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1.
The ultrastructural features of the primary auditory cortex of the cats and the character of the endings of geniculo-cortical afferent fibers in the early stages of experimental degeneration evoked by destruction of the medial geniculate body were studied. In all layers of the cortex asymmetrical synapses with round synaptic vesicles on dendritic spines and on thin dendritic branches of pyramidal and nonpyramidal neurons are predominant. Symmetrical synapses with flattened or polymorphic vesicles are distributed chiefly on the bodies of the neurons and their large dendrites. Because there are few symmetrical synapses which could be regarded as inhibitory it is postulated that inhibitory influences may also be transmitted through asymmetrical synapses with round vesicles. Other types of contacts between the bodies of neurons, dendrites, and glial processes also were found in the auditory cortex. Degenerating terminals of geniculo-cortical fibers were shown to terminate chiefly in layer IV of the cortex on pyramidal and nonpyramidal neurons. Degeneration was of the dark type in asymmetrical synapses with round vesicles. The results are dicussed in connection with electrophysiological investigations of the auditory cortex.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 5, No. 5, pp. 519–524, September–October, 1973.  相似文献   

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Anatomical studies propose that the primate auditory cortex contains more fields than have actually been functionally confirmed or described. Spatially resolved functional magnetic resonance imaging (fMRI) with carefully designed acoustical stimulation could be ideally suited to extend our understanding of the processing within these fields. However, after numerous experiments in humans, many auditory fields remain poorly characterized. Imaging the macaque monkey is of particular interest as these species have a richer set of anatomical and neurophysiological data to clarify the source of the imaged activity. We functionally mapped the auditory cortex of behaving and of anesthetized macaque monkeys with high resolution fMRI. By optimizing our imaging and stimulation procedures, we obtained robust activity throughout auditory cortex using tonal and band-passed noise sounds. Then, by varying the frequency content of the sounds, spatially specific activity patterns were observed over this region. As a result, the activity patterns could be assigned to many auditory cortical fields, including those whose functional properties were previously undescribed. The results provide an extensive functional tessellation of the macaque auditory cortex and suggest that 11 fields contain neurons tuned for the frequency of sounds. This study provides functional support for a model where three fields in primary auditory cortex are surrounded by eight neighboring “belt” fields in non-primary auditory cortex. The findings can now guide neurophysiological recordings in the monkey to expand our understanding of the processing within these fields. Additionally, this work will improve fMRI investigations of the human auditory cortex.  相似文献   

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Using an indirect immunoperoxidase technique, the localization of somatostatin-28 (1-12)-like immunoreactive fibers and cell bodies in the auditory cortex of the cat (anterior, primary, secondary, temporal, ventral, ventroposterior, posterior and dorsoposterior auditory fields) was studied. In general, the distribution of SOM-ir structures is widespread in the auditory cortex of the feline. A high density of immunoreactive fibers as well as a low density of cell bodies containing somatostatin were observed in all the layers of the eight above-mentioned auditory fields. These data indicate that somatostatin-28 (1-12) could act as a neurotransmitter and/or a neuromodulator in the auditory cortex of the cat. The origin of the SOM-ir fibers in the auditory cortex of the cat, as well as the issue of whether the cell bodies containing somatostatin-28 (1-12) are local or projecting neurons is discussed.  相似文献   

