首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 156 毫秒
1.
Deafferentation experiments during postembryonic development show morphological and/or physiological changes of receptor fibers and of identified auditory interneurons in the CNS of the locusts Locusta migratoria and Schistocerca gregaria after unilateral ablation of one tympanic organ either in the larva or the adult animal.
1.  In Locusta migratoria, 5 days after deafferentation, intact, contralateral receptor fibers had sprouted collaterals in the frontal acoustic neuropil of the metathoracic ganglion (Figs. 1, 2). Collateral sprouts were only rarely found in Schistocerca gregaria.
2.  After about 20 days the deafferented auditory interneurons receive new inputs from the contralateral receptors (Figs. 3, 5, 7, 10). This largely restores their thresholds and intensity/response functions. Collaterals from the first order interneurons cross the midline to the contralateral neuropil (BSN1 neuron, Fig. 4), which is never seen in intact animals. By contrast, in the TN1 neuron no consistent morphological change due to the deafferentation could be found (Fig. 6).
3.  Interneurons of higher order (AN1, TN3 neuron in locusts) regain their response pattern (Fig. 7) without morphological changes (Fig. 9). Bilateral recordings show that the deafferented interneurons respond more weakly to auditory stimuli than the intact neuron, but the response to vibration stimuli remains unchanged (TN3 neuron, Fig. 8).
  相似文献   

2.
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).
  相似文献   

3.
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.
  相似文献   

4.
This paper describes the morphology and response characteristics of two types of paired descending neurons (DNs) (classified as DNVII1 and DNIV1) and two lobula neurons (HR1 and HP1) in the honeybee, Apis mellifera.
1.  The terminal arborizations of the lobula neurons are in juxtaposition with the dendritic branches of the DNs (Figs. 2, 3b, 5). Both of the DNs descend into the ipsilateral side of the thoracic ganglia via the dorsal intermediate tract (Fig. 6) and send out many blebbed terminal branches into the surrounding motor neuropil (Figs. 3c, 7).
2.  Both the lobula and descending neurons respond in a directionally selective manner to the motion of widefield, periodic square-wave gratings.
3.  The neurons have broad directional tuning curves (Figs. 10, 11). HR1 is maximally sensitive to regressive (back-to-front) motion and HP1 is maximally sensitive to progressive (front-to-back) motion over the ipsilateral eye (Fig. 11). DNVII1 is maximally sensitive when there is simultaneous regressive motion over the ipsilateral eye and progressive motion over the contralateral eye (Fig. 12a). Conversely, DNIV1 is optimally stimulated when there is simultaneous progressive motion over the ipsilateral eye and regressive motion over the contralateral eye (Fig. 12b).
4.  The response of DNIV1 is shown to depend on the contrast frequency (CF) rather than the angular velocity of the periodic gratings used as stimuli. The peak responses of both regressive and progressive sensitive DNs are shown to occur at CFs of 8–10 Hz (Figs. 13, 14).
  相似文献   

5.
1.  In order to understand the functional organization of the crustacean olfactory system, we are using intracellular recording and staining techniques to correlate the structure and function of single, odorant-sensitive interneurons in the brain of the crayfishProcambarus clarkii. We describe here the anatomy and physiology of interneurons that connect the brain with the medullae terminales or other eyestalk ganglia.
2.  All of the interneurons in our study (Table 1, Figs. 3–15) are at least third-order olfactory neurons (second-order olfactory interneurons) because they respond to chemostimulation of the olfactory organ (the antennules) but do not branch in the olfactory lobe (the neuropil to which primary olfactory receptor cells of the antennules project).
3.  Much of the central nervous system, including the three main divisions of the brain (protocerebrum, deuterocerebrum, tritocerebrum) (Fig. 1) and the medullae terminales (Fig. 2), are involved in integrating olfactory or multimodal (including olfactory) information, since these areas contain neurites of olfactory interneurons. Previous studies have indicated that regions involved in such processing include the olfactory lobes and accessory lobes of the deuterocerebrum, and regions I, II, IV, and VII (in some species) of the medullae terminales. Our results show that also prominent among regions involved in olfactory or multimodal (including olfactory) integration are the anterior and posterior optic neuropils of the protocerebrum (Figs. 3–11, 14, 15), the lateral and medial antennular neuropils of the deuterocerebrum (Figs. 3, 4, 7), the tegumentary neuropils (Figs. 3, 4, 8, 11) and the antennal neuropils (Figs. 3–5) of the tritocerebrum, and neuropils III, VI, XII of the medullae terminales (Figs. 12, 13).
4.  These olfactory interneurons were sensitive to chemostimulation (unimodal), chemo- and mechanostimulation (bimodal), or chemo-, mechano-, and photostimulation (trimodal) (Table 1). Responses could be excitatory or inhibitory, even for a given neuron (Table 1). Morphologically complex interneurons (those having bilateral branching) were more likely to have complex response characteristics (trimodal sensitivity) (Figs. 8–12) than were morphologically simpler interneurons (those having unilateral branching) (Figs. 3–7, 14, 15). Olfactory interneurons with a soma in the medulla terminalis showed the most complex response profiles: they were trimodal, and were excited by odorants but were inhibited by touch and/or light (Figs. 12, 13). This finding suggests that these are complex, high order interneurons.
5.  Our studies reveal that olfactory and other sensory information is transmitted between the brain and the medullae terminales (and possibly other eyestalk ganglia) by a coactivated, parallel array of structurally and functionally diverse neurons.
  相似文献   

