The melanopic sensitivity function accounts for the spectral sensitivity of LGN responses in rodless/coneless mice.

<p>(<b>A</b>) Spectral profile of the 3 test stimuli and the melanopic sensitivity function (V^zλ: shaded area). (<b>B</b>) Example response of an <i>rd/rd cl</i> LGN neuron to the three test stimuli presented at a range of different irradiances (numbers above traces indicate log light intensity relative to the maximum achievable: 3.4 log m-lux). (<b>C</b>) Mean ± SEM responses to the three stimuli (and below in overlay) at maximum irradiance (n = 30 cells; each unit's response normalised to the largest change in firing rate across all stimuli). (<b>D–F</b>) Irradiance response relationship for <i>rd/rd cl</i> LGN responses to the three stimuli. A single curve best explains all the data (F-test) when irradiances are expressed in melanopic lux (<b>D</b>; P = 0.641), but not number of photons between 470–480 nm (<b>E</b>; P = 0.04), photopic lux (<b>F</b>; P = 0.001), total photons or total optical power (not shown).