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 31 毫秒
1.
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   

2.
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   

3.
The effects of temperature, over the range 10–40 °C, on properties of locust (Schistocerca gregaria) ocellar L-neurones and of their interconnections have been investigated. At cooler temperatures, a small change in temperature has a larger effect than an equivalent change at warmer temperatures. An increase in temperature leads to the following:
1.  A decrease in input resistance, which typically halves in value as temperature increases from 15 °C to 35 °C. When synaptic transmission between photoreceptor cells and L-neurones is blocked with cobalt, temperature still affects L-neurone resistance. The membrane time constant also decreases, but the resting potential is unaffected.
2.  An increase in the sizes of rebound spikes, which are produced when hyperpolarizing pulses end. Above 35 °C, the maximum size of rebound spike is smaller than that at cooler temperatures.
3.  A decrease in the latency to response to light, and an increase in the speeds of the transient responses to changes in light.
4.  A decrease in the latency of transmission at both excitatory and inhibitory synapses between L-neurones.
5.  At excitatory synapses between L-neurones, an increase in the postsynaptic current. This is compensated by a decrease in postsynaptic membrane resistance, so that there is little effect on the size of the postsynaptic potential.
6.  At inhibitory synapses between L-neurones, a decrease in the time for the postsynaptic potential to reach its peak. The time for recovery of transmission at inhibitory synapses is unaffected by temperature.
  相似文献   

4.
1.  We used laser vibrometry and free field sound stimulation to study the frequency responses of the eardrum and the lateral body wall of awake male Eleutherodactylus coqui.
2.  The eardrum snowed one of two distinct frequency responses depending on whether the glottis was open (GO response) or closed (GC response) during the measurement.
3.  The lateral body wall vibrated with a maximum amplitude close to that of the eardrum and in the same frequency range.
4.  Covering the frog's body wall with vaseline reduced the vibration amplitude of the GC response by up to 15 dB.
5.  When a closed sound delivery system was used to stimulate a local area of the body wall the eardrum also showed one of two types of responses.
6.  These results suggest that sound is transmitted via the lung cavity to the internal surface of the eardrum. This lung input has a significant influence on the vibrations of the eardrum even when the glottis is closed.
7.  The vibration amplitude of the eardrum changed with the angle of sound incidence. The directionality was most pronounced in a narrow frequency range between the two main frequencies of the conspecific advertisement call.
  相似文献   

5.
The wind-orientated walk of carrion beetles Necrophorus humator F. was analysed under closed-loop conditions with a walking compensator and under openloop conditions with a paired tread wheel (Fig. 1).
1.  On the walking compensator an animal runs stable courses with a preferred direction relative to an air current (velocity =; 100 cm/s, Fig. 2B-D). A change in the air-current direction causes a corresponding adjustment of the mean walking direction (Fig. 3). Such course adjustment works best for changes in the air-current direction by an absolute value of 90° (Table 2).
2.  Under closed-loop conditions the animal shows deviations of less than ± 45° around its preferred direction relative to the wind (Fig. 2B-D). The characteristic curve which describes the animal's angular velocity as a function of the animal's walking direction relative to the air-current stimulus is therefore revealed only in this angular range (Fig. 3, top).
3.  Under open-loop conditions, however, complete characteristic curves can be obtained because the animal's walking reaction in response to any given angle of air-current stimulus is measurable on the paired tread wheel (Fig. 4). The characteristic curves are approximately sinusoidal functions. They can either show a shift parallel to the ordinale by a superimposed direction-independent constant angular velocity alone or, at the same time, they can independently exhibit an angular shift along the abscissa (Fig. 5).
4.  The walking tracks straighten with increasing air-current velocity (Fig. 6A, insets), i.e. the animal more rapidly compensates deviations from a preferred course. This corresponds to higher amplitudes of the characterisic curve and steeper slopes at the negative zero-crossing point under open- as well as under closed-loop conditions (Fig. 6).
5.  Walking in an air-current field can be explained by a model of the course control system using a feedback loop (Fig. 7). This model operates according to a sinusoidal characteristic function on which is superimposed a Gaussian white noise process of angular velocity which is independent of walking direction. The model produces realistic walking tracks in an air-current field (Fig. 8).
  相似文献   

6.
1.  Intracellular recordings of suboesophageal neurons were performed in the cricketGryllus bimaculatus during applied changes of head temperature in the range 8 to 32.5 °C. The temperature was controlled by perfusing the head with Ringer solution of appropriate temperature. Subsequent staining with Lucifer Yellow revealed descending, ascending or T-shaped cells with ventrally located somata (Fig. 1).
2.  In 6 out of 7 neurons recorded (Fig. 1, neurons A, B, C, D, E, G) the firing rate was correlated with abdominal ventilatory pumping (Fig. 2a, b). These neurons also received input from cereal sensory hairs (Fig. 2c). Furthermore, one of them (Fig. 1, neuron A) showed responses to auditory (Fig. 2d) and another (Fig. 1, neuron E) to visual input (Fig. 2e).
3.  Activity of every tested neuron was correlated with the temperature of the perfusing Ringer solution: the amplitude and duration of spikes and excitatory postsynaptic potentials increased with cooling (Fig. 3). Two types of temperature-dependent changes in firing rate were identified. In type I the spiking rate was higher at higher temperature (Figs. 4a, b; 5). In type II spiking rate was related to the direction of temperature change (Fig. 4c, d).
4.  The possible involvement of one of the recorded cells (Fig. 1, neuron F) in thermoreception processes is discussed. Activity of this neuron was not related to the rhythm of abdominal ventilatory pumping, nor did the cell receive cereal, visual or auditory input. Its activity was related mainly to the direction of temperature changes i.e. with an increase in firing rate during cooling, independent of the temperature at which the cooling started and with a transient decrease in firing rate during warming from starting point of 10 °C.
  相似文献   

7.
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   

8.
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   

9.
1.  The effect of intracellularly injected cAMP on the amplitude of excitatory postsynaptic potentials was studied using identified neurons of the snailHelix pomatia.
2.  In 25% of the experiments, postsynaptic cAMP elevation caused a pronounced augmentation of the excitatory postsynaptic potential (EPSP) amplitude, lasting up to 15–30 min.
3.  The results suggest that a cAMP increase in the postsynaptic neuron may be involved in the enhancement of synaptic efficiency.
  相似文献   

10.
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.
  相似文献   

11.
The wind-orientation of carrion beetles (Necrophorus humator F.) was studied by use of a locomotion-compensator.
1.  Beetles walking on a horizontal surface for periods of several minutes in a dark environment without an air current and other orientational stimuli seldom keep straight paths. They walk along individually different circular paths (Fig. 1). The mean walking speed is 5.6±1.0 cm/s. The mean of the angular velocity reaches maximally 25 °/s for individual beetles (mean angular velocity of the analysed population of 152 beetles: 1.9±9.3 °/s). The distribution of the mean walking directions of the population shows that the beetles display no preference for one direction (Fig. 3 A). The instantaneous value of the individual angular velocity is independent of the instantaneous walking direction.
2.  During exposure to an air current the individual beetles keep straight and stable courses with any orientation relative to the direction of air flow (Fig. 4). The mean walking directions of 76 individuals point in all directions but there is a weak preference of windward tracks (Fig. 3B).
3.  Wind orientated walking starts at a threshold wind velocity of about 5 cm/s (Fig. 6). The walking tracks straighten with increasing air current velocity. This leads to a narrowing of the distribution of the instantaneous walking directions around the preferred walking direction (Fig. 7C). This narrowing is due to an increase in the slope of the characteristic curve (angular velocity as a function of walking direction) of the wind-orientation system.
4.  Twenty percent of the beetles show a spontaneous change of their anemotactic course during walks of 5 min duration. Neither the time of the change, its position on the track or the direction of the new course are predictable. There is, however, a slight preference for 90±20° changes in the walking direction (Fig. 8).
5.  The antennae (Fig. 9) act as the only sense organs responsible for the wind orientation. The capability for wind orientated walks is lost after ablation of both flagella (Fig. 10).
  相似文献   

