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 electrical responses by the medial geniculate bodies in Vespertilionidae and Rhinolophidae to ultrasonic stimuli with different frequencies

The total electrical responses and action potentials of the neurons in the medial geniculate bodies in Vespertilionidae and Rhinolophidae were investigated. Maximum sensitivity to ultrasonic stimuli was recorded inMyotis oxygnathus (Vespertilionidae) in the range 10–40 kc/sec and 65–80 kc/sec, and in Rhinolophidae in the ranges 10–70 kc/sec and 81–86 kc/sec. Low thresholds were observed inMyotis oxygnathus for the frequencies covered by their echo-location cries, whereas the thresholds recorded in Rhinolophidae in the 80 kc/sec band (the principal frequency of their echo location cries) were 15–30 dB higher than those for adjacent frequencies. Minimum thresholds of off-responses were observed inMyotis oxygnathus in the range 50–60 kc/sec, and in Rhinolophidae in the range 78–80 kc/sec. The regions of neuronal response in both species of bat were generally similar in form to those of responses recorded in the medial geniculate bodies of other mammals. Some of the neurons in Rhinolophidae with a characteristic frequency of about 80 kc/sec were also sensitive to stimuli with one-half and one-third of the principal frequency. In Rhinolophidae the greatest selectivity for frequencies was possessed by neurons that responded within the range from 80 to 90 kc/sec.A. A. Zhadanov Leningrad State University. Translated from Neirofiziologiya, Vol. 3, No. 2, pp. 138–144, March–April, 1971.     

Unit responses of the ventral cochlear nucleus in bats of the rhinolophidae family to ultrasonic stimuli after destruction of the ipsilateral cochlea

Investigation of single unit responses in the ventral cochlear nucleus of the Rhinolophidae to ultrasonic stimuli after destruction of the ipsilateral cochlea revealed two groups of neurons with latent periods of: 1) 2–4 msec and 2) 5–32 msec. The first group has responses of low thresholds confined to narrow regions of the spectrum, the second has responses with high thresholds in wide regions. Neurons of the second group are also characterized by small changes in latent period and number of action potentials in response to a change in stimulus strength, large changes in threshold at characteristic frequencies depending on the stimulus duration, but only slight dependence of the thresholds on the time of the increase in strength. The pathways of activation of these neurons and their functional role are discussed.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 1, No. 1, pp. 32–40, January–February, 1972.     

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.     

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.     

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.     

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.     

Sharply tuned cochlear nerve ensemble periodicity responses to sonic and ultrasonic frequencies

Vertebrates are able to perceive the pitch of a series of harmonics, even when the fundamental frequency has been removed from the acoustic stimulus. Neural periodicity responses corresponding to the “missing fundamental” frequency of sonic stimuli have been observed in the auditory system of several animal species, including our own. This paper examines periodic cochlear neural responses of the gerbil. Periodicity responses to both sonic and ultrasonic stimuli originate within the cochlea of this animal. Acoustic stimuli, consisting of 2–12 successive harmonic frequencies, were used to generate an ensemble cochlear nerve periodicity response that was recorded from the round window of the cochlea. This response had a frequency equal to that of the missing fundamental, and not to those of the harmonic stimuli. Forward masking of the stimuli used to produce the periodicity response was used to generate sharp tuning curves, with tip frequencies corresponding to the harmonics and not to the periodicities. The sharpness of these functions increased as the frequencies of the harmonics increased, up to at least 38 kHz. This property could be related to reception of ultrasonic vocalizations utilized by many rodent species. Accepted: 11 April 1997     

Somatosensory cortical unit responses in the waking cat to afferent stimuli

Extracellular and intracellular responses of 183 neurons in the primary projection area of the somatosensory cortex to electrical and tactile stimulation of the skin on the contralateral fore limb and to stimulation of the ventro-posterolateral thalamic nucleus of the ipsilateral hemisphere were studied in chronic experiments on cats. Spike responses to afferent stimuli are subdivided into three types: initial with a latent period of under 60 msec; initial followed by late responses with a latent period of over 60 msec; late with a latent period of over 60 msec. In addition another group of neurons responding to peripheral stimuli in the interval between the initial and the late response was identified. In nearly all cases the initial responses to peripheral stimulation had the form of a series of spikes, unlike responses to thalamic stimulation. It is concluded from the durations of the latent periods of these responses that about 70% of neurons in the primary projection area are activated mono- and disynaptically in response to peripheral stimulation; consequently, the intracortical spread of excitation in this zone is restricted.     

