Response of parietal association cortex neurons to acoustic stimulation before and after auditory cortex blockage in the cat

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.     

Tonotopic organization of the ventrorostral zone of the auditory cortex region AII in cats

The tonotopic organization of the ventrorostral (VR) zone of cortical auditory area AII was investigated in acute experiments on cats anesthetized with nembutal and unanesthetized immobilized animals. Response with the lowest threshold arose in 92% of test neurons to presentation of one or several sound frequencies. The majority (54%) were "tuned" to one characteristic frequency (CF), 38% to several frequencies, and 8% had no clear-cut CF. A connection was found between location of a unit within the VR zone and its CF. Neurons with the highest CF were located in the ventrocaudal AII. An increase was noted in numbers of neurons with the lowest CF with increasing distance (rost-rally) from the VR location zone of neurons tuned to a high frequency. Going by response to acoustic stimuli of frequencies ranging between 1 and 24 kHz, length of the VR projection zone of the AII was found to measure 1.8–2.0 mm. Location of the test zone in relation to auditory cortex sulci varied substantially from one animal to the next.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 22, No. 2, pp. 178–184, March–April, 1990.     

Responses of auditory cortex neurons in unanesthetized cats to best-frequency tones

The characteristics of extra- and intracellular responses of neurons in the AI region were studied in experiments with unanesthetized cats. It was established that auditory cortex neurons with similar best frequencies showed different forms of responses to tones of the corresponding frequency. About 40% of the auditory cortex neurons generated on responses to tone presentation. On — off and off responses were found in 27% of the neurons. Cortical neurons (27%) in which stimulation or inhibition of impulse discharge persisted throughout tone action were assigned to the tonic type group of cells. Approximately 6% of neurons in the AI region did not respond to a tone. During intracellular recording about 85% of the neurons responded to the turning on and/or off of a tone by generating an action potential followed by an IPSI. In 96% of the cortical neurons studied the IPSPs were a constant component of the intracellular responses to a tone. It is concluded that the inhibition of the impulse activity of the given neurons is of primarily a postsynaptic origin. Neurons showing one or another form of response differ from one another in the relative intensity and time characteristics of excitatory and inhibitory processes interacting on their postsynaptic membranes. In neurons of the phasic type inhibitory processes are dominant over excitatory, while excitatory processes are predominant in neurons of the tonic type.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 4, pp. 500–508, July–August, 1985.     

Tonotopic organization of the dorsocaudal zone of cortical area aii in the cat

The tonotopic organization of the dorsocaudal (DC) auditory cortex area AII was investigated during acute experiments on cats anesthetized with Nembutal. A capacity for selective response to presentation of auditory stimuli at a certain frequency was found in 93% of the neurons investigated. It was further observed that 75% of these cells were characterized by their fine tuning to one characteristic frequency (CF), the remaining 26% had several CF, and 7% reacted with a spike response to acoustic stimulation at all test frequencies and had no clearcut CF. A relationship was found between the location of a unit within the DC zone and its CF level. Neurons with the lowest CF were located in the upper position of the sylvian gyrus near the posterior ectosylvian sulcus. The CF of neurons rose progressively in step with increasing distance between the site of microelectrode recording and the low frequency focus of the DC zone travelling along the sylvian gyrus in a ventrorostral direction. Distance between low and high frequency foci of the DC zone measured 2.5–3.5 mm. Location of this zone in relation to the auditory cortex sulci varied considerably from one animal to another. Neurons with similar CF levels and arranged on this basis in vertical cortical columns could vary substantially in the dimensions of their receptive fields, sharpness of tunining to their own CF, and firing response pattern.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 20, No. 2, pp. 220–227, March–April, 1988.     

Excitatory and inhibitory frequency zones of responses of posterior declivus cerebelli neurons

The impulse responses of 260 neurons of the posterior declivus cerebelli of anesthetized white rats to the effect of one or two tones of different frequencies were investigated. The principal characteristics of the frequency-threshold curves (FTC) were measured. It was shown that neurons of the posterior declivus cerebelli differ considerably in optimum frequency (f₀), thresholds to f₀, and sharpness of the FTC. The lateral inhibitory zones (LIZ) of the neurons investigated in response to the effect of two tones of different frequencies in 85% of the cases are located on both sides of the f₀ and partially overlap the FTC. A low-frequency LIZ is more effective in width of the inhibitory frequency band and a high frequency LIZ is more effective in level of intensity of the frequencies causing an inhibitory effect. The width of the frequency zone of the response narrows sharply in the case of the inhibitory interaction of two tones.Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 3, No. 4, pp. 369–378, July–August, 1971.     

