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.     

Attention-like processes underlying optomotor performance in a Drosophila choice maze

The authors present a novel paradigm for studying visual responses in Drosophila. An eight-level choice maze was found to reliably segregate fly populations according to their responses to moving stripes displayed on a computer screen. Visual responsiveness was robust in wild-type flies, and performance depended on salience effects such as stimulus color and speed. Analysis of individual fly choices in the maze revealed that stereotypy, or choice persistence, contributed significantly to a strain's performance. On the basis of these observations, the authors bred wild-type flies for divergent visual phenotypes by selecting individual flies displaying extreme stereotypy. Selected flies alternated less often in the sequential choice maze than unselected flies, showing that stereotypy could evolve across generations. The authors found that selection for increased stereotypy impaired flies' responsiveness to competing stimuli in tests for attention-like behavior in the maze. Visual selective attention was further investigated by electrophysiology, and it was found that increased stereotypy also impaired responsiveness to competing stimuli at the level of brain activity. Combined results present a comprehensive approach to studying visual responses in Drosophila, and show that behavioral performance involves attention-like processes that are variable among individuals and thus sensitive to artificial selection.     

Neural correlates of the optomotor response in the fly

Summary Studies of the optomotor response, the tendency to turn in response to a moving pattern, have yielded some understanding of the motion detection capabilities of the fly. We present data from extracellular microelectrode recordings from the optic lobes of the housefly, Musca domestica and the blowflies Eucalliphora lilaea and Calliphora phaenicia. Directionally selective and directionally nonselective motion sensitive units were observed in the region between the medulla and the lobula of all three species. Employing similar stimulus conditions to those used in the optomotor reaction studies, it was found that the response of the directionally selective units exhibited most of the characteristics of the optomotor response torque measurements. It is concluded that these units code the information prerequisite to the optomotor response and hence, that much data processing is achieved in the first few synaptic layers of the insect visual nervous system.     

Orientation sensitivity of the visual movement detection system activating the landing response of the blowflies,Calliphora, and Phaenicia: A behavioural investigation

The orientation sensitivity of the visual movement detection system relative to the axes of the eye was investigated for the landing response by changing the direction of movement of a periodic striped pattern (unidirectional movement) and a two-stripe pattern consiting of two stripes moving apart (bidirectional movement). In the momocular, equatorial regions of the eye progressive motion proves to be most effective, whereas in the frontal (equational), binocular region descendive motion is most effective in eliciting the landing response, probably caused by binocular interactions. A strong enhancement of the response is induced by stimulation in the binocular region of the two eyes. The orientation of elementary movement detectors relative to the axes of the ommatidial array is discussed. The findings are summarized in a functional model of the landing response.     

Non-isotopic RNA probes. Comparison between different labels and detection systems

Several studies have shown the use of non-radioactive labelled DNA probes for in situ hybridisation, mainly to identify cellular DNA. In this study mRNA in situ hybridisation was performed on rat pituitary with biotinylated complementary (c) RNA probes for rat prolactin and growth hormone (GH), and compared with radioactive 35S-radiolabelled probes. Biotinylated cRNA probes were labelled with either biotin-11-UTP or with allylamine-UTP, the latter method being able to produce a higher yield of labelled RNA. Different detection systems were tested, and hybridisation signal was seen in cells of anterior pituitary with both types of biotinylated probes. The signals were detected using either avidin-biotin-complex with peroxidase (ABC), peroxidase-anti-peroxidase (PAP) or gold-silver methods. ABC peroxidase detected using glucose oxidase-diaminobenzidine (DAB)-nickel solution appeared to be the best method for detecting labelled RNA probes, with very strong signal and low background. The biotinylated probes were comparable in sensitivity to the radiolabelled probes in detecting prolactin and GH mRNAs in the anterior lobe of the rat pituitary. These results indicate an alternative methods of labelling and detection of biotinylated probes which could have a potential role in research and diagnostic techniques.     

Regional specialization for an optomotor response in the honeybee compound eye

ABSTRACT. The optomotor head-turning response of the honeybee ( Apis mellifera ) to a horizontally moving stripe pattern was analysed after occlusion of specific regions of the compound eye. The dorsal half of the eye and the medial region appear to be irrelevant to this behavioural reflex. Occlusion of the ventrolateral portion of the eye, however, even with the remainder of the eye unoccluded, rendered the optomotor system blind. The optomotor response was found to be mediated by an area roughly equal to one-fifth of the total eye surface with some redundancy in the system, since occlusion of at least half of the zone did not significantly impair the response. These results support the hypothesis of physically separate visual subsystems in the bee eye which are adapted for different functions.     

