Does White Matter Matter? Spatio-temporal Dynamics of Task Switching in Aging
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Summary
This study investigates the neurophysiological mechanisms underlying age-related deficits in task switching, specifically examining whether structural changes in white matter, particularly the anterior corpus callosum (CC), contribute to these difficulties. The authors hypothesized that executive function relies on connections between brain areas, which may weaken with age, and that such structural degradation would disproportionately affect switching to spatial tasks, which are right-hemisphere dominant, compared to verbal tasks, which are left-hemisphere dominant. The research employed a spatial Stroop task involving 16 younger adults (18–30 years) and 16 older adults (65–82 years). Participants performed trials requiring them to classify words based on either their meaning (verbal) or their position (spatial), with cues indicating the required dimension. Brain activity was measured using the event-related optical signal (EROS), which offers subcentimeter spatial and millisecond temporal resolution, allowing for the analysis of spatio-temporal dynamics in the prefrontal cortex. Additionally, structural MRI scans were acquired to measure the cross-sectional area of the anterior CC, adjusted for total brain volume. Behavioral results confirmed that older adults exhibited greater task-switching difficulties, but these deficits were largely restricted to switching to the spatial task and were most pronounced in individuals with smaller anterior CCs. EROS data revealed two distinct patterns of activity: general switching-related activation in the left middle frontal gyrus (MFG) with a latency of approximately 300 milliseconds, and task-specific activity in the inferior frontal gyrus (IFG). In younger adults, this task-specific activity was lateralized to the left hemisphere for verbal switches and to the right hemisphere for spatial switches. In older adults, however, the lateralization of activity for spatial switches depended on CC size: those with large CCs showed right-hemisphere lateralization, while those with small CCs showed left-hemisphere lateralization. These findings suggest that task switching involves both task-general and task-specific processes and that white matter integrity is a critical factor in maintaining efficient executive function during aging. The observed shift in lateralization for older adults with smaller CCs implies that structural disconnection between hemispheres may force the brain to rely on alternative, less efficient neural pathways. This supports the hypothesis that aging involves a degree of cortical disconnection, both functional and anatomical, which underlies specific patterns of executive dysfunction. The study highlights the importance of considering individual differences in structural connectivity when understanding age-related cognitive decline.
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| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | author_sweep | — | — | 2 | 2026-05-28 |
| archive | success | manual_pmc_pow_fetch | — | — | 41 | 2026-08-22 |
| extract | success | cached | — | — | 4 | 2026-08-23 |
| clean | success | clean | — | — | 1 | 2026-06-04 |
| chunk | success | chunk | — | — | 1 | 2026-06-04 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-04 |
| enrich | success | — | — | — | 1 | 2026-05-28 |
| promote | success | — | — | — | 1 | 2026-06-04 |
| summarize | success | llm | qwen3.8-27b-gittensor | summ-v5 | 2 | 2026-08-23 |
| tag | success | vector_similarity | — | — | 15 | 2026-06-11 |
Summary generated by qwen3.8-27b-gittensor on 2026-08-23; verification: pending re-verification.
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