• Default mode network – Activates when a person isn’t doing a specific task (think daydreaming about the grocery list) and is connected to the hippocampus—one of the first brain regions affected by Alzheimer’s disease. It’s also where Alzheimer’s and amyloid plaques, a prime suspect for Alzheimer’s disease found around nerve cells, show up in tests.
• Frontoparietal network—Regulates decisions made when a person is completing a task. It also involves memory.
• Salience network—Monitors the external world and stimuli and then decides what deserves attention. It also facilitates switching between networks to optimize performance.

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