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PROFESSOR: A little more
about the hindbrain.

9
00:00:27,740 --> 00:00:33,600
I want to talk about the
changes that sort of distorted

10
00:00:33,600 --> 00:00:38,720
that simple picture of
the embryonic hindbrain.

11
00:00:38,720 --> 00:00:41,550
We know it becomes a lot
more complicated looking

12
00:00:41,550 --> 00:00:45,000
in the adult, but
there's also this idea

13
00:00:45,000 --> 00:00:48,370
of changes in relative
size of parts.

14
00:00:48,370 --> 00:00:51,250
And more than that,
there are migrations

15
00:00:51,250 --> 00:00:54,670
of cells from the other plate
that form the cerebellum

16
00:00:54,670 --> 00:00:57,610
and really distort things.

17
00:00:57,610 --> 00:01:00,525
And we talked before about
some of these changes

18
00:01:00,525 --> 00:01:02,790
that you see in
specialized creatures,

19
00:01:02,790 --> 00:01:07,920
like these fish
specialized for taste

20
00:01:07,920 --> 00:01:10,790
like the buffalo
fish and the catfish,

21
00:01:10,790 --> 00:01:14,660
the catfish that tastes
with his whole body.

22
00:01:14,660 --> 00:01:18,260
And then the huge
cerebellum develops

23
00:01:18,260 --> 00:01:22,330
in some of the electric fish,
animals with electroreception.

24
00:01:26,387 --> 00:01:30,170
But we want to talk
now about cerebellum.

25
00:01:30,170 --> 00:01:33,604
So first of all, what's the
meaning of the word pons?

26
00:01:37,400 --> 00:01:42,920
And what's the major input
and output of the pons?

27
00:01:42,920 --> 00:01:43,610
Where is it?

28
00:01:46,380 --> 00:01:49,230
In the rostral
hindbrain, what part?

29
00:01:53,960 --> 00:01:56,680
Remember what pons means?

30
00:01:56,680 --> 00:01:57,430
It means bridge.

31
00:02:02,265 --> 00:02:04,190
Why do they call it a bridge?

32
00:02:04,190 --> 00:02:07,900
Well, if you look at the
brain from the ventral side,

33
00:02:07,900 --> 00:02:09,860
it's a really obvious structure.

34
00:02:09,860 --> 00:02:13,880
It's wider than the
rest of the hindbrain.

35
00:02:13,880 --> 00:02:17,736
It's way up at the top of the
rostral part of the hindbrain.

36
00:02:17,736 --> 00:02:20,065
It's white because
of myelinated fibers.

37
00:02:22,940 --> 00:02:26,340
What are all those fibers doing?

38
00:02:26,340 --> 00:02:29,250
There's a lot of cells there,
and there's a lot of fibers.

39
00:02:29,250 --> 00:02:34,463
The cells we call the pontine
gray, the pontine gray matter.

40
00:02:40,380 --> 00:02:45,082
And it projects to what?

41
00:02:45,082 --> 00:02:45,955
The cerebellum.

42
00:02:48,860 --> 00:02:53,272
So it gets very big in
animals with a big cerebellum.

43
00:02:53,272 --> 00:02:55,355
Well, what is its major input?

44
00:02:59,160 --> 00:03:03,210
I showed it once
in this picture.

45
00:03:06,990 --> 00:03:08,870
This is a picture
that was originally

46
00:03:08,870 --> 00:03:12,080
of the primitive brain, and
then I added the neocortex to it

47
00:03:12,080 --> 00:03:16,320
to show some of the
long pathways going up

48
00:03:16,320 --> 00:03:21,240
this neocortex, and then in this
one coming down from neocortex.

49
00:03:21,240 --> 00:03:26,310
And I'm showing axons
here that generally go on

50
00:03:26,310 --> 00:03:31,301
into the spinal cord,
but they have collaterals

51
00:03:31,301 --> 00:03:33,267
that terminate
there in the pons.

52
00:03:33,267 --> 00:03:37,110
And you can see here what
the output of the pons is.

