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1.
1.  Responses to moving contrast gratings and to flicker have been studied in cells in the medulla of the fleshfly Sarcophaga bullata using intracellular recordings and stainings. Medullary neurons responded periodically to flicker. Those which primarily discriminated motion had periodic responses or DC shifts in membrane potentials or increased noise. Intrinsic neurons included a T1a cell which was directionally selective (DS) and specific non-DS amacrine cells (6 types) arborizing either distal or proximal to the serpentine layer. Among the 12 types of output neurons recorded, 1 projected to the lobula plate, 6 to the lobula (Tm and T2 cells), 3 to both the lobula and lobula plate (Y cells), and 2 to the central brain.
2.  Irrespective of their projection, medulla neurons which arborize in the stratum of the L2 terminals respond to flicker as does L2 and have the simplest, primarily periodic, responses to motion. The responses have significant power at the second harmonic of the stimulus temporal frequency suggesting that a non-linear operation, such as multiplication, may occur in the L2 stratum. Cells with arbors coinciding with either of the two levels of L1 terminals have much more complex responses to motion. All cells projecting to the lobula plate responded periodically to movement in some direction(s).
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2.
Evidence is presented here from experiments on the visual system of the fly that questions participation of the large monopolar cells (LMCs) in the optomotor response.
1.  The response of a directionally-selective motion-detecting neuron (H1) in the lobula plate to small sudden jumps of a grating is directionally-selective (Fig. 1), indicating that at least one of the inputs to each of the elementary movement detectors (EMD) that feed into H1 must deliver a tonic signal. The responses of LMCs to the same stimulus are, however, entirely phasic (Fig. 2).
2.  In dual electrode experiments on Eristalis, injection of current into an LMC does not change the spiking rate of H1. Induction of spiking activity, or injection of current into an LMC, which alters the cell's response to a flash of light from a point source, does not affect the response of H1 to the same flash (Figs. 3, 4).
3.  The temporal properties of LMCs differ markedly from those of the optomotor response and of directionally-selective movement — detecting neurons in the lobula plate (Figs. 6, 9).
4.  There is poor correlation between LMC degeneration and the strength of the optomotor response in a mutant of Drosophila (Fig. 8).
5.  The optomotor response of Drosophila is strongly polarization sensitive, but Drosophila LMCs show no polarization sensitivity (Fig. 11).
While our results do not exclude the participation of the LMCs in the optomotor response, they do indicate that at least one other lamina channel that is tonic and/ or polarization sensitive must be involved.  相似文献   

3.
1.  Bees were trained to enter the central hole in a disc containing 89 holes and collect sugar-water from a box placed behind it (Fig. 1). Visual marks were offered on the inner surface of a cylinder placed in front of the disc (Fig. 2), thus projecting onto peripheral (nonfrontal) regions of the bees' eye. The trained bees were tested by recording their choices among the holes.
2.  Bees use the memorized position of peripheral marks to localize the frontally positioned goal (Figs. 6–9). The effectiveness of a mark depends on its retinal position, the most effective marks being lateral ones (Figs. 8, 9).
3.  Altering the dimensions of the mark does not influence the distribution of the bees' choice (Figs. 11–13). Thus, image motion rather than image size is used for distance estimation in the present task.
4.  Cinematographic recordings (Fig. 14) revealed that the searching bees' whereabouts are correlated with the choice distribution (Fig. 6a). The hypothesis that the bees stabilize the mark in the trained retinal position by correcting for retinal image slip is proposed.
5.  Experiments using coloured patterns revealed that the bees' performance is mediated by the green-sensitive channel (Figs. 17–22), as predicted by the above hypothesis.
Dedicated to Prof. Dr. Rüdiger Wehner on the occasion of his 50th birthday, in great appreciation for both his scientific work and his personality.  相似文献   

4.
1.  The European hawk moth Macroglossum stellatarum, while collecting nectar in hovering flight in front of flowers, follows moving stripe patterns in the lateral visual field. This response counteracts a second one, that is the animals' effort to stabilize their distance from dummy flowers. We investigated the response to motion stimuli in the lateral visual field using sinusoidally oscillating stripe patterns (Fig. 1), as well as its interaction with the distance stabilizing response.
