Figure 1.

Eyeblink conditioning setup and stimulus generalization test following differential training. (A) Mice were placed in a light- and sound- isolating chamber on a foam cylindrical treadmill that allowed them to walk freely with their heads fixed at a horizontal bar. The conditioned stimulus (CS+) consisted of a 10 kHz tone delivered using speakers placed on both upper front corners of the chamber and the unconditioned stimulus (US) was a weak air-puff to the left eye. Eyelid movements were recorded with a high-speed video camera. Speakers were placed on both upper front corners of the chamber at the same height. Eyelid movements were recorded using a high-speed video camera system (300 frames per second). (B) Schematics of eyelid conditioning differential training and generalization test. For each group, on the x-axis the time in milliseconds illustrates the presentation of the auditory stimuli. All groups underwent the same differential training of eyeblink CRs for 1–18 consecutive days using a 10 kHz as reinforced (CS+), while the non-reinforced frequency (CS−) was a tone frequency of 4 kHz for the Grp10CS + 4CS− (in red), 9 kHz for the Grp10CS + 9CS− (in yellow) and 9.5 kHz for the Grp10CS + 9.5CS− (in blue). Afterwards, all groups were tested for 1–4 consecutive days with frequencies which were never reinforced for any of the groups. For each protocol, the duration and the ratio of different trial types is presented at the top of the corresponding illustration.