Poster Session: Melanopsin modulation of cortical S-cone responses

Area of Science:

• Neuroscience
• Vision Science
• Photobiology

Background:

• Melanopsin is a non-image forming, intrinsically photosensitive retinal ganglion cell (ipRGC) photopigment.
• Melanopsin activation is slower and more sustained than cone photoreceptor responses.
• Previous research suggests melanopsin influences vision via cone modulation, but direct cortical stimulation remains unclear.

Purpose of the Study:

• To investigate whether melanopsin directly stimulates the primary visual cortex (V1).
• To differentiate melanopsin's contribution to V1 activity from cone photoreceptor input.
• To test the hypothesis that observed V1 responses to S-cone stimuli were due to un-silenced melanopsin.

Main Methods:

• Utilized a custom multi-primary LED system to generate S-cone isolating stimuli.
• Created stimuli that either activated or silenced melanopsin function.
• Employed a block design (15s ON / 30s OFF) with fMRI to measure V1 responses in 11 participants.

Main Results:

• Evidence of melanopsin-driven responses in human V1 was observed.
• The melanopsin-active condition showed a significantly larger V1 response after stimulus offset compared to the melanopsin-silenced condition.
• Sustained V1 activity persisted beyond stimulus offset, consistent with prolonged melanopsin signaling.

Conclusions:

• Melanopsin directly contributes to visual cortical processing in humans.
• Melanopsin signals can modulate activity in V1, independent of cone-driven pathways.
• These findings reveal a novel role for melanopsin in visual cortex function.