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.     

Frequency range of the auditory effect of UHF

Zero beats of radiosound with an acoustic signal from an electrodynamic emitter in the frequency range up to 8 kHz were recorded in a natural experiment, which were not obtained earlier. It has been shown that the zero beats between the acoustic tonal signal and the first harmonics of the impulse succession of UHF are recorded in the points which correspond to low values on the threshold curve of UHF auditory effect.     

Characteristics of borderline modulation frequencies in the differentiation of tonal and amplitude-modulated stimuli following the removal of the inferior colliculus in rats

Elaboration of differentiation between sound stimuli was carried out in 15 laboratory rats. After bilateral ablations of auditory inferior colliculi the border frequency of stimulus amplitude modulation was determined for all rats when they still could differentiate between tonal and amplitude-modulated stimuli. Decrease in frequency of modulation by 2 Hz and more from the border frequency caused a complete loss of ability to differentiate. In all rats bilateral inferior colliculi ablations completely disturbed differentiation between tonal and amplitude-modulated signals with modulation frequency below 183-191 Hz (the range of border frequencies). The surgery however did not affect differentiation between tonal and amplitude-modulated signals with the modulation frequencies above 183-191 Hz. The data suggest that the functions of completion of coding of amplitude-modulated stimuli in the auditory system is strictly linked with definite structures.     

Hearing of old world monkeys (Cercopithecinae)

The characteristics of normal hearing were examined in the laboratory for seven species of Old World monkeys. Operant conditioning procedures, coupled with standard audiometric testing methods, were used to assess thresholds of hearing, frequency range of hearing, and differential sensitivity to auditory intensity and frequency. To produce tonal stimulation, an animal was trained to touch and maintain manual contact with a contact-sensitive key and to report hearing the tone by lifting his hand from the key; this response was followed by food reinforcement. When the reporting response occurred without the auditory signal, the animal was punished by a short suspension from the experiment. Additional contingencies were added to ensure stable and reliable responding, and threshold and differential acuity determinations were then made. Threshold was defined as the stimulus value responded to correctly 50% of the time. The frequency range of hearing of all the cercopithecoids tested extended from 60 to 40,000 Hz, an octave above the upper bound of 20,000 Hz for man but well below the 60–70,000 Hz limit for some prosimians. Absolute sensitivity for tonal stimulation in the most sensitive frequency range (1–8 kHz) was about 2 × 10^?4 microbars, comparable to that of other primates tested, including man. Thus, the Old World monkey appears only slightly less sensitive than man to small changes in intensity and frequency of acoustic stimulation. At 1000 Hz at 60 dB above the threshold of audibility, his limit of resolution is about 5 Hz for frequency and 2 dB for intensity.     

Adaptation of differential sensitivity of auditory system neurons to amplitude modulation after abrupt change of signal level

Impulse activity of neurons of brainstem auditory nuclei (medulla dorsal nucleus and midbrain torus semicircularis) of the grass frog (Rana temporaria) was recorded under action of long amplitude-modulated tonal signals. After adaptation of neuronal response to acting stimulus (30–60 s after its onset), we performed a sharp change (by 20–40 dB) of the mean signal level with preservation of unchanged frequency and depth of modulation. We also recorded a change of density impulsation and of degree of its synchronization with the modulation period as well as the phase of maximum reaction at the modulation period and phase of the response every 2 or 4 s. In the adapted state, the sharp change of the mean level had been provided, while maintaining frequency and depth unchanged. During the adaptation to long signals with small modulation indexes the firing rate continuously decreased, but synchronization with envelope usually increased considerably. A sharp rise in the mean level resulted in an increase of firing rate, which could be accompanied either by a continuation of synchronization growth (the effect is more typical of the dorsal nucleus) or by a sharp fall in synchrony with its subsequent slow recovery (the effect is more typical of the torus semicircularis). Nature of the changes following the change of the intensity of the reaction could depend on the signal parameters (initial level, magnitude of the jump, frequency and depth of modulation). The connection between the observed physiological data and the psychophysics of differential intensity coding is discussed.     

