A Hyperpolarization Underlies Contrast Adaptation
Intracellular recordings from visual cortical neurons in anesthetized animals during contrast adaptation by Matteo Carandini and David Ferster revealed that adaptation was associated with an hyperpolarization of the membrane potential. The peristimulus histogram in A is the spike response to different contrast gratings before adaptation. The peristimulus histogram in B is the spike response after adaptation. Note that at the lower contrast levels, the spike response is markedly reduced. C represents the membrane potential of the recorded cell. The more hyperpolarized voltage trace is following adaptation. Adaptation causes a hyperpolarization that is most marked at low contrast levels.