[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:06.33,0:00:11.27,Default,,0000,0000,0000,,The vast majority of people \Nwho’ve lost a limb can still feel it—
Dialogue: 0,0:00:11.27,0:00:16.98,Default,,0000,0000,0000,,not as a memory or vague shape,\Nbut in complete lifelike detail.
Dialogue: 0,0:00:16.98,0:00:19.44,Default,,0000,0000,0000,,They can flex their phantom fingers
Dialogue: 0,0:00:19.44,0:00:22.72,Default,,0000,0000,0000,,and sometimes even feel \Nthe chafe of a watchband
Dialogue: 0,0:00:22.72,0:00:25.95,Default,,0000,0000,0000,,or the throb of an ingrown toenail.
Dialogue: 0,0:00:25.95,0:00:27.92,Default,,0000,0000,0000,,And astonishingly enough,
Dialogue: 0,0:00:27.92,0:00:33.46,Default,,0000,0000,0000,,occasionally even people born \Nwithout a limb can feel a phantom.
Dialogue: 0,0:00:33.46,0:00:36.65,Default,,0000,0000,0000,,So what causes phantom limb sensations?
Dialogue: 0,0:00:36.65,0:00:38.69,Default,,0000,0000,0000,,The accuracy of these apparitions
Dialogue: 0,0:00:38.69,0:00:42.36,Default,,0000,0000,0000,,suggests that we have a map \Nof the body in our brains.
Dialogue: 0,0:00:42.36,0:00:43.75,Default,,0000,0000,0000,,And the fact that it’s possible
Dialogue: 0,0:00:43.75,0:00:46.94,Default,,0000,0000,0000,,for someone who’s never had a limb \Nto feel one
Dialogue: 0,0:00:46.94,0:00:51.61,Default,,0000,0000,0000,,implies we are born with at least \Nthe beginnings of this map.
Dialogue: 0,0:00:51.61,0:00:55.17,Default,,0000,0000,0000,,But one thing sets the phantoms\Nthat appear after amputation
Dialogue: 0,0:00:55.17,0:00:58.46,Default,,0000,0000,0000,,apart from their flesh \Nand blood predecessors:
Dialogue: 0,0:00:58.46,0:01:01.59,Default,,0000,0000,0000,,the vast majority of them are painful.
Dialogue: 0,0:01:01.59,0:01:05.45,Default,,0000,0000,0000,,To fully understand phantom limbs \Nand phantom pain,
Dialogue: 0,0:01:05.45,0:01:09.80,Default,,0000,0000,0000,,we have to consider the entire pathway \Nfrom limb to brain.
Dialogue: 0,0:01:09.80,0:01:13.62,Default,,0000,0000,0000,,Our limbs are full of sensory neurons\Nresponsible for everything
Dialogue: 0,0:01:13.62,0:01:16.08,Default,,0000,0000,0000,,from the textures we feel \Nwith our fingertips
Dialogue: 0,0:01:16.08,0:01:20.05,Default,,0000,0000,0000,,to our understanding \Nof where our bodies are in space.
Dialogue: 0,0:01:20.05,0:01:24.34,Default,,0000,0000,0000,,Neural pathways carry this sensory input\Nthrough the spinal cord
Dialogue: 0,0:01:24.34,0:01:26.01,Default,,0000,0000,0000,,and up to the brain.
Dialogue: 0,0:01:26.01,0:01:30.04,Default,,0000,0000,0000,,Since so much of this path \Nlies outside the limb itself,
Dialogue: 0,0:01:30.04,0:01:34.18,Default,,0000,0000,0000,,most of it remains \Nbehind after an amputation.
Dialogue: 0,0:01:34.18,0:01:35.62,Default,,0000,0000,0000,,But the loss of a limb
Dialogue: 0,0:01:35.62,0:01:40.26,Default,,0000,0000,0000,,alters the way signals travel \Nat every step of the pathway.
Dialogue: 0,0:01:40.26,0:01:42.03,Default,,0000,0000,0000,,At the site of an amputation,
Dialogue: 0,0:01:42.03,0:01:46.26,Default,,0000,0000,0000,,severed nerve endings can thicken \Nand become more sensitive,
Dialogue: 0,0:01:46.26,0:01:50.70,Default,,0000,0000,0000,,transmitting distress signals \Neven in response to mild pressure.
