On the relationship between cortical excitability and visual oscillatory responses - A concurrent tDCS-MEG study

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Visual Perception

Background:

• Neuronal oscillations in the alpha band (8-12Hz) are linked to attentional gating in the visual cortex.
• Visual gamma-band activity (40-100Hz) is associated with bottom-up processing of visual information.
• The relationship between visual cortex excitability and these oscillatory mechanisms remains unclear.

Purpose of the Study:

• To investigate the direct relationship between visual cortex excitability and alpha/gamma band oscillations.
• To assess the feasibility of concurrent transcranial direct current stimulation (tDCS) and magnetoencephalography (MEG) for studying visual neuronal activity.
• To examine the effects of tDCS on visually evoked alpha and gamma responses.

Main Methods:

• Utilized an Oz-Cz tDCS montage to stimulate the visual cortex.
• Recorded whole-brain oscillatory activity using MEG during a visual task.
• Administered active (anodal, cathodal) and sham tDCS conditions.

Main Results:

• Visual stimuli reliably modulated alpha and gamma band activity, with a moving annulus stimulus increasing gamma and decreasing alpha.
• These modulations were observed across active and sham tDCS conditions.
• tDCS did not produce systematic alterations in the amplitude of stimulus-induced visual oscillatory responses.

Conclusions:

• Concurrent tDCS/MEG is a feasible technique for investigating visual neuronal oscillations.
• The current study found tDCS ineffective in altering the amplitude of visually evoked alpha and gamma responses.
• Further research is needed to understand why tDCS did not modulate these specific oscillatory responses.