Modeling the Evolution of Dynamic Brain Processes During an Associative Learning Experiment

Mark Fiecas*, Hernando Ombao

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

37 Scopus citations


We develop a new time series model to investigate the dynamic interactions between the nucleus accumbens and the hippocampus during an associative learning experiment. Preliminary analyses indicated that the spectral properties of the local field potentials at these two regions changed over the trials of the experiment. While many models already take into account nonstationarity within a single trial, the evolution of the dynamics across trials is often ignored. Our proposed model, the slowly evolving locally stationary process (SEv-LSP), is designed to capture nonstationarity both within a trial and across trials. We rigorously define the evolving evolutionary spectral density matrix, which we estimate using a two-stage procedure. In the first stage, we compute the within-trial time-localized periodogram matrix. In the second stage, we develop a data-driven approach that combines information from trial-specific local periodogram matrices. Through simulation studies, we show the utility of our proposed method for analyzing time series data with different evolutionary structures. Finally, we use the SEv-LSP model to demonstrate the evolving dynamics between the hippocampus and the nucleus accumbens during an associative learning experiment. Supplementary materials for this article are available online.

Original languageEnglish (US)
Pages (from-to)1440-1453
Number of pages14
JournalJournal of the American Statistical Association
Issue number516
StatePublished - Oct 1 2016


  • Bivariate time series
  • Local stationarity
  • Replicated time series
  • Signal heterogeneity
  • Spectral analysis
  • coherence

ASJC Scopus subject areas

  • Statistics and Probability
  • Statistics, Probability and Uncertainty


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