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.     

Differential rates of genic and chromosomal evolution in bats of the family Rhinolophidae

Data for nondifferentially stained chromosomes from 10 species of Rhinolophus (Chiroptera: Rhinolophidae) suggest a conserved chromosomal evolution. G-banded chromosomes for three well differentiated species (Rhinolophus hipposideros, Rhinolophus blasii, and Rhinolophus acuminatus) corroborate a low level of gross chromosomal rearrangements. Additionally, a comparison between G-banded chromosomes of Rhinolophus (Rhinolophidae) and Hipposideros (Hipposideridae) suggests extreme conservatism in chromosomal arms between these two distantly related groups. On the other hand, we report extensive genic divergence as assayed by starch gel electrophoresis among these 10 species, and between Rhinolophus and two hipposiderid genera (Hipposideros and Aselliscus). The present chromosomal data are not sufficient for phylogenetic analysis. Phylogenies based on electrophoretic data are in many aspects discordant with those based on the classical morphological criteria. Different (and as yet not clearly understood) evolutionary forces affecting chromosomal, morphologic, and electrophoretic variation may be the reason for the apparent lack of concordance in these independent data sets.     

Approaches to the identification of ectoparasite complexes of bats (Chiroptera: Vespertilionidae,Miniopteridae, Rhinolophidae,Molossidae) in the Palaearctic

The first attempt at identifying the faunal complexes of ectoparasites of Palaearctic bats is presented. Several approaches are used to estimate the distribution and dynamics of parasitocenoses of different host taxa in both latitudinal and meridional directions. Our analysis shows that the arid temperate zone is characterized by the highest number of species and the greatest taxonomic richness of bat ectoparasites in the Palaearctic. The results obtained reflect the phylogeography of the Palaearctic bat families and tribes.     

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.     

Characteristics of evoked potentials and single neuron responses in the cat sensorimotor cortex to sound stimuli with different frequencies.

The characteristics of the averaged evoked potentials (AEP) (experiments with awake non-paralysed animals), of the evoked potentials (EP) and of the responses of single sensorimotor cortical neurons (acute experiments) of cats to tone-bursts with frequencies within 0.1-6.0 kHz were studied. Response selectivity to the tone-burst frequencies which are energetically pronounced in some biologically significant sounds for the cat was observed. The averaged curve of the dependence of the amplitude of AEP in the somatosensory cortical region (S1) on the tone-burst frequency has reliable maximum values at the frequencies of 0.8, 1.6 and 2.0-3.0 kHz. Most pronounced changes in the heart rhythm were observed within the tone-burst frequency ranges in which the AEP of the highest amplitudes were recorded. The amplitude of the AEP was found to increase during the conditioned reflex elaboration. The curve of the dependence of the probability of the EP occurrence on the frequency at equal sound pressure levels had maximum values at the frequencies of 1.6 and 3.2 kHz. The highest amplitude values of EP were found at frequencies of 0.8, 1.6 and 3.2 kHz. More than half of the recorded neurons revealed the lowest values of the response thresholds and the maximum values of the occurrence probability under suprathreshold stimulation at frequencies close to 0.8, 1.6, and 3.2 kHz. It is supposed that the above mentioned feature of the input frequency organization in sensorimotor cortex is connected with the selectivity as to the biological significance of acoustic stimuli.     

Visual unit,EEG and sustained potential shift responses to biologically significant stimuli in the brain of toads (Bufo bufo)

Summary Visual unit activity, EEG changes and sustained potential shifts (SPS) were recorded from the toad tectum whilst the animal was presented with a visual stimulus. Telencephalic EEGs were also recorded.On the surface of the tectum, retinal unit activity preceded a sustained negative shift in potential and an increase in the amplitude and dominant frequency of the EEG. In deeper layers of the tectum, T5 units with configurational selectivity for wormlike stimuli were found. The activity of these units followed a pronounced SPS and EEG change.Visual unit activity was most pronounced during the negative-going phase of the synchronised EEG, when there was also a small decrease in amplitude of neuronal spikes. Similarities between the latencies and durations of EEGs and SPSs, and their response decrements, on repeated stimulus presentation, implies a close relationship between them not shared by the visual units studied. The specific activity of tectal units is discussed in relation to the correlated EEG and SPS changes, which may form part of an adaptive sensitizing mechanism.Abbreviations EEG electroencephalogram - ERF excitatory receptive field - SPS sustained potential shift - T4, T5 tectal neurons     

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: