1 00:00:06,614 --> 00:00:08,163 Every four seconds, 2 00:00:08,163 --> 00:00:09,697 someone is diagnosed with 3 00:00:09,697 --> 00:00:11,582 Alzheimer's disease. 4 00:00:11,582 --> 00:00:13,754 It's the most common cause of dementia, 5 00:00:13,754 --> 00:00:16,613 affecting over 40 million people worldwide, 6 00:00:16,613 --> 00:00:18,665 and yet finding a cure is something that still 7 00:00:19,133 --> 00:00:21,615 eludes researchers today. 8 00:00:21,615 --> 00:00:24,888 Dr. Alois Alzheimer, a German psychiatrist, 9 00:00:24,888 --> 00:00:27,935 first described the symptoms in 1901 10 00:00:27,935 --> 00:00:29,981 when he noticed that a particular hospital patient 11 00:00:30,395 --> 00:00:32,312 had some peculiar problems, 12 00:00:32,312 --> 00:00:34,115 including difficulty sleeping, 13 00:00:34,115 --> 00:00:37,152 disturbed memory, drastic mood changes, 14 00:00:37,485 --> 00:00:39,651 and increasing confusion. 15 00:00:39,651 --> 00:00:41,528 When the patient passed away, 16 00:00:41,528 --> 00:00:43,739 Alzheimer was able to do an autopsy 17 00:00:43,739 --> 00:00:45,743 and test his idea that perhaps 18 00:00:45,779 --> 00:00:48,200 her symptoms were caused by irregularities 19 00:00:48,002 --> 00:00:49,965 in the brain's structure. 20 00:00:50,163 --> 00:00:52,114 What he found beneath the microscope 21 00:00:52,114 --> 00:00:54,587 were visible differences in brain tissue 22 00:00:54,587 --> 00:00:56,781 in the form of misfolded proteins 23 00:00:56,781 --> 00:00:58,115 called plaques, 24 00:00:58,115 --> 00:01:00,548 and neurofibrillary tangles. 25 00:01:00,548 --> 00:01:02,926 Those plaques and tangles work together 26 00:01:02,926 --> 00:01:05,345 to break down the brain's structure. 27 00:01:05,345 --> 00:01:07,137 Plaques arise when another protein 28 00:01:07,137 --> 00:01:09,780 in the fatty membrane surrounding nerve cells 29 00:01:09,078 --> 00:01:11,775 gets sliced up by a particular enzyme, 30 00:01:12,477 --> 00:01:15,062 resulting in beta-amyloid proteins, 31 00:01:15,062 --> 00:01:16,861 which are sticky and have a tendency 32 00:01:16,861 --> 00:01:18,448 to clump together. 33 00:01:18,448 --> 00:01:20,400 That clumping is what forms the things 34 00:01:20,004 --> 00:01:22,135 we know as plaques. 35 00:01:22,531 --> 00:01:24,324 These clumps block signaling 36 00:01:24,324 --> 00:01:25,826 and, therefore, communication 37 00:01:25,826 --> 00:01:28,162 between cells, and also seem to trigger 38 00:01:28,162 --> 00:01:30,698 immune reactions that cause the destruction 39 00:01:30,698 --> 00:01:32,832 of disabled nerve cells. 40 00:01:32,832 --> 00:01:35,614 In Alzheimer's disease, neurofibrillary tangles 41 00:01:35,614 --> 00:01:38,699 are built from a protein known as tau. 42 00:01:38,699 --> 00:01:40,788 The brain's nerve cells contain a network of tubes 43 00:01:41,589 --> 00:01:43,613 that act like a highway for food molecules 44 00:01:43,613 --> 00:01:45,176 among other things. 45 00:01:45,176 --> 00:01:47,719 Usually, the tau protein ensures that these tubes 46 00:01:47,719 --> 00:01:49,975 are straight, allowing molecules 47 00:01:49,975 --> 00:01:51,892 to pass through freely. 48 00:01:51,892 --> 00:01:53,601 But in Alzheimer's disease, 49 00:01:53,601 --> 00:01:57,064 the protein collapses into twisted strands or tangles, 50 00:01:57,064 --> 00:01:58,896 making the tubes disintegrate, 51 00:01:58,896 --> 00:02:01,401 obstructing nutrients from reaching the nerve cell 52 00:02:01,401 --> 00:02:04,029 and leading to cell death. 53 00:02:04,029 --> 00:02:06,365 The destructive pairing of plaques and tangles 54 00:02:06,365 --> 00:02:08,697 starts in a region called the hippocampus, 55 00:02:08,697 --> 00:02:11,116 which is responsible for forming memories. 56 00:02:11,116 --> 00:02:12,829 That's why short-term memory loss 57 00:02:12,829 --> 00:02:15,531 is usually the first symptom of Alzheimer's. 58 00:02:15,531 --> 00:02:17,415 The proteins then progressively invade 59 00:02:17,415 --> 00:02:19,031 other parts of the brain, 60 00:02:19,031 --> 00:02:20,865 creating unique changes that signal 61 00:02:20,865 --> 00:02:23,281 various stages of the disease. 62 00:02:23,281 --> 00:02:24,516 At the front of the brain, 63 00:02:24,516 --> 00:02:28,052 the proteins destroy the ability to process logical thoughts. 64 00:02:28,052 --> 00:02:31,220 Next, they shift to the region that controls emotions, 65 00:02:31,022 --> 00:02:33,359 resulting in erratic mood changes. 66 00:02:33,557 --> 00:02:34,781 At the top of the brain, 67 00:02:34,781 --> 00:02:37,145 they cause paranoia and hallucinations, 68 00:02:37,145 --> 00:02:39,198 and once they reach the brain's rear, 69 00:02:39,198 --> 00:02:41,197 the plaques and tangles work together 70 00:02:41,197 --> 00:02:43,615 to erase the mind's deepest memories. 71 00:02:43,615 --> 00:02:45,236 Eventually the control centers governing 72 00:02:45,236 --> 00:02:48,030 heart rate and breathing are overpowered as well 73 00:02:48,003 --> 00:02:49,799 resulting in death. 74 00:02:49,826 --> 00:02:51,865 The immensely destructive nature of this disease 75 00:02:51,865 --> 00:02:54,864 has inspired many researchers to look for a cure 76 00:02:54,864 --> 00:02:58,616 but currently they're focused on slowing its progression. 77 00:02:58,616 --> 00:03:00,003 One temporary treatment 78 00:03:00,003 --> 00:03:02,630 helps reduce the break down of acetylcholine, 79 00:03:02,063 --> 00:03:04,716 an important chemical messenger in the brain 80 00:03:05,283 --> 00:03:07,802 which is decreased in Alzheimer's patients 81 00:03:07,802 --> 00:03:10,865 due to the death of the nerve cells that make it. 82 00:03:10,865 --> 00:03:13,181 Another possible solution is a vaccine 83 00:03:13,181 --> 00:03:15,642 that trains the body's immune system to attack 84 00:03:15,642 --> 00:03:19,229 beta-amyloid plaques before they can form clumps. 85 00:03:19,229 --> 00:03:22,030 But we still need to find an actual cure. 86 00:03:22,003 --> 00:03:23,078 Alzheimer's disease was discovered 87 00:03:23,078 --> 00:03:24,747 more than a century ago, 88 00:03:25,449 --> 00:03:28,113 and yet still it is not well understood. 89 00:03:28,113 --> 00:03:29,780 Perhaps one day we'll grasp 90 00:03:29,078 --> 00:03:31,994 the exact mechanisms at work behind this threat 91 00:03:32,696 --> 00:03:34,910 and a solution will be unearthed.