Digital ACT Reading Practice Question #1598

According to the passage, what is the primary neurobiological function of sleep spindles during NREM sleep? Passage Excerpt (Natural Science): For decades, neurobiologists viewed sleep as a passive state of metabolic quiescence. Modern electroencephalography (EEG) has overturned this paradigm, revealing that nocturnal brain activity is intensely dynamic. During non-rapid eye movement (NREM) slow-wave sleep, high-amplitude, low-frequency delta oscillations (0.5–4 Hz) coordinate with brief bursts of rhythmic thalamocortical activity known as 'sleep spindles' (11–16 Hz). Neuroimaging indicates that this synchronized dialogue between the hippocampus and the neocortex drives memory consolidation. Ephemeral, daytime memory traces initially stored in the fragile hippocampus are systematically transferred into the durable, distributed architecture of the neocortex. Sleep spindles act as neurochemical gatekeepers, shielding the cortex from sensory interruptions while synaptic connections are selectively strengthened and pruned.