Normalized compression distance to measure cortico-muscular synchronization

The neuronal functional connectivity is a complex and non-stationaryphenomenon creating dynamic networks synchronization determining thebrain states and needed to produce tasks. Here, as a measure that quantifiesthe synchronization between the neuronal electrical activity of two brainregions, we used the normalized compression distance (NCD), which is thelength of the compressed file constituted by the concatenated two signals,normalized by the length of the two compressed files including each singlesignal. To test the NCD sensitivity to physiological properties, we used NCDto measure the cortico-muscular synchronization, a well-known mechanismto control movements, in 15 healthy volunteers during a weak handgrip.Independently of NCD compressor (Huffman or Lempel Ziv), we foundout that the resulting measure is sensitive to the dominant-non dominantasymmetry when novelty management is required (p = 0.011; p = 0.007,respectively) and depends on the level of novelty when moving the non-dominant hand (p = 0.012; p = 0.024). Showing lower synchronization levelsfor less dexterous networks, NCD seems to be a measure able to enrich theestimate of functional two-node connectivity within the neuronal networksthat control the body.