Projects per year
Abstract
Background: Intrinsically photosensitive retinal ganglion cells (ipRGCs) drive an array of non-image-forming (NIF) visual responses including circadian photoentrainment and the pupil light reflex. ipRGCs integrate extrinsic (rod/cone) and intrinsic (melanopsin) photoreceptive signals, but the contribution of cones to ipRGC-dependent responses remains incompletely understood. Given recent data revealing that cone-derived colour signals influence mouse circadian timing and pupil responses in humans, here we set out to determine if the same is also true for pupil control in mice.
Results: We first recorded electrophysiological activity from the pretectal olivary nucleus (PON) of anaesthetised mice with a red-shifted cone population (Opn1mwR) and mice lacking functional cones (Cnga3-/-) or melanopsin (Opn1mwR; Opn4-/-). Using multispectral stimuli to selectively modulate the activity of individual opsin classes, we show that PON cells which receive ipRGC input also exhibit robust S- and/or L-cone opsin driven activity. This population includes many cells where the two cone opsins drive opponent responses (most commonly excitatory/ON responses to S-opsin stimulation and inhibitory/OFF responses to L-opsin stimulation). These cone inputs reliably tracked even slow (0.025Hz) changes in illuminance/colour under photopic conditions with melanopsin contributions becoming increasing dominant for higher contrast/lower temporal frequency stimuli. We also evaluated consensual pupil responses to in awake animals and show that, surprisingly, this aspect of physiology is insensitive to chromatic signals originating with cones. Instead, by contrast with the situation in humans, signals from melanopsin and both cone opsins combine in a purely additive manner to drive pupil constriction in mice.
Conclusion: Our data reveal a key difference in the sensory control of the mouse pupil relative to another major target of ipRGCs – the circadian clock. Whereas the latter uses colour information to help estimate time of day, the mouse pupil instead sums signals across cone opsin classes to provide broadband spectral sensitivity to changes in illumination. As such, while the widespread co-occurrence of chromatic responses and melanopsin input in the PON supports a close association between colour discrimination mechanisms and NIF visual processing, our data suggest that colour-opponent PON cells in the mouse contribute to functions other than pupil control.
Results: We first recorded electrophysiological activity from the pretectal olivary nucleus (PON) of anaesthetised mice with a red-shifted cone population (Opn1mwR) and mice lacking functional cones (Cnga3-/-) or melanopsin (Opn1mwR; Opn4-/-). Using multispectral stimuli to selectively modulate the activity of individual opsin classes, we show that PON cells which receive ipRGC input also exhibit robust S- and/or L-cone opsin driven activity. This population includes many cells where the two cone opsins drive opponent responses (most commonly excitatory/ON responses to S-opsin stimulation and inhibitory/OFF responses to L-opsin stimulation). These cone inputs reliably tracked even slow (0.025Hz) changes in illuminance/colour under photopic conditions with melanopsin contributions becoming increasing dominant for higher contrast/lower temporal frequency stimuli. We also evaluated consensual pupil responses to in awake animals and show that, surprisingly, this aspect of physiology is insensitive to chromatic signals originating with cones. Instead, by contrast with the situation in humans, signals from melanopsin and both cone opsins combine in a purely additive manner to drive pupil constriction in mice.
Conclusion: Our data reveal a key difference in the sensory control of the mouse pupil relative to another major target of ipRGCs – the circadian clock. Whereas the latter uses colour information to help estimate time of day, the mouse pupil instead sums signals across cone opsin classes to provide broadband spectral sensitivity to changes in illumination. As such, while the widespread co-occurrence of chromatic responses and melanopsin input in the PON supports a close association between colour discrimination mechanisms and NIF visual processing, our data suggest that colour-opponent PON cells in the mouse contribute to functions other than pupil control.
| Original language | English |
|---|---|
| Article number | 83 |
| Journal | BMC Biology |
| Volume | 16 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 31 Jul 2018 |
Keywords
- melanopsin
- pupil
- photoreceptor
- colour vision
- mouse
- electrophysiology
- silent substitution
- olivary pretectal nucleus
Fingerprint
Dive into the research topics of 'Additive contributions of melanopsin and both cone types provide broadband sensitivity to mouse pupil control'. Together they form a unique fingerprint.-
Centre for Biological Timing
Lucas, R. (PI), Bechtold, D. (PI), Fustin, J.-M. (PI), Ashe, H. (PI), Brown, T. (PI), Blaikley, J. (PI), Brass, A. (PI), Chandola, T. (PI), Durrington, H. (PI), Else, K. (PI), Hepworth, M. (PI), Hunter, L. (PI), Kadler, K. (PI), Kitchen, G. (PI), Loudon, A. (PI), Macdonald, A. (PI), Mcbeth, J. (PI), Milosavljevic, N. (PI), Rattray, M. (PI), Rutter, M. (PI), Sharrocks, A. (PI), Spiller, D. (PI), Storchi, R. (PI), Belle, M. (PI), Meng, Q.-J. (PI), Allen, A. (PI), Dixon, W. (PI), Gibbs, J. (PI), Hazel, A. (PI), Papalopulu, N. (PI), Ray, D. (PI), White, M. (PI) & Chang, J. (PI)
Project: Research
-