[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:06.66,0:00:10.79,Default,,0000,0000,0000,,You probably don't need to be told \Nhow important your brain is.
Dialogue: 0,0:00:10.79,0:00:13.17,Default,,0000,0000,0000,,After all, every single thing \Nyou experience,
Dialogue: 0,0:00:13.17,0:00:14.71,Default,,0000,0000,0000,,your thoughts and your actions,
Dialogue: 0,0:00:14.71,0:00:17.12,Default,,0000,0000,0000,,your perceptions and your memories
Dialogue: 0,0:00:17.12,0:00:20.35,Default,,0000,0000,0000,,are processed here \Nin your body's control center.
Dialogue: 0,0:00:20.35,0:00:23.94,Default,,0000,0000,0000,,But if this already seems like a lot\Nfor a single organ to handle,
Dialogue: 0,0:00:23.94,0:00:28.04,Default,,0000,0000,0000,,it's actually only a small \Npart of what the brain does.
Dialogue: 0,0:00:28.04,0:00:31.21,Default,,0000,0000,0000,,Most of its activities are ones \Nyou'd never be aware of,
Dialogue: 0,0:00:31.21,0:00:33.91,Default,,0000,0000,0000,,unless they suddenly stopped.
Dialogue: 0,0:00:33.91,0:00:36.14,Default,,0000,0000,0000,,The brain is made up \Nof billions of neurons,
Dialogue: 0,0:00:36.14,0:00:38.21,Default,,0000,0000,0000,,and trillions of connections.
Dialogue: 0,0:00:38.21,0:00:41.36,Default,,0000,0000,0000,,Neurons can be activated \Nby specific stimuli or thoughts,
Dialogue: 0,0:00:41.36,0:00:44.75,Default,,0000,0000,0000,,but they are also often \Nspontaneously active.
Dialogue: 0,0:00:44.75,0:00:47.26,Default,,0000,0000,0000,,Some fire cyclically in a set pattern.
Dialogue: 0,0:00:47.26,0:00:51.64,Default,,0000,0000,0000,,Others fire rapidly in short bursts \Nbefore switching off,
Dialogue: 0,0:00:51.64,0:00:54.01,Default,,0000,0000,0000,,or remain quiet for long periods
Dialogue: 0,0:00:54.01,0:01:00.05,Default,,0000,0000,0000,,until thousands of inputs from other \Nneurons line up in just the right way.
Dialogue: 0,0:01:00.05,0:01:01.22,Default,,0000,0000,0000,,On a large scale,
Dialogue: 0,0:01:01.22,0:01:05.56,Default,,0000,0000,0000,,this results in elaborate rhythms \Nof internally generated brain activity,
Dialogue: 0,0:01:05.56,0:01:07.40,Default,,0000,0000,0000,,humming quietly in the background
Dialogue: 0,0:01:07.40,0:01:09.19,Default,,0000,0000,0000,,whether we're awake, asleep,
Dialogue: 0,0:01:09.19,0:01:12.49,Default,,0000,0000,0000,,or trying not to think \Nabout anything at all.
Dialogue: 0,0:01:12.49,0:01:15.04,Default,,0000,0000,0000,,And these spontaneously \Noccurring brain functions
Dialogue: 0,0:01:15.04,0:01:20.13,Default,,0000,0000,0000,,form the foundation upon which\Nall other brain functions rely.
Dialogue: 0,0:01:20.13,0:01:23.58,Default,,0000,0000,0000,,The most crucial of these automatically\Noccurring activities
Dialogue: 0,0:01:23.58,0:01:25.83,Default,,0000,0000,0000,,are the ones that keep us alive.
Dialogue: 0,0:01:25.83,0:01:28.75,Default,,0000,0000,0000,,For example, while you've been\Npaying attention to this video
Dialogue: 0,0:01:28.75,0:01:32.66,Default,,0000,0000,0000,,spontaneous activity in your brain\Nhas been maintaining your breathing
Dialogue: 0,0:01:32.66,0:01:38.05,Default,,0000,0000,0000,,at 12 to 16 breaths a minute,\Nmaking sure that you don't suffocate.
Dialogue: 0,0:01:38.05,0:01:39.56,Default,,0000,0000,0000,,Without any conscious effort,
Dialogue: 0,0:01:39.56,0:01:43.24,Default,,0000,0000,0000,,signals from parts of your brainstem\Nare sent through the spinal cord
Dialogue: 0,0:01:43.24,0:01:45.77,Default,,0000,0000,0000,,to the muscles that inflate your lungs,
Dialogue: 0,0:01:45.77,0:01:50.45,Default,,0000,0000,0000,,making them expand and contract,\Nwhether or not you're paying attention.
