Optomotor Behavior Research Articles

The optomotor equilibrium of theDrosophila navigation system

In his discussion of the optomotor behaviour Kalmus claimed in 1964 that the visual systems of insects continuously resolve horizontal displacements relative to the surroundings into rotatory and translatory components, each associated with optomotor feedback of particular quality and sign. The feedback is supposed to achieve, simultaneously, minimization of the rotatory movements and maximization of the translatory movements, a behaviour repeatedly observed with actively moving insects such as the fruitflyDrosophila melanogaster. The present approach takes into account that the output of movement detectors in the visual system of insects is necessarily equivocal with respect to the speed of the stimulus (e.g. zero output at both zero and infinite speed). Decomposition of the stimulus is not feasible under these conditions. It is obviously the composite stimulus to which the insects respond. Moreover, there is experimental evidence that optomotor feedback on the translatory movement is not necessarily a response-determining factor in insects. The optomotor behaviour of the walking fruitfly is sufficiently described by the sum of itsrotatory responses to the composite stimuli on either side. A diagram representing the expected rotatory response of the walking fruitfly as a function of both the rotatory and the translatory stimulus component is used to derive the prevailing traits of the behaviour in resting, rotating and floating environments, respectively. Most conspicuous is the inversion of the course-control response in about one half of the possible states of stimulation. This effect gives rise to at least some of the apparently spontaneous turns of actively moving insects which have been ascribed by v. Holst and Mittelstaedt to efferent commands from higher centres of the brain, according to their principle of reafference. The present results merely disprove the necessity of these commands. Inversion of the response is also an inherent property of the course-control systems of the optomotorically active insects. The expected increase of these inversions with closer proximity of the visual environment is found by observation of walking fruitflies. The relation between the rotatory and translatory movements of the freely walking fly and its state of stimulation in a given environment is used to describe the expected behaviour in terms of the most probable transition of state. The approach is based on estimates of the power required by the fly in order to maintain a given state against the torque that is produced by its course-control system in response to the optomotor stimulation. The most probable transition of state is apparently determined by the tendency of the fly to decrease the power requirement by appropriate adaptation of its rotatory movement. The transition may come to an end in one of the states of minimum power requirement where the speed of the rotating fly is held in a stable optomotor equilibrium.

Sensory integration in the locust optomotor system-II: Direction selective neurons in the circumoesophageal connectives and the optic lobe

Three types of direction selective neurons responding to moving stripes were recorded. Two types, monocular type 1 and 2 neurons in the optic lobe (M1 and M2) and binocular type 1 and 2 neurons in the circumoesophageal connectives, (B1 and B2) are optomotor neurons. The responses of these neurons show the same decrease in magnitude with decrease in the movement amplitude or decrease in the number of stimulated ommatidia as the head movement response. Both type 1 and type 2 neurons show anomalous response to the movements of the single edge which elicits the anomalous optomotor behaviour. The third neuron type, a binocular directional neuron (BD) found only in the optic lobe has no direct relationship with optomotor behaviour. The responses of the optomotor neurons (M1, M2, B1, B2) to movement of a single edge compare well with responses predicted by the behavioural model and confirm the necessity for the new optomotor model in the locust.

Heritability and threshold determinations of the optomotor response in Drosophila melanogaster

The optomotor response to an illuminated, moving striped plate was measured in 104 flies from a wild type population of Drosophila melanogaster. Each fly was given ten opportunities to respond and optomotor scores ranged from zero (no response) to ten. Selective breeding procedures based on low, middle and high scores were instituted to investigate the heritability of these individual differences in optomotor responding. Three strains differing with respect to optomotor behaviour were successfully bred and maintained for thirty generations. The extent to which controlling individual differences with regard to a single value of stripe width and luminance would affect optomotor threshold functions was also studied. Minimum light intensities required to elicit the response for five different stripe widths were determined for the three strains using a method of limits. The resulting curves were identical in shape but displaced along the abscissa, the degree of displacement representing systematic differences between the strains.

Aggregation in Aphis fabae scop. II. Visual components

Summary An examination was made of the behaviour of apterous A. fabae alienicolae in a number of simple visual situations representing the different components of the visual situation presented by a live stationary aphid. o 1. Most walking aphids approached black objects in a manner typical of the simple optomotor behaviour which mediates ‘form vision’ or ‘skototaxis’. Newly moulted aphids approached and then orbited such objects in a manner suggesting that stimulation of the triommatidium of such aphids might also be involved. 2. Walking aphids stopped and probed (i) when the angle subtended by silhouettes directly ahead of them reached a critical value, (ii) when visual stimulation occurred with sufficient rapidity, (iii) when the aphids were constrained by their dorsal light reaction to walk along ridges past objects towards which they would otherwise have turned. The distribution of probes in (iii) was independent of the angular velocity of the object in the visual field of the moving aphid but again suggested that stimulation via the triommatidium might be involved.