Seismic and auditory tuning curves from bullfrog saccular and amphibian papular axons

We present seismic and auditory frequency tuning curves of individual bullfrog, Rana catesbeiana, saccular and amphibian papilla axons that responded to both seismic and auditory stimuli. In this study we found: 1) most saccular axons respond well to auditory stimuli with moderate signal strength (50-70 dB SPL) as well as to seismic stimuli; 2) most amphibian papilla axons respond well to seismic stimuli as well as to auditory stimuli, and their seismic sensitivities are comparable to those of saccular axons (responding to sinusoidal stimuli with peak accelerations in the range 0.001 to 0.1 cm/S2); 3) the responses to both seismic and auditory stimuli from both saccule and amphibian papilla are tuned, i.e. the strength of the response varies with the frequency of the stimulus; and this tuning is clearly not the result of second order resonance; 4) in individual axons the tuning properties for seismic stimuli often are not the same as those for auditory stimuli, a fact that may provide clues about how the stimulus signal energy is transferred to the hair cells in each case.     

Responses to features of the calling song by ascending auditory interneurones in the cricket Gryllus campestris

ABSTRACT. In female Gryllus campestris L., three functional types of ascending auditory intemeurones have been studied by recording from them extracellularly in the split cervical connectives using suction electrodes. Type 1 neurones are characterized by an optimal sensitivity to the carrier frequency of the species calling song (4–5 kHz). They copy the syllable and pause structure of the call at all intensities. The patterned spike discharge is observable at least 8 dB above absolute threshold. With suprathreshold stimulation, the neurones exhibit maximal responses (number of spikes/chirp) around the carrier frequency. The intensity response curves are approximately linear in the range of 40–90 dB SPL. The envelope of each syllable is reflected by a corresponding change in the firing rate, and syllable periods of 24ms and longer are resolved. This type can be considered as a neural correlate for phonotactic behaviour of the female where the syllable period has been found to be the most important temporal parameter. Type 2 neurones are most sensitive in the range of 4–6 and 11–13 kHz. They copy the syllable and pause structure of the species calling song at low and moderate intensities. However, the spikes invade the intersyllable pauses, when stimulated with the calling song at higher intensities (above 85 dB). This is particularly apparent at the onset of a chirp series. The slope of the intensity—response curve mimics that of type 1 units. The neurones cannot follow syllable periods shorter than 32 ms. Type 3 neurones differ from types 1 and 2 by a rather broad-band sensitivity in the range of 3–16 kHz, and in copying the chirp as a whole. Even at low stimulus intensities, the intersyllable pauses are filled with spikes, and information about the syllable—pause structure is lost. Stimulation with suprathreshold intensities gives rise to a rather uniform, broad-band response without distinctive peaks. The intensity—response curve is characterized by a higher absolute threshold, and by the reduction in the response magnitude starting above 70–80 dB. These units are not suitable for copying the calling song temporal structure in detail, but would indicate the chirping rhythm. Their strong response in the range of the species courtship song carrier frequency make them suitable to copy the courtship song.     

Development of the auditory sensitivity and formation of the acoustically guided defensive behavior in nestlings of the pied flycatcher Ficedula hypoleuca

Age dynamics of generation of the evoked potentials (EP) in the field L of caudal nidopallium (the higher integrative center of the avian auditory system) and development of the auditory-guided defensive behavior were studied in control and visually deprived pied flycatcher Ficedula hypoleuca nestlings. It was shown that the rhythmically organized monofrequency signals with sound frequency 3.5 kHz and higher produced the defensive behavior as the auditory sensitivity to these frequencies matured. After 9 days, the species-specific alarm signal produced more effectively the defensive behavior than the tonal signals. The rhythmically organized sound with filling frequency 0.5 kHz, occupying the less low-frequency diapason than the feeding signal, produced the effect opposite to the alarm signal to increase the nestling mobility. At the initial stage of the defensive behavior development the auditory threshold fell markedly in the frequency diapason corresponding to the frequency diapason of the alarm signal (5–6 kHz), which seemed to facilitate involvement of this diapason signals in the defensive integration. The auditory EP generation thresholds in the whole studied diapason were lower in the visually deprived nestlings than in the normally developing one; however, the ability of the acoustic signals to suppress alimentary reactions fell significantly.     

