked potential studies on children of alcoholics and learning disabled children are discussed.

Age Factors↗
PubMed1996

Genetic correlation of inhibitory gating of hippocampal auditory evoked response and alpha-bungarotoxin-binding nicotinic cholinergic receptors in inbred mouse strains.

One function of the hippocampus is to ascertain the novelty of incoming sensations and encode significant new information into memory. The regulation of response to repeated stimuli may prevent overloading of this function by redundant sensory input. Recent pharmacological studies implicate the role of alpha-bungarotoxin-sensitive nicotinic cholinergic receptors in the inhibition of hippocampal response to repeated auditory stimuli. The number of hippocampal alpha-bungarotoxin-sensitive receptors has a major genetic determinant, as demonstrated by a significant variance between different inbred mouse strains. The purpose of the present study was to determine whether there was a related genetic correlation for the gating of auditory response. Nine inbred mouse strains, representing a continuum of hippocampal alpha-bungarotoxin binding, were tested for the electrophysiological response to repeated auditory stimulation, followed by whole hippocampus membrane alpha-bungarotoxin binding studies. Several parameters of the auditory evoked response showed significant genetic variance over the nine strains, and a significant correlation was found between hippocampal alpha-bungarotoxin binding and both the amplitude of the initial evoked response and its inhibition to repeated auditory stimuli. There was no correlation of the auditory evoked response with high-affinity nicotine binding. These data further support the hypothesis that alpha-bungarotoxin-sensitive nicotinic receptors are involved in the regulation of hippocampal response to repeated auditory stimuli and suggest that this function is genetically controlled.

Acoustic Stimulation↗