Time course of the Houseflies' landing response

The landing response of stationary flying houseflies Musca domestica has been recorded on video tape. The leg movements were quantitatively evaluated. It could be demonstrated that:

1. only the first two pairs of legs are involved in the reaction (Fig. 1). Prothoracic tarsi are lifted beyond the head, mesothoracic tarsi are lowered and moved sidewards (Fig. 2a and b).
2. the movement of the tarsal tips is mainly due to an opening of one single joint per leg, i.e. the femurtibia joint of the prothoracic leg (Fig. 2c), and the coxa-femur joint of the mesothoracic leg.
3. the landing reaction is a fixed action pattern which does not seem to require further sensory input once it is released (Fig. 4d).
4. the landing responses to a light-off stimulus and to expanding patterns with different angular velocities are indistinguishable (compare Fig. 3a-c with Fig. 2a-c). The only parameter that is obviously dependent on the stimulus conditions, is the latency of the reaction (Fig. 4a-c).

     

The three-dimensional optomotor torque system ofDrosophila melanogaster

Summary The well known optomotor yaw torque response in flies is part of a 3-dimensional system. Optomotor responses around the longitudinal and transversal body axes (roll and pitch) with strinkingly similar properties to the optomotor yaw response are described here forDrosophila melanogaster. Stimulated by visual motion from a striped drum rotating around an axis aligned with the measuring axis, a fly responds with torque of the same polarity as that of the rotation of the pattern. In this stimulus situation the optomotor responses for yaw, pitch and roll torque have about the same amplitudes and dynamic properties (Fig. 2). Pronounced negative responses are measured with periodic gratings of low pattern wavelengths due to geometrical interference (Fig. 3). The responses depend upon the contrast frequency rather than the angular velocity of the pattern (Fig. 4). Like the optomotor yaw response, roll and pitch responses can be elicited by small field motion in most parts of the visual field; only for motion below and behind the fly roll and pitch responses have low sensitivity.The mutantoptomotor-blind ^H31 (omb ^H31) in which the giant neurones of the lobula plate are missing or severely reduced, is impaired in all 3 optomotor torque responses (Fig. 5) whereas other visual responses like the optomotor lift/thrust response and the landing response (elicited by horizontal front-to-back motion) are not affected (Heisenberg et al. 1978).We propose that the lobula plate giant neurons mediate optomotor torque responses and that the VS-cells in particular are involved in roll and pitch but not in lift/thrust control. This hypothesis accommodates various electrophysiological and anatomical observations about these neurons in large flies.Abbreviation EMD elementary movement detector     

Response characteristics of wide-field non-habituating non-directional motion detecting neurons in the optic lobe of the locust,Locusta migratoria

1. Extracellular recordings from wide-field nonhabituating non-directional (ND) motion detecting neurons in the second optic chiasma of the locust Locusta migratoria are presented. The responses to various types of stepwise moving spot and bar stimuli were monitored (Fig. 1)
2. Stepwise motion in all directions elicited bursts of spikes. The response is inhibited at stimulus velocities above 5°/s. At velocities above 10°/s the ND neurons are slightly more sensitive to motion in the horizontal direction than to motion in the vertical direction (Fig. 2). The ND cells have a preference for small moving stimuli (Fig. 3).
3. The motion response has two peaks. The latency of the second peak depends on stimulus size and stimulus velocity. Increasing the height from 0.1 to 23.5° of a 5°/s moving bar results in a lowering of this latency time from 176 to 130 ms (Fig. 4). When the velocity from a single 0.1° spot is increased from 1 to 16°/s, the latency decreases from 282 to 180 ms (Figs. 5–6).
4. A change-of-direction sensitivity is displayed. Stepwise motion in one particular direction produces a continuous burst of spike discharges. Reversal or change in direction leads to an inhibition of the response (Fig. 7).
5. It shows that non-directional motion perception of the wide-field ND cells can simply be explained by combining self-and lateral inhibition.

     

The orientation of flies towards visual patterns: On the search for the underlying functional interactions

The average optomotor response of insects to a given visual stimulus (measured in open-loop conditions) can be decomposed into a direction sensitive and a direction insensitive component. This decomposition is conceptual and always possible. The direction sensitive optomotor response represents the “classical” optomotor reflex, already studied in previous investigations; the direction insensitive optomotor response is strictly connected to the orientation and tracking behaviour (see the work of Reichardt and coworkers). Thus a characterization of the direction insensitive response is useful in clarifying the nervous mechanisms underlying the orientation behaviour. For this reason we study in this paper the direction insensitive optomotor (torque) response of fixed flying fliesMusca domestica. Periodic gratings, either moving or flickering, represent our main stimulus, since the dependence of the fly response on the spatial wavelength can unravel the presence and properties of the underlying lateral interactions. In this connection an extension of the Volterra series formalism to multi-input (nervous) networks is first outlined in order to connect our (behavioural) input-output data with the interactive structure of the network. A number of results concerning, for instance, the response of such networks to flickered and moving gratings are derived; they are not restricted to our behavioural results and may be relevant in other fields of neuroscience. These theoretical considerations provide the logical framework of our experimental investigation. The main results are:

1. the direction insensitive optomotor response depends on the spatial frequency of a moving grating, implying the existence of (nonlinear) lateral interactions,
2. its wavelength dependence changes with age, unlike the direction sensitive response,
3. both the direction insensitive response and the (closed loop) orientation behaviour are present only in the lower part of the eye; on the other hand the direction sensitive response is present in every part of the two eyes.

Furthermore the attraction towards a flickered periodic grating shows, as theoretically expected, a wavelength-dependence similar to that of the direction insensitive response, again present only in the lower part of the eye. The interactions which affect the orientation response are selective with respect to the spatiotemporal mapping of the pattern onto the receptor array. It is conjectured that these interactions are the basic mechanisms underlying spontaneous pattern discrimination in flies. Their possible organization is further discussed in terms of our formalism. Moreover our data suggest that two specific nervous circuitries correspond to our conceptual decomposition of the optomotor response.     

What kind of movement detector is triggering the landing response of the housefly?

As shown before, the latency of the housefly's landing response depends on the conditions of the visual stimulus (Borst 1986). Accordingly, the latency can be used to characterize the movement detection system which is triggering the landing response.The stimulus was a sinusoidal periodic pattern of vertical stripes presented bilaterally in the frontolateral eye region of the fly. It started to move, simultaneously on either side, from front to back at a given time. The latency of the response was measured by means of an infrared light-beam that was interrupted whenever the fly lifted its forelegs to assume a preprogrammed landing posture (Fig. 1). The latency was found to vary in a range from 60 ms up to several seconds depending on the pattern's spatial wavelength , contrast frequency cf and contrast C.For sufficiently high pattern contrast the optimum of the reaction (minimum latency) is found at spatial wavelengths of 30–40° and contrast frequencies of 8–17 periods/s (Fig. 3a). This is about 2–10 times more than is anticipated from the optomotor response under similar conditions. Evaluation of the optimum contrast frequency cf _OPT at different wavelengths shows that cf _OPT is not independent of (Fig. 3b, solid line). The same is true for the contrast dependence of the reaction: reduction of the contrast leads not only to a general decrease in the response amplitudes (prolongation of the latency) (Fig. 4a), but also to a shift of cf _OPT towards lower contrast frequencies (Fig. 4b, solid line).In the theory of the correlation-type movement detector (Reichardt 1961) which underlies the optomotor response of flies the dependence of cf _OPT on pattern wavelength and/or pattern contrast is not expected under stationary conditions. However, as shown by computer simulation all experimental results can be explained by a homogeneous retinotopic array of correlation movement detectors (Fig. 2) if their response under non-stationary conditions is taken into account. We simply assume that the spatially and temporally integrated output of the movement detectors is evaluated by a threshold device (Fig.5). The correlation-type movement detection in combination with a temporal integrator system predicts the rather complex dependence of the optimum contrast frequency on pattern wavelength and pattern contrast (dashed lines in Fig. 3b and 4b) and provides the missing explanation of the variable latencies of the landing response.Comparing the parameters of the correlation-type movement detector derived in the present study with those of the optomotor response, the landing response seems to use the same type of movement detection system. To account for the high wavelength optimum, however, the input elements of the movement detection system of the landing response might have an increased visual field (e.g. by pooling neighbouring visual elements) and, accordingly, a reduced visual acuity as compared with the input elements of the optomotor system.Abbreviations (°) spatial pattern wavelength - w(°/s) angular velocity of the pattern - cf (Hz) contrast frequency=w/ - cf _OPT(Hz) cf leading to the shortest latency - (Hz) angular frequency=2cf - I mean luminance of the pattern - I modulation amplitude of the pattern - C pattern contrast=I/ - (ms) time constant of a filter - (°) angle between the optical axis of neighbouring visual elements - (°) acceptance angle of visual elements     