Interactions Between Swarming Chironomus annularius (Diptera: Chironomidae) Males: Role of Acoustic Behavior

Males of swarming species of chironomids use their auditory system (Johnston's organs) to recognize a female within swarm and do not respond to male flight tones. However, in some cases the male–male interactions were observed at a high frequency. The role of acoustic behavior in this phenomenon in C. annularius was studied. The results showed that male Johnston's organs were sensitive to male flight tones from a distance of about 1–1.5 cm. The carrier frequencies of these sounds negatively correlated with male body size. Thus we would expect that male–male interactions will occur mainly between large males. Nonetheless, the analysis of caught pairs revealed that in both male–male and female–male interactions small males had an advantage. The ability of males to perceive the male flight tones is discussed with respect to swarming behavior and mating success.     

Neurons of the cat sensorimotor cortex: Responses related to differentiation of monomodal and heteromodal conditioning signals

Spike responses of the sensorimotor cortex neurons were studied in chronic experiments on cats trained to perform an operant reflex, a placing movement triggered by application of the distant stimuli. The responses recorded under conditions of differentiation of sound tones of various frequencies and of a heteromodal complex (light + tone) from its components were compared. The responses recorded from 125 neurons in 3 animals were analyzed. No neurons selectively responding either to monomodal or to heteromodal signals were found. Forty-five cells responded to positive signals by excitation or inhibition, irrespective of the signal modality. The shortest latencies of these responses were 30 and 40 msec, respectively. When inhibitory stimuli were applied, these neurons either generated much weaker responses, or did not respond at all. A correlation was found between the level of response depression and the level of differentiation of the signals by an animal. These findings allow us to hypothesize that the sensorimotor cortex does participate in differentiation of sensory signals, providing preparation for switching on the motor response after a positive stimulus or suppression of such a response after a negative one.Neirofiziologiya/Neurophysiology, Vol. 26, No. 4, pp. 251–261, July–August, 1994.     

Area 39 and 41 neurons sensitive to acoustic stimulation in the rat cortex: Polysensory properties

A comparative analysis of the polysensory properties of 102 neurons in areas 39 and 41 (the associative and auditory cortices, respectively) was performed in acute experiments on rats under chloralose-nembutal anesthesia. In the auditory cortex, the evoked potentials (EP) recorded from the surface of the above area in response to acoustic tonal, electrical cutaneous, and light stimulations almost always were distinguished by their shorter (4–5 msec) latency and higher amplitude. We studied neurons in both areas; their responses to the pure tones of various frequencies and to the stimulations of other modalities were compared. Bi- and polysensory neurons constituted 56.4% in area 39, and only 23% in area 41. The depth distribution of the responding neurons in areas 39 and 41 was different. Neurons with selective sensitivity to different frequencies of tonal signals were found in both areas. Usually monomodal neurons demonstrated selective properties in the auditory cortex, and 70% of them had a characteristic frequency. Over one-half of polymodal cells were frequency-selective in the associative cortex.Neirofiziologiya/Neurophysiology, Vol. 26, No. 3, pp. 223–229, May–June, 1994.     

Auditory sensitivity of the saccule in the American toad (Bufo americanus)

Summary Single unit recordings in the posterior nerve branchlet from the saccule have shown that, in the American toad (Bufo americanus), approximately 30% of the fibers respond to airborne sounds in a way similar to fibers from the two known auditory organs, the amphibian and basilar papillae. In response to tones, saccule fibers have best excitatory frequencies which fall into two disjoint populations: units in the low-frequency-sensitive group (below 300 Hz) show tone-on-tone suppression while those in the high-frequency-sensitive group (700–1,200 Hz) show no evidence of peripheral inhibition. Saccule units have somewhat higher thresholds than those from the other auditory organs. It is suggested that the high-frequency-sensitive fibers might be useful for discriminating mating calls in an intense chorus while the low-frequency-sensitive units likely respond to other high intensity sounds in the environment.Research supported by the U.S. Public Health Service (NIH grant NS-09244).     

Responses of auditory medullary units to sinusoidally amplitude-modulated tones in frogs

Spike discharges of medullary units ofRana ridibunda in response to tones of optimal frequency for the neuron, with sinusoidal amplitude modulation, was studied. Reproduction of sound modulation in unit activity was assessed by the use of phase histograms of responses corresponding to the period of modulation. Amplitude modulation was reproduced in the firing pattern of neurons of the dorsal nucleus over a wide range of modulation frequencies and carrier levels. Accentuation of small changes of amplitude for modulation frequencies of 70–150 Hz was observed in many neurons of the superior olives. The phase of the response was a linear function of modulation frequency both in the dorsal nucleus and in the superior olives. The greatest enhancement of amplitude changes corresponded to low modulation indices.Academician N. N. Andreev Acoustics Institute, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 17, No. 3, pp. 390–396, May–June, 1985.     

