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Contributed Talk Session: Thursday, August 6, 11:15 am – 12:15 pm, Skirball Theater
Poster C in Poster Session C: Wednesday, August 5, 9:30 – 11:15 am, Kimmel Center, Shorin & Rosenthal Rooms

Lexical representations are sequenced through a micro-scale dynamic code in inferior frontal gyrus

Irmak Ergin¹, Atlas Kazemian¹, Ernesto Rojas¹, Nick Hahn¹, Foram Kamdar², Christina Kim Vo¹, Sasi Sathya Madugula¹, Ryan Z Wang¹, Chaofei Fan¹, Erin Kunz¹, Donald Avasino³, Leigh Hochberg⁴, Jaimie M. Henderson¹, Francis R Willett¹, Laura Gwilliams¹; ¹Stanford University, ²University of Illinois at Chicago, ³Massachusetts General Hospital, ⁴Brown University

Presenter: Irmak Ergin

Naturalistic speech is transient and strictly time-ordered, creating a computational challenge for comprehension: the brain must preserve and integrate earlier input while new words continue to arrive. One proposed algorithmic solution is that linguistic representations are maintained dynamically across changing neural populations over time, but it remains unclear how such an algorithm is implemented at the neuronal scale for higher-level linguistic representations. Using microelectrode recordings from the inferior frontal gyrus (IFG) during continuous speech listening, we show that lexical information is decodable for over 2 seconds, which overlaps with multiple words into the future. Neural activity evolves along state-space trajectories, which encode both lexical content and elapsed processing time. These trajectories preserve traces of earlier speech input as new input arrives, while also encoding relative sequence order. Together, these findings provide the first micro-scale evidence for how dynamic neural sequencing is implemented by IFG neurons during continuous speech comprehension.

Topic Area: Auditory, Speech & Language Processing