Cortical Excitability and Role of rTMS in Nicotine Use Disorder

Nicotine is one of the main components of cigarettes and affects the central nervous system mainly via nicotinic acetylcholine receptors. It has further effects on neuromodulation by regulating the release of dopamine, serotonin, glutamate and adrenaline. In studies, it has been shown that nicotine improves attention and working memory in animals and humans, while nicotine withdrawal leads to reduced working and verbal memory capacity in otherwise healthy tobacco smokers. In schizophrenics and patients suffering from attention deficit hyperactivity disorder, nicotine improves cognitive performance. A likely basis of the nicotinic effects on cognitive functions is its effect on cortical excitability and activity. Here, neurophysiological studies mainly base on animal experiments and have shown in vitro that the nicotinic acetylcholine receptors elicit neuronal depolarisation by inducing transmembrane cationic inward currents (Calcium), thus being involved in induction and modulation of neuroplasticity and cortical excitability.

Repetitive transcranial magnetic stimulation: is a non-invasive brain stimulation technique that has shown positive results in the treatment of depression, schizophrenia, and more recently addiction. Repetitive transcranial magnetic stimulation uses alternating magnetic fields to induce electric currents in the cortical tissue. Low-frequency as one hertz repetitive transcranial magnetic stimulation is believed to inhibit neuronal firing in a localized area and is used to induce virtual brain lesions. High-frequency as more than three hertz repetitive transcranial magnetic stimulation is believed to be excitatory in nature and can result in neuronal depolarization under the stimulating coil. However, the effects of repetitive transcranial magnetic stimulation are not limited to the site of stimulation and can induce changes in distant interconnected sites of the brain, and consequently may influence subcortical regions.