Vibratory communication in spiders

We analyzed the response of the vibration sensitive lyriform organ on the metatarsus of female spiders (Cupiennius salei) to dummies of male courtship vibrations. One of the two representative slits studied is sharply tuned to 500 Hz. Only the other slit is sensitive enough at lower frequencies to represent the parameters contained in the behaviourally effective dummies:

1. Amplitude. The physiological threshold is similar to the behavioural threshold. The stimulus acceleration amplitudes leading to a good synchronization between response and temporal stimulus pattern coincide with those effectively eliciting a behavioural response. The most frequent spike intervals remain nearly constant in this range. At acceleration amplitudes above the natural range, syllable and pause durations are misrepresented by the receptor response.
2. Frequency. Varying the carrier frequency between 35–500 Hz changes the most frequent spike intervals. Interval histograms resulting from behaviourally effective stimuli (50–200 Hz), however, are similr for carrier frequencies differing by a factor of 2.
3. Temporal pattern. Response duration reflects the temporal parameters of the stimulus. The most frequent spike interval only changes with temporal stimulus characteristics far off the natural range. The number of spikes during a syllable decreases in ongoing stimulus series. The quality of copying the temporal stimulus pattern remains unchanged, however.

     

Multisensory control of escape in the cockroach Periplaneta americana

1. All giant interneurons (GIs) were ablated from the nerve cord of cockroaches by electrocautery, and escape behavior was analyzed with high-speed videography. Animals with ablations retained the ability to produce wind-triggered escape, although response latency was increased (Table 1, Fig. 4). Subsequent lesions suggested that these non-GI responses depended in part on receptors associated with the antennae.
2. Antennal and cereal systems were compared by analyzing escape responses after amputating either cerci or antennae. With standard wind stimuli (high peak velocity) animals responded after either lesion. With lower intensity winds, animals lost their ability to respond after cereal removal (Fig. 6).
3. Removal of antennae did not cause significant changes in behavioral latency, but in the absence of cerci, animals responded at longer latencies than normal (Fig. 7).
4. The cercal-to-GI system can mediate short latency responses to high or low intensity winds, while the antennal system is responsive to high intensity winds only and operates at relatively longer latencies. These conclusions drawn from lesioned animals were confirmed in intact animals with restricted wind targeting the cerci or antennae only (Fig. 9).
5. The antennae do not represent a primary wind-sensory system, but may have a direct mechanosensory role in escape.

