Fig. 1. (A) Visual responses to a 1 Hz flash stimulus to a primary visual cortical neuron in aged rat and the stimulus output Digital Analog Converter (DAC) wave. (B) PSTHs elicited from the visual response to flashing stimuli at 1 Hz. (C) Adaptation index (AI, average amplitude of the last two evoked response divided by average amplitude of the first and second evoked response) to flashing stimuli at different frequencies (1, 2, 4 and 8 Hz). There were no significant differences of AI between different sexes in young, mid-aged and aged groups.