Spatio-Temporal Investigation of Brain-Wide Sequences

In "The Organization of Behavior" (Hebb, 1949), Hebb suggested that the propagation of activity between transiently grouped neurons plays an important role in behavior. Since then, multiple studies have provided evidence supporting Hebb's claim; however, most findings have been found locally in confined brain regions during unimodal tasks. Here we report on brain-wide behavioral-specific sequences in humans performing a multimodal task. To investigate the structure of these sequences, we used MEG to record brain activity in multiple brain regions simultaneously in participants performing a sensory-motor synchronization task. We detected local transient events corresponding to synchronously activating populations of pyramidal neurons and searched for their global organization as spatio-temporal patterns of activation sequences between distant neural populations. We focused our analysis on two types of spatio-temporal patterns: the most frequently repeating patterns and the most discriminative patterns, to concentrate on patterns with high relevancy to behavior. The findings revealed that global temporally precise sequences can be found and that these sequences have partially stereotypical characteristics, both temporally and spatially, with consistent properties across subjects. By implementing a simplistic single-trial decoding approach, we found that brain-wide sequences have a temporal precision of 17-31 milliseconds, which resembles the temporal precision found locally in neural assemblies.