Figure 6.

Bimodal plasticity shifts from predominantly Hebbian to broader anti-Hebbian rules in guinea pigs with tinnitus and predominantly suppressive in guinea pigs without tinnitus. A, Mean timing rules showing bimodal plasticity of sound-evoked firing rates for units from Sham (gray), ENT (pink), and ET (red) guinea pigs. Diagram at top represents the relative order of Sp5 and sound stimuli. The brown vertical line indicates the Sp5 stimulation, and the sinusoid represents the tone stimulus. Mean timing rules were computed for all measurements from presumed principal cell units. Error bars indicate SEM. B, The percentage of units that showed Hebbian-like (H), anti-Hebbian-like (aH), enhancing (E), and suppressing (S) timing rules from Sham (left), ENT (middle), and ET (right) animals. Within the ET group of animals, stacked bars indicate units outside (white) and within (gray) identified tinnitus bands. ★Significant differences between Sham, ENT, and ET groups (p < 0.05; Tukey–Kramer's post hoc test).