Dialogue: 0,0:01:50.45,0:01:54.60,Default,,0000,0000,0000,,The neuronal circuits underlying such \Nrhythmic spontaneous activity
Dialogue: 0,0:01:54.60,0:01:57.61,Default,,0000,0000,0000,,are called central pattern generators,
Dialogue: 0,0:01:57.61,0:02:00.44,Default,,0000,0000,0000,,and control many \Nsimple repetitive behaviors,
Dialogue: 0,0:02:00.44,0:02:01.31,Default,,0000,0000,0000,,like breathing,
Dialogue: 0,0:02:01.31,0:02:02.40,Default,,0000,0000,0000,,walking,
Dialogue: 0,0:02:02.40,0:02:03.62,Default,,0000,0000,0000,,and swallowing.
Dialogue: 0,0:02:03.62,0:02:07.73,Default,,0000,0000,0000,,Ongoing neural activity also underlies\Nour sensory perception.
Dialogue: 0,0:02:07.73,0:02:08.91,Default,,0000,0000,0000,,It may seem
Dialogue: 0,0:02:08.91,0:02:12.08,Default,,0000,0000,0000,,that the neurons in your retina\Nthat translate light into neural signals
Dialogue: 0,0:02:12.08,0:02:14.22,Default,,0000,0000,0000,,would remain quiet in the dark,
Dialogue: 0,0:02:14.22,0:02:15.26,Default,,0000,0000,0000,,but in fact,
Dialogue: 0,0:02:15.26,0:02:18.57,Default,,0000,0000,0000,,the retinal ganglion cells \Nthat communicate with the brain
Dialogue: 0,0:02:18.57,0:02:20.35,Default,,0000,0000,0000,,are always active.
Dialogue: 0,0:02:20.35,0:02:25.33,Default,,0000,0000,0000,,And the signals they send are increases \Nand decreases in the rate of activity,
Dialogue: 0,0:02:25.33,0:02:27.33,Default,,0000,0000,0000,,rather than separate bursts.
Dialogue: 0,0:02:27.33,0:02:31.65,Default,,0000,0000,0000,,So at every level, our nervous system\Nis teeming with spontaneous activity
Dialogue: 0,0:02:31.65,0:02:36.25,Default,,0000,0000,0000,,that helps it interpret and respond\Nto any signals it might receive.
Dialogue: 0,0:02:36.25,0:02:40.88,Default,,0000,0000,0000,,And our brain's autopilot isn't just \Nlimited to our basic biological functions.
Dialogue: 0,0:02:40.88,0:02:42.52,Default,,0000,0000,0000,,Have you ever been on the way home,
Dialogue: 0,0:02:42.52,0:02:44.75,Default,,0000,0000,0000,,started thinking \Nabout what's for dinner,
Dialogue: 0,0:02:44.75,0:02:48.38,Default,,0000,0000,0000,,and then realized you don't remember\Nwalking for the past five minutes?
Dialogue: 0,0:02:48.38,0:02:50.91,Default,,0000,0000,0000,,While we don't understand all the details,
Dialogue: 0,0:02:50.91,0:02:54.66,Default,,0000,0000,0000,,we do know that the ongoing activity\Nin multiple parts of your brain
Dialogue: 0,0:02:54.66,0:02:58.52,Default,,0000,0000,0000,,is somehow able to coordinate \Nwhat is actually a complex task
Dialogue: 0,0:02:58.52,0:03:02.12,Default,,0000,0000,0000,,involving both cognitive \Nand motor functions,
Dialogue: 0,0:03:02.12,0:03:04.68,Default,,0000,0000,0000,,guiding you down the right path\Nand moving your legs
Dialogue: 0,0:03:04.68,0:03:06.71,Default,,0000,0000,0000,,while you're getting dinner figured out.
Dialogue: 0,0:03:06.71,0:03:10.07,Default,,0000,0000,0000,,But perhaps the most interesting thing\Nabout spontaneous brain function
Dialogue: 0,0:03:10.07,0:03:12.58,Default,,0000,0000,0000,,is its involvement in one \Nof the most mysterious
Dialogue: 0,0:03:12.58,0:03:16.92,Default,,0000,0000,0000,,and poorly understood phenomena\Nof our bodies: sleep.
Dialogue: 0,0:03:16.92,0:03:20.04,Default,,0000,0000,0000,,You may shut down \Nand become inactive at night,
Dialogue: 0,0:03:20.04,0:03:22.24,Default,,0000,0000,0000,,but your brain doesn't.
