Exploring age and hemispheric differences in cortical plasticity after iTBS using fNIRS.

Area of Science:

• Neuroscience
• Cognitive Science
• Gerontology

Background:

• Non-invasive brain stimulation of the prefrontal cortex (PFC) can improve cognitive function in older adults.
• The specific effects of stimulating the left versus right dorsolateral prefrontal cortex (DLPFC) on brain oxygenation and how these effects vary with age are not well understood.

Purpose of the Study:

• To investigate the differential impact of left and right DLPFC stimulation on prefrontal oxygenation levels.
• To examine how these effects are modulated across different age groups (younger, middle-aged, and older adults).

Main Methods:

• 45 adults underwent intermittent theta-burst stimulation (iTBS) on the left and right DLPFC (F3 and F4) in a within-subjects design.
• Functional near-infrared spectroscopy (fNIRS) measured prefrontal oxygenation (HbO) changes during four cognitive tasks before and after stimulation.
• fNIRS data from 12 channels covered the left, medial, and right PFC.

Main Results:

• Age-related differences in brain oxygenation responses to DLPFC iTBS were observed.
• Younger adults showed increased HbO with left iTBS during inhibition tasks.
• Middle-aged adults exhibited bilateral HbO increases with right iTBS during learning tasks, while older adults showed decreases.
• Older adults displayed decreased HbO post-stimulation, particularly in midline regions after right iTBS and bilaterally after left iTBS.

Conclusions:

• The dispersion of oxygenation changes in response to DLPFC iTBS is age-dependent.
• Younger adults showed 'up-regulation' of brain activity, suggesting increased efficiency, whereas older adults showed 'down-regulation'.