     

Physiological and pharmacological properties of responses to GABA and ACh by abdominal motor neurons in Manduca sexta

1. GABA, ACh, and other agents were applied by pressure ejection to the neuropil of the third abdominal ganglion in the isolated nerve cord of Manduca sexta. Intersegmental muscle motor neurons with dendritic arborizations in the same hemiganglion were inhibited by GABA (Fig. 2) and excited by ACh (Fig. 5).
2. Picrotoxin was a potent antagonist of GABA (Fig. 4A). Bicuculline reduced GABA responses in some motor neurons (Fig. 4C), but had no effect on many other motor neurons. Curare reduced ACh responses (Fig. 6A). Bicuculline was an effective ACh antagonist in most motor neurons tested (Fig. 6B).
3. Motor neurons with dendrites across the ganglion from the ejection pipette exhibited different responses to GABA and ACh. Contralateral motor neurons often showed smaller, delayed hyperpolarizing GABA responses (Fig. 7). On two occasions, contralateral motor neurons had excitatory responses (Fig. 8). Contralateral motor neurons were hyperpolarized by ACh (Fig. 9). The inhibitory responses had only slightly longer latencies than ipsilateral excitatory ACh responses (Fig. 10A). The contralateral inhibitory ACh responses, but not the ipsilateral excitatory ACh responses, were eliminated by TTX (Fig. 10B).
4. A model, which includes inhibitory interneurons that cross the ganglionic midline to inhibit their contralateral homologs and motor neurons (Fig. 11), is proposed to account for contralateral responses to GABA and ACh and antagonistic patterns of activity of motor neurons during mechanosensory reflex responses.

     

Morphological and physiological properties of pheromone-triggered flipflopping descending interneurons of the male silkworm moth,Bombyx mori

1. The morphology of descending interneurons (DNs) which have arborizations in the lateral accessory lobe (LAL) of the protocerebrum, the higher order olfactory center, and have an axon in the ventral nerve cord (VNC), were characterized in the male silkworm moth, Bombyx mori.
2. Two clusters (group I, group II) of DNs which have arborizations mainly in the LALs were morphologically characterized. The axons of these DNs are restricted to the dorsal part of the each connective (Figs. 1–5).
3. Pheromonal responses of the group I and group II DNs were characterized. Flipflopping activity patterns, which have two distinct firing frequencies (high and low) in response to sequential pheromonal stimulation, were usually recorded (Figs.6–10).
4. Two types of flipflopping activity patterns were classified into those that had an antiphasic relationship (called the ‘FF’ type) between the left and right connectives and those with a synchronized relationship (‘ff’ type) (Figs. 8–12). We propose that some group II DNs show ‘FF’ flipflopping activity patterns (Fig. 10).
5. A state transition was usually elicited by less than 10 ng bombykol, the principal pheromone component. Extra impulses were elicited during constant light stimulation (Fig. 9).
6. Our results suggest that the LAL olfactory pathways might be important for producing flipflopping activity patterns (Fig. 11).

     

The pursuit response of the housefly and its interaction with the optomotor response

Summary Pursuit responses that are probably involved in chasing behavior can be evoked and quantitatively measured in male houseflies under conditions of tethered flight (Figs. 2, 3, 5). Pursuit responses of females are significantly different from those of males (Table 1).Characteristics of the pursuit response are compared with those of the optomotor response to show that they are mediated by different neural subsystems that are in parallel. A slow system mediates the optomotor response, while a much faster system mediates the pursuit response (Table 1).The interaction between the pursuit response and the optomotor response is one of switching. The optomotor stimulus, when presented alone, evokes the optomotor response. When the pursuit stimulus is superposed, the fly switches from the optomotor system to the pursuit system, and ignores the optomotor stimulus. When the pursuit stimulus is removed, the animal switches back to the optomotor system (Fig. 8).We wish to thank Dr. M.F. Land for his valuable suggestion for measuring the optomotor response. This work was supported by NEI grants EY 01140 and EY 00785.     