Properties of a motor output system involved in the optomotor response in flies

1. The optomotor response of tethered flying houseflies (Musca domestica) has been studied at the level of the neural output which controls the activities of some non-fibrillar flight muscles (N-muscles).-a) During visually induced turning responses in a given direction some N-muscles on the right side of the thorax are synergistically active together with other N-muscles on the left side of the thorax. The same muscles are inactive during turning reactions in the opposite direction while the corresponding antagonists are now active (synopsis in Table 1).-b) The response activities of the N-mussles show a considerable variation during the course of time in spite of constant visual input.-c) There is a strong tendency for N-muscle spikes to be phase-locked with respect to the wingbeat period.-d) The findings obtained fromMusca are in accordance with the corresponding results obtained fromCalliphora (Heide, 1971b).
2. TheN-muscle activities have also been investigated in tethered flying blowflies (Calliphora erythrocephala) which tried to yaw spontaneously with both wings beating. In spontaneous left (right) turn reactions the features of the observed neural output are nearly identical with the features of the motor output showing up during visually induced left (right) turn reactions.-A different motor output pattern has been found in flies with only one wing beating.
3. The wingbeat synchronous rhythm observed in spike trains from activeN-muscles is produced in the thorax without the participation of higher stages of the fly's CNS. On the other hand no distinct rhythms can be found in spike trains fromN-muscles of non-flying flies when their motoneurons are artificially activated by non-rhythmic stimuli. Afferent information from thoracic sense organs seems to be essential for the production of the rhythm observed during flight.
4. The results about the production of the wingbeat synchronous rhythm in spike trains fromN-muscles suggest that the information derived from the motion detectors only acts to gate the output needed to achieve yaw-turn reactions. The strength of the influence of signals from the motion detectors on the output producing system can be modified by the animals “state of excitement”.
5. A model is presented which summarizes some features of information processing in the output systems supplying theN-muscles of flies. Available physiological data are discussed in relation to the model.

     

Visual signals in an optomotor reflex: systems and information theoretic analysis

Compensatory optomotor reflexes were examined in crayfish (Procambarus clarkii) with oscillating sine wave gratings and step displacements of a single stripe. A capacitance transducer was used to measure the rotation of the eyestalk about its longitudinal axis. System studies reveal a spatial frequency response independent of velocity and stimulus amplitude and linear contrast sensitivity similar to that of neurons in the visual pathway. The reflex operates at low temporal frequencies (<0.002 Hz to 0.5 Hz) and exhibits a low-pass temporal frequency response with cut-off frequency of 0.1 Hz. Eyestalk rotation increases as a saturable function of the angular stimulus displacement. When compared to the oscillatory response, transient responses are faster, and they exhibit a lower gain for large stimulus displacements. These differences may reflect system nonlinearity and/or the presence of at least two classes of afferents in the visual pathway. Our metric for information transmission is the Kullback-Leibler (K-L) distance, which is inversely proportional to the probability of an error in distinguishing two stimuli. K-L distances are related to differences in responsiveness for variations in spatial frequency, contrast, and angular displacement. The results are interpreted in terms of the neural filters that shape the system response and the constraints that the K-L distances place on information transmission in the afferent visual pathway.     

The optomotor yaw response of the desert locust, Schistocerca gregaria

Abstract The optomotor yaw response of the desert locust, Schistocerca gregaria (Forsk.), was investigated under open- and closed-loop conditions. When flying tethered in the centre of a vertically striped hollow sphere, the polarity of response of the locust was always the same as the stimulus. The response, therefore, appears suitable to stabilize body posture against passive rotations around the yaw-axis in free flight. Responses were induced by contrast frequencies up to 150 Hz with a maximum of amplitude at about 20 Hz. The characteristic curve, measured between 0.3 and 160 Hz, is widened up towards higher frequencies as compared with those of bees and flies.
Variability was the most striking feature in the locust's yaw response. The amplitude of modulation not only varied greatly between individuals but also changed with the same visual stimulus in the course of an experiment. We therefore suppose that the locust's turning behaviour is subject to gain control mechanisms and that spontaneous gain modulations are responsible for the observed variability in the stimulus-response conversion.     

