Improvement-related functional plasticity following pitch memory training.

Functional activation patterns of an auditory working memory task were examined prior to and after 5 days of training (1 h/day). A control group with no training was scanned twice at the same intervals to assess test-retest effects. Based on behavioral improvement scores, the training group (n = 14) was divided into "Strong-Learners (SL)" and "Weak-Learners (WL)". No significant functional or structural brain differences were seen between the SL and WL groups prior to training. Imaging contrasts comparing post- with pre-training sessions showed a significant signal increase in the left Heschl's gyrus (HG) as well as in the left posterior superior temporal and supramarginal gyrus for the SL group, while the WL group showed significant signal increases in the left HG and anterior insular cortex as well as in a lingual-orbitofrontal-parahippocampal network. The test-retest analysis in the control group revealed only minimal signal increases in a right dorsolateral prefrontal region. A random effects analysis comparing the SL group with the WL group using the post- and pre-training contrast images showed increased activation only in the left supramarginal gyrus but not in HG. The importance of HG in pitch discrimination has been established in previous studies. The pitch memory component differentiated our task from a straight pitch discrimination task. It is most likely that the activation of the SMG reflects its importance in the short-term storage of auditory material, and it was this activation that best differentiated between subjects' levels of performance.