2.  In both responses moths attempt to compensate for image speed. The balance between the two depends on the number of elementary motion detectors stimulated by the dummy flower and the stripe pattern, respectively. Increasing the diameter of the dummy flower (Figs. 2 to 4) or the spatial frequency of the stripe pattern (Fig. 7) shifts the balance in favour of distance stabilization. The reverse is true when the length of the stripes in the pattern (Fig. 5) or their number is increased (Fig. 6). It does not matter whether the stripe pattern is presented in the lateral (Fig. 4A) or in the dorsal and ventral visual field (Fig. 4B).
3.  The gain-frequency relations of the response to the lateral stripe pattern obtained with dummies in two different positions within the drum have their maxima around 3 Hz and decline rapidly towards lower and higher frequencies like the response of a bandpass filter. The distance stabilizing response also has bandpass properties, but with a broad plateau between 0.15 and 5 Hz (Fig. 8). The most likely explanation for this difference is that there is a regional or direction-dependent variation of motion detector properties.
4.  The responses to ramp-like stimuli are phasic in accordance with the amplitude frequency characteristics, but the responses to progressive (front to back) and regressive motion of the pattern differ (Figs 9, 10).
5.  The response appears to depend on the azimuthal position of the stripe pattern within the visual field (Fig. 11). It is strongest when the pattern covers equally large parts of the frontal and caudal visual fields. The optomotor sensitivity to translational pattern motion is higher in the frontal than in the caudal visual field (Fig. 12, Table 1).
6.  When the stripe pattern on one side is removed, the response amplitude is halved. There is no detectable turning response around the vertical axis to the oscillation of the stripe pattern (Fig. 13, Table 2).
7.  The possible role of the response to pattern movements parallel to the longitudinal body axis under natural conditions is discussed.
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5.
1.  The terminal ganglion ofLocusta migratoria contains a number of non-giant, wind-sensitive, ascending and local interneurones. Six ascending (Figs. 1, 2) and 6 local (Figs. 6, 7) interneurones have been identified morphologically on the basis of intracellular stains with Lucifer Yellow.
2.  The physiological responses of the various cell types were recorded as the cerci were exposed to sound, wind, or electrical stimulation (Figs. 3, 8). Some cells summate the input from both cerci (Fig. 3), while others are excited by input from one side and inhibited by input from the other (Fig. 8). Conduction velocities for several non-giant ascending interneurones range from 1.5 m/s (cell 1) –2.1 m/s (cell 25).
3.  The morphologies and physiological responses of giant (GIN 1) and non-giant ascending interneurones (cells la, b) with somata in cluster 1 of neuromere 9 were compared using simultaneous intracellular recordings (Figs. 2A, 4). These neurones have very similar dendritic arborizations (Fig. 4A, B), and respond almost identically to cercal stimulation (Fig. 4Ci), but there do not appear to be any connections with GIN 1 (Fig. 4Cii, iii).
4.  The morphology (Fig. 5A, C), and response to cercal stimulation by wind (Fig. 5B) of a nongiant interneurone (cell 7) with its soma in cluster 1 of segment 8 (Fig. 5), are very similar to those of cluster 1 cells such as GIN 1 in segment 9.
5.  Of the 6 local interneurones (Figs. 6, 7) all except one (cell 9) have bilateral arborizations which may extend over several neuromeres within the ganglion (cells 10, 22). Several of the interneurones (cells 5, 9, 24) do not produce action potentials in response to cercal stimulation (Figs. 8, 10) or injection of depolarizing current (Fig. 11).
6.  Simultaneous recordings from pairs of interneurones demonstrate that giants and locals (GIN 2/cell 5; GIN 1/cell 9), as well as different local interneurones (cell 24/cell 5), receive input from the same wind-sensitive filiform afferent (Fig. 9).
7.  Local interneurones 5 and 22 are in different neuromeres of the terminal ganglion but have a similar gross morphology (Figs. 6, 7, 10). Cell 5, however, has arborizations projecting into both posterior cercal glomeruli (Fig. 7 A, inset), whereas only the ipsilateral branches of cell 22 extend posteriorly to the cercal glomerulus (Fig. 10C). Physiologically, cell 5 is depolarized by wind directed at both cerci (Fig. 10 A), cell 22 mainly by wind directed at the ipsilateral cercus (Fig. 10C). Cell 5 does not produce action potentials in response to wind whereas cell 22 does.
