Conditioning chamber

Training and assessment of each subject was conducted in the same chamber for all sessions, which were conducted at the same time each day. Assessment of tinnitus was carried out in a homemade conditioning system. The conditioning chamber (40 cm × 30 cm × 45 cm) was housed in a sound-attenuating surrounding box (80 cm × 45 cm × 60 cm, minimal attenuation of 45 dB at 10 kHz). The conditioning system consisted of a tungsten bar floored cage, sound generator, camera, apparatus for producing electric shocks and remote controls for sound and electric shock generators, and a computer. Videos were recorded by a camera (Microsoft, HD5000) which was located on the most appropriate position at the left side of the cage. A drinking bottle was positioned 5 cm above the floor, which can be seen best by the camera positioned at the left hand side of the cage. The illumination of the system was provided by a house light, which was placed on the ceiling of the cage. The house lights within the chamber were low-wattage bulbs, so there were no audible background sounds in the chamber due to the illumination. The current shock stimuli for Pavlovian conditioning training was generated by a constant current shock source (0.5 mA, 1 s) and delivered by tungsten bars (4 mm) which were lined on the floor with 1.0 cm spaces. A pure tone (10 kHz, 65 dB) was turned on before placing the animal in the conditioning chamber and delivered during the 30-min testing session. The sound was delivered to the conditioning chamber by a speaker which was located on the ceiling of the cage. Licking number for each animal was determined by the observation of the videos in slow motion, which was taken during the assessment.