Email updates

Keep up to date with the latest news and content from BMC Neuroscience and BioMed Central.

This article is part of the supplement: Twentieth Annual Computational Neuroscience Meeting: CNS*2011

Open Access Poster presentation

Quantifying the visual information sourced from melanopsin photoreceptors in mouse LGN field responses

Sohail Siadatnejad*, Timothy M Brown, John Gigg, Hugh D Piggins, Robert J Lucas and Marcelo A Montemurro

Author Affiliations

Faculty of Life Sciences, University of Manchester, Manchester, M13 9PT, UK

For all author emails, please log on.

BMC Neuroscience 2011, 12(Suppl 1):P226  doi:10.1186/1471-2202-12-S1-P226

The electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1471-2202/12/S1/P226


Published:18 July 2011

© 2011 Siadatnejad et al; licensee BioMed Central Ltd.

This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Poster presentation

Melanopsin photoreceptors make a third type of photoreceptor along with rods and cones in human and mouse. Until recently melanopsin was thought to participate only in subconscious responses to light (such as pupillary reflexes and regulating the circadian rhythm) and not in image-forming visual responses. Recently, it has been shown that melanopsin derived signals are also widespread in image-forming visual pathways of mice [1]. The goal of this study is to quantify their contribution in the visual pathway. We used information theoretic measures [2,3] on field potentials [3] to quantify the amount of information that is originated in melanopsin photoreceptors. The continuous field potentials were recorded from lateral geniculate nucleus (LGN) of transgenic mice (Opn1mwR) [1] using multichannel electrodes.

The role of melanopsin was quantified by estimating the information [2] found in LGN responses, about the intensity of constant blue (460nm) and red (655nm) light (7 levels of irradiance were used). The intensities of these two lights were carefully matched to provide equal stimulation of the red-sensitive cones of Opn1mwR animals and to control for the influence of rod photoreceptors. Since the long wavelength (red) light was essentially invisible to melanopsin, subtracting the amount of information in 655nm stimuli from the 460nm should reveal the visual information that is sourced from melanopsin photoreceptors in each recording channel. To investigate the local continuous response signals, the power and phase of recorded field signals were examined at various frequency bands and time points. For each spectrotemporal component of the responses, information about the intensity of light was estimated [1,3] separately for blue and red lights for each recording channel.

The main conclusion is that in different spectrotemporal components of field responses the presence of melanopsin information was confirmed and quantified for both power and phase. Information in response to blue light was significantly higher than red (Fig. 1). Melanopsin influence on the phase of field oscillations was stronger than field power. The results were confirmed in mice that genetically lacked melanopsin photoreceptors [1] (Fig. 1). This confirms that LGN receives visual content through functional pathways that are specifically sourced from melanopsin photoreceptors.

thumbnailFigure 1. Quantification of melanopsin information. Information estimated for responses to blue and red are averaged and shown with SEM (averaged over total 372 channels that lay in LGN for 17 animals). Information in response to blue light is on average greater than the information estimated in responses of the same units to red light. Panel A shows this information comparison for power and B for phase of field potentials recorded in each channel. The power and phase response values were discretized into four levels for information estimations. A. Power of the 20-24Hz band of field potentials at 45-50 msec after light onset. B. Phase of the 20-24Hz band at 45-50 msec after light onset. The third column labelled K.O. shows the information found in responses to blue light in melanopsin knock out mice (396 channels, 17 animals). Since they genetically lack melanopsin they are used to confirm the amount of visual information that is lacked when melanopsin is not activated.

Acknowledgments

This work was funded by a Wellcome Trust grant to RJL and HDP.

References

  1. Brown TM, Gias C, Hatori M, Keding SR, Semo M, Coffey PJ, Gigg J, Piggins HD, Panda S, Lucas RJ: Melanopsin contributions to irradiance coding in the thalamo-cortical visual system.

    PLoS Biol 2010, 8(12):e1000558. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  2. Montemurro MA, Senatore R, Panzeri S: Tight data-robust bounds to mutual information combining shuffling and model selection techniques.

    Neural Comp 2007, 19:2913-2957. Publisher Full Text OpenURL

  3. Montemurro MA, Rasch MJ, Murayama Y, Logothetis NK, Panzeri S: Phase-of-firing coding of natural visual stimuli in primary visual cortex.

    Curr Biol 2008, 18(5):375-80. PubMed Abstract | Publisher Full Text OpenURL