Oscillatory brain activity and transcranial direct current stimulation in humans

Area of Science:

• Neuroscience
• Cognitive Science
• Neurophysiology

Background:

• Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique.
• tDCS can induce prolonged, polarity-dependent changes in cortical excitability.
• High-frequency oscillations (beta and gamma) in the visual cortex correlate with early visual processing components like the N70 peak of the visual evoked potential (VEP).

Purpose of the Study:

• To investigate the effects of tDCS on oscillatory activity in the human visual cortex.
• To determine if tDCS can modulate neuronal excitability and subsequent visual evoked potentials.
• To assess the transient and reversible nature of tDCS-induced changes in cortical activity.

Main Methods:

• Healthy human subjects received 10 minutes of either anodal or cathodal tDCS.
• Visual evoked potentials (VEPs) were recorded using sinusoidal luminance gratings before, immediately after, and at 10, 20, and 30 minutes post-stimulation.
• Analysis focused on changes in normalized beta and gamma frequency powers within the VEP.

Main Results:

• Cathodal tDCS significantly decreased beta and gamma frequency powers.
• Anodal tDCS showed a slight increase in beta and gamma frequency powers.
• These changes in oscillatory activity were observed to be transient and reversible.

Conclusions:

• tDCS can transiently and reversibly modulate oscillatory activity in the visual cortex.
• The findings suggest tDCS influences organized cortical activity related to visual processing.
• Given the link between gamma activity and higher-order information processing, tDCS may offer a method for affecting cognitive functions.