Response in tonic type neurons of the cat auditory cortex to tones of different frequencies and intensities

In experiments on immobilized cats, intra- and extracellular response in tonic type neurons to tones of differing frequencies and intensities were investigated, as well as the organizational pattern of receptive fields in these units. Tonic type neurons were encountered at different cortical layers, but mostly (93% of the total) were located at a depth of 1.0–2.2 mm. Minimum thresholds required for response in these neurons were on average 7.7 dB below that found in neurons generating a phasic reaction in response to a tone. "Tonic" differed from "phasic" neurons in their inferior frequency-discriminative ability, with a Q₁₀ value averaging 4.1±0.4 as against 9.1±0.7 in phasic neurons. Size of receptive fields in tonic neurons (as revealed by occurrence of spike response in these units) was 3.5 times that observed in phasic cells. Length of action potentials in the majority (80%) of tonic neurons was about one and a half times to twice that found in phasic units. Tonic neurons also displayed a high degree of sensitivity to changes in the duration and intensity of acoustic stimulation.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 4, July–August, pp. 498–506, 1969.     

Discharge patterns of chicken cochlear ganglion neurons following kanamycin-induced hair cell loss and regeneration

Hair cells in the basal, high frequency region (>1100 Hz) of the chicken cochlea were destroyed with kanamycin (400 mg/kg/d × 10 d) and allowed to regenerate. Afterwards, single unit recordings were made from cochlear ganglion neurons at various times post-treatment. During the first few weeks post-treatment, only neurons with low characteristic frequencies (<1100 Hz) responded to sound. Despite the fact that the low frequency region of the cochlea was not destroyed, neurons with low characteristic frequencies had elevated thresholds, abnormally broad U-shaped or W-shaped tuning curves and low spontaneous discharge rates. At 2 days post-treatment, the spontaneous discharge rates of some acoustically unresponsive units fluctuated in a rhythmical manner. As recovery time increased, thresholds decreased, tuning curves narrowed and developed a symmetrical V-shape, spontaneous rate increased and neurons with higher characteristic frequencies began to respond to sound. In addition, the proportion of interspike interval histograms with regularly spaced peaks increased. These improvements progressed along a low-to-high characteristic frequency gradient. By 10–20 weeks post-treatment, the thresholds and tuning curves of neurons with characteristic frequencies below 2000 Hz were within normal limits; however, the spontaneous discharge rates of the neurons were still significantly lower than those from normal animals.Abbreviations KM kanamycin - BrdU bromodeoxyuridine - CF characteristic frequency - CAP compound action potential - ISI interspike interval     

Intracellular responses of primary auditory cortical neurons to tones of different frequencies and to electrical stimulation of spiral ganglion fibers in cat

Experiments on cats anesthetized with pentobarbital showed that, depending on the intensity and frequency of acoustic stimulation, neurons in auditory area AI give responses of EPSP, EPSP-spike-IPSP, EPSP-IPSP, and IPSP type. Presentation of a tone of characteristic or near-characteristic frequency and above-threshold intensity, and also electrical stimulation of nerve fibers of the spiral ganglion, innervating the central zone of the receptive field of the neuron, evoke in most cases a response of EPSP-spike-IPSP type. Tone differing considerably in frequency from the characteristic, and electrical stimulation of peripheral zones of the receptive field, evoked responses of EPSP-IPSP or IPSP type. The range of frequencies of tones to which, at threshold intensity, an action potential is generated by the neuron is considerably narrower than the range of frequencies of tones evoking an EPSP and IPSP. Above the intensity of tone threshold IPSP is an invariable component of the response of most neurons in area AI. The appearance of an IPSP in the neuron is accompanied by depression of spontaneous activity and the neuronal response to testing stimulation. Two types of IPSP were distinguished: One type is a component of the EPSP-spike-IPSP response and arises during excitation of auditory receptors located in the central part of the receptive field of the neuron, the other arises during excitation of receptors located at the periphery of the field, and which project to neurons with other characteristic frequencies. The former arise after spike excitation of the neuron, the latter after EPSP or primarily.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 16, No. 1, pp. 123–131, January–February, 1984.     

