Neural Noise

Memory-dependent modulation of hippocampal theta power through frontoparietal phase-synchronous tACS

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  • Frontoparietal phase-synchronous tACS modulates hippocampal theta power in a memory-dependent manner.1
  • This supports theta-coupled neuromodulation for memory enhancement and validates theta oscillation targeting.1 1

Weekly enrichment (2026-07-20)

  • The pilot study applied dual-site in-phase theta-tACS (6 Hz) over left inferior frontal and posterior parietal regions during a temporal-order (sequence) memory task in 20 healthy young adults aged 19–29, using a double-blind, sham-controlled crossover design.2
  • Hippocampal theta power and cortico-hippocampal connectivity were estimated from 64-channel EEG through subcortical source analysis with a hierarchical subspace pursuit algorithm that restricts cortical activity to a sparse set of sources.2
  • Overall memory performance did not differ between in-phase tACS and sham; the effect was memory-dependent, with hippocampal theta power increasing specifically in participants with superior memory performance.2
  • Beyond the hippocampus, in-phase theta-tACS raised theta power in the left temporal cortex at the group level, and both middle-frontal and temporal theta effects interacted with individual memory performance.2
  • The work provides first-time evidence that phase-synchronized frontoparietal tACS can reach deep subcortical targets, addressing the long-standing problem that scalp tACS electric fields are predominantly cortical.2
  • In a separate amnestic-MCI trial, dual-node tACS over the right frontoparietal network (DLPFC + posterior parietal cortex; 10 sessions, 2 mA, 6 Hz, 25 min) beat single-node DLPFC stimulation on global cognition (MoCA) and enhanced theta–gamma phase-amplitude coupling and frontal-to-parietal theta synchronization.3
  • The TRANSFORM-AD randomized trial (46 mild-AD patients, 40 Hz tACS) showed no change on its primary ADAS-Cog outcome but improved MMSE and MoCA and enhanced hippocampal theta–gamma coupling that correlated with cognitive gains, supporting cross-frequency coupling as a candidate therapeutic mechanism.4

Footnotes

  1. https://www.sciencedirect.com/science/article/pii/S1935861X26000196?dgcid=rss_sd_all ↩ ↩2 ↩3

  2. https://www.nature.com/articles/s41598-025-09841-y ↩ ↩2 ↩3 ↩4 ↩5

  3. https://www.nature.com/articles/s41398-026-04019-0 ↩

  4. https://link.springer.com/article/10.1186/s13195-024-01570-0 ↩

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