More than just a name: retrieval of unique entities in the anterior temporal lobe

The capacity to retrieve semantic information, particularly related to unique entities, is thought to depend on the anterior temporal lobe (ATL). Evidence underpinning the ATL's characterization as a hub of the semantic network has depended largely on naming tasks requiring lexical retrieval. Consequently, questions about its role in accessing and integrating different types of information (e.g., that Puss in Boots is a charming trickster who wears a cavalier-style hat) remain unanswered. Here, we scanned participants performing a semantic decision task that minimized lexical retrieval containing both unique (famous people and landmarks) and common (everyday objects) probes. We included a sample of patients with left temporal lobe epilepsy (LTLE), whose seizures cause dysfunction in both the temporal neocortex and the hippocampus, a structure that has also been implicated in retrieving information about unique entities. Both groups demonstrated a wide network of regions exhibiting greater activation for unique entity decisions, including the left ATL, bilateral hippocampi, precunei and angular gyri. The LTLE group, who were impaired on the proper noun condition, showed reduced activation compared to the control group in the ipsilateral anterior temporal cortex and hippocampus. Interestingly, higher activation in the left ATL in the LTLE group during the proper noun condition was negatively associated with task performance. Our results support and expand on models of semantic memory by showing that not only the ATL but also the hippocampus and broader parts of the posterior-medial network contribute to retrieval of specific information, even when demands on lexical retrieval are minimized.