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.     

Unit responses of the superior olives in bats to single and paired ultrasonic stimuli

Single unit responses in the superior olive of the greater horseshoe bat to ultrasonic stimuli with a filling frequency within the echolocation range were investigated. Some neurons were found to have three completely unconnected response regions with characteristic frequencies of 1/2 and 1/3 of the basic frequency, which was within the 80–86 kHz band. An increase in strength of the stimulus with filling frequency equal to the characteristic frequency of the neuron changed the tonic regime of activity into phasic. Presentation of two stimuli, overlapping in time, replaced the phasic regime by tonic. The frequency of the tonic response corresponded exactly to the beating frequency up to 1200 Hz (synchronization of unit discharges with each beating cycle). The synchronized tonic regime was preserved to definite strengths and filling frequencies of the two stimuli.A. A. Zhdanov State University, Leningrad. Translated from Neirofiziologiya, Vol. 8, No. 1, pp. 30–38, January–February, 1976.     

Characteristics of unit responses of the cochlear nuclei of bats (Rhinolophidae) to single and paired ultrasonic stimuli

Characteristics of single unit responses of the cochlear nuclei of greater horseshoe bats to ultrasonic stimuli with a filling frequency within the echolocation range were investigated. In most neurons three unconnected regions of responses were found, with characteristic frequencies equal to 1/2 and 1/3 of the basic frequency, within the range 80–90 kHz. The response regions had inhibitory zones, one of which was higher than the basic characteristic frequency whereas the other two were overlapped by the complementary response regions. Selectivity of the neurons to the frequency of stimulation increased with a change in the characteristic frequency from 90 to 80 kHz; it was maximal in the band 80–80.5 kHz.     

Neural organization and responses to complex stimuli in the dorsal cochlear nucleus.

The dorsal division of the cochlear nucleus (DCN) is the most complex of its subdivisions in terms of both anatomical organization and physiological response types. Hypotheses about the functional role of the DCN in hearing are as yet primitive, in part because the organizational complexity of the DCN has made development of a comprehensive and predictive model of its input-output processing difficult. The responses of DCN cells to complex stimuli, especially filtered noise, are interesting because they demonstrate properties that cannot be predicted, without further assumptions, from responses to narrow band stimuli, such as tones. In this paper, we discuss the functional organization of the DCN, i.e. the morphological organization of synaptic connections within the nucleus and the nature of synaptic interactions between its cells. We then discuss the responses of DCN principal cells to filtered noise stimuli that model the spectral sound localization cues produced by the pinna. These data imply that the DCN plays a role in interpreting sound localization cues; supporting evidence for such a role is discussed.     

Unit responses of the cat caudate nucleus to cortical stimulation before and after destruction of nonspecific thalamic nuclei

Responses of caudate neurons to stimulation of the anterior sigmoid and various parts of the suprasylvian gyrus were studied in acute experiments on cats. The experiments consisted of two series: on animals with an intact thalamus and on animals after preliminary destruction of the nonspecific thalamic nuclei. Stimulation of all cortical areas tested in intact animals evoked complex multicomponent responses in caudate neurons with (or without) initial excitation, followed by a phase of inhibition and late activation. The latent periods of the initial responses to stimulation of all parts of the cortex were long and averaged 14.5–25.5 msec. Quantitative and qualitative differences were established in responses of the caudate neurons to stimulation of different parts of the cortex. Considerable convergence of cortical influences on neurons of the caudate nucleus was found. After destruction of the nonspecific thalamic nuclei all components of the complex response of the caudate neurons to cortical stimulation were preserved, and only the time course of late activation was modified.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 5, pp. 464–471, September–October, 1980.     