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The electrical reactions of 294 neurons of the auditory cortex to a click were recorded in experiments on cats immobilized with tubocurarine (174 intra- and 120 extracellularly). The value of the membrane potential varied from 30 to 70 mV with intracellular leads. The following types of reactions were obtained (the number of neurons is given in parentheses): a peak without slow oscillations in the membrane potential (4), EPSP (3), EPSP-peak (6), EPSP-peak-IPSP (17), EPSP-IPSP (9), primary IPSP (114, including 23 with an after-discharge). Twenty one neurons did not react to a click. The amplitude of the sub-threshold EPSP was 1–1.5 mV, the duration of the ascending part was about 10 and of the descending part 20–30 msec. The peak potential on the ascending part of the EPSP developed at the critical level of 3–4 mV. The amplitude of the peaks varied from several millivolts to 50–60. In 17 neurons prolonged hyperpolarization having all the properties of an IPSP, developed after the peak. The amplitude of these IPSP varied in different neurons from 1 to 10 mV and the duration varied from 20 to 80 msec. IPSP without preceding excitation of the given neuron were the predominant types of reaction. The latent period of these primary IPSP varied from 7 to 20 msec and the amplitude from 1 to 15 msec with a duration of 30–200, more frequently 80–100 msec. It is suggested that two types of inhibition develop in neurons of the auditory cortex in response to a click: recurrent and afferent. The functional significance of the first consists in limiting the duration of the discharge in the reacting neurons, the second prevents the development of excitation in adjacent neurons, thereby limiting the area of neuronal activity.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSSR, Kiev. Translated from Neirofiziologiya, Vol. 3, No. 4, pp. 339–349, July–August, 1971.  相似文献   

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Plexuses of cholinergic varicose fibers, differing in density in different layers of the neuropil, were found in area AI of the cat's auditory cortex by the histochemical reaction for acetylcholinesterase: Their density was maximal or average in layer I or deeper layers and minimal in layers II and III. Among cells in area AI those which are cholinergic are a few stellate neurons located in layers II–VI. Axons of some neurons terminate on neighboring cells, those of others (some neurons in layer VI) run into the subcortical layer of arcuate association fibers. Cholinergic terminals are located on the bodies and proximal areas of dendrites of neurons most of which do not contain acetylcholinesterase. Choliniceptive neurons of different sizes and shapes are found in all layers of this region of the auditory cortex.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. I. I. Mechnikov Odessa State University. Translated from Neirofiziologiya, Vol. 16, No. 1, pp. 75–81, January–February, 1984.  相似文献   

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Spectral integration properties show topographical order in cat primary auditory cortex (AI). Along the iso-frequency domain, regions with predominantly narrowly tuned (NT) neurons are segregated from regions with more broadly tuned (BT) neurons, forming distinct processing modules. Despite their prominent spatial segregation, spectrotemporal processing has not been compared for these regions. We identified these NT and BT regions with broad-band ripple stimuli and characterized processing differences between them using both spectrotemporal receptive fields (STRFs) and nonlinear stimulus/firing rate transformations. The durations of STRF excitatory and inhibitory subfields were shorter and the best temporal modulation frequencies were higher for BT neurons than for NT neurons. For NT neurons, the bandwidth of excitatory and inhibitory subfields was matched, whereas for BT neurons it was not. Phase locking and feature selectivity were higher for NT neurons. Properties of the nonlinearities showed only slight differences across the bandwidth modules. These results indicate fundamental differences in spectrotemporal preferences--and thus distinct physiological functions--for neurons in BT and NT spectral integration modules. However, some global processing aspects, such as spectrotemporal interactions and nonlinear input/output behavior, appear to be similar for both neuronal subgroups. The findings suggest that spectral integration modules in AI differ in what specific stimulus aspects are processed, but they are similar in the manner in which stimulus information is processed.  相似文献   

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Ultrastructural features of thalamic afferent fibers were studied in the cat auditory cortex in the early stages (on the 4th day) of experimental degeneration produced by destruction of the medial geniculate body. A coordinate grid was used in conjunction with an electron micro-scope to study the topography of the degenerating elements over wide areas of sections, so that the density of degeneration could be determined quantitatively in different layers of the cortex. Degenerating axons were found in all layers. Most of the large (5–7 µ) degenerating axons are located in layer VI; their diameters were smaller in the upper layers of the cortex. Degenerative changes affecting synaptic terminals of thalamo-cortical afferents were of the "dark" type. Fibers of the geniculo-cortical tract were shown to terminate mainly in cortical layer IV. A few degenerating synapses were found in the molecular layer. Terminals with sperical synaptic vesicles are found mainly on the spines of dendrites where they form "asymmetrical" contacts. A few degenerating axo-somatic synapses were observed on stellate neurons in layer IV. The results are discussed in connection with electrophysiological investigations of the cat auditory cortex during stimulation of specific afferent fibers.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 6, pp. 612–620, November–December, 1972.  相似文献   

