Overview

This study investigates how a non-invasive form of brain stimulation, called transcranial direct current stimulation (tDCS), affects brain activity and information processing in younger and older adults. The stimulation uses a very weak electrical current applied through electrodes placed on the scalp. This method is safe and widely used in research to study brain function.

Participants will complete computer-based tasks while receiving either active brain stimulation or a placebo (sham) stimulation. The task is designed to engage specific mental processes so that the investigators can study how the brain responds under different conditions. Brain activity will be measured using magnetic resonance imaging (MRI), both while participants perform the tasks and while they are resting.

The study will compare healthy younger (ages 20-40) and older (ages 60-80) adults to explore whether age influences how the brain responds to stimulation. By examining patterns of brain activation and connectivity, the investigators aim to better understand how tDCS can modulate cognitive processing across the adult lifespan.

The hypothesis is that applying tDCS to the left dorsolateral prefrontal cortex will change patterns of brain activity related to cognitive processing, and that these changes may differ between younger and older adults. This knowledge could help inform future research into brain stimulation techniques in different age groups.

Eligibility

Inclusion Criteria:

• Healthy younger adults (ages 20-40) or healthy older adults (ages 60-80)
• Normal or corrected-to-normal vision and hearing
• Right-handed (for consistency in brain stimulation)
• Able to give written informed consent and comply with study procedures

Exclusion Criteria:

• History of neurological or psychiatric disorders
• Current use of medications that affect the central nervous system
• Metal implants, pacemakers, or other contraindications for MRI or tDCS
• History of seizures or epilepsy
• Pregnancy
• Participation in another brain stimulation study within the last 3 months
• Any condition judged by investigators to interfere with safe participation