Abstract
How do we solve new problems on the first attempt, such as when we imitate a novel dance or draw an imaginary animal? This ability does not seem to rely on gradual learning or exact recall. Instead, we seem capable of combinatorial construction, or recombining atomic units of knowledge in new ways using internal rule systems. Although behavioural signatures are widespread, whether and how the brain implements construction is unclear. A major reason has been the difficulty in establishing an animal lab task that requires such construction. I addressed this limitation by developing a drawing task in which participants reconstruct geometric figures by tracing with touchscreen strokes. Instead of motor-efficient tracing, both humans and trained macaques use a combinatorial strategy: they sequence stroke types that resemble distinct shapes (action symbols) using a system of rules such as repetition (action grammar). Neural recordings across eight macaque frontal areas revealed a division of labor: action symbols are represented in ventral premotor cortex and action grammar structure is represented in the presupplementary motor area. Thus, analogous to words and syntax, these two connected areas form a system for generating novel hierarchical action programs (“repeat circle twice, then connect to squiggle”).
Biography
Lucas is a systems and computational neuroscientist fascinated by the brain’s remarkable ability to generate new representations that instantiate novel ideas and behaviours, an ability critical for general-purpose intelligence. Towards this, he specifically studies how primates solve physical problems by constructing grammatically structured action sequences, and does so by combining behavioural, cognitive, neural, and modeling studies in macaques and humans. He is a postdoc with Winrich Freiwald (Rockefeller) and works closely with Josh Tenenbaum (MIT) and Xiao-Jing Wang (NYU). His Ph.D. was on circuit mechanisms of motor skill learning in songbirds, with Michael Brainard (UCSF). In his free time he rides his motorcycle through the winding roads of upstate New York.