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Poster Session B: Wednesday, August 13, 1:00 – 4:00 pm, de Brug & E‑Hall

Neural Substrates of a Symbolic Action Grammar in Primate Frontal Cortex

Lucas Y. Tian¹, Kedar U. Garzón², Daniel Hanuska¹, Xiao-Jing Wang³, Joshua B. Tenenbaum⁴, Winrich Freiwald¹; ¹Rockefeller University, ²Columbia University, ³New York University, ⁴Massachusetts Institute of Technology

Presenter: Lucas Y. Tian

At the core of intelligence is the capacity to solve new problems. In turn, problem-solving has been hypothesized to depend on cognitive operations resembling symbolic grammars (Newell & Simon, 1976), with two core components: discrete units (symbols) and rules for recombining symbols into new composite representations (syntax). Whether and how symbolic grammars are implemented in neuronal substrates remains unknown. Here, we establish a research program to elucidate the neural basis of action grammars. In a drawing task, macaque monkeys learn action grammars, which guides how they compositionally generalize to draw new images. Our behavioral analyses indicate that these grammars consist of symbolic action primitives and syntactic rules. In recordings of neuronal activity across motor, premotor, and prefrontal areas, we identified separate populations encoding action grammar components, including motor primitives, action symbols, and syntactic rules. Here, we report the discovery of an action symbol representation in ventral premotor cortex (PMv). Specifically, we found that PMv encodes planned stroke primitives, and does so in a manner exhibiting three symbolic properties: abstraction, categorical structure, and recombination. Thus, we have established a paradigm to study compositional generalization using action grammars, and identified a representation of action symbols in PMv. In ongoing work, we are studying how neural activity, in PMv and interconnected areas, may implement the systematic composition of symbols using syntactic rules.

Topic Area: Language & Communication

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