Response characteristics of inferior colliculus neurons of the awake CF-FM batRhinolophus ferrumequinum

Summary The responses of 230 single neurons in the inferior colliculus of the horseshoebat to single tones have been studied, emphasizing systematic analysis of the effective frequency bands, dynamic properties and the time course of responses. Distribution of the units' best excitatory frequencies (BEF) is: low frequency neurons 23% (BEF 3–65 kHz); FM-frequency neurons 25% (BEF 65–81 kHz, i.e., frequencies occurring in the FM-part of the bat's echo signal); filter neurons 45% (BEF 81–88 kHz, i.e., frequencies occurring in the stabilized CF-part of the bat's echo=reference frequency (RF)); high frequency neurons about 7% (BEF > 88 kHz). Tuning curves show conventional shapes (Fig. 1), apart from those of filter neurons, which are extremely narrow. Accordingly, Q_10dB-values (BEF divided by the bandwidth of the tuning curve at 10 dB above threshold) are 80–450 in filter neurons (Fig. 2). Response patterns (Fig. 3) are similar to those of Nucleus cochlearis units (transient, sustained, negative and complex responders) with an increased percentage of complex responders up to 38% and a decreased number of transient responders.All types of spike-count functions are found (Fig. 4); nonmonotonic ones dominating. Maximal spike counts are not at the BEF but a few kHz below. Distinct upper thresholds, especially at the BEF of filter neurons (Fig. 5) lead to abrupt changes in activity by slightly shifting stimulus frequency or intensity.The hallmark of inferior colliculus neurons is inhibition, disclosed by distinct inhibitory areas enfolding and overlapping excitatory ones (Figs. 3 and 5). Duration of inhibition varies with stimulus frequency, but is largely independent of stimulus duration (Fig. 6), whereas rebound of inhibition depends on stimulus duration building up periodic rebound activities, if stimulus duration is lengthened. In addition, there are neurons responding only periodically, regardless of stimulus frequency and intensity (Fig. 7). Inhibition is discussed in terms of improving the neuronal signal/spontaneous noise ratio and altering responsiveness of neurons after stimulation, so that these neurons may be suited to time processing in the acoustic pathway.Supported by grants from Stiftung Volkswagenwerk Az. 111858 and DFG Ne. 146/6ffWe thank Mrs. Nasrin Chayegan and Mrs. Martha Gonnert for technical assistance and Mrs. Angie Barker for her suggestions concerning the English.     

Functional correlates of characteristic frequency in single cochlear nerve fibers of the Mongolian gerbil

Summary Single-unit recordings obtained from the auditory nerve of the Mongolian gerbil, Meriones unguiculatus, revealed functional differences in the response properties of neurons tuned to low and high frequencies. The distribution of neural thresholds displayed a distinct rise for auditory nerve fibers with characteristic frequencies] (CFs) between 3–5 kHz. This frequency band also marked abrupt changes in both the distribution of spontaneous discharge rates and the shape of the neural tuning curve. For neurons of all CFs, spontaneous firing rates were inversely related to neural threshold but unrelated to sharpness of neural tuning. The range of CF thresholds encountered, even when data from many animals were combined, rarely exceeded 20 dB, suggesting that cochlear nerve responses obtained from this species display little inter-animal variability. These results are compared with similar data from other species and discussed in terms of recent studies on sound communication and cochlear anatomy in gerbils.Abbreviations CF characteristic frequency - SR spontaneous discharge rate     

Responses of single units in the bat cochlear nuclei to simultaneously presented cones

Investigation of single unit responses in the cochlear nuclei of bats (Vespertilionidae) to pure-tone and frequency-modulated stimuli overlapping in time showed that most (85%) of them respond to combination tones f₂–f₁ and 2f₁–f₂ (f₁ is the filling frequency of the first and f₂ of the second cone) resulting from nonlinearity in the auditory system. As a rule responses appeared whenever the frequency of the combination tone was close to the characteristic frequency of the neuron, regardless of the filling frequency of the basic tones. It is postulated that nonlinearity in the auditory system may lie at the basis of analysis of complex frequency-modulated stimuli.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 10, No. 3, pp. 252–260, May–June, 1978.     

Single unit responses to ultrasonic stimuli in the cochlear nuclei of bats

Measurement of the thresholds of single unit responses in the cochlear nuclei of Vespertilionidae and Rhinolophidae to ultrasonic stimuli of different frequencies showed that some neurons in animals of both families have 2 or 3 characteristic frequencies. If the maximal of them is taken as the basic frequency, the other two characteristic frequencies are in the ratio of 1:2 and 1:3 to it. Corresponding to these characteristic frequencies, basic and complementary response regions were recorded. InMyotis oxygnathus (Vespertilionidae), using frequency-modulated echolocation signals, some neurons in the complementary response regions respond only to stimuli of average strength, i.e., the complementary response regions are "closed." The latent periods of the single unit responses are independent of stimulus frequency. Consequently, correlative reception of echolocation signals is absent at the level of the auditory system in bats.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 9, No. 1, pp. 41–47, January–February, 1977.     