53
00:03:39,822 --> 00:03:41,820
It goes to the
cerebellar cortex.

54
00:03:50,360 --> 00:03:52,350
So that's the
answer to number 16.

55
00:04:00,890 --> 00:04:04,120
If you wanted to give a general
answer to that next question,

56
00:04:04,120 --> 00:04:07,500
what causes
quantitative distortions

57
00:04:07,500 --> 00:04:09,930
of the basic structural
layout of the hindbrain?

58
00:04:13,910 --> 00:04:16,005
What's the major
distortion that occurs

59
00:04:16,005 --> 00:04:17,879
in the development of
the hindbrain of humans

60
00:04:17,879 --> 00:04:20,649
and other primates?

61
00:04:20,649 --> 00:04:24,490
And that's mainly what I
want to talk about here.

62
00:04:24,490 --> 00:04:31,310
The distortion has to do
with the size of structures.

63
00:04:31,310 --> 00:04:34,530
Just like you saw the
hindbrain distortions caused

64
00:04:34,530 --> 00:04:39,750
by these fish with a very
specialized taste input.

65
00:04:39,750 --> 00:04:44,590
What were the cell groups that
grew so much, became so big

66
00:04:44,590 --> 00:04:50,810
and distorted the brain stem
in those animals like this?

67
00:04:50,810 --> 00:04:53,540
That's a hindbrain
distortion, yet it's

68
00:04:53,540 --> 00:04:57,440
become the biggest
part of the brain.

69
00:04:57,440 --> 00:04:58,520
What's the cell group?

70
00:05:01,040 --> 00:05:04,950
What kind of neuron are they?

71
00:05:04,950 --> 00:05:05,538
Sorry?

72
00:05:05,538 --> 00:05:06,760
AUDIENCE: Gustatory.

73
00:05:06,760 --> 00:05:08,550
PROFESSOR: Gustatory,
yes-- taste.

74
00:05:08,550 --> 00:05:11,720
They have specialized
taste, so a lot of them

75
00:05:11,720 --> 00:05:16,810
must be secondary sensory
cells representing taste.

76
00:05:16,810 --> 00:05:21,000
Now, there are other cells in
that lobe too, because they

77
00:05:21,000 --> 00:05:27,830
actually in their specialized
taste organ in the palate,

78
00:05:27,830 --> 00:05:31,730
way in the back of
the throat, they also

79
00:05:31,730 --> 00:05:36,230
have some contractile
organs there,

80
00:05:36,230 --> 00:05:38,430
so that it has a
motor component that's

81
00:05:38,430 --> 00:05:40,080
included in that huge lobe.

82
00:05:45,110 --> 00:05:45,610
OK.

83
00:05:45,610 --> 00:05:57,000
So why is that the cerebellum
gets so large in the primates?

84
00:05:57,000 --> 00:06:01,860
It has to do with a
very large neocortex.

85
00:06:01,860 --> 00:06:07,292
The neocortex seems
to need a cerebellum

86
00:06:07,292 --> 00:06:10,040
to coordinate its output.

87
00:06:10,040 --> 00:06:14,950
For one thing, output isn't
controlled just by neocortex.

88
00:06:14,950 --> 00:06:17,960
It's controlled
by sending inputs

89
00:06:17,960 --> 00:06:22,770
that also go the cerebellum--
mainly proprioceptive, but also

90
00:06:22,770 --> 00:06:31,810
somatosensory and visual,
even some auditory input.

91
00:06:31,810 --> 00:06:35,140
So all these different senses
with slightly different timing

92
00:06:35,140 --> 00:06:38,010
getting there have to be
adjusted and coordinated

93
00:06:38,010 --> 00:06:41,460
so they can get to the
output at the right time,

94
00:06:41,460 --> 00:06:44,000
and that's what the
cerebellum is largely about.

95
00:06:48,090 --> 00:06:51,295
That's not what most
neuroscience classes will teach

96
00:06:51,295 --> 00:06:54,770
you, but that's
what I'm teaching.