Dialogue: 0,0:01:50.70,0:01:52.39,Default,,0000,0000,0000,,Under normal circumstances,
Dialogue: 0,0:01:52.39,0:01:56.99,Default,,0000,0000,0000,,these signals would be curtailed \Nin the dorsal horn of the spinal cord.
Dialogue: 0,0:01:56.99,0:02:00.96,Default,,0000,0000,0000,,For reasons we don’t fully understand,\Nafter an amputation,
Dialogue: 0,0:02:00.96,0:02:05.62,Default,,0000,0000,0000,,there is a loss of this inhibitory\Ncontrol in the dorsal horn,
Dialogue: 0,0:02:05.62,0:02:08.78,Default,,0000,0000,0000,,and signals can intensify.
Dialogue: 0,0:02:08.78,0:02:13.21,Default,,0000,0000,0000,,Once they pass through the spinal cord,\Nsensory signals reach the brain.
Dialogue: 0,0:02:13.21,0:02:17.19,Default,,0000,0000,0000,,There, the somatosensory cortex \Nprocesses them.
Dialogue: 0,0:02:17.19,0:02:20.61,Default,,0000,0000,0000,,The entire body is mapped in this cortex.
Dialogue: 0,0:02:20.61,0:02:23.38,Default,,0000,0000,0000,,Sensitive body parts \Nwith many nerve endings,
Dialogue: 0,0:02:23.38,0:02:25.14,Default,,0000,0000,0000,,like the lips and hands,
Dialogue: 0,0:02:25.14,0:02:27.71,Default,,0000,0000,0000,,are represented by the largest areas.
Dialogue: 0,0:02:27.71,0:02:30.99,Default,,0000,0000,0000,,The cortical homunculus is a model \Nof the human body
Dialogue: 0,0:02:30.99,0:02:36.48,Default,,0000,0000,0000,,with proportions based on the size of each\Nbody part’s representation in the cortex,
Dialogue: 0,0:02:36.48,0:02:41.41,Default,,0000,0000,0000,,The amount of cortex devoted \Nto a specific body part can grow or shrink
Dialogue: 0,0:02:41.41,0:02:46.12,Default,,0000,0000,0000,,based on how much sensory input \Nthe brain receives from that body part.
Dialogue: 0,0:02:46.12,0:02:51.21,Default,,0000,0000,0000,,For example, representation of the left\Nhand is larger in violinists
Dialogue: 0,0:02:51.21,0:02:53.69,Default,,0000,0000,0000,,than in non-violinists.
Dialogue: 0,0:02:53.69,0:02:56.38,Default,,0000,0000,0000,,The brain also increases \Ncortical representation
Dialogue: 0,0:02:56.38,0:02:58.49,Default,,0000,0000,0000,,when a body part is injured
Dialogue: 0,0:02:58.49,0:03:02.26,Default,,0000,0000,0000,,in order to heighten sensations \Nthat alert us to danger.
Dialogue: 0,0:03:02.26,0:03:06.70,Default,,0000,0000,0000,,This increased representation \Ncan lead to phantom pain.
Dialogue: 0,0:03:06.70,0:03:09.62,Default,,0000,0000,0000,,The cortical map is also \Nmost likely responsible
Dialogue: 0,0:03:09.62,0:03:13.22,Default,,0000,0000,0000,,for the feeling of body parts \Nthat are no longer there,
Dialogue: 0,0:03:13.22,0:03:16.50,Default,,0000,0000,0000,,because they still \Nhave representation in the brain.
Dialogue: 0,0:03:16.50,0:03:22.17,Default,,0000,0000,0000,,Over time, this representation may shrink\Nand the phantom limb may shrink with it.
Dialogue: 0,0:03:22.17,0:03:26.76,Default,,0000,0000,0000,,But phantom limb sensations \Ndon’t necessarily disappear on their own.