Frequency as a releaser in the courtship song of two crickets,Gryllus bimaculatus (de Geer) and Teleogryllus oceanicus: a neuroethological analysis

1. The courtship behavior of male field crickets, Gryllus bimaculatus (De Geer) and Teleogryllus oceanicus, is a complex, multimodal behavioral act that involves acoustic signals (a courtship song; Fig. 1A,B). The dominant frequency is 4.5 kHz for T. oceanicus song (Fig. 1A) and 13.5 kHz for G. bimaculatus (Fig. IB).
2. When courting males are deprived of their courtship song by wing amputation, their courtship success declines markedly but is restored when courting is accompanied by tape-recordings of their courtship songs or a synthetic courtship song with only the dominant frequency of the natural song; other naturally occurring frequency components are ineffective for restoring mating success (Figs. 4, 5).
3. It has been suggested that an identified auditory interneuron, AN2, plays a critical role in courtship success. Chronic recordings of AN2 in an intact, tethered female show that AN2's response to the natural courtship song and synthesized songs at 4.5 and 13.5 kHz is similar in T. oceanicus. By contrast, in G. bimaculatus, AN2's response to the natural courtship song and synthesized song at 13.5 kHz, but not at 4.5 kHz, is similar (Figs. 2,3).
4. In behavioral experiments, playback of a 30 kHz synthetic courtship song in G. bimaculatus does not restore courtship success, yet this same stimulus elicits as strong a response from AN2 as does the normal courtship song (Fig. 6). Thus, contrary to earlier work by others, we conclude AN2 is not, by itself, a critical neural link in the courtship behavior of these two species of crickets.

     

Are the large monopolar cells of the insect lamina on the optomotor pathway?

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.

Discrimination of phase spectra in complex sounds by the bullfrog (Rana catesbeiana)

1. Male bullfrogs at two different natural calling sites were presented with playbacks of synthetic advertisement calls differing in phase spectra. Sounds were presented in a ABA design to analyze the ability of the animals to perceive changes in repeated series of stimuli.
2. The number of individual croaks in an answering call significantly increased over repeated presentations of two of the three stimulus phase types in condition A1. There were significantly fewer croaks to the third stimulus. These data suggest that two stimuli were perceived in a similar manner.
3. Latency of calling to stimuli presented in conditions A and B changed in response to shifts in phase spectrum at a low density calling site. These differences were significant when comparing latency to playbacks where shifts in the phase spectrum changed the temporal fine-structure and waveform periodicity of the stimulus.
4. The increase in number of croaks and decrease in response latency across condition A1 and the increase in latency in condition B suggest that discrimination may take the form of stimulus-specific sensitization. In this context, sensitization might reflect an increase in arousal due to repeated presentation of a salient stimulus.
5. The operation of a hypothetical ‘mating call detector,’ based on linear summation of temporal responses from the eighth nerve, provides output similar to the behavioral results.

     

Basic processes of locomotor coordination in the rock lobster

Rock lobsters are able to perform long and stereotyped stepping sequences above a motor driven treadmill. Forward walking samples are estimated by mean of statistical methods to draw out the basic rules involved in the locomotor behaviour (Fig. 1).

- The spatial and temporal parameters defined in a single propulsive leg are either invariable in respect to the imposed speed, as the mean step length (L), the return stroke duration (Tr) and the pause times (T's, T'r), or speed dependent as the power stroke duration (Ts) and the whole period (Figs. 2 and 3).

- The interleg phase coupling is strong and stable in the ipsilateral rear pairs (4–5), these legs acting most of the time in absolute coordination (1:1) or in harmonic ratio (2:1). In the contralateral pairs (R4-L4, R5-L5) the legs roughly operate in antiphase, but the relationship appears much weaker and variable, with frequent episodes of relative coordination (Fig. 4).

- The time intervals between the ground contact of any leg and the swing initiation in the nearest ones appear somewhat constant and could be closely related to the mechanism of stepping synchronization. The “5 on - 4 off” delay, very stable and always positive, suggests that the rear legs could exert a predominant influence upon the rhythmical movements of the next anterior ipsilateral appendages (Fig. 5).