97
00:06:54,770 --> 00:06:58,400
I have to see why
that appeared, why

98
00:06:58,400 --> 00:07:01,980
it was so important
throughout development.

99
00:07:01,980 --> 00:07:02,929
Yeah?

100
00:07:02,929 --> 00:07:03,845
AUDIENCE: [INAUDIBLE].

101
00:07:14,594 --> 00:07:16,010
PROFESSOR: That's
a good question.

102
00:07:16,010 --> 00:07:18,760
Is there a correlation
between proprioceptive

103
00:07:18,760 --> 00:07:21,800
input-- you mean in
quantitative terms, the amount

104
00:07:21,800 --> 00:07:23,520
of proprioception,
the amount of it?

105
00:07:23,520 --> 00:07:26,240
Well, you could look
at vestibular input

106
00:07:26,240 --> 00:07:29,370
as a kind of proprioception.

107
00:07:29,370 --> 00:07:32,950
It's affected by our
movements all the time.

108
00:07:32,950 --> 00:07:37,020
It's giving us feedback on our
movement, just like feedback

109
00:07:37,020 --> 00:07:42,050
from the joints, feedback
from the muscles.

110
00:07:42,050 --> 00:07:45,220
They all give feedback,
monitoring our movements.

111
00:07:49,280 --> 00:07:52,230
So I would expect
some correlation.

112
00:07:52,230 --> 00:07:55,240
But it's interesting that the
cerebellum develops very early,

113
00:07:55,240 --> 00:08:01,560
and it develops as basically
a vestibular organ.

114
00:08:01,560 --> 00:08:06,420
And then later it acquires
all these other inputs.

115
00:08:06,420 --> 00:08:09,910
As they expanded,
they all seem to want

116
00:08:09,910 --> 00:08:13,480
to get to the cerebellum as
well as into the forebrain.

117
00:08:18,280 --> 00:08:23,440
Then I introduce another
term in question 18 here.

118
00:08:23,440 --> 00:08:26,090
What is the role
of the rhombic lip?

119
00:08:26,090 --> 00:08:28,884
It's a structure seen
during the development

120
00:08:28,884 --> 00:08:29,925
of the rostral hindbrain.

121
00:08:33,250 --> 00:08:35,600
You remember what
the rhombic lip is?

122
00:08:35,600 --> 00:08:37,610
Did you read the chapter?

123
00:08:37,610 --> 00:08:40,720
I realize you're getting
some of these concepts

124
00:08:40,720 --> 00:08:42,820
for the first time.

125
00:08:42,820 --> 00:08:45,990
We're going to talk a lot
more about development

126
00:08:45,990 --> 00:08:50,770
in a couple of the later
sections of the class.

127
00:08:50,770 --> 00:08:54,350
One coming up pretty soon, where
we'll talk about axon growth.

128
00:08:54,350 --> 00:08:57,800
But here we're talking
about-- and we'll

129
00:08:57,800 --> 00:09:00,790
talk about this actually
in the very next class when

130
00:09:00,790 --> 00:09:01,790
we talk about forebrain.

131
00:09:05,370 --> 00:09:08,130
So what is the rhombic lip?

132
00:09:08,130 --> 00:09:09,655
It's a transient structure.

133
00:09:12,260 --> 00:09:19,420
There are very large
numbers of neuroblasts there

134
00:09:19,420 --> 00:09:25,989
that migrate from that
region into the cerebellum,

135
00:09:25,989 --> 00:09:27,530
into the roof plate
of the hindbrain,

136
00:09:27,530 --> 00:09:30,800
forming the cerebellum at the
rostral end of the hindbrain.

137
00:09:30,800 --> 00:09:35,932
But they also migrate from
there to other positions

138
00:09:35,932 --> 00:09:36,640
in the hindbrain.

139
00:09:39,300 --> 00:09:45,870
They form the structures that
project to the cerebellar

140
00:09:45,870 --> 00:09:46,370
cortex.

141
00:09:49,050 --> 00:09:52,846
Those structures all seem
to arise in the rhombic lip.

