Posterior language areas share electrophysiological signatures of word retrieval in context-driven object and action naming

Claims about shared neural processing between object and action words have mainly been based on spatial overlap. Spatial overlap alone, however, provides an incomplete understanding of neural (dis)similarity. Here, we compared object and action word retrieval within participants utilising temporal, spectral, and spatial information in the electroencephalogram (EEG) recorded during context-driven object and action picture naming. Constrained sentence contexts elicited pre-picture lexical-semantic word planning for object and action words, indexed by power decreases in the alpha-beta frequency range (8 - 30 Hz). Using a novel approach based on mutual information and source-reconstructed EEG signal, we computed joint temporo-spectro-spatial (dis)similarity indices across object and action naming in the constrained condition where information retrieval occurred. Spatially, dissimilarities were found in bilateral frontal, anterior superior temporal, and right anterior-to-middle temporal areas. Similarity, by contrast, was linked to the precunei and right temporo-parietal areas, regions associated with lexical-semantic processing and word retrieval. Crucially, similarity in the precunei compared to the temporo-parietal regions was characterised by differential patterns of the alpha-beta activity, implying processing and, potentially, functional differences between the areas. This finding highlights how conclusions about shared neural processes depend on the degree of abstraction (e.g., spatial, spatial-spectral) chosen to define the compared neural mechanisms. We tentatively interpret the contribution of the right hemisphere and left frontal areas to (dis)similarity as coarser, less fine-grained lexical-semantic computations.