8.  Cell 5 occurs as a bilateral pair in the terminal ganglion (Figs. 7B, inset; 11). Simultaneous recordings of the bilateral homologues show that they share the input of at least one wind-sensitive filiform afferent (Fig. 11D), and that there are no connections between them (Fig. 11E). Simultaneous penetrations of local interneurone 5 and giant interneurones demonstrate a short-latency excitatory connection from GIN 3 to cell 5 (Fig. 12 A), and a long-latency excitatory connection from GIN 2 to cell 5.
9.  The roles of giant and non-giant interneurones in transmitting information to thoracic motor centres are discussed.
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6.
1.  The effects of the biogenic amines serotonin and octopamine on motion-sensitive neurons in the lobula of the honey bee were analysed electrophysiologically. Single cell activity was recorded intracellularly during application of amines. Field potentials in the lobula were recorded to measure the effects on populations of motion-sensitive neurons.
2.  Serotonin and octopamine modulate the response properties of motion-sensitive neurons in the lobula in a functionally antagonistic way.
3.  The application of serotonin, in most cases, reduces background activity as well as responses to moving stripe patterns by motion-sensitive lobula neurons. The direction specificity can also decrease after serotonin application. In accordance with the single cell recordings, the amplitudes of lobula field potentials evoked by moving stripe patterns are also reduced by application of serotonin.
4.  Octopamine leads to an increase in the amplitude and the initial slope of field potentials evoked by moving stripe patterns. However, there were no uniform effects at the single cell level after octopamine application.
5.  The modulatory effects of serotonin and octopamine on motion-sensitive neurons correlate well with some behavioral modifications elicited by these substances (Erber et al. 1991; Erber and Kloppenburg, companion paper).
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7.
In response female pheromone the male gypsy moth flies a zigzagging path upwind to locate the source of odor. He determines wind direction visually. To learn more about the mechanism underlying this behavior, we studied descending interneurons with dye-filled micro-electrodes. We studied the interneuronal responses to combinations of pheromone and visual stimuli.
1.  We recorded 5 neurons whose directionally selective visual responses to wide field pattern movement were amplified by pheromone (Figs. 2–6).
2.  The activity of the above neurons was more closely correlated with the position of the moving pattern than with its velocity (Fig. 4).
3.  One neuron showed no clearly directional visual response and no response to pheromone. Yet in the presence of pheromone it showed directionally selective visual responses (Fig. 6).
4.  We recorded 4 neurons whose directionally selective visual responses were not modulated by pheromone (Fig. 7), ruling out the possibility that the effect of the pheromone was simply to raise the activity of all visual neurons.
5.  Our results suggest that female pheromone amplifies some neural pathways mediating male optomotor responses, especially the directionally selective responses to the transverse movement of the image, both below and above the animal.
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8.
Locusts (Locusta migratoria) were flown in a flight simulator which converts yaw torque into angular motion of the visual environment (Fig. 1). The modalities and the time-course of steering behavior under these closed-loop conditions have been investigated.
1.  Locusts flying under visual closed-loop conditions stabilize their visual environment by performing correctional steering manoeuvres. Besides torque production, due to differential wing movements and ruddering, correctional steering also involves head movements (Fig. 6).
2.  During open-loop steering, ruddering and yaw torque begin some 60 ms after the onset of the visually simulated deviation from course. Head movements occur some 90 ms after stimulus onset, i.e. some 30 ms later than yaw torque (Figs. 3, 5) and therefore do not initiate thoracic steering outputs.
3.  Open- and closed-loop correctional steering do not differ in their behavioral components or temporal organization (Figs. 2, 6, Table 1).
4.  In the absence of major disturbances, correctional steering under closed-loop conditions is performed with minimal ruddering (only a few degrees in amplitude), that probably produces little or no aerodynamic drag (Fig. 6).
5.  Locusts prevented from moving their heads still stabilize their visual environment in the closed-loop situation. However, the precision of steering is affected by this constraint (Figs. 8, 9, 10, 12). Head immobilization also alters the temporal coordination of correctional steering (Figs. 7, 11).
6.  These results show that head movements, in addition to their generally accepted role in vision improvement, also contribute to the precision and temporal coordination of correctional flight manoeuvres. The mechanism is partly via proprioceptive feedback.
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9.
