Light adaptation of primate cones: an analysis based on extracellular data

Area of Science:

• Vision Science
• Photoreceptor Physiology
• Primate Visual System

Background:

• Cone cells are crucial for color vision and visual acuity in bright light.
• Understanding photoreceptor adaptation is key to deciphering visual processing.

Purpose of the Study:

• To isolate and characterize extracellular photo-cone responses in the intact rhesus monkey.
• To determine the cone response versus intensity function under various adapting backgrounds.
• To analyze the mechanisms contributing to Weberian behavior in cone responses.

Main Methods:

• Fractional recording of extracellular photo-cone responses in the fovea of intact rhesus monkey eyes using a bipolar microelectrode.
• Measurement of cone response versus intensity functions with adapting backgrounds up to 10^6 trolands (td).
• Recording of increment, decrement, and steady-state responses.

Main Results:

• A consistent cone response function, V/Vm = In/(In + sigma n) with n=0.74, described both steady-state and transient responses.
• Increasing background intensity shifted this function along both intensity and response axes.
• Sensitivity decrease was attributed to cellular adaptation, pigment bleaching, and response compression.

Conclusions:

• The invariant cone response function provides a quantitative model for photoreceptor behavior.
• Cellular adaptation, pigment bleaching, and response compression collectively explain Weberian behavior in cone vision.
• This research offers insights into the adaptive strategies of the primate visual system.