12.
1.  The physiology and morphology of olfactory interneurons in the brain of larval Manduca sexta were studied using intracellular recording and staining techniques. Antennal olfactory receptors were stimulated with volatile substances from plants and with pure odorants. Neurons responding to the stimuli were investigated further to reveal their response specificities, dose-response characteristics, and morphology.
2.  We found no evidence of specific labeled-lines among the odor-responsive interneurons, as none responded exclusively to one plant odor or pure odorant; most olfactory interneurons were broadly tuned in their response spectra. This finding is consistent with an across-fiber pattern of odor coding.
3.  Mechanosensory and olfactory information are integrated at early stages of central processing, appearing in the responses of some local interneurons restricted to the primary olfactory nucleus in the brain, the larval antennal center (LAC).
4.  The responses of LAC projection neurons and higher-order protocerebral interneurons to a given odor were more consistent than the responses of LAC local interneurons.
5.  The LAC appears to be functionally subdivided, as both local and projection neurons had arborizations in specific parts of the LAC, but none had dendrites throughout the LAC.
6.  The mushroom bodies and the lateral protocerebrum contain neurons that respond to olfactory stimulation.
  相似文献   

13.
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   

14.
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   

15.
The caudal photoreceptors (CPRs) of crayfish (Procambarus clarkii) can trigger walking and abdominal movements by their response to light.
1.  In a restrained, inverted crayfish, illumination of A6 evoked a CPR discharge followed by leg movements and bursting from the abdominal tonic flexor (TF) motoneurons. Intracellular electrical stimulation of a single CPR at high frequency (80 Hz) evoked similar responses.
2.  Responses only occurred when a single CPR axon was driven at 60 Hz or more and outlasted the stimulus.
3.  CPR stimulation also excites the pattern-initiating network (Moore and Larimer 1987) in the abdomen.
4.  The axon of the CPR projects from ganglion A6 to the brain. Terminal branches occur in the subesophageal ganglion and the brain. A small descending interneuron is dye-coupled to CPR in the subesophageal ganglion.
5.  In animals with cut circumesophageal connectives, the CPRs can evoke walking and the abdominal motor pattern.
6.  The relationship of the abdominal motor pattern to walking is altered by restraint and/or inversion. In freely moving crayfish, the cyclic abdominal motor pattern is only observed with backward walking. In restrained, inverted crayfish, the motor pattern occurs with both forward or backward walking.
  相似文献   

16.
Müller  D. G.  Frenzer  K. 《Hydrobiologia》1993,(1):37-44
Culture studies with healthy and virus-infected isolates of Ectocarpus siliculosus, Feldmannia simplex and F. irregularis gave the following results:
–  Virus particles are produced in deformed reproductive organs (sporangia or gametangia) of the hosts and are released into the surrounding seawater.
–  Their infective potential is lost after several days of storage under laboratory conditions.
–  New infections occur when gametes or spores of the host get in contact with virus particles. The virus genome enters all cells of the developing new plant via mitosis.
–  Virus expression is variable, and in many cases the viability of the host is not impaired. Infected host plants may be partly fertile and pass the infection to their daughter plants.
–  Meiosis of the host can eliminate the virus genome and generate healthy progeny.
–  The genome of the Ectocarpus virus consists of dsDNA. Meiotic segregation patterns suggest an intimate association between virus genome and host chromosomes.
–  An extra-generic host range has been demonstrated for the Ectocarpus virus.
–  Field observations suggest that virus infections in ectocarpalean algae occur on all coasts of the world, and many or all Ectocarpus and Feldmannia populations are subject to contact with virus genomes.
  相似文献   