Intracellular recordings and Lucifer-yellow fillings were used in a wandering spider,Cupiennius salei Keys., to identify central neuronal correlates of local reflex activity in muscle c2, which inserts on the leg coxa. Here we describe related neuronal elements in the hindleg neuromere of the fused, subesophageal-ganglion complex:
1.  Projectionsof primary sensory axons excited by hair deflection are confined to ventral parts of the ipsilateral leg-neuromere (Fig. 1); their central terminals end near longitudinal, interganglionic tracts.
2.  Two identified excitatorymotor neurons for muscle c2 (which is a promotor/adductor of the coxa) are also confined to the ipsilateral (hindleg) ganglion. The dendritic branches and the efferent axonal segment extend in regions well dorsal to the sensory projections (Fig. 2); we found neither morphological nor electrophysiological evidence for direct synaptic contacts between hair afferents and motor neurons (Fig. 3).
3.  Various types of identifiedinterneurons give responses correlated with the reflex. We classified them, by anatomical criteria, aslocal interneurons confined to the ipsilateral hindleg neuromere (Figs. 4, 5) and asplurisegmental interneurons arborizing in more than one neuromere (Figs. 6, 7, 8).
Although detailed electrophysiological tests of functional connections are not available for all these elements, we discuss how the various interneurons identified here may be involved in the local reflex response and in the coordinated, intersegmental reflex behavior that is observed when the unrestrained spider uses all 8 legs to raise its body (see the companion paper by Eckweiler and Seyfarth 1988).  相似文献   

10.
1.  Certain species of tiger moths emit clicks when stimulated by bat-like sounds. These clicks are generated by modified thoracic episterna (tymbals) (Fig. 1) and constitute a rhythmic behaviour activated by simple sensory input.
2.  Tymbal periods are indirectly related to stimulus intensity and periods (Fig. 3). Moths initiate sounds with the tymbal opposite to the stimulated ear and once a sequence commences it continues in an undisrupted fashion.
3.  The tymbal is innervated by a pleural branch (IIIN2a) of the metathoracic leg nerve, a similar anatomy to that in the unmodified episterna of silent moths (Fig. 5). Backfills of the IIIN2a in Cycnia tenera reveal sensory fibres and a cluster of 5–9 motor neurons with densely overlying dendritic fields (Fig. 6).
4.  Extracellular recordings of the IIIN2a reveal a large impulse preceding each tymbal sound (Fig. 7). I suggest that this impulse results from the synchronous firing of 2–3 motor neurons and is the motor output of the tymbal central pattern generator (CPG). The spikes alternate (Figs. 9, 10) and are bilaterally co-related (Fig. 11) but with an phase asymmetry of 2–3 ms (Fig. 12).
5.  Normal motor output continues in the absence of tymbal sounds (Fig. 13) and when all nerve-tymbal connections are severed (Fig. 14, Table 1) therefore this CPG operates independent of sensory feedback. A model is proposed for the tymbal circuitry based upon the present data and the auditory organization of related noctuid moths (Fig. 15). I propose that the tymbal response in modern arctiids evolved from either flight or walking CPGs and that preadaptive circuitry ancestral to tymbal movements still exists in modern silent Lepidoptera.
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11.
1.  Tethered flies (Musca domestica) walking on an air-suspended ball show a spontaneous response to the e-vector of polarized light presented from above, i.e. a slowly rotating e-vector induces periodic changes in the flies' turning tendency. Suitable control experiments exclude the possibility that the response is elicited by intensity gradients in the stimulus (Figs. 1 and 2).
2.  Presence of the e-vector response in both white and UV light and its complete absence in yellow light equally support the concept that the specialized dorsal rim area of the compound eye with its highly polarization sensitive UV receptors R7marg and R8marg mediates polarization vision in flies (Fig. 3).
3.  E-vector orientations inducing no turning response additional to the fly's inherent turning tendency are either parallel (avoided e-vector) or perpendicular (preferred e-vector) to the animal's body axis (Figs. 1 and 4).
4.  Considering the fanlike arrangement of the microvillar orientations of R7marg and R8marg in the dorsal rim area of the eye of Calliphora and Musca, a stabilizing function of polarization vision in controlling the flight course is suggested and discussed in the context of results from other behavioural studies.
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12.
1.  The neural mechanisms responsible for flashing in the firefly,L. lusitanica, were investigated by means of localized electrolytic lesions and electrical stimulations.
