0:02 my name is Steve Lewis burger I'm
0:04 neuroscientist I'm the chair of the
0:05 Department of Neurobiology at Duke
0:12 University the vestibular system is a
0:17 set of sensors inside our ear near were
0:20 we in in in the temporal bone and they
0:23 are exquisitely sensitive to our motion
0:26 through space and our position with
0:29 respect to gravity so if I tilt my head
0:31 this way those sensors indicate that my
0:33 head is tilted to the left if I turn my
0:35 head like that those sensors indicate
0:38 that I turned my head to the right it's
0:39 important for us to be exquisitely aware
0:42 of our position in space and if you
0:45 think about if you slip on the ice or
0:46 trip over a step when you're climbing
0:49 the very first thing that happens is you
0:52 put out your hand to try to prevent
0:54 yourself from falling and hitting your
0:57 face and that's driven by the vestibular
0:59 system it's sensitive to when you start
1:02 to fall and it immediately with very
1:05 after very short times on the orders of
1:09 fractions of a second it causes your
1:11 motor system to take actions that will
1:14 rescue you from serious damage the
1:18 primary sensory cell is a hair cell and
1:20 it basically is a cell that has little
1:22 cilia sticking out of it and the way it
1:26 works is that if the cilia Bend then the
1:27 electrical potential of the cell changes
1:32 and that creates that that transforms a
1:35 mechanical signal into an electrical
1:36 signal and the electrical signals are
1:40 the currency of the brain now different
1:43 parts of the vestibular system use those
1:45 hair cells in different ways and so
1:47 there's a simple mechanical system
1:50 that's a tube like a doughnut and it has
1:52 the hair is sticking out into it so that
1:55 when you turn the tube the hairs this
1:57 fluid inside that tube deflects the
1:59 hairs and so that's how we're sensitive
2:04 to our head turns and then the other two
2:06 organs are quote their two organs called
2:07 the otolith organs
2:09 they basically have the hair sticking
2:12 out into a rock and if I tilt my head
2:16 back like that the rock slides back it
2:18 pulls on the hairs and it takes a
2:20 mechanical event turns it into an
2:22 electrical signal so that the brain can
2:31 we know that motion sickness is caused
2:33 when where your vestibular system is
2:35 telling your brain is different from
2:37 what your visual system is telling your
2:43 brain we do not know exactly how that
2:46 works and we don't even know why we
2:49 would have motion sickness there are
2:52 some just-so stories we do know that the
2:54 middle midline of the stimulus
2:55 cerebellum is important for motion
2:58 sickness but I guess I would point out
3:01 that I get motion sick when I'm on a
3:05 boat and when you're on a boat and
3:07 you're in the waves and you're rolling
3:10 back and forth very slowly that seems to
3:13 be the kind of stimulus that when it
3:15 doesn't match with what you're seeing
3:18 creates the sensation of motion sickness
3:20 and nausea and you think about our
3:23 astronauts it was not widely publicized
3:25 but our astronauts were motion sick for
3:28 the first at least three to five days
3:31 that they were in orbit because without
3:35 gravity the system that senses where
3:37 gravity is and your head position in
3:40 space no longer functions and so they
3:43 had completely lost that part of the
3:44 vestibular input that tells them whether
3:47 they're tilting their head or whether
3:48 they're looking whether whether whether
3:51 you know that's down or that's down and
3:54 so there's a complete loss of the
3:57 matching of what they're seeing and what
3:58 they're feeling from their their
4:00 vestibular system so they were they were
4:09 vertigo is when your vestibular system
4:12 isn't is giving you a wrong signal and
4:14 so it's telling you that you're moving
4:16 when you're not and so you might get the
4:18 sensation that you're just turning
4:20 around in a circle or you might get the
4:21 sensation that you're falling this way
4:26 and that comes from you know a part of
4:29 the vestibular system being broken [Music]
4:36 it's an incredibly simple reflex
4:40 behavior that is really important to us
4:44 and many animals so the job of the
4:48 visual system is to process images so
4:51 that you can see what's happening and if
4:55 images slip of move a little bit and the
4:58 eye doesn't move to track them then they
5:00 slip across the retina and we're not
5:01 capable of processing and processing
5:04 them with nearly the same acuity and so
5:08 the vestibular ocular reflex is a reflex
5:11 that uses our head turns to guide our
5:13 movements and if I turn my head back and
5:16 forth like this my eyes keep looking
5:18 directly at you and that's that would
5:20 happen if I had closed my eyes and we're
5:20 in the dark
5:22 that's the vestibular ocular reflex
5:25 making sure that my eyes remain sort of
5:28 like gyroscopically stabilized so that
5:32 even as I move my head around the place
5:34 I'm looking is nice and stable and so
5:35 the images that are coming from the
5:37 external world don't slip across my
5:40 retina and I have a good vision
5:42 I'm Steeve less burger and I'm a neuroscientist
5:50 you [Music]
