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July 3rd (Fri) 16:45-17:30

Color vision in butterflies

Speaker:
Kentaro Arikawa, PhD

The Graduate University for Advanced Sciences (SOKENDAI), Japan

Prof. Arikawa graduated from Jiyu-Gakuen college (natural science course) and Sophia University graduate school (behavioral biology). As the 1st year graduate student, He found butterflies detect light by their genitalis, and analysed the mechanism and function of this unique photoreceptive system for his Ph.D. study. After being a Biology Professor at Yokohama City University, He moved to SOKENDAI in 2006. He also served as a Visiting Fellow at Australian National University (neurobiology), a Research Student at Mitsubishi-Kasei Institute of Life Science, a Research Fellow at NIH (visual science), a Researcher of JST-PRESTO, etc.

Abstract: Flower-visiting butterflies have color vision, including some sophisticated aspects such as color constancy and simultaneous color contrast. Unlike the trichromatic retinas of humans (blue, green and red cones (plus rods)) and honeybees (UV, blue and green cells), the compound eyes of butterflies are typically furnished with six or more photoreceptor types with distinct spectral sensitivities. We found that the eyes of the Japanese yellow swallowtail, Papilio xuthus, contain UV, violet, blue, green, red and broad-band receptors, with each ommatidium housing nine photoreceptor cells in one of three fixed combinations. This makes the Papilio eye a patchwork of three types of spectrally heterogeneous ommatidia. How do Papilio use their complex retina to see flowers? First, we measured their wavelength discrimination ability by recording the sensitivity of feeding responses toward monochromatic lights, and identified the set of receptors involved in the task. The behavioral data indicate that Papilio can discriminate 1 nm difference at least in three wavelength regions, which appears even better than in humans. Analysis of the data using the receptor-noise limited color opponency model indicated that their vision is tetrachromatic based on UV, blue, green and red receptors.

July 4th (Sat) 13:30-14:15

Evolutionary diversity of colour vision in primates: implications from field and genetic studies

Speaker:
Shoji Kawamura, PhD

The University of Tokyo, Japan

Prof. Kawamura received his D.Sc of Anthropology from University of Tokyo in 1991. He served as a Postdoctoral Research Fellow of the Japan Society for the Promotion of Science at University of Tokyo, then a Postdoctoral Research Associate at Syracuse University, Shozo Yokoyama laboratory. After served as an Assistant Professor at Department of Biological Sciences, Graduate School of Science, University of Tokyo, an Associate Professor at Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, He became a Professor at Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo in 2010.

Abstract: Primate colour vision is unique among vertebrates in its evolutionary history. The form of trichromacy found uniquely in primates was generated from ancestral dichromacy via allelic differentiation (e.g. most New World monkeys) or gene juxtaposition (e.g. Old World primates) of the L/M opsin gene. The allelic differentiation results in extensive colour vision variability in New World monkeys, where trichromats and dichromats are found in the same breeding population, enabling us to directly compare visual performances among different colour vision phenotypes. Our genetic studies have shown that polymorphic colour vision is maintained by balancing selection in New World monkeys and uniform trichromacy is maintained by purifying selection in most Old World primates. On the other hand, our field behavioral studies have cast a controversy concerning the advantages of trichromatic colour vision and of polymorphic colour vision. A deeper knowledge of the functional significance of colour vision in non-human primates will help us to understand the selective pressures acting on colour vision in our own species. Further interdisciplinary studies on genes, physiology and behaviour will provide a wealth of data for increasing our understanding of the evolution of colour vision and will generate important advances in the near future.

July 6th (Mon) 13:30-14:15

How are the rays coloured in the brain?

Speaker:
Hidehiko Komatsu, PhD

National Institute for Physiological Sciences, Japan.
The Graduate University for Advanced Sciences (SOKENDAI), Japan

Prof. Komatsu received his Ph.D. in Engineering from Osaka University in 1982. His thesis was on "Analysis of monkey prefrontal neuron activity during a color discrimination GO/NO-GO task and its reversal." He served as a Research Associate at Department of Physiology, Faculty of Medicine, Hirosaki University, Hirosaki, Japan, a Visiting Associate at Laboratory of Sensorimotor Research, National Eye Institute, Bethesda, Maryland, U.S.A., then a Senior Researcher at Neuroscience Section, Electrotechnical Laboratory, Tsukuba, Japan. He has been a professor at Division of Sensory and Cognitive Information, National Institute for Physiological Sciences since 1995.

Abstract: Sir Isaac Newton wrote that the rays are not coloured. Then how are the perceived colors generated from the rays in the brain? After 300 years from the days of Newton, we are now approaching to the stage where we can talk about the entire story of color signal transformation from the retina to the higher cortical areas. At the early stage in the retina and LGN, color signals are decomposed by the color opponent neurons into two axes (L-M, S-(L+M)). A significant step occurs at the primary visual cortex where nonlinear transformation of color signals convert two-axes into multi-axes representation of color. At the higher cortical stage, neurons exhibit properties closely associated with colour perception. We are now having gradually detailed picture on the functional organization of the higher cortical areas in relation to color where constellation of multiple subregions exist. Our recent study (Namima et al. J Neurosci 2014) have shown that there is some important difference between these subregions in a way color signal is represented.

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