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Functional topography of cat primary auditory cortex: response latencies   总被引:6,自引:0,他引:6  
Minimum onset latency (Lmin) of single- and multiple-unit responses were mapped in the primary auditory cortex (AI) of barbiturate-anesthetized cats. Contralateral Lmin for multiple units was non-homogeneously distributed along the dorso-ventral/isofrequency axis of the AI. Responses with shorter latencies were more often located in the central, more sharply tuned region while longer latencies were more frequently encountered in the dorsal and ventral portions of the AI. For single units, a large scatter of Lmin values was found throughout the extent of the AI including cortical depth. The relationship between Lmin and previously reported spectral, intensity and temporal parameters was analyzed and revealed statistically significant correlations between minimum onset latency and the following response properties in some but not all studied animals: sharpness of tuning of a frequency response area 10 dB above threshold, broadband transient response, strongest response level, monotonicity of rate/level functions, dynamic range, and preferred frequency modulation sweep direction. This analysis suggests that Lmin is determined by several independent factors and that the prediction of Lmin based on relationships with other spectral and temporal response properties is inherently weak. The spatial distribution and the functional relationship between these response parameters may provide an important aspect of the time-based cortical representation of specific features in the animal's natural environment. Accepted: 13 August 1997  相似文献   

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As it has been demonstrated microscopically, the corticofugal fibers in the AII and Ep zones of the auditory cortex in all the auditory subcortical centers (medial geniculate body, posterior colliculi of the tectum mesencephali and the superior olive nuclei) terminate by means of single axodendritic synapses, having an asymmetrically active zone, and mixed (by their form) synaptic vesicles. Small and middle dendrites make their postsynaptic part. A comparison has been carried out on distribution and form of synapses, completing the projection fibers from the zone of the primary acoustic responses (AI) and of the primary acoustic zone (AIV). Basing on the morphological data, concerning distribution and form of the synaptic terminals, a suggestion is made that physiological influence of each acoustic cortex zone is different for the medial geniculate body and posterior colliculi of the tectum mesencephali, but it is unitypical for the superior olive level.  相似文献   

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A set of impulsive transient signals has been synthesized for earphone delivery whose waveform and amplitude spectra, measured at the eardrum, mimic those of sounds arriving from a free-field source. The complete stimulus set forms a "virtual acoustic space" (VAS) for the cat. VAS stimuli are delivered via calibrated earphones sealed into the external meatus in cats under barbiturate anesthesia. Neurons recorded extracellularly in primary (AI) auditory cortex exhibit sensitivity to the direction of sound in VAS. The aggregation of effective sound directions forms a virtual space receptive field (VSRF). At about 20 dB above minimal threshold, VSRFs recorded in otherwise quiet and anechoic space fall into categories based on spatial dimension and location. The size, shape and location of VSRFs remain stable over many hours of recording and are found to be shaped by excitatory and inhibitory interactions of activity arriving from the two ears. Within the VSRF response latency and strength vary systematically with stimulus direction. In an ensemble of such neurons these functional gradients provide information about stimulus direction, which closely accounts for a human listener's spatial acuity. Raising stimulus intensity, introducing continuous background noise or presenting a conditioning stimulus all influence the extent of the VSRF but leave intact the gradient structure of the field. These and other findings suggest that such functional gradients in VSRFs of ensembles of AI neurons are instrumental in coding sound direction and robust enough to overcome interference from competing environmental sounds.  相似文献   