2.  Restricted lesions of the median protocerebral neuropile produced the irreversible abolition of spontaneous flashing and of the associated photogenic volleys. Single electric shocks applied to the same structure were followed by a propagated action potential in the lanternal nerves; a short (40 ms) train of stimuli at 200/s evoked a fully developed photogenic volley and the related flash, both of which were identical in all respects to the spontaneous ones (Figs. 2, 3).
3.  Separation of the protocerebrum from the optic lobes led to the disappearence of rhythmic flashing, which was replaced by a continuous, dull luminescence; at the same time the photogenic volleys of the lanternal nerves were replaced by a continuous, asynchronous discharge at low frequency (Fig. 15).
4.  Ablation of theretina-lamina ganglionaris complex was followed by a marked increase of flashing frequency. Electrical stimulation of theretina at low repetition rate (5/s) was followed by depression of both frequency and intensity of spontaneous flashing; opposite effects (i.e. increase in flashing frequency and intensity) were obtained by high rate (30/s) retinal stimulation (Figs. 6–9).
5.  Electrolytic lesions of the medulla performed after ablation of theretina-lamina complex, did not produce any change in the patterns of spontaneous flashing. Electrical stimulation of the medulla produced facilitatory effects on flashing at all repetition rates used, with the lowest threshold at 30/s. This effect disappeared after localized electrolytic lesion (Figs. 12–14).
6.  These findings are discussed and it is concluded that (a) the photomotor neurons of the firefly's brain are located in the deep protocerebral neuropile; (b) their rhythmic activity is the result of the interaction with an oscillator located in the optic lobes, possibly in the lobula; (c) the retina-lamina complex exerts a tonic inhibitory influence on flashing; (d) a phasic facilitatory influence is exerted by neural structures located at the level of the medulla.
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13.
In the grasshopperChorthippus biguttulus the stridulatory movements of males with surgically manipulated ventral nerve cords were investigated.
1.  The stridulation pattern of animals with a hemisected mesothoracic ganglion was indistinguishable from that of intact animals.
2.  After hemisection of the metathoracic ganglion several animals were still able to stridulate in the species-specific pattern (Figs. 3, 5). Different structural elements of the song, however, were affected to different degrees by this operation. Although the stereotyped up-and-down movements were normal, the rhythm of pauses, which in intact animals are inserted after every third to fourth up- and-down cycle, was disturbed. As a result, the variation of syllable lengths was much higher (Fig. 4).
3.  A prominent feature after hemisection of the metathoracic ganglion was an almost complete loss of coordination between left and right hind legs (Figs. 5–7). Only in the coarse structure of the song (e.g. the beginning and termination of song sequences) was a correlation of the leg movements still discernible. This was especially obvious in songs of the rivalry type and in precopulatory kicking movements (Fig. 8).
4.  If in addition to hemisection of the metathoracic ganglion one of the neck connectives was transected the animals stridulated only with the hind leg ipsilateral to the intact connective (Fig. 11).
5.  Even after hemisection of both the meso- and metathoracic ganglia, animals were able to produce the species-specific stridulation pattern (Fig. 9).
6.  In animals with hemisected metathoracic ganglia and both connectives between pro- and mesothoracic ganglia transected, components of the species-specific pattern could be induced by current injection into the mesothoracic ganglion (Fig. 10).
7.  These results suggest that the stridulation rhythm-producing neuronal network is composed of hemisegmental subunits. A hemiganglionic structure of rhythm generators might reflect the ancestral organization of locomotion-controlling networks.
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14.
1.  The behaviour of isolated individual forager honeybees during the night has been investigated with a variety of experimental methods. Prolonged rest in these diurnal insects is accompanied by: reduced muscle tone (Figs. 1, 6, 10–12), decreased motility (Figs. 2, 3, Table 1), lowered body temperature (Figs. 7, 8) and raised reaction threshold (Fig. 9). These phenomena strongly resemble four characteristic features of sleep in humans, mammals and birds. It is thus very likely that the profound rest which forager bees experience at night is sleep. This assumption is further supported by the results of previous investigations of visual interneurones in the bee.
2.  The antennae of sleeping bees manifest characteristic postural constellations (Fig. 6). High reaction thresholds are associated with particular antennal positions.
3.  The total sleep time (duration of antennal immobility plus duration of small antennal movements) in 24 h for two bees was 7.6 h and 4.9 h (Table 1).
