Stimulus-independent neural coding of event semantics: Evidence from cross-sentence fMRI decoding

Abstract

Multivariate neuroimaging studies indicate that the brain represents word and object concepts in a format that readily generalises across stimuli. Here we investigated whether this was true for neural representations of simple events described using sentences. Participants viewed sentences describing four events in different ways. Multivariate classifiers were trained to discriminate the four events using a subset of sentences, allowing us to test generalisation to novel sentences. We found that neural patterns in a left-lateralised network of frontal, temporal and parietal regions discriminated events in a way that generalised successfully over changes in the syntactic and lexical properties of the sentences used to describe them. In contrast, decoding in visual areas was sentence-specific and failed to generalise to novel sentences. In the reverse analysis, we tested for decoding of syntactic and lexical structure, independent of the event being described. Regions displaying this coding were limited and largely fell outside the canonical semantic network. Our results indicate that a distributed neural network represents the meaning of event sentences in a way that is robust to changes in their structure and form. They suggest that the semantic system disregards the surface properties of stimuli in order to represent their underlying conceptual significance.

Decoding semantic representations in mind and brain

“…Standard sequences yield especially poor signal in orbitofrontal and ventral anterior temporal regions thought critical to semantic cognition [127]. Strategies for improving signal, including distortion-corrected spin-echo [127,128] and multi-echo protocols [129,130], have been available for several years but have only rarely been applied in semantic studies [131]. Indeed, many studies have restricted the field of view to exclude ventral ATL completely [132].…”