Applications of transcranial direct current stimulation for understanding brain function

• tDCS can modulate membrane potentials, synaptic processes, and functional networks.
• Neural oscillations can be modified by tDCS, affecting perception and cognition.
• Different tDCS protocols can enhance or disrupt attention, learning, and memory.
• Variability in polarity-specific modulations may reflect neural coding properties.
• tDCS is complementary to, and can be used in parallel with, methods such as TMS.

In recent years there has been an exponential rise in the number of studies employing transcranial direct current stimulation (tDCS) as a means of gaining a systems-level understanding of the cortical substrates underlying behaviour. These advances have allowed inferences to be made regarding the neural operations that shape perception, cognition, and action. Here we summarise how tDCS works, and show how research using this technique is expanding our understanding of the neural basis of cognitive and motor training. We also explain how oscillatory tDCS can elucidate the role of fluctuations in neural activity, in both frequency and phase, in perception, learning, and memory. Finally, we highlight some key methodological issues for tDCS and suggest how these can be addressed.