Adaptive Changes of Spatial Characteristics of Hearing in the Dolphin Tursiops truncatus

Adaptive abilities of the dolphin auditory system at perception of tonal signals of different frequencies were studied under conditions of spatial uncertainty of their presentation in the noise field. It has been shown that a transition from the threshold to the suprathreshold detection is accompanied by adaptive changes of spatial characteristics of auditory perception: transformation of the one-lobe direction diagrams into the two-lobe ones is observed, as well as their broadening and a shift of the sensitivity maximum from the frontal direction to the side one. The dependence of direction characteristics on frequency of the perceived signal is lost.     

Modulation of auditory responsiveness in the locust

The auditory responsiveness of a number of neurones in the meso- and metathoracic ganglia of the locust, Locusta migratoria, was found to change systematically during concomitant wind stimulation. Changes in responsiveness were of three kinds: a suppression of the response to low frequency sound (5 kHz), but an unchanged or increased response to high frequency (12 kHz) sound; an increased response to all sound; a decrease in the excitatory, and an increase in the inhibitory, components of a response to sound. Suppression of the response to low frequency sound was mediated by wind, rather than by the flight motor. Wind stimulation caused an increase in membrane conductance and concomitant depolarization in recorded neurones. Wind stimulation potentiated the spike response to a given depolarizing current, and the spike response to a high frequency sound, by about the same amount. The strongest wind-related input to interneuron 714 was via the metathoracic N6, which carries the axons of auditory receptors from the ear. The EPSP evoked in central neurones by electrical stimulation of metathoracic N6 was suppressed by wind stimulation, and by low frequency (5 kHz), but not high frequency (10 kHz), sound. This suppression disappeared when N6 was cut distally to the stimulating electrodes. Responses to low frequency (5 kHz), rather than high frequency (12 kHz), sounds could be suppressed by a second low frequency tone with an intensity above 50-55 dB SPL for a 5 kHz suppressing tone. Suppression of the electrically-evoked EPSP in neurone 714 was greatest at those sound frequencies represented maximally in the spectrum of the locust's wingbeat. It is concluded that the acoustic components of a wind stimulus are able to mediate both inhibition and excitation in the auditory pathway. By suppressing the responses to low frequency sounds, wind stimulation would effectively shift the frequency-response characteristics of central auditory neurones during flight.     

Role of the geniculate body in performing conditioned reflexes to amplitude-modulated stimuli in the rat

In 13 laboratory rats with bilateral auditory cortex ablation, the border frequency of amplitude-modulation still allowing differentiation between tonal and amplitude-modulated stimuli, did not change after bilateral section of the brachii of the posterior colliculi. Bilateral auditory cortex ablation and section of the brachii drastically disturbed this differentiation when the modulation frequencies were higher than 27-31 Hz. The data suggest that the completion of coding of amplitude-modulated stimuli does not take place at the level of the medial geniculate body, and that border frequencies defined after auditory cortex ablation are linked with the frontier posterior colliculi--thalamo-cortical system.     

Multidimensional auditory stimulus control in a chimpanzee (Pan troglodytes)

An adolescent female chimpanzee (Pan troglodytes) was trained to discriminate auditory compound stimuli differing in tonal frequency and/or tone on-off rate. Following acquisition training and overtraining, she was shifted to multidimensional stimulus control testing using redundant relevant auditory stimulus sets with discriminability of elements in each dimension varied systematically. Although the control by both dimensions changed significantly as a function of discriminability, the degree of dimensional control was stronger in the tone on-off rate than in the tonal frequency. These results clearly demonstrated “attentional” control of the chimpanzee's auditory discrimination behavior and the interaction between two dimensions of auditory stimuli. The author is now at the Department of Psychology, Primate Research Institute, Kyoto University as a transfer student of the Doctor course.     

