Cortical remodelling induced by activity of ventral tegmental dopamine neurons

Representations of sensory stimuli in the cerebral cortex can undergo progr essive remodelling according to the behavioural importance of the stimuli(1 ,2). The cortex receives widespread projections from dopamine neurons in th e ventral tegmental area (VTA)(3-5), which are activated by new stimuli or unpredicted rewards(6,7), and are believed to provide a reinforcement signa l for such learning-related cortical reorganization(8). In the primary audi tory cortex (AI) dopamine release has been observed during auditory learnin g that remodels the sound-frequency representations(9,10). Furthermore, dop amine modulates longterm potentiation(11,12), a putative cellular mechanism underlying plasticity(13). Here we show that stimulating the VTA together with an auditory stimulus of a particular tone increases the cortical area and selectivity of the neural responses to that sound stimulus in AI. Conve rsely, the AI representations of nearby sound frequencies are selectively d ecreased. Strong, sharply tuned responses to the paired tones also emerge i n a second cortical area, whereas the same stimuli evoke only poor or non-s elective responses in this second cortical field in naive animals. In addit ion, we found that strong long-range coherence of neuronal discharge emerge s between AI and this secondary auditory cortical area.