How Does the Brain Create Language?

ETH Zurich Distinguished Computer Science Colloquium
Christos Papadimitriou, Columbia University
Host: Emo Welzl

ABSTRACT:
There is little doubt that cognitive phenomena are the result of neural activity, and yet there has been slow progress toward articulating a computational theory of how exactly this happens. I will discuss a simplified mathematical model of the brain, which we call NEMO, involving brain areas, spiking neurons, random synapses, local inhibition, Hebbian plasticity, and long-range interneurons – crucially, there is no backpropagation in NEMO. Emergent behaviors of the resulting dynamical system – established both analytically and through simulations – include assemblies of neurons, sequence memorization, one-shot learning, and universal computation. NEMO is also a software-based neuromorphic system that can be simulated efficiently at the scale of tens of millions of neurons, emulating certain high-level cognitive phenomena such as planning and parsing of natural language. I will describe current work aiming at creating through NEMO a neuromorphic language organ: a neural tabula rasa which, on input consisting of a modest amount of grounded language, is capable of language acquisition: learning lexicon, syntax, semantics, comprehension, and generation. Finally, and on the plane of scientific methodology, I will argue that experimenting with such brain-like devices, devoid of backpropagation, can reveal novel avenues to learning, and may end up advancing AI.

BIOGRAPHY:
Christos Harilaos Papadimitriou is the Donovan Family Professor of Computer Science at Columbia University. Before joining Columbia in 2017, he was a professor at UC Berkeley for the previous 22 years, and before that he taught at Harvard, MIT, NTU Athens, Stanford, and UCSD. He has written five textbooks and many articles on algorithms and complexity, and their applications to optimization, databases, control, AI, robotics, economics and game theory, the Internet, evolution, and the brain. He holds a PhD from Princeton (1976), and nine honorary doctorates, including from ETH, University of Athens, EPFL, and Univ. de Paris Dauphine. He is a member of the National Academy of Sciences of the US, the American Academy of Arts and Sciences, and the National Academy of Engineering, and he has received the Knuth prize, the Gödel prize, the Babbage award, the von Neumann medal, the IEEE women of the Edvac Computer Pioneer Award, as well as the 2018 Harvey Prize by Technion. In 2015 the president of the Hellenic Republic named him commander of the order of the Phoenix. He has also written three novels: “Turing,” “Logicomix” and his latest “Independence.”