Dialogue: 0,0:03:26.76,0:03:29.63,Default,,0000,0000,0000,,Treatment for phantom pain \Nusually requires
Dialogue: 0,0:03:29.63,0:03:31.50,Default,,0000,0000,0000,,a combination of physical therapy,
Dialogue: 0,0:03:31.50,0:03:33.30,Default,,0000,0000,0000,,medications for pain management,
Dialogue: 0,0:03:33.30,0:03:34.38,Default,,0000,0000,0000,,prosthetics,
Dialogue: 0,0:03:34.38,0:03:36.05,Default,,0000,0000,0000,,and time.
Dialogue: 0,0:03:36.05,0:03:38.30,Default,,0000,0000,0000,,A technique called mirror box therapy
Dialogue: 0,0:03:38.30,0:03:41.37,Default,,0000,0000,0000,,can be very helpful in developing \Nthe range of motion
Dialogue: 0,0:03:41.37,0:03:43.97,Default,,0000,0000,0000,,and reducing pain in the phantom limb.
Dialogue: 0,0:03:43.97,0:03:48.08,Default,,0000,0000,0000,,The patient places the phantom limb \Ninto a box behind a mirror
Dialogue: 0,0:03:48.08,0:03:50.70,Default,,0000,0000,0000,,and the intact limb \Nin front of the mirror.
Dialogue: 0,0:03:50.70,0:03:53.87,Default,,0000,0000,0000,,This tricks the brain \Ninto seeing the phantom
Dialogue: 0,0:03:53.87,0:03:55.91,Default,,0000,0000,0000,,rather than just feeling it.
Dialogue: 0,0:03:55.91,0:03:59.04,Default,,0000,0000,0000,,Scientists are developing \Nvirtual reality treatments
Dialogue: 0,0:03:59.04,0:04:03.73,Default,,0000,0000,0000,,that make the experience \Nof mirror box therapy even more lifelike.
Dialogue: 0,0:04:03.73,0:04:06.70,Default,,0000,0000,0000,,Prosthetics can also \Ncreate a similar effect—
Dialogue: 0,0:04:06.70,0:04:08.32,Default,,0000,0000,0000,,many patients report pain
Dialogue: 0,0:04:08.32,0:04:11.59,Default,,0000,0000,0000,,primarily when they remove \Ntheir prosthetics at night.
Dialogue: 0,0:04:11.59,0:04:13.80,Default,,0000,0000,0000,,And phantom limbs may in turn
Dialogue: 0,0:04:13.80,0:04:18.73,Default,,0000,0000,0000,,help patients conceptualize\Nprosthetics as extensions of their bodies
Dialogue: 0,0:04:18.73,0:04:21.14,Default,,0000,0000,0000,,and manipulate them intuitively.
Dialogue: 0,0:04:21.14,0:04:24.53,Default,,0000,0000,0000,,There are still many questions \Nabout phantom limbs.
Dialogue: 0,0:04:24.53,0:04:27.69,Default,,0000,0000,0000,,We don’t know why some amputees\Nescape the pain
Dialogue: 0,0:04:27.69,0:04:30.01,Default,,0000,0000,0000,,typically associated \Nwith these apparitions,
Dialogue: 0,0:04:30.01,0:04:32.49,Default,,0000,0000,0000,,or why some don’t have phantoms at all.
Dialogue: 0,0:04:32.49,0:04:35.15,Default,,0000,0000,0000,,And further research into phantom limbs
Dialogue: 0,0:04:35.15,0:04:38.53,Default,,0000,0000,0000,,isn’t just applicable to the people \Nwho experience them.
Dialogue: 0,0:04:38.53,0:04:40.80,Default,,0000,0000,0000,,A deeper understanding \Nof these apparitions
Dialogue: 0,0:04:40.80,0:04:45.03,Default,,0000,0000,0000,,will give us insight into the work\Nour brains do every day
Dialogue: 0,0:04:45.03,0:04:47.62,Default,,0000,0000,0000,,to build the world as we perceive it.
Dialogue: 0,0:04:47.62,0:04:49.27,Default,,0000,0000,0000,,They’re an important reminder
Dialogue: 0,0:04:49.27,0:04:53.41,Default,,0000,0000,0000,,that the realities we experience are,\Nin fact, subjective.