- To test the contralateral relationships, the treadmill belts can be decoupled in order to impose different walking speeds on each side. Such a conflicting stimulus reveals that:

1. The relative hierarchy always observed between the ipsilateral legs can be artificially created between the two sides (Fig. 6).
2. The driving influence of a given leg is closely linked to the intensity of EMG's discharges in its power stroke muscles.
3. The contralateral appendages are able to walk in absolute coordination despite a large speed difference between the two sides (up to 4 cm/s). Under such a constraint, the walking legs alter its invariable parameters (L and Tr) to reach a common step period and steadily maintain the alternating pattern (Figs. 6 and 7).

     

用红外方法对蝇翅视动行为的探索

本文报告了利用红外装置对蝇翅视动行为实验研究的初步结果及其分析:1.在红外探测器探测到的信号中找到了一个能反映蝇翅拍动幅度的参数.2.双侧、单侧刺激域的宽度及刺激域的高度对视动反应发生几率在一定范围内正相关,当超过一阈值(即饱和阈值)后,即出现稳定的视动反应,它们的饱和阈值分别为60°,30°,40°刺激条纹的亮度生有类似情况.刺激条纹的运动速度在一定范围内对视动反应无影响.3.当刺激没有达到饱和时,蝇翅出现断续的典型的视动反应,即“0-1波动反应”.4.单侧条纹由前向后运动时,蝇翅出现典型反应,而条纹从后向前运动时,不出现典型的视动反应或反应很弱.双侧刺激时,条纹向前运动几乎不诱发反应;条纹向后运动诱发明显的蝇翅视动反应,且蝇翅平面的方向在拍动过程中发生变化.     

Optomotorische Untersuchungen am visuellen System der Stubenfliege Musca domestica L

The compound eye of the housefly Musca domestica L. contains two different types of receptors. The visual acuity of the eye is determined by the divergence angle Δ? between the optical axes of neighbouring ommatidia. Δ? and its dependence on the mean pattern brightness is determined by an evaluation of the optomotor responses elicited from various test patterns. Based on the assumption that the visual fields of both types of receptors approximate the shape of a spatial Gaussian distribution they can be characterized by their half-width, designated as the acceptance angle ΔQ. The contrast transfer from the optical environment onto the receptor cells is limited by ΔQ. It is shown experimentally that ΔQ depends on the mean environmental brightness. The characteristic values Δ? and ΔQ constitute the limiting factors for the light flux received by the receptors. The light flux Φ exciting the receptor cells is proportional to (ΔQ·Δ?)². If the product ΔQ·Δ? is kept constant, there exists a certain ratio \(\frac{{\Delta _\rho }}{{\Delta _\varphi }}\) that leads to an optimal combination of both, contrast transfer and resolution. The ratio \(\frac{{\Delta _\rho }}{{\Delta _\varphi }}\) is experimentally determined and compared with the optimal condition. The torque exerted by fixed flying Muscae has been used as a measure of the reaction strength of the optomotor response elicited by the rotation of cylindrical patterns consisting of periodic distributions of surface brightness. The responses were investigated under different spatial wavelengths, contrasts, contrast frequencies and mean pattern brightness. Detailed results are:

1. The visual acuity (optical resolution power) of the compound eye of Musca is determined by the divergence angle Δ _? between the optical axes of those adjacent ommatidia which are not positioned in the same horizontally oriented row but — closer together — in neighboured rows.
2. Δ? and consequently also the visual acuity do not depend on the mean environmental brightness.
3. The acceptance angle ΔQ changes with the mean brightness of the environment. According to experimental conditions only the minimal acceptance angle Δ _min can be experimentally determined. Δ _min decreases with increasing mean pattern brightness from 3.6°–4.1° to 1.7°.
4. The decrease of ΔQ _min with increasing mean pattern brightness is not caused by a change of the acceptance angles of single receptors. The present tentative explanation is that the centrally located receptors No. 7 and 8 are participating in the uptake of relevant visual information at a critical brightness level.
5. Near the optomotor threshold the large acceptance angle ΔQ _min=3.6° at very dim light would thus be associated with the receptors No. 1 to 6, whereas the smaller acceptance angle ΔQ _min=1.7° with the receptors No. 7 and 8.
6. Due to a sample spacing of Δ?=2°, the acceptance angles of neighbouring receptors No. 1 to 6 show a considerable overlap.
7. Based on anatomical data, the difference in absolute light sensitivity for both receptor systems is calculated. It is predicted that the absorption rate of light quanta in the less sensitive system of the receptors No. 7 and 8 should be reduced by a factor of 24–48 compared to the more sensitive system of the receptors No. 1 to 6. This factor nicely meets the experimentally determined brightness thresholds of both receptor systems.
8. The optimal condition \(\frac{{\Delta _\rho }}{{\Delta _\varphi }}\) is nearly fulfilled by the receptor system No. 7 and 8 of Musca. The experimentally determined ratio amounts to \(\frac{{\Delta _\rho }}{{\Delta _\varphi }}\) =0.83. For the receptor system No. 1 to 6 one finds \(\frac{{\Delta _\rho }}{{\Delta _\varphi }}\) =1.86; in that system the transfer of spatial wavelengths is mainly limited by the reduced contrast transfer which drops to low values before the optical resolution limit is reached.
9. Based on the hypothesis that movement perception of the fly Musca is due to a correlation of sensory data one would expect an optomotor peak reaction at a spatial wavelength of λ _max=8° and a decrease of the optomotor response towards longer spatial wavelengths. The experimental data are in conflict with these predictions. The present notion is that the absence of the expected reaction decrease is not likely to be caused by a saturation effect in the reaction but rather is explainable in terms of a receptor system consisting of larger numbers of receptor types No. 1 to 6 whose excitations being summed before a correlation evaluation takes place.

     

Wind-evoked evasive responses in flying cockroaches

1. A standing cockroach (Periplaneta americana) responds to the air displacement made by an approaching predator, by turning away and running. The wind receptors on the cerci, two posterior sensory appendages, excite a group of ventral giant interneurons that mediate this response. While flying, these interneurons remain silent, owing to strong inhibition; however, the dorsal giant interneurons respond strongly to wind. Using behavioral and electromyographic analysis, we sought to determine whether flying cockroaches also turn away from air displacement like that produced by an approaching flying predator; and if so, whether the cerci and dorsal giant interneurons mediate this response.
2. When presented with a wind puff from the side, a flying cockroach carries out a variety of maneuvers that would cause a rapid turn away and perhaps a dive. These are not evoked if the cerci are ablated (Figs. 4, 5, 6).
3. This evasive response appears to be mediated by a circuit separate from that mediating escape when the cockroach is standing (Fig. 7).
4. The dorsal giant interneurons respond during flight in a directional manner that is suited to mediate this behavior (Fig. 8).
5. Recordings of the wind produced by a moving model predator (Fig. 9), together with measurements of the behavioral latency of tethered cockroaches, suggest that the evasive response would begin just milliseconds before a predator actually arrives. However, as explained in the Discussion section, under natural conditions, the evasive response may well begin earlier, and could indeed be useful in escaping from predators.
6. If cockroaches had a wind-mediated yaw-correcting behavior, as locusts have, this could conflict with the wind-evoked escape. In fact, cockroaches show the opposite, yaw-enhancing response, mediated by the cerci, that does not present a conflict with escape (Figs. 10–14).

     

The role of amino acid neurotransmitters in the descending control of electroreception

The roles of amino acid neurotransmitters in determining the processing characteristics of the electrosensory lateral line lobe (ELL) in Apteronotus leptorhynchus were investigated by studying the responses of ELL output neurons to pressure ejection of various neurotransmitter agonists and antagonists alone and in combination with simple electrosensory stimuli.