Reactions of neurons of the orbitofrontal cortex to stimulation of optic thalamic nuclei

The reactions of 288 neurons of the orbitofrontal cortex (OFC) to stimulation of the posteroventral (VP), ventral anterior (VA), and reticular (R) nuclei, as well as the median center (CM) of the thalamus, were investigated in acute experiments on cats. OFC neurons can be divided into four groups by their reactions to stimulation of thalamic nuclei: 1) those which respond with an increase in the frequency of the discharges to single and serial stimuli with a frequency of up to 20/sec; 2) those which respond doubtfully to single stimuli with a frequency of 4–12/sec; 3) those which respond with inhibition of the background impulses; 4) those which do not respond to stimulation of the nuclei. Stimulation of the thalamic nuclei evoked responses of OFC neurons with a large scatter of the latent period duration. The responses of neurons to stimulation of the VP (mean latent period 19.1±6.1 msec) had the shortest latent period (sometimes less than 3–4 msec). Reactions with a longer latent period developed upon stimulation of the VA (23.8±7.4 msec) and CM (42.8±12.8 msec). The uniqueness of the links of the OFC with the various optic thalamic nuclei is shown in an analysis of the material obtained and possible methods of the activation of the neurons of this region from thalamic structures are discussed.State Medical Institute, Kemerovo. Translated from Neirofiziologiya, Vol. 3, No. 4, pp. 350–358, July–August, 1971.     

The generation of direction selectivity in the auditory system

Both human speech and animal vocal signals contain frequency-modulated (FM) sounds. Although central auditory neurons that selectively respond to the direction of frequency modulation are known, the synaptic mechanisms underlying the generation of direction selectivity (DS) remain elusive. Here we show the emergence of DS neurons in the inferior colliculus by mapping the three major subcortical auditory nuclei. Cell-attached recordings reveal a highly reliable and precise firing of DS neurons to FM sweeps in a preferred direction. By using in vivo whole-cell current-clamp and voltage-clamp recordings, we found that the synaptic inputs to DS neurons are not direction selective, but temporally reversed excitatory and inhibitory synaptic inputs are evoked in response to opposing directions of FM sweeps. The construction of such temporal asymmetry, resulting DS, and its topography can be attributed to the spectral disparity of the excitatory and the inhibitory synaptic tonal receptive fields.     

Convergence of heterotopic nociceptive information onto neurons of the subnucleus reticularis dorsalis in the rat

The nature of stimuli that activate neurones located within the Subnucleus Reticularis Dorsalis (SRD) was determined. These neurones do not respond to visual, auditory or proprioceptive stimuli but are preferentially or even exclusively activated by noxious stimuli applied to any part of the body; only neurones of a sub-group have a predominantly contralateral activation. All the neurones were exclusively activated by stimulation of A delta or A delta and C afferent fibres. These observations suggest that this well-delimited reticular structure is specifically involved in the processing of nociceptive information.     

Characteristics of unit responses of the cat cerebellar cortex to acoustic stimuli

Investigation of unit responses of the cerebellar cortex (lobules VI–VII of the vermis) to acoustic stimulation showed that the great majority of neurons responded by a discharge of one spike or a group of spikes with a latent period of 10–40 msec and with a low fluctuation value. Neurons identified as Purkinje cells responded to sound either by inhibition of spontaneous activity or by a "climbing fiber response" with a latent period of 40–60 msec and with a high fluctuation value. In 4 of 80 neurons a prolonged (lasting about 1 sec or more), variable response with a latent period of 225–580 msec was observed. The minimal thresholds of unit responses to acoustic stimuli were distributed within the range from –7 to 77 dB, with a mode from 20 to 50 dB. All the characteristics of the cerebellar unit responses studied were independent of the intensity, duration, and frequency of the sound, like neurons of short-latency type in the inferior colliculi. In certain properties — firing pattern, latent period, and threshold of response — the cerebellar neurons resemble neurons of higher levels of the auditory system: the medial geniculate body and auditory cortex.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 5, No. 1, pp. 3–12, January–February, 1973.     

