The Movie After-Effect: widespread adaptation of human cortex following naturalistic sensory experience

Neural systems adapt to prolonged sensory input through mechanisms such as gain control or homeostatic plasticity to maintain stable operating ranges. However, this phenomenon has so far been documented under extreme, non-ecological stimuli targeting specific sensory systems. Here, we reveal a widespread adaptation process across diverse human cortical regions following naturalistic movie watching conditions. The effect was evident in 218 out of 251 cortical regions (87%) that exhibit significant stimulus-driven activations. Analyzing the HCP fMRI data set in which 170 participants watched 14 movie clips, followed by rest periods - we found robust evidence for a movie-induced adaptation process, revealed in the post-movies rest periods. Within a region, voxels highly activated at the end of movies subsequently reduced their activity below baseline during rest, with the magnitude of this drop proportional to initial activation levels, manifested as a consistent voxel-population inversion effect. Conversely, persistently movie-inactivated voxels exhibited increased activation above baseline. Importantly, this Movie After-Effect (MvAE) enabled successful decoding of the specific rest periods following individual movie clips. Our findings suggest that under naturalistic conditions, cortical neurons dynamically change their gain to achieve homeostatic balance in a process akin to batch instance normalization in artificial neural networks. Whether this ubiquitous MvAE has additional cognitive and memory-related implications remains to be explored.