From Functional Imaging to Free Energy: Dedicated Professor Karl Friston on the Occasion of His 65th Birthday

Karl Friston's contributions to the brain sciences are difficult to overstate. From the development of statistical parametric mapping-a ubiquitous technique employed in the analysis of functional neuroimaging data-to the free energy principle and active inference, his ideas have changed the way in which many of us engage with neuroscience, psychology, biology, and the philosophy of the mind. As if his unparalleled influence in understanding how the brain works was not enough, Friston's work has dissolved interdisciplinary boundaries (or perhaps blankets) and has informed fields as diverse as statistics, epidemiology, morphogenesis, climate science, the physics of sentience, evolution, and artificial intelligence.This Special Issue-on the occasion of Karl Friston's 65th birthday-celebrates his body of work and the many directions of research and the many researchers-young or more experienced-that it continues to inspire. The articles in this collection illustrate how our collective generative models have been optimised through the application of dynamic causal modelling (to neural circuits, pandemics, or climates) through the study of predictive coding and active inference in the brain, as well as through structure learning by curious machines.