Unit responses of the ventral posterior and ventral lateral thalamic nuclei to electrical stimulation of the thalamic reticular nucleus

A microelectrode investigation was made of responses of 72 physiologically identified neurons of the ventral posterior (VP) and 116 neurons of the ventral lateral (VL) thalamic nuclei to electrical stimulation of the reticular (R) thalamic nucleus. Mainly those neurons of VP and VL (73.7 and 86.2% respectively) which responded to stimulation of the first motor area and nucleus interpositus of the cerebellum responded to stimulation of R; 19.8% of VL neurons tested responded to stimulation of R by an antidromic action potential with latent period of 0.5–2.0 msec and 46.6% of neurons responded by orthodromic excitation; 23% of orthodromic responses had a latent period of 0.9–3.5 msec and 77% a latent period of 4.0–21.0 msec; 19.8% of VL neurons tested were inhibited. Among IPSPs recorded only one was monosynaptic (1.0 msec) and the rest polysynaptic. It is postulated that both R neurons are excitatory and that the inhibition which develops in VL neurons during stimulation of R are connected mainly with activation of inhibitory interneurons outside the reticular nucleus.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 9, No. 5, pp. 477–485, September–October, 1977.     

Unit responses in area 5b of the suprasylvian gyrus to stimulation of the ventral posterolateral thalamic nucleus

Unanesthetized cats were immobilized with D-tubocurarine. Single unit responses in area 5b of the suprasylvian gyrus to stimulation of the ventral posterolateral thalamic nucleus were recorded extracellularly. Of the total number of neurons tested, 32% were excited and 3% inhibited. In 65% of neurons the responses were mixed, most of them being predominantly excitatory. Repetitive stimulation of the ventral posterolateral nucleus (6–9/sec) frequently intensified the excitatory component of the responses. Sometimes inhibition, present in the response to a single stimulus, was replaced by increased excitation. However, the same response as to a single stimulus frequently appeared in response to each consecutive stimulus of a series. Stimulation of the ventral posterolateral nucleus had a mainly excitatory effect on neurons in area 5b. Stimulation of the dorsal lateral nucleus, on the other hand, inhibited their activity. This antagonism could also be observed on the same neuron. It was concluded from the short latent periods of the orthodromic responses (3–6 msec) and from the antidromic responses of the cortical neurons to stimulation of the ventral posterolateral nucleus that this nucleus has direct two-way connections with the cortex of area 5b.     

A new type of synapse in the ventral cochlear nucleus

Summary In this paper we report the appearance of flat vesicle-containing endings in aldehyde-fixed ventral cochlear nucleus of rats with qualitative and quantitative properties suggesting they should be identified as calyceal processes. Their synaptic vesicles are elongate and significantly smaller than the vesicles in the calyces of Lenn and Reese (1966). Therefore these endings are flat vesicular calyceal processes, possibly of inhibitory function.Dedicated in grateful appreciation to Professor Dr. Ewald Wüstenfeld     

Characteristics of electrical responses by cochlear nuclei in Vespertilionidae and Rhinolophidae to ultrasonic stimuli with various fill frequencies

The total electrical response and action potentials of separate neurons in the cochlear nuclei in Vespertilionidae and Rhinolophidae were investigated. Maximum sensitivity to ultrasound was recorded in Vespertilionidae in the frequency ranges 10–30 and 70–80 kc/sec, and in Rhinolophidae in the frequency ranges 10–30 and 84–86 kc/sec. Mininum off-response thresholds were observed in Vespertilionidae in the range 50–60 kc/sec, and in Rhinolophidae in the range 78–80 kc/sec. The areas of responses by neurons in the cochlear nuclei in both species of bats were similar in shape to those recorded in the same structure in other animals. An exception was provided by Rhinolophidae, in which three peculiar types of neurons were observed: 1) neurons whose response area lay in the frequency ranges up to 78 kc/sec or from 80 to 90 kc/sec; 2) neurons responding in the range 40–90 kc/sec, but not sensitive to stimuli with a fill frequency of 78–80 kc/sec; and 3) neurons whose response area lay in the range 78–80 kc/sec, but in which the character of the response changed from tonic to phasic when there was a change in the fill frequency of the stimulus. Maximum selectivity with regard to fill frequency of stimulus was observed in the neurons of Rhinolophidae in the frequency range 70–90 kc/sec.The term "fill frequency" can be rendered as frequency — Consultants Bureau.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 3, No. 4, pp. 379–385, July–August, 1971.     

