Figure 4. iTBS but not cTBS improved rat learning performance in relation to changes in cortical protein expression.

Rats were trained to distinguish rewarded from non-rewarded arms of a radial maze by tactile cues sensed via the whiskers of the rat (Aa). Other sensory cues, like visual, olfactory and spatial, were prevented (for details see Mix et al. 2010). Rats received iTBS, cTBS or sham-stimulation prior to each training block of 8 trials each. Intermittent TBS, but not cTBS, improved learning by reducing the number of trials needed by the rats to reach the threshold criterion of 75% correct choices (Ab and c). Subsequent to the learning experiments, rats were perfused either directly after the training when just reaching the threshold criterion (early effects, Ca) or 1 day after the last training block when reaching stable learning performance (late effects, Ca). Here, analysis of cortical protein expression is shown for the barrel cortex involved in learning task and for the visual cortex not involved (Ba). Eight groups of rats received different rTMS protocols and were either trained or not (learner, non-learner, Bb). Strong early (Cb) and late (Cc) changes in protein expression (c-Fos, GAD65, PV) were evident for iTBS treatment and learning but less for cTBS. For the relationship between changes in protein expression and learning performance, see discussion in the main text. Asterisks on top of bars indicate statistically significant differences from sham controls (yellow left-most bar) with *P < 0.05, **P < 0.01, ***P < 0.001 (ANOVA + Fisher's LSD). Results according to and figures taken and modified from Mix et al. (2010), with permission of Wiley-Blackwell.