Effect of temperature on auditory receptor functions in bushcrickets (Orthoptera, Tettigonioidea)

By electrophysiological methods, effect of temperature on bushcricket tympanal organ functions was studied. Activity of auditory receptors was recorded intracellularly in the 5th nerve of I thoracic ganglion in Tettigonia cantans, Metrioptera roeselii, M. bicolor, Platycleis albopunctata, Pholidoptera griseoaptera, and Phaneroptera falcata. The temperature was changed in the range from 17 to 34 degrees C. Heating of the tympanal organ to 30-32 degrees C led to a decrease of impulse amplitude, shortening of their duration, an increase of sensitivity, of the burst instantaneous frequency, and of the number of impulses in responses as well as to a decrease of latent periods (LP) of receptor reaction. The optimal frequency in all studied cells did not change, although range of perceived frequencies was enlarged. The frequency threshold curve of receptors either was shifted down along the ordinate scale without changes of its shape or the thresholds at various frequencies decreased non-uniformly. Thus, the obtained data indicate the absence of changes in the frequency tuning of the auditory receptors with changes of temperature.     

Effect of dominant motivation on the functional organization of the auditory input into the sensorimotor cortex of the cat brain

To consider the role of dominant motivation in functional organization of acoustic input to the sensorimotor cortex (SMC), a comparison was made of frequency reflection of tonal bursts in the rostral neocortex summary reactions, and for comparison, in the parietal association cortical area (PC), in the normal state, during pregnancy and after the kittens birth. During pregnancy an increase of the amplitude of averaged evoked potentials (AEP) of SMC and PC was observed practically in the whole studied frequency range. After kittens birth the range of changes narrowed and reactions with maximum amplitude were recorded in females to presentation of tonal bursts with frequencies which corresponded to spectral characteristics of their own kittens vocalizations. However, absolute value of changes of AEPs amplitude, observed in PC were less expressed. As a role the obtained data testify that reorganization of frequency selectivity of SMC acoustic input observed under the influence of dominant motivation, conforms to a change of kittens acoustic signals biological meaning for females in lactation period.     

Processing of vibratory and acoustic signals by ventral cord neurones in the cricket Gryllus campestris

The responses of single vibratory receptors and ascending ventral cord interneurones were studied extracellularly in Gryllus campestris L. The physiology of the vibration receptors resembled those found in tettigoniids and locusts. The frequency responses of the subgenual receptors provide two possible cues for central frequency discrimination: differences in mean tuning between groups of receptors in the different leg pairs and a range of receptors tuned to different frequencies within one subgenual organ.Most of the ascending vibratory interneurones were highly sensitive in either the low or high frequency range. Broadbanded neurones were less sensitive. The characteristic sensitivity peaks of these units are due mainly to receptor inputs from a particular leg pair, although most central neurones receive inputs from all 6 legs. Only one neurone type, TN1 received excitatory inputs from both auditory and vibratory receptors; its responses were greatly enhanced by the simultaneous presentation of both stimulus modes. The responses to sound stimuli of AN2, on the other hand, were inhibited by vibration. No other auditory interneurones investigated were influenced by inputs from vibration receptors. Central processing of vibratory information in the cricket is compared with that of tettigoniids and locusts.     

Postsynaptic potentials in the myocardium of snails in the genus Helix

Cardioregulating neurones in the right parietal and visceral ganglia of the snail evoke postsynaptic potentials of various duration, amplitude and polarity in the auricular and ventricular myocardium. Inhibitory neurones with a marked background activity (1-2 imp/s) evoke IPSPs with a duration of 150-200 msec and a latent period of 160-220 msec in the auricle, these potentials being blocked by tubocurarine. EPSPs of approximately the same duration may be recorded in the ventricle during stimulation of the commanding neurones of the pneumostome LPa3 and PPa/3, as well as unidentified neurones. Action potentials in some other identified cardiostimulating neurones (PPa7, V1, V6) induce slow and sustained depolarization in the myocardium. Functional specificity of elements within fast and slow regulatory systems is suggested: discrete IPSPs and EPSPs account mainly for coordination of the systolic contractions of the auricle and ventricle, whereas long-lasting PSPs affect the frequency and intensity of the whole heart.