4.  Bees which rest in a hive at night also display phenomena which have been encountered during the laboratory investigations.
5.  Sleep in mammals is an active, controlled process; the same seems to be true of sleep in honeybees (Figs. 3, 4). Unlike mammals, bees experience their deepest sleep towards the end of the sleep phase (Figs. 3, 9, 10, 12).
Dedicated to Prof. Dr. D. Burkhardt on the occasion of his 60th birthday  相似文献   

15.
Intracellular recordings have been made of responses to step, ramp and sinusoidal changes of light by second-order L-neurones and a third-order neurone, DNI, of locust (Locusta migratoria) ocelli.
1.  The membrane potential at the peak response by an L-neurone to a change in light is proportional to the light increment or decrement, independent of background, over a range of at least 4 log units. As background increases, response latency and time-course decrease, and responses become more phasic (Fig. 1).
2.  Adaptation to a changed mean light level involves a change in sensitivity and a slow change in resting membrane potential, which never adapts completely to dark resting potential in the presence of light (Fig. 3).
3.  L-neurones can follow changes in light which last several seconds, but responses to fast changes are enhanced in amplitude (Figs. 4, 5). An increase in background light causes an increase in the frequency of sinusoidally modulated light at which the largest response occurs (Fig. 4).
4.  The responses of DNI to increased light saturate at lower intensities than those of L-neurones. During adaptation to different background light intensities, there is no change in the input-output relation of the synapse between an L-neurone and DNI (Figs. 6, 7).
5.  For a rapid decrease in light, DNI produces a rebound spike, followed by a period of silence (Figs. 5, 8).
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16.
1.  The actions of GABA on three classes of visual interneurons in crayfish, Procambarus clarkii, medulla externa are examined. The effect of GABA on the visual response is compared to GABA's action on agonist-elicited responses purported to mediate the visual response.
2.  GABA produces a shunting type of inhibition in medullary amacrine cells which is associated with a small depolarization (Figs. 2, 3), a large increase in input conductance (Gn) and a reversal potential close to rest (Fig. 4). GABA is a potent antagonist to the depolarizing action of acetylcholine (ACh) (Fig. 5).
3.  GABA depolarizes dimming fibers (Fig. 2), and the response is mediated by an increase in Gn (Fig. 6). GABA antagonizes the light-elicited IPSP and the hyperpolarizing action of ACh (Fig. 7).
4.  Sustaining fibers (SF) do not appear to have GABA receptors but GABA inhibits the excitatory visual input pathway to the SFs (Fig. 8). Conversely, the GABA antagonist, bicuculline, potentiates the SF light response (Fig. 9).
5.  GABA has at least three different modes of antagonist action in the medulla: i) Increased conductance and depolarization in dimming fibers and medullary amacrine neurons; ii) Decreased chloride conductance in tangential cells; and iii) An inhibitory action on the visual pathway which drives SFs.
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17.
1.  The swimmerets ofJasus lalandii, in contrast to those well known in the nephropid lobsters (e.g.Homarus) and astacurans (crayfish), do not display spontaneous antero-posterior beating, but are either apposed actively to the ventral surface of the abdomen, or rotated outward (Fig. 2). These movements are imposed by the geometrical arrangement of the bicondylar joints at the base of the swimmeret (Fig. 3), and involve contraction of either the remotor muscle, or the promotor-rotator muscles (Figs. 2, 3). Each swimmeret includes a short, thick blade-like exopodite that contains two antagonistic muscles, a large curler and a small adductor muscle (Fig. 3). Each swimmeret is innervated by 80 motor neurons (MNs) which are disposed in two clusters in the ganglion.
2.  The modulation of the tonic discharge of the muscles which maintain the swimmeret position at rest (remotor and curler) has been studied in two situations: body rolling (Fig. 4) and walking activity (Fig. 5). In the female, in which the most anterior pair of swimmerets are biramous, both endopodite and exopodite curler muscles display the same responses to body rolling (Fig. 4). In all these situations no overt swimmeret movement occurs.
3.  Nevertheless, rhythmicity exists inJasus, but it is limited to the gravid female when the swimmerets bear the eggs (Fig. 6). In contrast to other decapod Crustacea, this swimmeret beating is not metachronous (Fig. 6).
