Ultrafast pulse shaping modulates perceived visual brightness in living animals

Vision is usually assumed to be sensitive to the light intensity and spectrum but not to its spectral phase. However, experiments performed on retinal proteins in solution showed that the first step of vision consists in an ultra-fast photoisomerization that can be coherently controlled by shaping the phase of femtosecond laser pulses, especially in the multiphoton interaction regime. The link between these experiments in solution and the biological process allowing vision was not demonstrated. Here, we measure the electric signals fired from the retina of living mice upon femtosecond multipulse and single-pulse light stimulation. Our results show that the electro-physiological signaling is sensitive to the manipulation of the light excitation on a femtosecond time scale. The mechanism relies on multiple interactions with the light pulses close to the conical intersection, like pump-dump (photoisomerization interruption) and pump-repump (reverse isomerization) processes. This interpretation is supported both experimentally and by dynamics simulations.

Automated summary

Experiments have shown that the initial step of vision involves ultra-fast photoisomerization controlled by shaping the phase of femtosecond laser pulses. The electric signals fired from the retina of living mice in response to light stimulation on a femtosecond time scale were found to be sensitive to manipulation of light excitation. This sensitivity is attributed to interactions with light pulses near conical intersections, involving processes like pump-dump and pump-repump.