A distinct contribution of short-wavelength-sensitive cones to light-evoked activity in the mouse pretectal olivary nucleus

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Summary

This study reveals that short-wavelength-sensitive (S-cones) and medium-wavelength-sensitive (M-cones) cones make qualitatively distinct contributions to non-image-forming light responses, with S-cones uniquely able to sustain responses to gradual illuminance changes—a role previously attributed mainly to melanopsin. For lighting designers targeting circadian and pupillary responses, these findings suggest that short-wavelength light acts through multiple photoreceptor pathways (not just melanopsin), complicating simple melanopic-only models of NIF light exposure.

Key Findings

M-cones (responsive to 600/655 nm) supported only transient firing changes and responded primarily to abrupt illuminance changes, not gradual ramps.
S-cones (sensitive to ~460 nm) drove sustained responses to gradual illuminance changes and produced distinct off-inhibition, partially recapitulating melanopsin-driven sustained responses even in melanopsin-knockout (Opn4⁻/⁻) mice.
Dim stimuli drove minimal changes in pretectal olivary nucleus (PON) activity, indicating rods contribute little to PON responses under the tested conditions.
Experiments using red-shifted cone mice (Opn1mw®) and melanopsin-null mice (Opn4⁻/⁻) allowed isolation of individual photoreceptor contributions, confirming S-cones as a distinct and previously underappreciated driver of non-image-forming visual responses.