1,721,200 research outputs found
Colour Vision : Random Retina of Butterflies Explained
No full textButterfly eyes are random mosaics built of three ommatidia types, each with a different set of photoreceptors and pigments. What defines the combined features in each ommatidium? A new study has solved the puzzle
Alternative use of chromatic and achromatic cues in a hawkmoth
No full textThe diurnal hummingbird hawkmoth Macroglossum stellatarum can learn the achromatic (intensity-related) and the chromatic (wavelength-related) aspect of a spectral colour. Free-flying moths learn to discriminate two colours differing in the chromatic aspect of colour fast and with high precision. In contrast, they learn the discrimination of two stimuli differing in the achromatic aspect more slowly and less reliably. When trained to use the chromatic aspect, they disregard the achromatic aspect, and when trained to use the achromatic aspect, they disregard the chromatic aspect, at least to some degree. In a conflicting situation, hummingbird hawkmoths clearly rely on the chromatic aspect of colour. Generally, the moths pay attention to the most reliable cue that allows them to discriminate colours in the learning situation. This is usually the chromatic aspect of the colour but they can learn to attend to the achromatic aspect instead. There is no evidence for relative colour learning, i.e. moths do not learn to choose the longer or shorter of two wavelengths, but it is possible that they learn to choose the darker or brighter shade of a colour, and thereby its relative intensities
Vertebrate vision : New light on the enigmatic double cone
No full textDouble cones have been described in the retinae of both fishes and tetrapods. While fish double cones are two closely attached single cones, the two members of tetrapod double cones each evolved to be distinctly different from all single cones
Colour in the eye of the beholder : receptor sensitivities and neural circuits underlying colour opponency and colour perception
No full textColour vision — the ability to discriminate spectral differences irrespective of variations in intensity — has two basic requirements: (1) photoreceptors with different spectral sensitivities, and (2) neural comparison of signals from these photoreceptors. Major progress has been made understanding the evolution of the basic stages of colour vision–opsin pigments, screening pigments, and the first neurons coding chromatic opponency, and similarities between mammals and insects point to general mechanisms. However, much work is still needed to unravel full colour pathways in various animals. While primates may have brain regions entirely dedicated to colour coding, animals with small brains, such as insects, likely combine colour information directly in parallel multisensory pathways controlling various behaviours
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Infrared Imaging : A Motion Detection Circuit for Rattlesnake Thermal Vision
No full textPit vipers detect moving warm-blooded prey with infrared receptors in their pit organs. Neurons in two brain nuclei extract the direction of prey motion by lateral inhibition circuits similar to those known from visual systems
What a hawkmoth remembers after hibernation depends on innate preferences and conditioning situation
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