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Responses of 98 auditory cortical neurons to electrical stimulation of the medial geniculate body (MGB) were recorded (45 extracellulary, 53 intracellularly) in experiments on cats immobilized with tubocurarine. Responses of the same neurons to clicks were recorded for comparison. Of the total number of neurons, 75 (76%) responded both to MGB stimulation and to clicks, and 23 (24%) to MGB stimulation only. The latent period of extracellularly recorded action potentials of auditory cortical neurons in response to clicks varied from 7 to 28 msec (late responses were disregarded), and that to MGB stimulation varied from 1.5 to 12.5 msec. For EPSPs these values were 8–13 and 1–4 msec respectively. The latent period of IPSPs arising in response to MGB stimulation varied from 2.2 to 6.5 msec; for 34% of neurons it did not exceed 3 msec. The difference between the latent periods of responses to clicks and to MGB stimulation varied for different neurons from 6 to 21 msec. Responses of 11% of neurons to MGB stimulation, recorded intracellularly, consisted of sub-threshold EPSPs, while responses of 23% of neurons began with an EPSP which was either followed by an action potential and subsequent IPSP or was at once cut off by an IPSP; 66% of neurons responded with primary IPSPs. Neurons responding to MGB stimulation by primary IPSPs are distributed irregularly in the depth of the cortex: there are very few in layers III and IV and many more at a depth of 1.6–2 mm. Conversely, excited neurons are predominant in layer III and IV, and they are few in number at a depth of 1.6–2 mm. It is concluded that the afferent volley reaching the auditory cortex induces excitation of some neurons therein and, at the same time, by the principle of reciprocity, induces inhibition of others. This afferent inhibition takes place with the participation of inhibitory interneurons, and in some cells the inhibition is recurrent. The existence of reciprocal relationships between neurons in different layers of the auditory cortex is postulated.A. A. Bogomolets' Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 1, pp. 23–31, January–February, 1972.  相似文献   

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Experiments using intracellular recording of potentials from neurons of the primary auditory cortex of cats anesthetized with pentobarbital showed that under the influence of tones of characteristic frequency for the neuron under test, or of electrical stimulation of nerve fibers of the spiral ganglion, innervating the center of the receptive field of the neuron, transient excitation of the latter is followed by the development of prolonged (20–250 msec) inhibition. The cause of this inhibition is an IPSP arising in the neuron after the action potential. On the basis of data showing a close connection between inhibition and the preceding spike it is concluded that it arises through the participation of a mechanism of recurrent inhibition. During the action of tones of uncharacteristic frequency or electrical stimulation of the peripheral part of the receptive field of the neuron, a response consisting of EPSP-IPSP arises in the neuron. This IPSP is accompanied by inhibition of spontaneous activity of the neuron and its responses to testing stimulation. It has been shown that this inhibition is lateral in its genesis. Characteristics of these two types of inhibition are given.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 194–201, March–April, 1984.  相似文献   

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Theoretical investigations of competitive dynamics have noted that numbers of predator and prey influence each other. However, few empirical studies have demonstrated how a life-history trait of the prey (such as fecundity) can be affected simultaneously by its own density and the density of predators. For instance, density dependence can reduce fecundity with increasing number of prey, while inverse density dependence or Allee effects may occur especially when the prey is a social organism. Here we analysed an intraguild predator-prey system of two seabird species at a large spatio-temporal scale. As expected, we found that fecundity of prey was negatively affected by predator density. Nevertheless, fecundity of prey also increased nonlinearly with its own density and strikingly with the prey-predator ratio. Small groups of prey were probably not able to defend their nests especially against large number of predators. At the highest prey densities (i.e. when anti-predator strategies should be most efficient), prey fecundity also lowered, suggesting the appearance of density dependence mediated by food competition. Allee effects and density dependence occurred across a broad range of population sizes of both the prey and the predator at several local populations facing different ecological environments.  相似文献   

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The effect of auditory cortex blockade on response patterns of parietal association cortex neurons responding to different frequency tones was investigated in the cat. Blockade was produced by two methods: bilateral isolation and application of a 6% Nembutal solution to the auditory cortex surface. Frequency threshold curves were plotted for all test neurons. The majority of test neurons (84%) displayed one or two characteristic frequencies before blockade, as against only 63% of all neurons responding following blockade. Changes also affect the range of frequencies at which the cells could respond. Virtually all test neurons responded to application of a broad spectrum of frequencies under normal conditions. After blockade of the auditory cortex 69% of neurons no longer responded to tones above 8–10 kHz. This would suggest that mainly information on high frequency tones is transmitted via the auditory cortex. The question of where acoustic information for parietal association cortex neurons mostly originates is also discussed; association thalamic nuclei are thought to be the main source.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 18, No. 3, pp. 354–360, May–June, 1986.  相似文献   

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