Photoreceptor projections and receptive fields in the dorsal rim area and main retina of the locust eye (original) (raw)
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Photoreceptor design and optical properties affecting polarization sensitivity in ants and crickets
Journal of Comparative Physiology A, 1987
Anatomically and physiologically specialized ommatidia at the dorsal rim of insect compound eyes play a key role in polarization vision. In this eye region the polarization sensitivity (PS) of photoreceptors is significantly higher than elsewhere in the eye. We have compared the optical properties of the dorsal rim area and normal eye region of desert ants, Cataglyphis bicolor, and field crickets, Gryllus campestris. The objective was to find the cause of the enhanced PS in the dorsal rim area of eyes where the situation is not complicated by rhabdom twist. Three pieces of information were derived:
Neurons sensitive to non-celestial polarized light in the brain of the desert locust
Journal of Comparative Physiology A
Owing to alignment of rhodopsin in microvillar photoreceptors, insects are sensitive to the oscillation plane of polarized light. This property is used by many species to navigate with respect to the polarization pattern of light from the blue sky. In addition, the polarization angle of light reflected from shiny surfaces such as bodies of water, animal skin, leaves, or other objects can enhance contrast and visibility. Whereas photoreceptors and central mechanisms involved in celestial polarization vision have been investigated in great detail, little is known about peripheral and central mechanisms of sensing the polarization angle of light reflected from objects and surfaces. Desert locusts, like other insects, use a polarization-dependent sky compass for navigation but are also sensitive to polarization angles from horizontal directions. In order to further analyze the processing of polarized light reflected from objects or water surfaces, we tested the sensitivity of brain inte...
Neurobiology of polarization vision in the locustSchistocerca gregaria
Acta Biologica Hungarica, 2004
The polarization pattern of the blue sky serves as an important reference for spatial orientation in insects. To understand the neural mechanisms involved in sky compass orientation we have analyzed the polarization vision system in the locust Schistocerca gregaria. As in other insects, photoreceptors adapted for the detection of sky polarization are concentrated in a dorsal rim area (DRA) of the compound eye. Stationary flying locusts show polarotactic yaw-torque responses when illuminated through a rotating polarizer from above. This response is abolished after painting the DRAs. Central stages of the polarization vision system, revealed through tracing studies, include dorsal areas in the lamina and medulla, the anterior lobe of the lobula, the anterior optic tubercle, the lateral accessory lobe and the central complex. Physiological analysis of polarization-sensitive (POL) neurons has focussed on the optic tubercle and on the central complex. Each POL neuron was maximally excited at a certain e-vector (Φ max) and was maximally inhibited at an e-vector perpendicular to Φ max. The neurons had large visual fields, and many neurons received input from both eyes. The neuronal organization of the central complex suggests a role as a spatial compass within the locust brain.
Central neural coding of sky polarization in insects
Philosophical Transactions of the Royal Society B: Biological Sciences, 2011
Many animals rely on a sun compass for spatial orientation and long-range navigation. In addition to the Sun, insects also exploit the polarization pattern and chromatic gradient of the sky for estimating navigational directions. Analysis of polarization–vision pathways in locusts and crickets has shed first light on brain areas involved in sky compass orientation. Detection of sky polarization relies on specialized photoreceptor cells in a small dorsal rim area of the compound eye. Brain areas involved in polarization processing include parts of the lamina, medulla and lobula of the optic lobe and, in the central brain, the anterior optic tubercle, the lateral accessory lobe and the central complex. In the optic lobe, polarization sensitivity and contrast are enhanced through convergence and opponency. In the anterior optic tubercle, polarized-light signals are integrated with information on the chromatic contrast of the sky. Tubercle neurons combine responses to the UV/green contr...
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 2002
Many animals have been shown to use the pattern of polarized light in the sky as an optical compass. Specialised photoreceptors are used to analyse this pattern. We here present evidence for an eye design suitable for polarized skylight navigation in the flightless desert scarab Pachysoma striatum. Morphological and electrophysiological studies show that an extensive part of the dorsal eye is equivalent to the dorsal rim area used for polarized light navigation in other insects. A polarization-sensitivity of 12.8 (average) can be recorded from cells sensitive to the ultraviolet spectrum of light. Features commonly known to increase the visual fields of polarization-sensitive photoreceptors, or to decrease their spatial resolution, are not found in the eye of this beetle. We argue that in this insect an optically unspecialised area for polarized light detection allows it not be used exclusively for polarized light navigation.
Regional differences in the preferred e-vector orientation of honeybee ocellar photoreceptors
The Journal of Experimental Biology, 2017
In addition to compound eyes, honeybees (Apis mellifera) possess three single lens eyes called ocelli located on the top of the head. Ocelli are involved in head-attitude control and in some insects have been shown to provide celestial compass information. Anatomical and early electrophysiological studies have suggested that UV and blue-green photoreceptors in ocelli are polarization sensitive. However, their retinal distribution and receptor characteristics have not been documented. Here, we used intracellular electrophysiology to determine the relationship between the spectral and polarization sensitivity of photoreceptors and their position within the visual field of the ocelli. We first determined a photoreceptor’s spectral response through a series of monochromatic flashes (340 - 600 nm). We found UV and Green receptors, with peak sensitivities at 360 nm and 500 nm respectively. We subsequently measured polarization sensitivity at the photoreceptor’s peak sensitivity wavelength...
Author response: A visual pathway for skylight polarization processing in Drosophila
eLife, 2021
Many insects use patterns of polarized light in the sky to orient and navigate. Here, we functionally characterize neural circuitry in the fruit fly, Drosophila melanogaster, that conveys polarized light signals from the eye to the central complex, a brain region essential for the fly's sense of direction. Neurons tuned to the angle of polarization of ultraviolet light are found throughout the anterior visual pathway, connecting the optic lobes with the central complex via the anterior optic tubercle and bulb, in a homologous organization to the 'sky compass' pathways described in other insects. We detail how a consistent, map-like organization of neural tunings in the peripheral visual system is transformed into a reduced representation suited to flexible processing in the central brain. This study identifies computational motifs of the transformation, enabling mechanistic comparisons of multisensory integration and central processing for navigation in the brains of insects.
Integration of polarization and chromatic cues in the insect sky compass
Journal of Comparative Physiology A, 2014
navigational purposes, is widespread. Behavioral experiments, particularly in ants and bees, have addressed the relative contribution of different sky compass cues to an orientation decision. In addition, recent Abstract Animals relying on a celestial compass for spatial orientation may use the position of the sun, the chromatic or intensity gradient of the sky, the polarization pattern of the sky, or a combination of these cues as compass signals. Behavioral experiments in bees and ants, indeed, showed that direct sunlight and sky polarization play a role in sky compass orientation, but the relative importance of these cues are species-specific. Intracellular recordings from polarization-sensitive interneurons in the desert locust and monarch butterfly suggest that inputs from different eye regions, including polarized-light input through the dorsal rim area of the eye and chromatic/intensity gradient input from the main eye, are combined at the level of the medulla to create a robust compass signal. Conflicting input from the polarization and chromatic/intensity channel, resulting from eccentric receptive fields, is eliminated at the level of the anterior optic tubercle and central complex through internal compensation for changing solar elevations, which requires input from a circadian clock. Across several species, the central complex likely serves as an internal sky compass, combining E-vector information with other celestial cues. Descending neurons, likewise, respond both to zenithal polarization and to unpolarized cues in an azimuth-dependent way.