Enhancement and Distortion in the Temporal Representation of Sounds in the Ventral Cochlear Nucleus of Chinchillas and Cats

A subset of neurons in the cochlear nucleus (CN) of the auditory brainstem has the ability to enhance the auditory nerve''s temporal representation of stimulating sounds. These neurons reside in the ventral region of the CN (VCN) and are usually known as highly synchronized, or high-sync, neurons. Most published reports about the existence and properties of high-sync neurons are based on recordings performed on a VCN output tract—not the VCN itself—of cats. In other species, comprehensive studies detailing the properties of high-sync neurons, or even acknowledging their existence, are missing.Examination of the responses of a population of VCN neurons in chinchillas revealed that a subset of those neurons have temporal properties similar to high-sync neurons in the cat. Phase locking and entrainment—the ability of a neuron to fire action potentials at a certain stimulus phase and at almost every stimulus period, respectively—have similar maximum values in cats and chinchillas. Ranges of characteristic frequencies for high-sync neurons in chinchillas and cats extend up to 600 and 1000 Hz, respectively. Enhancement of temporal processing relative to auditory nerve fibers (ANFs), which has been shown previously in cats using tonal and white-noise stimuli, is also demonstrated here in the responses of VCN neurons to synthetic and spoken vowel sounds.Along with the large amount of phase locking displayed by some VCN neurons there occurs a deterioration in the spectral representation of the stimuli (tones or vowels). High-sync neurons exhibit a greater distortion in their responses to tones or vowels than do other types of VCN neurons and auditory nerve fibers.Standard deviations of first-spike latency measured in responses of high-sync neurons are lower than similar values measured in ANFs'' responses. This might indicate a role of high-sync neurons in other tasks beyond sound localization.     

Dependence of inhibitory zones of inferior collicular unit responses on temporal parameters of acoustic stimuli

Single unit activity was studied in the inferior colliculi of anesthetized albino rats in response to pure tones of different frequencies. The dependence of inhibitory interaction between neurons on temporal parameters of the acoustic stimuli (duration, time interval between tones) was investigated. Quantitative characteristics of the lateral inhibitory zones, defined as ranges of frequencies inhibiting spike generation in response to the optimal or near-optimal frequency, were examined. The inhibitory zones were found to depend essentially on the interval between application of the conditioning and testing stimuli. With an increase in the interval the inhibitory interaction decreased. If the duration of the acoustic stimuli was shortened, interaction was reduced as regards both the width of the frequency band and the intensity evoking the inhibitory effect.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 4, No. 3, pp. 236–244, May–June, 1972.     

Central auditory neurophysiology of a sound-producing fish: the mesencephalon of Pollimyrus isidori (Mormyridae)

This paper describes the auditory neurophysiology of the mesencephalon of P. isidori, a soundproducing mormyrid fish. Mormyrids have a specialized pressure-sensitive auditory periphery, and anatomical studies indicate that acoustic information is relayed to the mesencephalic nucleus MD. Fish were stimulated with tone bursts and clicks, and responses of MD neurons were recorded extracellularly. Auditory neurons had best frequencies (BF) and best sensitivities (BS) that fell within the range of frequencies and levels of the natural communication sounds of these fish. BSs were in the range of 0 to — 35 dB (re. 1.0 dyne/cm²). Many of the neurons were tuned (Q_{10 dB}: 2–6), and had BFs in the range of 100–300 Hz where the animal's sounds have their peak energy. A range of different physiological cell types were encountered, including phasic, sustained, and complex neurons. Some of the sustained neurons showed strong phase-locking to tones. Many neurons exhibited non-monotonic rate-level functions. Frequencies flanking the BF often caused a reduction in spontaneous activity suggesting inhibition. Many neurons showed excellent representation of click-trains, and some showed a temporal representation of inter-click-intervals with errors less than 1 ms.Abbreviations BF best frequency - BS best sensitivity - ELa anterior exterolateral toral nucleus - ELp posterior exterolateral toral nucleus - EOCD electric organ command discharge - FFT fast Fourier transform - HRP horseradish peroxidase - ICI inter-clickinterval - MD mediodorsal toral nucleus (=auditory nucleus) - OR onset response rate - PSTH peri-stimulus-time-histogram - R synchronization coefficient - RA response area - SS steady state response rate