therapist in Shanghai, Zheng Wang worked with people recovering from strokes after their brains had been damaged by oxygen deprivation. They usually followed a predictable recovery pattern, making lots of progress over the first few visits, then hitting a wall. Patients asked when they’d finally feel normal, and Wang told them that they’d get better with time. “But actually,” he remembers, “I knew from the bottom of my heart that they wouldn’t improve much, no matter how hard we tried.
For its relatively small size, the brain consumes a ridiculous amount of power: 20 to 30 percent of the body’s energy at rest. To fuel all of its neurons, the brain depends on oxygen. When someone has a stroke or a head injury, the flow of oxygenated blood to the brain gets disrupted. Starved of oxygen, the brain tissue is damaged, leading to a host of problems with memory, speech, strength, and motor control.