Projections of auditory ventral-cord neurons in the supraesophageal ganglion ofLocusta migratoria

Summary The neuropile regions in the supraesophageal ganglion ofLocusta migratoria were revealed by Bodian staining of frontal and parasagittal sections.A combined recording and staining technique (CoS method, Rehbein et al., 1974) was used to identify physiologically five different types of auditory ventral cord neurons and mark the course of their axons and the positions of the terminal arborizations. The boundaries of the projection regions are described; they include the various multimodal neuropile regions in the ventrolateral protocerebrum.Previously demonstrated instances of convergence with neurons of other sensory systems, and others likely to exist, are considered with respect to their possible significance in neuronal processing within the auditory system.Supported by the Deutsche Forschungsgemeinschaft, as part of the program Sonderforschungsbereich Bionach, Bochum. The investigations were done at Lehrstuhl für Allgemeine Zoologie, Ruhr-UniversitÄt, D-4630 Bochum     

The coding of airborne-sound and vibration signals in bimodal ventral-cord neurons of the grasshopperTettigonia cantans

Summary In grasshoppers, the auditory and vibrational senses converge on the same ventral-cord neurons. All neurons in the ventral cord that discharge impulses in response to either airborne-sound or vibration stimuli also receive synaptic inputs from the other sensory system. The latter elicit either subthreshold excitation or inhibition.The coding of the conspecific song in the responses of most ventral-cord neurons ofTettigonia cantans is considerably improved when the stimulus consists not of simulated natural sounds alone, but of such sounds together with either maintained vibration or vibration matched to the temporal structure of the song.Stridulating tettigoniids produce both airborne and substrate-conducted sound. Thus the perception of airborne sound and vibration, and their simultaneous processing in individual ventral-cord neurons, may be of fundamental importance — not only in localizing a nearby sound source, but also in facilitating the recognition of conspecific signals.Abbreviations SNS simulated natural song The work was supported by the Deutsche Forschungsgemeinschaft, as part of the program Neurale Mechanismen des Verhaltens (Ka 498/1)We are grateful to Dr. M.A. Biederman-Thorson for the translation of the text and to Mrs. A. Scheiding for technical help.     

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.     

Neurophysiology of the vibration sense in locusts and bushcrickets: The responses of ventral-cord neurones

In the locustid Locusta migratoria and the tettigoniids Decticus verrucivorus and Tettigonia cantans, comparative aspects of physiological properties of vibratory/auditory ventral-cord neurones were studied by single cell recordings.These neurones all receive inputs from both vibratory and auditory receptors. Nevertheless, they can be classified into “V neurones” responding preferentially to vibration stimuli, “VS neurones” responding to vibration and airborne sound, and “S neurones” responding preferentially to airborne sound. In every group, there are several types with different physiological properties, normally represented by one neurone on each body side.In Locusta and in the tettigoniid species, the same physiological types of vibratory/auditory neurones were found, although there are differences in the synaptic connectivity of the vibration receptors of the different legs. In Locusta, the middle leg receptors have the strongest influence on the generation of suprathreshold responses of the central neurones, whereas in the tettigoniids the receptors of the ipsilateral fore leg are the most influential.Two of the V neurones receive inputs mainly from campaniform sensilla and other low-frequency vibration receptors, the other V and VS neurones are mainly influenced by the subgenual receptors. Central information processing results in preferential responses to different frequency/intensity ranges in different neurones.Most VS neurone types show the same response characteristics (e.g. time pattern of response, habituation) either to vibration or to airborne-sound stimuli. Simultaneous presentation of both stimuli leads to qualitative changes in the response characteristics. Therefore, the co-processing of auditory and vibratory signals seems to be very important in the acoustic behaviour of grasshoppers.     

Responses of neurons in the auditory cortex to sound stimuli

The evoked potential (EP) and the pulse activity of single auditory cortex neurons were recorded simultaneously in response to a click and to a tone for cats under nembutal and nembutal — chloralose anesthesia. Both extra- and intracellular taps were employed. The experiments showed that the reaction of auditory cortex neurons in response to a click lasts from 200 to 300 msec. It consists of pulse discharges from several groups of neurons. Out of 174 neurons observed 8 responded within 4 to 7 msec after a click (before the EP). One hundred and nine neurons reacted in the range from 7 to 25 msec which coincided with the initial electropositivity of the EP; 11 neurons were in the range from 40 to 100 msec and 4 were between 180 and 270 msec. Such a sequence of involvement of different neuron groups in the reaction is probably accounted for to a large extent by the time dispersion of the afferent volley. With an intracellular tap slow alterations of membrane potential were observed in the form of an EPSP with pulses together with subsequent hyperpolarization lasting 50 to 70 msec and slowly increasing depolarization that reached a maximum after 170 to 200 msec.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 1, No. 2, pp. 147–157, September–October, 1969.     