6.
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.
  相似文献   

7.
Locusts (Locusta migratoria) were stimulated with pulses of pure tones of frequencies between 5 kHz and 25 kHz. Interneurons responding to these stimuli (auditory interneurons) were recorded intracellularly and identified by dye injection. Their output functions were investigated by injection of depolarizing current during simultaneous registration of components of flight steering behavior of the animals, i.e. movements of the head and the abdomen and flight activity. Three different types of effects were found, corresponding to 3 functional classes of interneurons:
(1)  Auditory interneurons in the metathoracic ganglion can activate (Fig. 1) or inhibit (Fig. 2) the flight oscillator when depolarized.
(2)  Resting tethered locusts can perform lateral bending of the abdomen and, less prominent, head turns towards the sound source at frequencies between 5 and 15 kHz and at high intensities (70 dB and up, Fig. 3). Auditory interneurons were found which are sensitive to sound pulses with frequencies of 5 kHz to 15 kHz and some of them are directional (Fig. 4). Injection of depolarizing current into these cells causes movements of head and abdomen to the same side (Figs. 6, 7).
(3)  A third population of metathoracic and abdominal interneurons is also excited by pure tone pulses (Figs. 9, 11, 12). Current injected into these cells, and into a descending auditory interneuron (Fig. 8) results in spike activity, driving the head and the abdomen in opposite directions. These movements are components of the characteristic steering behavior seen in the negatively phonotactic response to pulsed ultrasound of intact tethered animals, which is thought to be involved in bat avoidance (Robert 1989).
The frequency responses of the interneurons and their output effects are discussed in the context of two basically different behaviors: a positive phonotaxis, which might be used during intraspecific communication, and an avoidance steering behavior to escape hunting bats.  相似文献   

8.
In this paper, I have examined the behavioral functions of feedback loops between the cockroach (Periplaneta americana) giant interneurons (GIs) and the flight thoracic rhythm generator.
1.  During sequences of flight-like activity, I have recorded from identified giant interneurons from the dorsal (dGIs) or the ventral (vGIs) group and stimulated them either with current pulses or with wind stimuli delivered to the cerci.
2.  Removal of the dGIs' activity which normally occurs during natural flight reduced both the wingbeat frequency and flight duration, and increased the variability of the wingbeat frequency (Fig. 6). Intracellular rhythmic stimulation of a single dGI during flight increased the wingbeat frequency and the duration of flight (Figs. 7, 8). The wind sensitivity of the dGIs was unchanged during flight compared with at rest (Fig. 2). A single short burst of spikes in a dGI had complex effects on the flight muscle recording but apparently did not reset the flight rhythm (Fig. 9). These results suggest that the rhythmic activation of the dGIs during natural light participates in the control of the wingbeat frequency and the flight duration (Fig. 12).
3.  In contrast to the dGIs, the vGIs became significantly less sensitive to wind during flight (Fig. 3). Stimulation of one of the vGIs (GI1) with 10 spikes at roughly 180/s during flight evokes immediate cessation of flight (Figs. 10, 11). Given that the vGI activity can stop flight, the inhibition imposed on the ventral group during flight appears to be designed to prevent this group from interfering with the flight program (Fig. 12).
  相似文献   

9.
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.
  相似文献   

10.
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.
  相似文献   

11.
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.
  相似文献   

12.
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).
  相似文献   

13.
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).
  相似文献   

14.
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   

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).
  相似文献   

16.
1.  Interactions of cockroaches with 4 different predator species were recorded by videography. Some predators, especially spiders, struck from relatively short distances and usually contacted a cockroach prior to initiation of escape (Table 1, Fig. 3). This touch frequently occurred on an antenna. Cockroaches turned away from the side on which an antenna was touched.
2.  We then measured the success of escape from predators for cockroaches with either cerci or antennae ablated. Only antennal removal caused a significant decrease in the success of escape from spiders (Fig. 5).
3.  With controlled stimuli, cockroaches responded reliably to abrupt touch of antennae, legs or body (Fig. 6). Responses resembled wind-elicited escape: they consisted of a short latency turn (away from the stimulus) followed by running (Figs. 7, 8). However, lesions show that touchevoked escape does not depend on the giant interneuron system (Table 2).
4.  Following section of one cervical connective, cockroaches continued to respond to touching either antenna, but often turned inappropriately toward, rather than away from, stimuli applied to the antenna contralateral to the severed connective (Table 3, Fig. 10).
5.  For certain types of predators touch may be a primary cue by which cockroaches detect predatory attack. Descending somatosensory pathways for escape are distinct from the GI system.
  相似文献   