Electrophysiological responses in guinea pig cochlea to low frequency sound stimuli: distortion of cochlear microphonic (CM) wave form

The present experiment investigated whether or not auditory responses of the middle and/or inner ear in guinea pigs to low frequency sound stimuli [ 60 Hz-2 kHz at 90-120 dB(SPL) ] exhibited the harmonic distortion phenomenon resulting from cochlear microphonics (CM). Measurement of CM leading in turn I by the differential electrode recording method involved measurement of 50 microV isopotential responses, output voltages and CM wave form distortion at each constant sound pressure. The results obtained were as follows: (1) On the 50 microV isopotential response curve and the output voltage curves, the changes at 60-90 Hz were different from those at higher frequencies. (2) At stimuli of 90 or 100 dB(SPL), CM wave form distortion appeared frequently at frequencies below 120 Hz, but were less pronounced above approximately 200 Hz. (3) When raised to 110 and 120 dB(SPL), almost all CM wave forms were distorted at all test frequencies between 60 and 500 Hz. (4) The patterns of CM wave form distortion at frequencies below approximately 120 Hz showed peak clipping and triangular wave distortions, while those at frequencies above approximately 200 Hz showed little of these distortions.     

Unit responses of the sensomotor cortex to paired electrical stimuli

Unit responses of the sensomotor cortex to paired electrical stimulation and visual cortex, applied either simultaneously or after various delays (from 0 to 200 msec) depend on the order of application of the stimuli and on the interval between them. If stimulation of the sensomotor cortex was used in a conditioning role the response continued unchanged when the intervals between stimuli were increased to 200 msec. If, however, stimulation of the sensomotor cortex had a testing role interaction was observed between the stimuli so that responses to both first and second stimuli were blocked; this was exhibited most clearly for intervals of 40–80 msec between stimuli. The blocking effect persisted on some neurons with delays of up to 200 msec between stimuli, while the response of others to both the first and the second stimulus was restored.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 5, No. 6, pp. 628–635, November–December, 1973.     

Electric reactions of the auditory cortex areas in bats to ultrasonic stimuli with various fill frequencies

The overall electric reactions and action potentials of single neurons in the auditory cortex were investigated for Vespertilionidae (Myotis oxygnathus) and Rhinolophidae (Rhinolophus ferrum equinum) narcotized with Hexenal. In the Vespertilionidae the greatest sensitivity to ultrasound is manifest at frequencies from 10 to 50 kHz, and in the Rhinolophidae for the ranges from 10 to 40 and from 82 to 84 kHz. The shapes of the response areas of single neurons in both types of bats are similar except for neurons discovered in Rhinolophidae that have three response areas with characteristic frequencies in the ranges 27–28, 40–42, and 80–84kHz. Narrow response areas with characteristic frequencies in the range from 70 to 90kHz appear on a considerable proportion of the neurons in the Rhinolophidae, but not the Vespertilionidae. Low thresholds are recorded to the stimulus cutoff in the range from 76 to 86 kHz.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 3, No. 5, pp. 526–532, September–October, 1971.     

A quantitative analysis of ipsilateral tectal unit responses to moving stimuli in frogs

Ipsilateral retino-tecto-tectal (IRTT) units were recorded extracellularly in the rostral optic tectum of the frog (Rana esculenta). The activity of 79 superficial units (II type) was quantified in response to black disks of various sizes, moved vertically at various angular velocities and against a white background. The contrast ¦C¦ was constant during the experiments. Neuronal activity was analysed by two methods, yielding identical results:

