Sleep and learning — the consolidation of knowledge

During sleep — particularly during slow-wave and REM phases — the brain transfers the day's learning from the fragile hippocampal buffer into more stable cortical storage, a process that cannot be adequately replicated while awake. Sleep deprivation does not merely impair performance; it directly disrupts the consolidation process, meaning that learning done without adequate subsequent sleep is learning that will not persist. The Sutras' recognition of nidrā as one of the five categories of citta-vṛtti — equal in importance to waking experience — anticipates what neuroscience has confirmed.