A visually evoked escape response of the housefly

Summary Flies (Musca domestica) avoid danger by initiating a rapid jump followed by flight. To identify the visual cues that trigger the escape response in the housefly, we measured the timing and probability of escapes when the fly was presented with a variety of visual stimuli created by moving targets toward it. Our results show that an escape response is triggered by an approaching dark disk, but not by a receding dark disk. On the other hand, a bright disk elicits escape only when it recedes. A disk with black and white rings is less effective at eliciting escape than is a dark solid disk of the same size. This indicates that the darkening contrast produced by an approaching stimulus is a more crucial parameter than expansion cues contained in the optical flow. Escape is also triggered by a horizontally moving dark edge, but not by a moving bright edge or by a grating. An examination of several visual parameters reveals that the darkening contrast, measured from the onset of stimulation to the start of escape is nearly constant for a variety of stimuli that trigger escape reliably. Thus darkening contrast, coupled with motion may be crucial in eliciting the visually evoked escape response. Other visual parameters such as time-to-contact or target angular velocity seem to be relatively unimportant to the timing of escapes.Abbreviations P _s Probability of successful escape - r _disk radius of disk target - r _arena radius of shielding arena - v _disk linear velocity of disk target - v _edge linear velocity of edge - d _disk angular velocity of disk target boundary - _edge angular velocity of edge - _escape target distance at escape - d _start target distance before onset of target movement - h _edge height of the edge above fly - x _start distance from corner of triangle to start position of edge (0 or 50 mm) - x _escape distance from corner of triangle to the position of the edge when the fly escapes - x _center distance from corner of triangle to point above the center of the pad - x _total distance from the corner of the triangle to the base (height of triangle = base of triangle)     

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).

     

Plasticity of the landing response of Drosophila melanogaster

Summary Fruitflies (Drosophila melanogaster) may respond with landing reactions in tethered flight to unilateral progressive motion of single vertical dark stripes. The response frequency to repeated unilateral stimulation has a characteristic time course, a fast increase followed by a slower decrease. This behaviour is explained by the habituation of the input channels to a leaky integrator. The half-life of the integrated signal is in the range of 1 s. Contralateral sensitization (CoS) describes the sensitization of the landing response to unilateral stimuli by preceding contralateral stimulation. It acts by increasing the initial reactivity, which habituates. The effects of CoS are thus still obvious after 1 min of repetitive stimulation. CoS can effectively be mediated by movement stimuli as well as by flickering light. We also show that binocular rotation rather than unilateral back to front motion inhibits the landing response (in the monocular part of the visual field). The biological significance of the described temporal characteristics of the landing response system and their possible neuronal basis are discussed.Abbreviations CoS contralateral sensitization     

Comparison between subjective and ultrasound assessments of fetal movement.

Forty pregnant women participated in a study to compare subjective with ultrasound assessments of fetal movements. A real-time ultrasound scanner was used. Movements were recorded for 45 minutes in all cases. There was a significant positive correlation between the number of movements recorded by the two methods, but the 95% confidence limits were wide and no correlation was found in those patients who recorded fewer than 20 movements in the study period. Thus "false-positive" information may be obtained from purely subjective data, and in patients reporting low "kick counts" fetal activity should be assessed from real-time ultrasound recordings.     

The aerial and aquatic visual acuity of the optomotor response in the crested newt (Triturus cristatus)

Summary Behavioural and electrophysiological experiments using equidistant vertical stripe patterns were performed. The coherence between the visual acuity of the optomotor response and of the recordings from the accessory optic tract could be shown. The possibility of the existence as well of a background movement system as a tectal nearness system with a greater myopia in the newt is discussed.Supported by the Deutsche Forschungsgemeinschaft (Me 365/4 and Sch 132/4)     

Arousal changes in the locust optomotor system

The activity of the optomotor interneurons in the locust optic lobe varies with arousal states. Two behaviourally different arousal situations can be readily reproduced in the locust, a spontaneous and an evoked arousal change. These produce different neuronal correlates in the optomotor interneurons, suggesting the presence of different arousal pathways possibly acting at different sites in the motion detection chain. Furthermore, an additional arousal effect can be demonstrated at the motoneurons showing that a reflex system is sensitive to arousal modulation at several levels.