1. Pressure ejection of L-glutamate into the ELL dorsal molecular layer caused either excitation or inhibition of ELL efferent neurons (pyramidal cells). The sign of these responses reversed with changes in the position of the pressure pipette. Histological verification of drug ejection sites relative to recorded cells and diffusion estimates indicate that excitatory and inhibitory responses result from glutamate activation of pyramidal cells and of inhibitory interneurons, respectively.
2. ELL output cells respond to both NMDA and non-NMDA glutamate agonists and the responses are attenuated by co-ejection of specific antagonists indicating that both AMPA/kainate and NMDA receptors exist on pyramidal cell apical dendrites.
3. Gamma-aminobutyric acid inhibits basilar and nonbasilar pyramidal cells when ejected near their apical dendrites and disinhibits them when ejected near surrounding inhibitory interneurons confirming the presence of GABA receptors on these cell types.
4. An NMDA antagonist did not alter pyramidal cell responses to electrosensory stimuli but a non-NMDA antagonist altered both responses to the stimuli and firing frequency shortly following stimulus cessation.

     

Selective phonotaxis to advertisement calls in the gray treefrog Hyla versicolor: behavioral experiments and neurophysiological correlates

1. The significance of particular acoustic properties of advertisement calls for selective phonotaxis by the gray treefrog, Hyla versicolor (= HV), was studied behaviorally and neurophysiologically. Most stimuli were played back at 85 dB SPL, a level typically measured at 1–2 m from a calling male.
2. Females preferred stimuli with conspecific pulse shapes at 20° and 24°C, but not at 16°C. Tests with normal and time-reversed pulses indicated the preferences were not influenced by the minor differences in the long-term spectra of pulses of different shape.
3. Pulse shape and rate had synergistic or antagonistic effects on female preferences depending on whether the values of one or both of these properties in alternative stimuli were typical of those in HV or heterospecific (H. chrysoscelis = HC) calls.
4. More auditory neurons in the torus semicircularis were temporally selective to synthetic calls (90%) than to sinusoidally AM tones and noise (< 70%).
5. Band-pass neurons were tuned to AM rates of 15–60 Hz. Neurons were more likely to be tuned to HV AM rates ( < 40 Hz) when stimuli had pulses with HV rather than HC shapes.
6. Sharp temporal tuning was uncommon and found only in neurons with band-pass or low-pass characteristics.
7. Many neurons differed significantly in response to HV and HC stimulus sets. Maximum spike rate was more often elicited by an HV stimulus (74%) than by an HC stimulus (24%).
8. Differences in spike rates elicited by HV and HC stimuli were attributable to combinations of differences in the rise times and shapes of the pulses.

     

In vivo buccal nerve activity that distinguishes ingestion from rejection can be used to predict behavioral transitions in Aplysia

1. We are studying the neural basis of consummatory feeding behavior in Aplysia using intact, freely moving animals.
2. Video records show that the timing of radula closure during the radula protraction-retraction cycle constitutes a major difference between ingestion (biting or swallowing) and rejection. During ingestion, the radula is closed as it retracts. During rejection, the radula is closed as it protracts.
3. We observed two patterns of activity in nerves which are likely to mediate these radula movements. Patterns I and II are associated with ingestion and rejection, respectively, and are distinguished by the timing of radula nerve activity with respect to the onset of buccal nerve 2 activity.
4. The association of ingestion with pattern I is maintained when the animal feeds on a polyethylene tube, the same food substrate used to elicit rejection responses. Under these conditions, pattern I is associated with either swallowing or no net tube movement.
5. Most transitions from swallowing to rejection were preceded by one or more occurrences of pattern I in which there was no net tube movement, suggesting that these transitions can be predicted.
6. Our data suggest that these two patterns can be used to distinguish ingestion from rejection.