Dialogue: 0,0:03:22.24,0:03:23.29,Default,,0000,0000,0000,,While you sleep,
Dialogue: 0,0:03:23.29,0:03:28.26,Default,,0000,0000,0000,,ongoing spontaneous activity gradually \Nbecomes more and more synchronized,
Dialogue: 0,0:03:28.26,0:03:32.62,Default,,0000,0000,0000,,eventually developing into large, \Nrhythmic neural oscillations
Dialogue: 0,0:03:32.62,0:03:34.93,Default,,0000,0000,0000,,that envelop your brain.
Dialogue: 0,0:03:34.93,0:03:38.04,Default,,0000,0000,0000,,This transition to the more \Norganized rhythms of sleep
Dialogue: 0,0:03:38.04,0:03:42.88,Default,,0000,0000,0000,,starts with small clusters of neurons\Ntucked in the hypothalamus.
Dialogue: 0,0:03:42.88,0:03:44.64,Default,,0000,0000,0000,,Despite their small number,\N
Dialogue: 0,0:03:44.64,0:03:46.46,Default,,0000,0000,0000,,these neurons have a huge effect
Dialogue: 0,0:03:46.46,0:03:51.10,Default,,0000,0000,0000,,in turning off brainstem regions\Nthat normally keep you awake and alert,
Dialogue: 0,0:03:51.10,0:03:53.48,Default,,0000,0000,0000,,letting other parts, \Nlike the cortex and thalamus,
Dialogue: 0,0:03:53.48,0:03:57.23,Default,,0000,0000,0000,,slowly slip into their \Nown default rhythms.
Dialogue: 0,0:03:57.23,0:03:58.74,Default,,0000,0000,0000,,The deeper we fall into sleep,
Dialogue: 0,0:03:58.74,0:04:02.73,Default,,0000,0000,0000,,the slower and more synchronized\Nthis rhythm becomes,
Dialogue: 0,0:04:02.73,0:04:09.30,Default,,0000,0000,0000,,with the deepest stages dominated by large\Namplitude, low frequency delta waves.
Dialogue: 0,0:04:09.30,0:04:12.56,Default,,0000,0000,0000,,But surprisingly, in the middle \Nof this slow wave sleep,
Dialogue: 0,0:04:12.56,0:04:15.56,Default,,0000,0000,0000,,the brain's synchronized \Nspontaneous activity
Dialogue: 0,0:04:15.56,0:04:19.13,Default,,0000,0000,0000,,repeatedly transitions\Ninto the sort of varied bursts
Dialogue: 0,0:04:19.13,0:04:21.42,Default,,0000,0000,0000,,that occur when we're wide awake.
Dialogue: 0,0:04:21.42,0:04:24.24,Default,,0000,0000,0000,,This is the sleep stage\Nknown as REM sleep,
Dialogue: 0,0:04:24.24,0:04:28.51,Default,,0000,0000,0000,,where our eyes move rapidly \Nback and forth as we dream.
Dialogue: 0,0:04:28.51,0:04:33.46,Default,,0000,0000,0000,,Neuroscientists are still trying to answer\Nmany fundamental questions about sleep,
Dialogue: 0,0:04:33.46,0:04:36.52,Default,,0000,0000,0000,,such as its role in rejuvenating\Ncognitive capacity,
Dialogue: 0,0:04:36.52,0:04:38.36,Default,,0000,0000,0000,,cellular homeostasis,
Dialogue: 0,0:04:38.36,0:04:40.18,Default,,0000,0000,0000,,and strengthening memory.
Dialogue: 0,0:04:40.18,0:04:41.95,Default,,0000,0000,0000,,And more broadly, they are exploring
Dialogue: 0,0:04:41.95,0:04:46.69,Default,,0000,0000,0000,,how it is that brain can accomplish \Nsuch important and complex tasks,
Dialogue: 0,0:04:46.69,0:04:51.14,Default,,0000,0000,0000,,such as driving, or even breathing,\Nwithout our awareness.
Dialogue: 0,0:04:51.14,0:04:53.22,Default,,0000,0000,0000,,But for now, until we are better able
Dialogue: 0,0:04:53.22,0:04:57.07,Default,,0000,0000,0000,,to understand the inner workings\Nof their spontaneous functioning,
Dialogue: 0,0:04:57.07,0:05:00.15,Default,,0000,0000,0000,,we need to give our brains credit\Nfor being much smarter
Dialogue: 0,0:05:00.15,0:05:02.28,Default,,0000,0000,0000,,than we ourselves are.