Neuroimaging has advanced our understanding of human psychology using reductionist stimuli that often do not resemble information the brain naturally encounters. It has improved our understanding of the network organization of the brain mostly through analyses of 'resting-state' data for which the functions of networks cannot be verifiably labelled. We make a ' Naturalistic Neuroimaging Database ' (NNDb v1.0) publically available to allow for a more complete understanding of the brain under more ecological conditions during which networks can be labelled. Eighty-six participants underwent behavioural testing and watched one of 10 full-length movies while functional magnetic resonance imaging was acquired. Resulting timeseries data are shown to be of high quality, with good signal-to-noise ratio, few outliers and low movement. Data-driven functional analyses provide further evidence of data quality. They also demonstrate accurate timeseries/movie alignment and how movie annotations might be used to label networks. The NNDb can be used to answer questions previously unaddressed with standard neuroimaging approaches, progressing our knowledge of how the brain works in the real world. judgement about these stimuli, with a corresponding button response (e.g., a '2AFC' indicating whether a sound is 'ba' or 'pa').The result of relying on unnatural stimuli and tasks is that our neurobiological understanding derived from task-fMRI may not be representative of how the brain processes information. This is perhaps why fMRI test-retest reliability is low 6,7 . Indeed, more ecologically valid stimuli like movies have higher reliability than resting-or task-fMRI. This is not only because these enhance activity, decrease head movement and improve participant compliance 8,9 . Rather, natural stimuli have higher test-retest reliability mostly because they are more representative of operations the brain normally performs and provide more constraints on processing 10-15 .
Resting-fMRIThere has arguably been a significant increase in our understanding of the network organization of the human brain because of the public availability of large resting-fMRI datasets, analysed with dynamic and other functional connectivity methods 16,17 . These include the INDI '1000 Functional Connectomes Project' 18 , 'Human Connectome Project' (HCP) 19 and UK Biobank 20 . Collectively, these datasets have more than 6,500 participants sitting in a scanner 'resting'. Resulting resting-state networks are said to represent the 'intrinsic' network architecture of the brain, i.e., networks that are present even in the absence of exogenous tasks. These networks are often claimed to be modular and to constrain the task-based architecture of the brain 21 .As with task-fMRI, one might ask how representative resting-state networks are given that participants are anything but at rest. They are switching between fixating on a cross-hair, trying to stay awake, visualising, trying not to think and thinking through inner speech 21,22 . Some of these are not particular...