Luigi Grisoni | Predictive semantic activity in the brain: New arguments for the relevance of sensory and motor systems in meaning processing

Semantic and conceptual grounding theories emphasise functional interaction between perceptual, motor, and conceptual knowledge (Pulvermüller, 1999; Barsalou, 2008). Although much evidence shows consistent activation in sensorimotor brain areas during language comprehension (e.g., Hauk et al., 2004; Grisoni et al., 2016), it has been argued that such activations may index post-hoc, epiphenomenal re-processing (Mahon and Caramazza, 2008; Bedny and Caramazza, 2011) rather than genuine semantic processing. In recent works, however, we showed evidence of a significant contribution of sensorimotor areas before predictable words appear in comprehension (Grisoni et al., 2017; Grisoni et al., 2021) and before predictable words are pronounced to complete sentence fragments (Grisoni et al., 2024). Sentence fragments that strongly predict subsequent words induced slow-wave potentials before the expected words; this potential was weaker if the preceding fragments were unpredictable. This Prediction Potential (PP) indexed predictive semantic processing was further demonstrated by the observation of cortical sources in specific sensorimotor brain areas for action-related (e.g., action verbs, tool nouns) words but in posterior, visual, areas for visual-related words (e.g., animal nouns). Furthermore, inverse correlations between the PP and the well-known brain index of semantic processing, N400, suggest that these two responses have a similar semantic discriminatory function. Overall, these data show that activity in sensorimotor brain areas also reflects the meaning subjects expect and, therefore, it cannot originate from re-processing but from genuine semantic processing.