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.     

Analysis of acoustically evoked call suppression behaviour in a neotropical treefrog

We broadcast synthetic call notes to male Eleutherodactylus coqui treefrogs in their natural habitat. The frogs avoided acoustic overlap with relatively long duration tone stimuli by calling only within the short silent interval between tones. We also observed a temporal change in call pattern in response to tone stimuli of various frequencies and intensities. This response is the basis for construction of a behavioural auditory threshold function for this species. This function does not show a sensitivity maximum at frequencies corresponding to those in the advertisement call, and demonstrates that the frogs are capable of behaviourally responding to sounds over a frequency range which is greater than that required for detection of the species-specific vocalizations and sufficient for detection of at least one sympatric anuran species.     

Responses of central auditory neurons to frequency-modulated stimuli

Unit responses of the inferior colliculi of albino rats to frequency-modulated stimuli were investigated. The number of spikes, firing pattern, and duration of the discharge were determined. Parameters of unit responses obtained with different directions of frequency modulation were compared with the results of testing the effect of constant-frequency tones on the neurons. The distinguishing features of the unit responses to stimuli with different directions of frequency modulation were compared with the characteristics of the frequency-threshold curve and the lateral inhibitory zones, taken as indices of the unit responses to constant-frequency tones. With a change in stimulus frequency upward or downward from the initial level the unit responses to both directions could be similar as regards the number of spikes per discharge and the firing pattern or could differ sharply depending on the direction or, finally, they could arise only if the stimulus frequency changed in one direction. In some cases selectivity for the direction of the change in stimulus frequency was due to the width and position of the lateral inhibitory zones. However, for one-third of the neurons tested analysis of the spatial characteristics of the excitatory and inhibitory zones alone was insufficient to explain the high selectivity in the formation of a response to a stimulus with frequency modulation in one direction only.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol.6, No.3, pp.237–245, May–June, 1974.     

Role of cortical inhibition in heterosensory interaction of neurons of the cat sensorimotor cortex

Background and evoked neuronal activity in the cat sensorimotor cortex was recorded under a-chloralose anesthesia. Pairs of heterogeneous stimuli were applied, spaced at intervals of 0, 100, 200, 300, and 400 msec. A clicking sound, flashing light, and electroshock to the contralateral forepaw were used as stimuli. Partial or complete blockade of response to test stimuli presentations spaced 100–200 msec apart were observed when using stimulation of varying modality. The greatest test response was recorded at interstimulus intervals of 200–300 msec. Intracellular mechanisms of heterosensory interaction were investigated by applying the inhibitory transmitter antagonist picrotoxin microiontophoretically to the test cell to produce local attenuation of inhibitory effects. This substance also reduced the duration of blockage following the conditioning stimulus and the occurrence of peak level test response at a lower interstimulus interval than in the controls. Either a consistent increase in the number of spikes per response at one of the interstimulus intervals or a uniform reinforcement in unit response to several different interstimulus intervals were observed in a proportion of the cells. The contribution of intracortical inhibitory influences to the mechanisms of heterosensory interaction on neurons of the cat sensorimotor cortex is discussed in the light of our findings.A. A. Ukhtomskii Institute of Physiology, A. A. Zhdanov State University, Leningrad. Translated from Neirofiziologiya, Vol. 19, No. 2, pp. 147–156, March–April, 1987.     

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.     

Responses of caudate neurons to acoustic stimulation in cats

Responses of 141 neurons of the caudate nucleus to acoustic stimuli — tones (500 and 2000 Hz) and clicks of different frequency (0.2 and 0.8/sec) and intensity (75, 80, 95 dB) — were recorded extracellularly in chronic experiments on cats. The responses recorded showed great variability with respect to character (phasic, tonic), structure (one or two phases of excitation), latent periods (from 7.5 to 300.0 msec), and burst discharge frequency (from 90 to 800 spikes/sec). Analysis of averaged poststimulus histograms and graphs of the dynamics of the responses showed that responses of 74% of neurons were much better expressed if less frequent stimuli were used: The regularity of the responses and the number of spikes in each response increased. Responses of neurons also increased and acquired a more distinct temporal structure if the intensity of the clicks increased. The character of responses to clicks and tones differed qualitatively in 17% of neurons studied: Phasic excitation arose in response to clicks, tonic changes in spike activity to tones. The particular features of responses of caudate neurons to acoustic stimulation with different parameters are discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 6, pp. 588–595, November–December, 1980.     

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.     

