Serotonin affects transcranial direct current-induced neuroplasticity in humans

Area of Science:

• Neuroscience
• Psychopharmacology
• Neurophysiology

Background:

• Serotonergic system modulation impacts learning and memory (LTP/LTD) in animals.
• Serotonin's role in depression is linked to altered neuroplasticity.
• Human data on serotonin's direct effect on neuroplasticity is lacking.

Purpose of the Study:

• To investigate the impact of citalopram on neuroplasticity induced by transcranial direct current stimulation (tDCS) in humans.
• To determine if serotonin influences the brain's ability to change and adapt.

Main Methods:

• A single-blinded, placebo-controlled, randomized crossover study.
• 12 healthy subjects received either 20mg citalopram or placebo.
• Anodal or cathodal tDCS applied to motor cortex, with excitability monitored via TMS.

Main Results:

• Placebo: Anodal tDCS increased, cathodal tDCS decreased, motor cortex excitability.
• Citalopram enhanced and prolonged anodal tDCS-induced facilitation.
• Citalopram converted cathodal tDCS-induced inhibition into facilitation.

Conclusions:

• Serotonin significantly impacts human neuroplasticity, favoring facilitation.
• Serotonin's facilitatory effect may explain learning/memory deficits in depression.
• Enhancing serotonin could improve efficacy of brain stimulation therapies for neuropsychiatric disorders.