Figure 2.

Rats trained in a two-choice operant conditioning paradigm to press a “tone” lever when tones were presented or a “0 Hz” (silence) lever during periods in which no sound was presented in order to receive a food reward. Changes in tone lever pressing during silent intervals were observed following exposure to salicylate (A) or unilateral acoustic trauma (B). Thin lines represent individual animal data while bold lines depict group data. An increase in tone lever pressing during silence was used to indicate the presence of tinnitus following exposure [from Ref. (17), with permission].