The role of inhibition in shaping the type of single neuron responses in the auditory system of the frog

The responses of single neurons of the auditory center in the frog mesencephalon to tonal stimuli of varying frequencies have been studied. It has been found that some neurons which respond to the signal of the characteristic frequency (CF) by a long-lasting discharge respond to tones of higher frequencies only at the start of stimulation. It is shown, that the tones giving rise to a phasic response inhibit impulsation brought about by the action of the CF tone.Acoustics Institute, Moscow. Translated from Neirofiziologiya, Vol. 2, No. 3, pp. 236–241, May–June, 1970.     

Neuronal response in nucleus reticularis thalami and neighboring thalamic structures to natural stimulation during chronic experiments on cats

Spike response was investigated in 104 neurons of the nucleus reticularis thalami (R) and adjoining thalamic nuclei to acoustic, tactile, and visual stimuli during chronic experiments on cats. Of the test neurons, 29% responded to acoustic stimulation and 11% showed no preference in relation to different acoustic stimuli. Minimum latencies of response to sounds measured 12–37 msec in excitatory and 18–27 msec in inhibitory cells. Duration of excitation produced by acoustic stimuli reached 50–250 msec; inhibition lasted 27–190 msec. Most cells belonging to this nucleus were excited by different stimuli; the proportion of inhibitory neurons did not exceed 4–10%.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 4, pp. 451–461, July–August, 1989.     

Responses of central auditory neurons to frequency-modulated stimuli and temporal characteristics of inhibitory interaction

Responses to frequency-modulated stimuli of 118 inferior collicular neurons were compared with quantitative characteristics of the frequency — threshold curves and lateral inhibitory zones during time-varying two-tone stimulation in anesthetized albino rats. In one third of neurons high sensitivity to the direction of frequency modulation does not correspond to their spatial characteristics (the shape, width, and arrangement of the lateral inhibitory zones relative to the frequency — threshold curve). The specificity of response of these neurons to a particular direction of frequency modulation is evidently based on differences in the temporal course of inhibition evoked by high-frequency and low-frequency tones.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 7, No. 6, pp. 603–607, November–December, 1975.     

Spectral and temporal gating mechanisms enhance the clutter rejection in the echolocating bat,Rhinolophus rouxi

Summary Doppler shift compensation behaviour in horseshoe bats, Rhinolophus rouxi, was used to test the interference of pure tones and narrow band noise with compensation performance. The distortions in Doppler shift compensation to sinusoidally frequency shifted echoes (modulation frequency: 0.1 Hz, maximum frequency shift: 3 kHz) consisted of a reduced compensation amplitude and/or a shift of the emitted frequency to lower frequencies (Fig. 1).Pure tones at frequencies between 200 and 900 Hz above the bat's resting frequency (RF) disturbed the Doppler shift compensation, with a maximum of intererence between 400 and 550 Hz (Fig. 2). Minimum duration of pure tones for interference was 20 ms and durations above 40 ms were most effective (Fig. 3). Interfering pure tones arriving later than about 10 ms after the onset of the echolocation call showed markedly reduced interference (Fig. 4). Doppler shift compensation was affected by pure tones at the optimum interfering frequency with sound pressure levels down to –48 dB rel the intensity level of the emitted call (Figs. 5, 6).Narrow bandwidth noise (bandwidth from ± 100 Hz to ± 800 Hz) disturbed Doppler shift compensation at carrier frequencies between –250 Hz below and 800 Hz above RF with a maximum of interference between 250 and 500 Hz above resting frequency (Fig. 7). The duration and delay of the noise had similar influences on interference with Doppler shift compensation as did pure tones (Figs. 8, 9). Intensity dependence for noise interference was more variable than for pure tones (-32 dB to -45 dB rel emitted sound pressure level, Fig. 10).The temporal and spectral gating in Doppler shift compensation behaviour is discussed as an effective mechanism for clutter rejection by improving the processing of frequency and amplitude transients in the echoes of horseshoe bats.Abbreviations CF constant frequency - FM frequency modulation - RF resting frequency - SPL sound pressure level     

