What kind of effect does cathodal transcranial direct current stimulation (tDCS) have on neural excitability?

Cathodal transcranial direct current stimulation (tDCS) is known to have an inhibitory effect on neural excitability. When cathodal stimulation is applied, it typically results in a decrease in the excitability of the neurons in the stimulated area, which can lead to lower likelihood of action potentials being fired. This decrease in excitability is particularly relevant in therapeutic contexts, such as the treatment of conditions like depression or chronic pain, where reducing excitatory activity in certain brain regions can help alleviate symptoms.

This effect arises from the changes in membrane potential induced by the cathodal current. The negative polarity of the cathodal stimulation hyperpolarizes the neuronal membrane, making it more difficult for the neuron to reach the threshold needed for firing an action potential. Consequently, this modulation of excitability can influence cognitive and motor functions, depending on which areas of the brain are targeted.

In contrast, anodal tDCS is known to increase excitability, while the effects are distinctly different in terms of their therapeutic applications. Understanding this difference is crucial in the field of biomedical engineering, especially for designing effective neural modulation techniques.