Search Abstracts | Symposia | Slide Sessions | Poster Sessions
State- and task-dependent contributions of the anterior temporal lobes to familiarity and naming: Evidence from HD-tDCS
Poster Session B, Wednesday, September 30, 4:30 - 6:30 pm, Wangari Maathai
Sepideh Damirchi1, Karim Johari2, Rutvik H. Desai1; 1University of South Carolina, 2Louisiana State University
The anterior temporal lobes (ATL) are consistently recruited during lexico-semantic processing, yet what exactly they contribute remains debated. They are broadly considered a domain-general semantic hub, though an alternative account suggests a more specific role in mapping semantic representations onto lexical form. They are also associated with naming unique entities, such as famous people and places. We used high-definition transcranial direct current stimulation (HD-tDCS) over the left and right ATL to probe this during naming and familiarity recognition tasks involving famous faces and places. Neurologically healthy young adults completed active and sham HD-tDCS sessions targeting the left (n = 41) or right (n = 31) ATL. Tasks followed a 2 × 2 design crossing stimulus domain (famous faces, famous places) with retrieval demand (picture naming, word recognition). In the picture naming tasks, participants named the item if they could (successful name retrieval), otherwise either indicated that the item was known (familiarity without name retrieval), or unknown (no recognition). Known responses were followed by semantic verification questions (e.g., nationality and occupation for faces; location for places); correctly verified responses were classified as TOT (tip-of-the-tongue), whereas incorrect responses were excluded. In the recognition tasks, participants made familiarity-based known/unknown judgments. Reaction times, response probabilities, false familiarity endorsements, and signal detection measures were analyzed using mixed-effects models. Left ATL anodal stimulation selectively sped up TOT response times in famous face naming but had no effect on response times for successful naming. When successful naming and TOT response times were collapsed, the effect disappeared entirely, suggesting the effect was tied to the retrieval process itself, not to semantic access generally. Anodal stimulation also reduced incorrect familiarity endorsements for nonfamous items, an effect strongest in face-based tasks and absent in place-based tasks, suggesting stimulation selectively reduced erroneous familiarity-based responding without broadly improving performance. Hemisphere differences emerged in the other tasks: left and right ATL stimulation had opposing effects on reaction times for unknown responses in place naming and on overall response speed in name recognition. Place recognition showed no reliable effects of stimulation. Across tasks, overall naming accuracy, d′, and response bias were unaffected. These findings suggest that ATL contributions to semantic retrieval are neither uniform nor domain-general. Stimulation effects were most pronounced during incomplete retrieval, pointing to a particular role for the left ATL in establishing item-name mappings. This pattern is more consistent with a dynamic lexical-semantic mapping account than with a fully uniform semantic hub model.
Topic Areas: Meaning: Lexical Semantics, Language Production