Journal of Computational Neuroscience

, Volume 29, Issue 3, pp 599-613

First online:

Open Access This content is freely available online to anyone, anywhere at any time.

Estimating the contribution of assembly activity to cortical dynamics from spike and population measures

  • Michael DenkerAffiliated withRIKEN Brain Science Institute Email author 
  • , Alexa RiehleAffiliated withMediterranean Institute of Cognitive Neuroscience (INCM), CNRS—Univ. Aix-Marseille 2
  • , Markus DiesmannAffiliated withRIKEN Brain Science InstituteBrain and Neural Systems Team, RIKEN Computational Science Research Program
  • , Sonja GrünAffiliated withRIKEN Brain Science Institute


The hypothesis that cortical networks employ the coordinated activity of groups of neurons, termed assemblies, to process information is debated. Results from multiple single-unit recordings are not conclusive because of the dramatic undersampling of the system. However, the local field potential (LFP) is a mesoscopic signal reflecting synchronized network activity. This raises the question whether the LFP can be employed to overcome the problem of undersampling. In a recent study in the motor cortex of the awake behaving monkey based on the locking of coincidences to the LFP we determined a lower bound for the fraction of spike coincidences originating from assembly activation. This quantity together with the locking of single spikes leads to a lower bound for the fraction of spikes originating from any assembly activity. Here we derive a statistical method to estimate the fraction of spike synchrony caused by assemblies—not its lower bound—from the spike data alone. A joint spike and LFP surrogate data model demonstrates consistency of results and the sensitivity of the method. Combining spike and LFP signals, we obtain an estimate of the fraction of spikes resulting from assemblies in the experimental data.


LFP Synchrony Oscillations Network dynamics Motor cortex