142
00:09:56,650 --> 00:10:02,340
Basically, the rhombic lip
is in the [INAUDIBLE] plate,

143
00:10:02,340 --> 00:10:05,370
cells migrate from
that region, and that's

144
00:10:05,370 --> 00:10:08,200
what leads to these distortions.

145
00:10:08,200 --> 00:10:10,005
They migrate into
the cerebellum.

146
00:10:10,005 --> 00:10:12,870
They migrate into cell groups.

147
00:10:12,870 --> 00:10:15,080
This is where it is.

148
00:10:15,080 --> 00:10:16,575
This is where the
cerebellum forms.

149
00:10:19,140 --> 00:10:21,855
And the rhombic
lip is huge numbers

150
00:10:21,855 --> 00:10:28,650
of neuroblasts that
form [INAUDIBLE] here.

151
00:10:28,650 --> 00:10:33,780
And that's what leads to the
formation of the cerebellum.

152
00:10:33,780 --> 00:10:35,900
And here, if you
look at this picture

153
00:10:35,900 --> 00:10:41,550
where I've sort of depicted--
I don't have an animation,

154
00:10:41,550 --> 00:10:43,970
so you've got to use
your imagination.

155
00:10:43,970 --> 00:10:48,480
Here's the original
embryonic rostral hindbrain.

156
00:10:48,480 --> 00:10:50,070
And there with
the red arrows I'm

157
00:10:50,070 --> 00:10:53,240
showing migration cells
from the rhombic lip

158
00:10:53,240 --> 00:10:55,320
into the roof
plate, so those are

159
00:10:55,320 --> 00:11:00,120
going to form the
cerebellum itself.

160
00:11:00,120 --> 00:11:04,650
But they also migrate
down to form the pons.

161
00:11:04,650 --> 00:11:06,610
And then some of them
migrate more caudally

162
00:11:06,610 --> 00:11:12,710
and form the inferior olive,
another major source of input.

163
00:11:12,710 --> 00:11:14,610
These are really the
two major sources

164
00:11:14,610 --> 00:11:20,060
of input from the hindbrain into
the cerebellum, from the pons

165
00:11:20,060 --> 00:11:22,170
and from the inferior olive.

166
00:11:25,130 --> 00:11:28,500
And then as these
migrations occur,

167
00:11:28,500 --> 00:11:34,190
as the cerebellar cortex grows,
you can see in relative terms,

168
00:11:34,190 --> 00:11:35,710
it gets very, very large.

169
00:11:35,710 --> 00:11:39,040
I've not even shown its
full size in a human.

170
00:11:42,350 --> 00:11:47,790
And it grows on the ventral
side too as the pons forms.

171
00:11:47,790 --> 00:11:50,260
And here I'm just showing
that the projections

172
00:11:50,260 --> 00:11:54,280
from the pontine
cells are decussating.

173
00:11:54,280 --> 00:12:00,210
They cross there within the
pons and go to the cerebellum.

174
00:12:00,210 --> 00:12:01,110
on the opposite side.

175
00:12:10,500 --> 00:12:13,270
You say, well, why did
they have to cross?

176
00:12:13,270 --> 00:12:15,170
Remember, we talked
about decussations

177
00:12:15,170 --> 00:12:18,886
and how the sensory world
comes to be represented

178
00:12:18,886 --> 00:12:23,450
on the opposite side in
the midbrain and forebrain.

179
00:12:23,450 --> 00:12:26,100
But this is hindbrain.

180
00:12:26,100 --> 00:12:29,330
So why are they crossing?

181
00:12:29,330 --> 00:12:33,820
Well, that projection
from the neocortex

182
00:12:33,820 --> 00:12:36,300
is not a cross projection.

183
00:12:36,300 --> 00:12:40,620
So the right hemisphere projects
to the right side of the pons.

184
00:12:40,620 --> 00:12:43,640
The right side of the
midbrain tectum, for example,

185
00:12:43,640 --> 00:12:45,830
projects to the right
side of the pons.

