Neuropsychiatric disorders are extremely common, severe, and disabling conditions. In the field of psychiatry, they notably include schizophrenia, mood disorders (depressive and bipolar disorders), autism spectrum or neurodevelopmental disorders, obsessive-compulsive disorder, eating disorders, and personality disorders. In the field of neurology, one can cite neurodegenerative diseases (such as Alzheimer's disease, but also frontotemporal dementia or Parkinson's disease, which often represent frequent and challenging differential diagnoses of psychiatric disorders), focal neurological lesions (notably strokes and tumors), or epilepsy. Cognitive impairments are present in nearly all neuropsychiatric disorders and contribute significantly to disability. While impairments in working memory and attention, executive functions, and social cognition have been relatively well studied, other cognitive domains remain largely unexplored in these populations. This is particularly the case for various aspects of motivation, metacognition, conscious access, or causal (Bayesian) inference. Although these domains likely play an important role in prognosis, no consensus currently exists regarding the methods for evaluating these functions. The main objective of this study is to define a multidimensional, transdiagnostic atlas of high-level cognitive impairments-both specific and shared-across severe psychiatric disorders (notably schizophrenia, depressive disorder, bipolar disorder, autism spectrum or neurodevelopmental disorders, and obsessive-compulsive disorder) and neurological disorders (notably neurodegenerative diseases, focal neurological lesions, and epilepsy), by comparing them to healthy volunteers. The investigators also aim to investigate the progression of cognitive impairments over time, across different phases of illness (symptom stabilization or exacerbation) or therapeutic intervention, through longitudinal follow-up of patients being monitored within the recruiting center. Finally, in a more exploratory manner, the investigators aim to investigate the neural correlates of the identified cognitive impairments.