Movements of the hindwings ofLocusta migratoria,measured with miniature coils

Summary Tethered migratory locusts were induced to fly in an airstream for hours at a time, carrying on their extremely delicate hindwings miniature induction coils by which the hindwing movements were recorded in three dimensions.The two coils were mounted at right angles to one another on the central field of the hindwing, which is in close aerodynamic contact with the forewing. Each coil emitted three signals to define the components of a 3-dimensional vector. The movements of the central field can be described completely by the rotations of the two vectors. The main component of the hindwing movement thus becomes accessible to detailed kinematic analysis (Figs. 2, 3).The results obtained with this inductive method are consistent with the few published data based on photogrammetric samples of the movement.The various forms of movement can all be observed during the flight experiment. The movement spectrum is very broad even in an undisturbed flying animal (Figs. 4, 5).Various wingbeat parameters were calculated, including oscillation period, the durations of upstroke and downstroke, and their ratio (Fig. 6).Simultaneous measurement of the movements of the fore- and hindwings has provided the first documentation of the varying interactions of the wings on side of the body during a long flight. Even small changes in the relative positions of the two wings are measurable (Fig. 7).     

缰核痛相关神经元对伤害性刺激和吗啡的反应

目的:观察缰核痛相关神经元对经典镇痛药吗啡的反应,了解缰核的痛觉属性.方法:实验在浅麻醉下的成年大鼠进行.通过脑室插管微量注射,或经五管微电极电泳吗啡、纳络酮、八肽胆囊收缩素(CCK-8)等,并记录缰核内痛相关神经元的单位放电.结果:在内侧缰核、外侧缰核记录的痛相关神经元放电,又可分为痛兴奋性神经元和痛抑制性神经元.在缰核微电泳吗啡后,痛兴奋性神经元以抑制反应为主,痛抑制性神经元以兴奋反应为主.微电泳纳洛酮可以翻转吗啡对缰核的作用.在吗啡耐受大鼠腹腔注射吗啡10 mg/kg,LHb痛相关神经元表现为镇痛效应的数量远大于MHb痛相关神经元的,表明外侧缰核受吗啡的作用程度高于内侧缰核.对吗啡耐受大鼠脑室注入CCK拮抗剂后,再由腹腔注射吗啡,可减弱对吗啡的耐受程度.反之,在腹腔注射吗啡(10 mg/kg)10 min后,侧脑室注射CCK-8(15 ng/10μl),CCK-8可拮抗吗啡对LHb的镇痛作用,但对MHb的拮抗作用不明显.结论:缰核的痛兴奋性神经元和痛抑制性神经元对伤害性(痛)刺激敏感而不易发生适应.其中外侧缰核神经元对吗啡的敏感性高于内侧缰核神经元.     

Neurochemistry of GABAergic activities in the central nervous system ofLocusta migratoria

Summary The biochemical elements of GABA-ergic synapses in the central nervous tissue were examined by a comparative neurochemical approach. The high concentration of GABA as well as the activities of glutamate decarboxylase and GABA-transaminase suppose a high content of GABAergic elements in the nervous system of the locust.Nerve endings isolated from the ganglia of locusts accumulated exogenous GABA in a carriermediated, sodium dependent process into compartments from where it could partially be released under depolarizing conditions. The transport was stimulated by extracellular chloride, was modulated by specific ionophores (enhanced by valinomycin, inhibited by CCCP) and could effectively be blocked by GABAergic ligands (DABA, muscimol). Binding studies revealed the existence of multiple binding sites for GABA which differ in number, affinity, pharmacology and ion dependency. The putative receptors for GABA (Na⁺-independent binding sites) in locust nervous tissue exceeded the concentrations found in vertebrate brain tissue and showed different binding pharmacology.Abbreviations GABA -amino butyric acid - GAD glutamate decarboxylase - GABA-T GABA-transaminase - DABA diamino butyric acid     

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.