Stimulation of the ventral tegmental area induces visual cortical plasticity at the neuronal level

fMRI studies have shown that pairing of a task-irrelevant visual feature with electrical micro-stimulation of the ventral tegmentum area (VTA-EM) is sufficient to increase the sensory cortical representation of the paired feature and to improve perceptual performance. However, since fMRI provides an indirect measure of neural activity, the neural response changes underlying the fMRI activations are unknown. Therefore, we paired a task-irrelevant grating orientation with VTA-EM while attention was directed to a difficult orthogonal task. Meanwhile, we examined the changes in neural response properties in macaques by recording spiking activity in the posterior inferior temporal cortex, the locus of fMRI-defined plasticity in previous studies. We observed a relative increase in mean spike rate and preference for the VTA-EM paired orientation compared to unpaired orientation, which was unrelated to attention. These results demonstrate that VTA-EM–stimulus pairing is sufficient to induce sensory cortical plasticity at the spiking level in nonhuman primates.