186
00:12:48,592 --> 00:12:52,950
But the cerebellum is
not a crossed system.

187
00:12:52,950 --> 00:12:59,820
So they'd have to
cross there in order

188
00:12:59,820 --> 00:13:01,870
to match the inputs
they're getting

189
00:13:01,870 --> 00:13:04,960
from the spinal cord and
more caudal hindbrain.

190
00:13:10,940 --> 00:13:18,610
This is a picture of a
human rostral hindbrain.

191
00:13:18,610 --> 00:13:22,020
So here's the original
cross-section,

192
00:13:22,020 --> 00:13:24,080
and look what's happened
to the roof plate.

193
00:13:24,080 --> 00:13:26,240
Here, you're just
seeing the deepest part.

194
00:13:26,240 --> 00:13:28,590
There's only a little bit of
cortex even showing there.

195
00:13:31,230 --> 00:13:35,630
It would go way out to
here someplace and way up

196
00:13:35,630 --> 00:13:40,110
above the seal, if you
saw the whole thing.

197
00:13:40,110 --> 00:13:43,220
What you're seeing there
is the output structures

198
00:13:43,220 --> 00:13:44,680
of the cerebellum.

199
00:13:44,680 --> 00:13:48,410
These are called
the deep nuclei.

200
00:13:48,410 --> 00:13:51,326
The one that looks
like it's corrugated

201
00:13:51,326 --> 00:13:54,498
is the dentate nucleus.

202
00:13:54,498 --> 00:13:58,330
The animals with the
largest cerebral hemispheres

203
00:13:58,330 --> 00:14:01,120
have the largest
dentate nucleus.

204
00:14:01,120 --> 00:14:03,320
So it's very large in humans.

205
00:14:03,320 --> 00:14:08,190
And then there's an intermediate
one, the emboliform nucleus.

206
00:14:08,190 --> 00:14:15,170
And then medial ones here,
the fastigial nucleus,

207
00:14:15,170 --> 00:14:18,570
more concerned with
axial muscle control.

208
00:14:18,570 --> 00:14:21,280
And the most primitive
parts of the cerebellum

209
00:14:21,280 --> 00:14:25,680
are those, this
medial area here.

210
00:14:25,680 --> 00:14:26,180
OK.

211
00:14:26,180 --> 00:14:30,500
So all of this is pontine
gray, the light areas,

212
00:14:30,500 --> 00:14:32,960
because this is a fiber stain.

213
00:14:32,960 --> 00:14:35,270
And then the
corticospinal tract,

214
00:14:35,270 --> 00:14:37,960
which is at the base
of the midbrain,

215
00:14:37,960 --> 00:14:41,570
it penetrates right through
the middle of the pons.

216
00:14:41,570 --> 00:14:45,312
So here you see those axons,
the corticospinal tract axons,

217
00:14:45,312 --> 00:14:46,400
cut in cross-section.

218
00:14:49,030 --> 00:14:52,430
They form a more
compact bundle, again,

219
00:14:52,430 --> 00:14:55,480
at the very base
of the hindbrain.

220
00:14:55,480 --> 00:14:57,360
They form the
pyramidal tract there.

221
00:15:02,986 --> 00:15:05,720
So we'll come back to
that again in a little bit

222
00:15:05,720 --> 00:15:07,530
when we talk about
the motor system.

223
00:15:11,180 --> 00:15:15,666
Right now, we want to
talk about the midbrain.

224
00:15:21,650 --> 00:15:25,800
This question, why a
midbrain, occurred to me

225
00:15:25,800 --> 00:15:31,710
when I thought about traditional
neuroanatomy textbooks

226
00:15:31,710 --> 00:15:34,880
and the way they
treat the midbrain.

227
00:15:34,880 --> 00:15:38,790
It generally is given
pretty short shrift.

