Poster Session: Melanopsin modulation of cortical S-cone responses

Melanopsin is a non-image forming light sensitive retinal photopigment. Melanopsin activation takes longer to peak and has a prolonged response relative to cone photoreceptors. Recent evidence suggests that melanopsin-driven signals may influence vision (through cone photoreceptor modulation), but it is unclear whether melanopsin can directly stimulate visual cortex (e.g. V1), in addition to subcortical pathways. Our lab recently observed unusual fMRI time course responses in V1 for S-cone isolating stimuli, where the response was maintained for the duration of the stimulus 'off' period - it did not return to baseline after stimulus offset (at 12 seconds). We hypothesised that this was due to an effect of lingering melanopsin activation, which was activated by the S-cone isolating stimuli because we did not explicitly silence melanopsin in that study. In the present study, we used a custom-made multi-primary LED system, to create S-cone isolating stimuli that either activated or silenced melanopsin. Stimuli were presented in a block design, 15s ON / 30s OFF to allow time for a sustained response to return to baseline between conditions. Here we present evidence from 11 participants of melanopsin-driven responses in cortical area V1 - where the S-cone melanopsin-active condition showed a larger response after stimulus offset than the S-cone melanopsin-silenced condition.