17.
In the rift valley (North-East of France/South-West of Germany), the Rhine runs freely for 300 km from South to North. The absence of natural obstacles allows the development of a very regular profile of the river. We have therefore an opportunity to study very gradual modifications of the alluvial forest communities of the fluvial corridor from upstream to downstream, according to the gradual evolution of the ecological factors, related to slope decrease and hydrological modifications.We describe, from Basel to Mainz:
1)  modification of dynamic processes in the forest communities such as successional sequences or sylvigenetic mosaïcs of the terminal stages.
2)  modification of species richness.
3)  reduction of species diversity.
4)  simplification of the forest stratification.
5)  modification of efficiency of the biogeochemical cycling.
6)  ecological vicariances.
7)  modification in species behaviour.
  相似文献   

18.
1.  Most studies examining interactions between insectivorous bats and tympanate prey use the echolocation calls of aerially-feeding bats in their analyses. We examined the auditory responses of noctuid (Eurois astricta) and notodontid (Pheosia rimosa) moth to the echolocation call characteristics of a gleaning insectivorous bat, Myotis evotis.
2.  While gleaning, M. Evotis used short duration (mean ± SD = 0.66 ± 0.28 ms, Table 2), high frequency, FM calls (FM sweep = 80 – 37 kHz) of relatively low intensity (77.3 + 2.9, –4.2 dB SPL). Call peak frequency was 52.2 kHz with most of the energy above 50 kHz (Fig. 1).
3.  Echolocation was not required for prey detection or capture as calls were emitted during only 50% of hovers and 59% of attacks. When echolocation was used, bats ceased calling 324.7 (±200.4) ms before attacking (Fig. 2), probably using prey-generated sounds to locate fluttering moths. Mean call repetition rate during gleaning attacks was 21.7 (±15.5) calls/s and feeding buzzes were never recorded.
4.  Eurois astricta and P. rimosa are typical of most tympanate moths having ears with BFs between 20 and 40 kHz (Fig. 3); apparently tuned to the echolocation calls of aerially-feeding bats. The ears of both species respond poorly to the high frequency, short duration, faint stimuli representing the echolocation calls of gleaning M. evotis (Figs. 4–6).
5.  Our results demonstrate that tympanate moths, and potentially other nocturnal insects, are unable to detect the echolocation calls typical of gleaning bats and thus are particularly susceptible to predation.
  相似文献   

19.
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.
  相似文献   

20.
1.  The cochlea of the horseshoe bat,Rhinolophus ferrumequinum, was frequency mapped by exposing for 30 min to one or two continuous pure tones of intensities between 70 and 110 dB SPL. The evaluation was made by differentiating between normal and swollen nuclei of the outer hair cells (OHC) of the organ of Corti and by measuring the diameter of the nuclei of the OHC.
2.  In control animals the radial diameter of the OHC nuclei varies systematically from a mean of 2.85 m at the base to 3.2 um at the apex (Fig. 1).
3.  All frequencies used for exposure were normalized to the resting frequency (FR), which is the frequency of the pure tone component of the orientation sound in a non-flying bat. The individual FR lay between 82.6 and 83.3 kHz.
4.  For analysing the small frequencies between 83.0 to 86.0 kHz in which relevant echoes occur, 3.15 mm length of the basilar membrane is used, about the same length as for the octaves from FR/4 to FR/2 (2.85 mm) and from FR/2 to FR (3.2 mm) (Fig. Ca, b).
5.  The discontinuity of the mechanical data at 4.5 mm of the length of the basilar membrane (part I of this paper) coincides with FR and the less pronounced discontinuity at 7.8 mm coincides with FR/2.
6.  Location and mechanism of the auditory filter are discussed.
  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