4.  Movement monitoring (Fig. 7) and EMG recordings (Figs. 9, 10) have demonstrated the involvement of the swimmerets in the three phases of the tail flick response (preparation, flexion, extension). During the preparatory phase, in response to mechanical stimulation of the legs, the swimmerets open on the stimulated side (on both sides in the case of a symmetrical stimulation) (Fig. 7). During the rapid abdominal flexion of the tail flick all swimmerets open fully regardless of the stimulus (Figs. 7, 8). Two different units in the rotator muscle EMG are responsible for swimmeret opening during the preparatory and the flexion phases of the tail flick (Figs. 9, 10).
5.  The curler muscle of the endopodite in the female displays antagonistic activities to that of the exopodite during tail flicks (Fig. 10).
6.  Selective swimmeret blockage demonstrates that they contribute to the thrust efficacy in tail flicks. In particular they are responsible for the variation of the maximal force produced at its onset. This effect could be interpreted as a consequence of force redistribution by the swimmerets acting on water flow (produced by the tail fan). This mechanism implies a functional role for the swimmerets in righting and steering responses (Fig. 11).
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18.
1.  The activity of tympanal high- and low-frequency receptors in the migratory locustLocusta migratoria was recorded with glass capillary microelectrodes, and Lucifer Yellow was then injected through the microelectrode to reveal the cells' metathoracic projections.
2.  A photodetector device was used to monitor the abdominal respiratory movements, which caused clearly visible deflections of the tympanal membrane.
3.  The auditory receptors respond not only to sound stimuli but also to the respiratory movements; these phasic (Figs. 1–3) or tonic (Fig. 4) responses are especially pronounced during the inspiration and expiration movements, and less so during the constriction phases.
4.  The magnitude of the response to sound depends on the phase of the stimulus with respect to the respiratory movements. At certain phases sound elicits no response at all (Fig. 5).
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19.
1.  L3 is a prothoracic auditory interneuron which has an ascending axon projecting to the brain. It is rather broadly tuned and most sensitive to carrier frequencies around 16 kHz (mean threshold=60 dB) and at 4–5 kHz (mean threshold=70 dB, Fig. 1).
2.  During open field stimulation L3's excitatory response increases rather linearly as sound intensity is increased and is 10–15 dB more sensitive to ipsilateral stimulation (Fig. 2). With closed field stimulation L3 is 45 dB more sensitive to ipsilateral sound at 16 kHz, and at least 20 dB more sensitive at 5 kHz (Fig. 3). With closed field sound, contralateral stimulation at subthreshold intensities (5 and 16 kHz) usually results in hyperpolarization (Fig. 3).
3.  L3's excitatory response to 16 kHz on the ipsilateral side is suppressed by low frequencies on the same side and by low and high frequency sounds from the contralateral side (Fig. 4).
4.  In open and closed field conditions, the number of spikes/syllable decrements in response to successive syllables of each chirp (Fig. 5). This response is dependent on the syllable period (SP) of the song, with the greatest decrement occurring in response to SPs of 50–70 ms; longer and shorter SPs cause less decrement (Figs. 6–7). At both 5 kHz and 16 kHz the ability of L3 to encode syllables (standard SD = 23 ms) within a chirp is dependent on the SP. At short SPs L3 fires throughout the chirp, while at longer SPs (50–200 ms) L3 responds with a distinct burst of firing for each pulse. At SPs of 200 ms or more, no decrement occurs (Fig. 8).
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20.
1.  We studied the response of plurisegmental interneurons in the suboesophageal ganglionic mass of female spiders (Cupiennius salei) to male vibratory courtship signals.
2.  The opisthosomal vibrations (low frequency component) and the pedipalpal percussions (high frequency component) are processed in parallel by interneuron type I and type II, respectively (Figs. 3, 7).
3.  Type III, IV and V interneurons represent the macrostructure of the male courtship signals (Figs. 8, 9, 10), i.e. the beginning and the end of a series (type III, V) or the end of the series only (type IV). The macrostructure is known to influence the response probability of the female. The spontaneous bursting activity of a type VI neuron undergoes slow and long lasting changes upon stimulation with natural courtship signals (Fig. 11).
4.  Many interneurons responded to natural signals but not to behaviourally effective computer models. This is presumably due to the lack of spectral complexity of the model compared to natural signals. Differences in the natural conspecific and heterospecific signals, however, are represented by the neuronal response (Fig. 3).
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