Plastic changes in the auditory cortex induced by intensive frequency discrimination training

The slow auditory evoked (wave NIm) and mismatch field (MMF) elicited by se quences of pure tones of 1000 Hz and deviant tones of 1050, 1010 and 1005 H z were measured before, during and 3 weeks after subjects were trained at f requency discrimination for 15 sessions (over 3 weeks) using an odd-ball pr ocedure. The task of the subject was to detect deviants differing by progre ssively smaller frequency shifts from the standard stimulus. Frequency disc rimination improved rapidly in the first week and was followed by small but constant improvements thereafter. Nlm and MMF responses to the deviant sti muli increased in amplitude during training. This enhancement persisted unt il training was finished, but decreased 3 weeks later. The results suggest a plastic reorganization of the cortical representation for the trained fre quencies. NeuroReport 11:817-822 (C) 2000 Lippincott Williams & Wilkins.