The critical role of phase difference in theta oscillation between bilateral parietal cortices for visuospatial working memory

Philip Tseng, Kai Chi Iu, Chi Hung Juan

Research output: Contribution to journalArticle

9 Citations (Scopus)


Visual working memory (VWM) refers to people's ability to maintain and manipulate visual information on line. Its capacity varies between individuals, and neuroimaging studies have suggested a link between one's VWM capacity and theta power in the parietal cortex. However, it is unclear how the parietal cortices communicate with each other in order to support VWM processing. In two experiments we employed transcranial alternate current stimulation (tACS) to use frequency-specific (6 Hz) alternating current to modulate theta oscillation between the left and right parietal cortex with either in-phase (0° difference, Exp 1), anti-phase (180° difference, Exp 2), or sham sinusoidal current stimulation. In Experiment 1, in-phase theta tACS induced an improved VWM performance, but only in low-performers, whereas high-performers suffered a marginally-significant VWM impairment. In Experiment 2, anti-phase theta tACS did not help the low-performers, but significantly impaired high-performers' VWM capacity. These results not only provide causal evidence for theta oscillation in VWM processing, they also highlight the intricate interaction between tACS and individual differences - where the same protocol that enhances low-performers' VWM can backfire for the high-performers. We propose that signal complexity via coherent timing and phase synchronization within the bilateral parietal network is crucial for successful VWM functioning.

Original languageEnglish
Article number349
Pages (from-to)349
JournalScientific Reports
Issue number1
Publication statusPublished - Jan 10 2018



  • Adult
  • Analysis of Variance
  • Electroencephalography
  • Female
  • Humans
  • Male
  • Memory, Short-Term
  • Parietal Lobe/physiology
  • Photic Stimulation
  • Theta Rhythm
  • Visual Perception
  • Young Adult

ASJC Scopus subject areas

  • General

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