Harmonic analysis of two-tone discharge patterns in cochlear nerve fibers

Discharges in cochlear nerve fibers evoked by low frequency phase-locked sinusoidal acoustic stimuli are synchronized to the stimulus waveform. Excitation and suppression regions of single units were explored using a stimulus composed of either a fixed intensity test tone at the characteristic frequency, a variable intensity interfering tone with a simple integer frequency relation to the characteristic frequency, or both. Compound period histograms were constructed from period histograms in response to normal and reversed polarity stimuli. Discharge patterns were characterized by Fourier components of the histogram envelopes. The two stimulus frequencies constituted the principal harmonics in the histogram envelopes and their combination accounted for observed rate changes. Suppression of the test tone harmonic as a function of interfering tone intensity was always seen; rate suppression was not. The harmonic was typically suppressed by 20–30 dB compared to the value for the test tone alone and often reached the 40–60 dB resolution limit of the experiment. Suppression plots were nearly linear on a power scale with an average slope of-0.8. The onset of suppression occurred for an interfering tone 9 dB greater on average than the test tone intensity. Information transfer through the peripheral system was described by the ratio of the principal harmonic amplitudes versus the ratio of the intensities of the two stimulus tones. These plots were nearly linear on a power scale with an average slope of 0.9. Neither the onset of suppression nor the slopes of the harmonic plots displayed strong dependence on characteristic frequency or interfering tone frequency. These features of harmonic behavior, however, are closely related to system nonlinearity. Comparison of measured harmonics to the predictions of two phenomenological models suggest the presence of complex nonlinear transformations in the peripheral auditory system.     

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.     

Responses of neurons in the rat auditory and associative cortices to tonal stimuli

Activity of single neurons and mass evoked potentials (EP) were recorded from the auditory (area 41) and associative (area 39) cortices in acute experiments on rats anesthetized with urethane, nembutal, or chloralose; pure tones were used as acoustic stimuli. The EP appearing in response to a wide range of sound tones on the surface of the auditory and associative cortices were dissimilar in their latency and shape. For neurons exhibiting stable responses, the frequency-threshold curves (FTC) were plotted.Weak and variable responses of neurons were observed under slight urethane anesthesia. Nembutal anesthesia increased the responsiveness of neurons and the probability of appearing of late components in the responses. Chloralose anesthesia was characterized by extension of frequency range perceived by a neuron, while its sharpness of tuning remained unchanged. Under all types of anesthesia employed, the responses recorded from the associative cortex neurons had longer latencies than those recorded from the auditory cortex neurons. Neurons exhibiting the frequency selectivity were much less numerous in the associative cortex than in the auditory cortex. The former neurons were often characterized by intermittent FTC and they responded to a more extended frequency range. No clear tonotopic organization was found in the associative cortex.Neirofiziologiya/Neurophysiology, Vol. 25, No. 5, pp. 343–349, September–October, 1993.     

Auditory units in the medulla of the marsh frog with unusual patterns of spontaneous activity

Statistical properties of spontaneous firing were studied in 79 single auditory units located in the dorsal medullar (cochlear) nucleus of unanaesthetized curarized marsh frogs (Rana ridibunda). The great majority of these units showed irregular spontaneous activity with mean rates in the range 1–30 spikes · s^–1. In 53% of the cells the auto-renewal functions of the spontaneous activity monotonically rose to an asymptotic value, but 41% of the cells produced auto-renewal functions which showed a pronounced peak after a dead-time period. Five low-frequency auditory neurons revealed periodic firing in the absence of controlled stimuli. The preferred period did not correspond to the unit's best frequency but demonstrated a modest correlation with the best modulation frequency of the unit's response to amplitude-modulated tones and with the duration of the after-onset dip in peri-stimulus time histograms.Abbreviations AM amplitude modulation - ARF auto-renewal function - DMN dorsal medullar nucleus - PST peristimulus time - SA spontaneous activity - TID time interval distribution - RMG response modulation gain     

Unit responses of the torus semicircularis of frogs to acoustic stimuli of different duration

The action of tonal stimuli of a characteristic frequency but of varied duration on 76 neurons of the mesencephalic auditory center (the torus semicircularis) of the frogRana temporaria was investigated. Responses to short stimuli (10 msec) of five groups of neurons differentiated by their responses to a long (300 msec) stimulus, were studied. Responses of some neurons were strengthened on shortening of the stimulus, while others responded only to tones of longer than the critical duration; this critical duration is independent of stimulus intensity over a wide range. The possible synaptic mechanisms lying at the basis of the observed effects are discussed.Acoustic Institute, Moscow. Translated from Neirofiziologiya, Vol. 5, No. 1, pp. 13–20, January–February, 1973.     

