Medial pulvinar nucleus as a causal hub for heteromodal naming

Our ability to retrieve the names of objects in our environment is a fundamental aspect of everyday life. This process requires a complex, dynamic network of cortical and subcortical interactions. While the cortical constituents of this network have been extensively studied with intracranial recordings, the subcortical nodes of the naming network are unclear. We probed the role of the left medial pulvinar nucleus in naming with direct intracranial recordings and stimulation in eight humans (3 male, 5 female) as they named objects using pictures, and auditory and written descriptions. We found a spectrotemporal signature of naming in the left medial pulvinar nucleus, characterized by a low frequency (8-20Hz) suppression, consistent across sensory modalities during naming, and absent during other non-naming language tasks. Within this frequency band, Granger causal interactions showed that the pulvinar nucleus received strong inputs from early visual, ventral temporal, and parahippocampal cortices. Direct thalamic stimulation reliably induced anomia, confirming that the left medial pulvinar nucleus is a critical node in the distributed naming network. Significance Statement for most people, the ability to retrieve the names of objects is a rapid, effortless process. However, damage to the brain’s naming network can disrupt this ability. While the cortical hubs of the naming network have been extensively documented, the contributions of subcortical regions to naming are unclear. We used the rare opportunity to record directly from one such subcortical region, the medial pulvinar nucleus, in patients who were having electrodes placed for the treatment of epilepsy, to characterise its role in naming. Based on its neural activation, functional connectivity with cortical naming hubs, and causal role in behaviour when disrupted, this work provides direct evidence of the critical role of pulvinar in naming.