17.
1.  While collecting nectar in hovering flight the European hawk moth Macroglossum stellatarum efficiently regulates its distance relative to flowers that are shaken by wind. This can be demonstrated in laboratory experiments by moving dummy flowers (blue cardboard disks) towards and away from the feeding animal (Fig. 1).
2.  Distance regulation is predominantly mediated by visual cues. Mechanoreceptors on the proboscis appear to contribute little to the response.
3.  Movements of dummy flowers can be simulated by expanding and contracting a pattern projected onto a screen. With this technique we investigated the dynamical properties of the servo mechanism underlying distance regulation. The system behaves as a bandpass filter with corner frequencies of 0.15 and 5 Hz (Figs.2,3).
4.  When a high-speed ramp-like movement of the flower is simulated, there is an asymmetry in the response. During simulated approach the reaction is phasic-tonic with a pronounced overshoot at the beginning, during simulated retraction it remains tonic (Fig.5B,C).
5.  During distance regulation the animals compensate for the speed of the edge of the projected pattern. Distance regulation improves substantially when the number of stimulated elementary movement detectors is increased through increasing the number of contour lines by projecting concentric rings instead of a homogeneous disk (Figs.7, 8).
  相似文献   

18.
1.  By penetrating axons in the ventral nerve cord of the dragonfly, Aeshna umbrosa, we measured the intracellular responses of target-selective visual interneurons to movement of black square targets ranging from 1° to 32° visual angle at several levels of mean background luminance.
2.  Neuronal responses, measured both in number of spikes and in the magnitude of integrated postsynaptic potentials, showed a preference for larger target size at lower mean luminance (Table 1, Figs. 1–3). The latency of postsynaptic potential (psp) and spike responses from onset of target movement increased with a decrease in mean luminance (Fig. 1).
3.  A measure of mean target size preference (Eqn. 1) for one identified interneuron (MDT4) in both laboratory and outdoor lighting shows a continuous decrease of preferred size with increases of mean luminance over more than 4 orders of magnitude.
4.  The time to reach the new steady state of cell response after the decrease of mean luminance was ordinarily less than 30 s, but sometimes longer (Fig. 4).
  相似文献   

19.
1.  In an arena, female Acheta domesticus, which walked directly to a standard model calling song (CS) in a pretest, displayed angular deviations and complete 360° circling following unilateral occlusion of the posterior and anterior tympana. Following removal of the occlusion, the crickets once again oriented directly to the sound source (Fig. 1). Following unilateral removal of the tibia of a prothoracic leg just distal to the ear, crickets oriented directly to a standard CS. Unilateral leg amputation just proximal to the ear caused angular deviations and circling which was similar to that following occlusion of an ear (Fig. 2).
2.  Thresholds of auditory interneurons increased dramatically (to greater than 85 dB) following occlusion of the ear which provides excitatory input to these neurons. Removal of the occlusion restored responsiveness (Fig. 3).
3.  The mean number of complete turns by a cricket with one ear occluded is greatest in response to syllable periods that are most attractive and thus can be used as a measurement of the relative attractiveness of the CS presented (Figs. 4, 5). Females that did not significantly discriminate between different syllable periods before unilateral occlusion of an ear, discriminated between CS syllable periods by their degree of circling following occlusion.
  相似文献   

20.
1.  Filiform hairs of various lengths on the cerci of adult crickets vibrate in a sound field. These movements were measured with a photodetector for sound frequencies from 10 Hz to 200 Hz in the species Acheta domestica, Gryllus bimaculatus and Phaeophilacris spectrum.
2.  With low air-particle velocities, the hair shafts were deflected sinusoidally from their resting position, without bending or secondary oscillations (Figs. 2 A, 3 A). At higher velocities (from ca. 80 mm/s peak velocity, depending on the properties of the individual hairs), the shaft struck the cuticular rim of the socket in which the base of the hair is seated (Fig. 2B). This contact was made at an average angular displacement from the resting position of 5.16°±1.0°.
3.  The best frequencies of the hairs were found to be between 40 Hz and 100 Hz (Fig. 5A). The slope of the amplitude curve for constant peak air-particle velocity at frequencies below the best frequencies was between 0 and 6 dB/octave. Long hairs had smaller slope values than short hairs (Fig. 5C).
4.  At its best frequency the ratio of maximal tip displacement of a hair to the displacement of the air particles in the sound field was between 0.2 and 2. Only a small number of hairs (2 out of 36) showed tip displacements exceeding twice the air-particle displacement. The values of maximal angular displacement were not correlated to hair length (Fig. 5 B).
5.  The angular displacement of the hairs was phase shifted with respect to the air-particle velocity by 0° to +45° (phase lead) at sound frequencies around 10 Hz and by -45° to -120° (phase lag) at 200 Hz (Figs. 3C, 4B). At a particular frequency long hairs tended to have larger phase lags than shorter hairs (Fig. 5D).
  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号