Multisensory convergence on neurons of the motor cortex in unanesthetized cats

Postsynaptic potentials (PSPs) of 83 neurons in the motor cortex of unanesthetized cats in response to electrodermal, photic, and acoustic stimulation were investigated by intra-and quasi-intracellular recording methods. Most cells responded to stimulation of at least one limb. About 60% of neurons of the posterior and over 75% of neurons of the anterior sigmoid gyrus responded to stimulation of two (or more) limbs. In 29 of 39 neurons of the anterior and 12 of 44 of the posterior sigmoid gyrus PSPs with a short (less than 50 msec) and stable latent period were evoked by flashes and clicks. On presentation of two somesthetic stimuli complete blocking (if the interval was less than 30–60 msec) or weakening (interval 30–200 msec) of responses to the second (testing) stimulus was observed. On presentation of paired photic (or acoustic) stimuli or paired stimuli of different modalities at various intervals from 0 to 100 msec, the testing response was often potentiated. The character of the responses and their interaction thus differed from those obtained under chloralose anesthesia [6, 7]. It is postulated that under the action of chloralose a system of neurons with strong excitatory feedback is formed in the motor cortex which may respond to stimuli of different modalities by something resembling the "all or nothing" principle.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 3, No. 6, pp. 563–573, November–December, 1971.     

Reaction of neurons of the medial geniculate body to acoustic stimulation

Responses of medial geniculate body (MGB) neurons to pure tones and clicks were studied in acute experiments in immobilized cats, preliminary operations being performed under calypsol anaesthesia. MGB units were identified by their reactions to cortical zone AI and brachium of inferior colliculus stimulations. When tonal stimuli were applied relay neurons of pars principalis of MGB usually demonstrated either unimodal tuning curves with narrow frequency band or fragmental ones with several narrow bands. On-response with subsequent inhibition of the background activity or without such an inhibitory period was most frequent type of the reaction (66.6%) of relay MGB neurons to tonal stimulation. The group of relay neurons with the tonic type of reaction (9.1%) was classified for which the duration of tonic response depends on the duration of tonal stimulus. Change of the excitatory reaction to the inhibitory one when the characteristic tone frequency is changed by non-characteristic++ ones is supposed to be a mechanism supplying sharpness of tuning at relay MGB neurons. It is concluded that responses of acoustic cortical neurons to sound stimulation depend to a great extent on the pattern of impulsation that comes from MGB relay units.     

Pattern of human motoneuron activity during voluntary muscular contraction

The pattern of motor unit activity of the rectus femoris muscle during isometric contraction was studied. Interspike interval sequences were analyzed. At frequencies below 8–10/sec the interval histograms were asymmetrical (long intervals predominated), the standard deviation was high and depended on the mean interval, and adjacent intervals were independent. At frequencies above 10–13/sec the interval distribution became normal in type, the standard deviation was low and independent of the mean interval duration, and negative correlation was found between adjacent intervals. During brief contraction specific for this particular (fast) muscle the activity of most neurons was of the second type, while during prolonged contraction it was of the first type. The change from activity of the first to the second type took place approximately when, with an increase in frequency, spikes began to appear against the background of after-hyperpolarization. A hypothesis is put forward to the effect that after-hyperpolarization creates the rhythm of activity (low variability of the intervals), and that the duration of after-hyperpolarization is correlated with the lower limit of working frequencies of the motoneurons. The motoneuron is regarded as performing not only a summating, but also a damping function, reducing the effect of random fluctuations of the synaptic inflow and coding information for transmission as a mean frequency.Institute of Problems of Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 3, No. 6, pp. 609–619, November–December, 1971.     

Prepulse Inhibition of Acoustic Startle Reflex as a Function of the Frequency Difference between Prepulse and Background Sounds in Mice

Background

Prepulse inhibition (PPI) depicts the effects of a weak sound preceding strong acoustic stimulus on acoustic startle response (ASR). Previous studies suggest that PPI is influenced by physical parameters of prepulse sound such as intensity and preceding time. The present study characterizes the impact of prepulse tone frequency on PPI.

Methods

Seven female C57BL mice were used in the present study. ASR was induced by a 100 dB SPL white noise burst. After assessing the effect of background sounds (white noise and pure tones) on ASR, PPI was tested by using prepulse pure tones with the background tone of either 10 or 18 kHz. The inhibitory effect was assessed by measuring and analyzing the changes in the first peak-to-peak magnitude, root mean square value, duration and latency of the ASR as the function of frequency difference between prepulse and background tones.

Results

Our data showed that ASR magnitude with pure tone background varied with tone frequency and was smaller than that with white noise background. Prepulse tone systematically reduced ASR as the function of the difference in frequency between prepulse and background tone. The 0.5 kHz difference appeared to be a prerequisite for inducing substantial ASR inhibition. The frequency dependence of PPI was similar under either a 10 or 18 kHz background tone.

Conclusion

PPI is sensitive to frequency information of the prepulse sound. However, the critical factor is not tone frequency itself, but the frequency difference between the prepulse and background tones.