Does the motor cortex want the full story? The influence of sentence context on corticospinal excitability in action language processing

Abstract

According to the embodied language framework, reading action verbs leads to a mental representation involving motor cortex activation. As sentence context has been shown to greatly influence the meaning of words, the present study aimed at better understanding its role in motor representations. We manipulated the presence of manual actions and sentence context. We hypothesized that context would serve to focus the representation of the described actions in the motor cortex, reflected in context-specific modulation of corticospinal excitability.Participants read manual action verbs and non-manual verbs, preceded by a full sentence (rich context) or not (minimal context). We assessed the level of corticospinal excitability by means of transcranial magnetic stimulation pulses delivered at rest or shortly after verb presentation. The coil was positioned over the cortical representation of right first dorsal interosseous (pointer finger).We observed a general increase of corticospinal excitability while reading both verb types in minimal context, whereas the modulation was action-specific in rich context: corticospinal excitability increased while reading manual verbs, but did not differ from baseline for non-manual verbs. These findings suggest that the context sharpens motor representations, activating the motor cortex when relevant and eliminating any residual motor activation when no action is present.