Cell Reports (Aug 2021)

Synchronization patterns reveal neuronal coding of working memory content

  • Fahimeh Mamashli,
  • Sheraz Khan,
  • Matti Hämäläinen,
  • Mainak Jas,
  • Tommi Raij,
  • Steven M. Stufflebeam,
  • Aapo Nummenmaa,
  • Jyrki Ahveninen

Journal volume & issue
Vol. 36, no. 8
p. 109566

Abstract

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Summary: Neuronal oscillations are suggested to play an important role in auditory working memory (WM), but their contribution to content-specific representations has remained unclear. Here, we measure magnetoencephalography during a retro-cueing task with parametric ripple-sound stimuli, which are spectrotemporally similar to speech but resist non-auditory memory strategies. Using machine learning analyses, with rigorous between-subject cross-validation and non-parametric permutation testing, we show that memorized sound content is strongly represented in phase-synchronization patterns between subregions of auditory and frontoparietal cortices. These phase-synchronization patterns predict the memorized sound content steadily across the studied maintenance period. In addition to connectivity-based representations, there are indices of more local, “activity silent” representations in auditory cortices, where the decoding accuracy of WM content significantly increases after task-irrelevant “impulse stimuli.” Our results demonstrate that synchronization patterns across auditory sensory and association areas orchestrate neuronal coding of auditory WM content. This connectivity-based coding scheme could also extend beyond the auditory domain.

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