Unit responses in the posterior suprasylvian gyrus of cats to different stimuli

Extracellular responses of 151 spontaneously active neurons in a small area of the cortex of the posterior suprasylvian gyrus to flashes, clicks, and electrodermal stimulation were studied in unanesthetized cats immobilized with D-tubocurarine. Altogether 63% of neurons responded to the stimuli, of which flashes were the most effective. The proportions of polybi-, and monosensory responding neurons were 60, 18, and 22% respectively. Responding neurons were found throughout the thickness of the cortex, but most frequently at depths of 1000–2000 µ from the brain surface. The latent periods varied not only for different cells (from 20 to 90 msec to all stimuli), but also for the same cell. Responses were unstable, prolonged (over 1 sec) and complex in their dynamic pattern (several phases of increase and decrease in frequency of spontaneous discharges or merely a prolonged increase or decrease in its frequency). In the character of their responses the neurons were divided into 4 groups: 1) poly- and bisensory with equivalent responses to all stimuli; 2) poly- and bi-sensory with nonequivalent responses; 3) monosensory, and 4) nonresponding. The results show that this area of the posterior suprasylvian gyrus is part of the associative cortex with projection predominantly of the visual receptor.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 4, pp. 375–383, July–August, 1972.     

Unit responses of the squirrel visual cortex to shaped visual stimuli

Visual cortical unit responses of the squirrelSciurus vulgaris to shaped visual stimuli (stationary and moving spots and bands) were studied. Neurons responding selectively to the direction of stimulus movement and orientation of lines and those not responding selectively to these features were distinguished. Many neurons, whether responding selectively or not to movement direction, were specifically sensitive to high speeds of movement, of the order of hundreds of degrees per second. This selectivity in neurons responding selectively to movement direction persisted at these high speeds, despite the short time taken by the stimulus to move across the receptive field. Neurons responding selectively to line orientation were sensitive to lower speeds of stimulus movement — from units to tens of degrees per second. Neuronal sensitivity to high speeds of stimulus movement is achieved through rapid summation of excitation from large areas of the receptive field crossed by the fast-moving stimulus. Selectivity of the response to movement direction is produced under these conditions with the aid of directed short-latency inhibition, inhibiting unit activity for stimulus movement in "zero" direction.     

The ultrasonic responses of albino mouse pups to tactile stimuli

Tactile stimuli, like environmental temperature changes, can evoke ultrasonic responses from albino mouse pups. But the changes with age in the intensity of ultrasounds so produced follow a different pattern from those due to temperature changes. The responses begin with very high intensity pulses in the very young pups and then gradually decline with the age of the pups. The present report arises from a systematic study of this phenomenon, the results of which are discussed in relation to those of previous ones.     

Resonance phenomena in the cochlea of the mustache bat and their contribution to neuronal response characteristics in the cochlear nucleus

Summary The cochlea of the mustache bat, Pteronotus parnellii, is very sensitive and sharply tuned to the frequency range of the dominant second harmonic of the echolocation call around 61 kHz. About 900 Hz above this frequency the cochlear microphonic potential (CM) reaches its maximum amplitude and lowest threshold. At exactly the same frequency, pronounced evoked otoacoustic emissions (OAE) can be measured in the outer ear canal, indicating mechanical resonance. The CM amplitude maximum and the OAE are most severely masked by simultaneous exposure to tones within the range from about 61–62 kHz up to about 70 kHz. The data suggest that the mechanism of mechanical resonance involves cochlear loci basal to the 61 kHz position.The resonance contributes to auditory sensitivity and sharp tuning: At the frequency of the OAE, single unit responses in the cochlear nucleus have the lowest thresholds. Maximum tuning sharpness occurs at frequencies about 300 Hz below the OAE-frequency, where the threshold is about 10 dB less sensitive than at the OAE-frequency. In addition, in the frequency range around the OAE-frequency several specialized neuronal response features can be related to mechanical resonance: Long lasting excitation after the end of the stimulus, asymmetrical tuning curves with a shallow high frequency slope and phasic on-off neuronal response patterns. In particular the latter phenomenon indicates the occurrence of local mechanical cancellations in the cochlea.Abbreviations CF constant frequency component of echolocation calls - CM cochlear microphonic potential - FM frequency modulated component of echolocation calls - N1 compound action potential of the auditory nerve - OAE octoacoustic emission - SEOAE synchronous evoked OAE