Karl John Friston FRS FMedSci FRSB (born 12 July 1959) is a British neuroscientist and theoretician at University College London. He is an authority on brain imaging and theoretical neuroscience, especially the use of physics-inspired statistical methods to model neuroimaging data and other random dynamical systems. He is a key architect of the free energy principle and active inference. In imaging neuroscience he is best known for statistical parametric mapping and dynamic causal modelling. In October 2022, he joined VERSES Inc, a California-based cognitive computing company focusing on artificial intelligence designed using the principles of active inference, as Chief Scientist. Friston is one of the most highly cited scientists of all time and in 2016 was ranked No. 1 by Semantic Scholar in the list of top 10 most influential neuroscientists. Education Karl Friston attended the Ellesmere Port Grammar School, later renamed Whitby Comprehensive, from 1970–1977. Friston studied natural sciences (physics and psychology) at the University of Cambridge in 1980, and completed his medical studies at King's College Hospital, London. Career Friston subsequently qualified under the Oxford University Rotational Training Scheme in Psychiatry, and is now a Professor of Neuroscience at University College London. He was a Wellcome Trust Principal Fellow and is currently Scientific Director of the Wellcome Trust Centre for Neuroimaging. He also holds an honorary consultant post at the National Hospital for Neurology and Neurosurgery. He invented statistical parametric mapping: SPM is an international standard for analysing imaging data and rests on the general linear model and random field theory (developed with Keith Worsley). In 1994 his group developed voxel-based morphometry. VBM detects differences in neuroanatomy and is used clinically and as a surrogate in genetic studies. These technical contributions were motivated by schizophrenia research and theoretical studies of value-learning (with Gerry Edelman). In 1995, this work was formulated as the dysconnection hypothesis of schizophrenia (with Chris Frith). In 2003, he invented dynamic causal modelling (DCM), which is used to infer the architecture of distributed systems like the brain. Mathematical contributions include Variational Laplace and Generalized filtering, which use variational Bayesian methods for time-series analysis. Friston is principally known for models of functional integration in the human brain and the principles that underlie neuronal interactions. His main contribution to theoretical neurobiology is a variational free energy principle (Active inference in the Bayesian brain). According to Google Scholar, Friston's h-index is 263. In 2020 he applied dynamic causal