How the brain encodes the semantic concepts represented bywordsisafundamental questionincognitive neuroscience. Hemodynamic neuroimaging studies have robustly shown that different areas of posteroventral temporal lobe are selectively activated by images of animals versus manmade objects. Selective responses in these areas to words representing animals versus objects are sometimes also seen, but they are task-dependent, suggesting that posteroventral temporal cortex may encode visual categories, while more anterior areas encode semantic categories. Here, using the spatiotemporal resolution provided by intracranial macroelectrode and microelec-trode arrays, we report category-selective responses to words representing animals and objects in human anteroventral temporal areas including inferotemporal, perirhinal, and entorhinal cortices. This selectivity generalizes across tasks and sensory modalities, suggesting that it represents abstract lexicosemantic categories. Significant category-specific responses are found in measures sensitive to synaptic activity (local field potentials, high gamma power, current sources and sinks) and unit-firing (multiunit and single-unit activity). Category-selective responses can occur atshort latency (as earlyas130ms) in middle cortical layers and thus are extracted in the first pass of activity through the anteroventral temporal lobe.Thisactivation may provide inputtoposterior areas for iconic representations when requiredby the task,aswellastothe hippocampal formation for categorical encoding and retrievalofmemories, andtothe amygdala for emotionalassociations.More generally, these results support modelsinwhichthe anteroventral temporal lobe playsaprimary roleinthe semantic representation of words.
ASJC Scopus subject areas
- General Neuroscience