228
00:15:38,790 --> 00:15:45,050
They treat it as basically a
reflex center, controlling eye

229
00:15:45,050 --> 00:15:52,040
movements, the pupillary light
reflex, auditory reflexes,

230
00:15:52,040 --> 00:15:54,972
and it serves as a relay
of auditory information

231
00:15:54,972 --> 00:15:55,680
to the forebrain.

232
00:15:58,520 --> 00:16:03,840
And it serves as a very
important visual center

233
00:16:03,840 --> 00:16:07,320
in primitive animals.

234
00:16:07,320 --> 00:16:12,540
But there's been
enough studies now

235
00:16:12,540 --> 00:16:17,690
of the membrane and
especially motor control

236
00:16:17,690 --> 00:16:20,860
that we can say a
lot more about it now

237
00:16:20,860 --> 00:16:26,990
than the information that
led to those medical school

238
00:16:26,990 --> 00:16:27,780
traditions.

239
00:16:27,780 --> 00:16:32,705
So we get a good idea about
the evolution of the midbrain

240
00:16:32,705 --> 00:16:35,790
and forebrain from animals
resembling the most primitive

241
00:16:35,790 --> 00:16:38,640
chordates that we
discussed earlier.

242
00:16:38,640 --> 00:16:41,420
And of course we get many
ideas from comparative studies

243
00:16:41,420 --> 00:16:42,045
of vertebrates.

244
00:16:44,670 --> 00:16:46,850
We don't get much
information from skulls

245
00:16:46,850 --> 00:16:54,390
because the midbrain is--
primitive skulls, of course,

246
00:16:54,390 --> 00:16:56,180
can tell us something
because they

247
00:16:56,180 --> 00:17:00,340
will be the shape
of the midbrain,

248
00:17:00,340 --> 00:17:03,816
will be visible in some skills,
where the forebrain is not

249
00:17:03,816 --> 00:17:04,315
so huge.

250
00:17:09,440 --> 00:17:12,109
So these are my
initial answers to why

251
00:17:12,109 --> 00:17:15,722
we have a midbrain as
well as the forebrain.

252
00:17:15,722 --> 00:17:18,770
So I say the midbrain
together with early components

253
00:17:18,770 --> 00:17:21,125
of the forebrain, there's
a kind of rostral extension

254
00:17:21,125 --> 00:17:24,630
of the hindbrain that enabled
visual and olfactory control

255
00:17:24,630 --> 00:17:27,690
of the motor patterns,
because olfaction

256
00:17:27,690 --> 00:17:29,970
develops at the
very rostral end.

257
00:17:29,970 --> 00:17:32,240
That was the reason
the endbrain started

258
00:17:32,240 --> 00:17:36,350
to form-- the
olfactory input there.

259
00:17:36,350 --> 00:17:39,630
Otherwise, think of amphioxus
before-- it probably

260
00:17:39,630 --> 00:17:42,400
doesn't even have olfaction.

261
00:17:42,400 --> 00:17:46,810
But it's got a forebrain, and
it's mainly just a diencephalon

262
00:17:46,810 --> 00:17:52,220
with some secretory cells,
important in endocrine control

263
00:17:52,220 --> 00:17:55,090
and probably control
of motivation,

264
00:17:55,090 --> 00:17:58,120
just like it remains
important in vertebrates.

265
00:18:02,350 --> 00:18:05,010
But for vision--
and vision comes in.

266
00:18:05,010 --> 00:18:05,560
Where?

267
00:18:05,560 --> 00:18:09,740
Even amphioxus has the
pigmented cells right here.

268
00:18:09,740 --> 00:18:11,490
We already said it
was diencephalon.

269
00:18:11,490 --> 00:18:14,370
That's where the
visual inputs come in.

270
00:18:14,370 --> 00:18:18,490
OK, so for vision and olfaction
ought to affect movement,

271
00:18:18,490 --> 00:18:23,730
they formed links
in the midbrain.

272
00:18:23,730 --> 00:18:26,840
Generally, when
connections first evolve,

273
00:18:26,840 --> 00:18:31,360
they're not long connections,
because connections start out

274
00:18:31,360 --> 00:18:34,050
from structures that are small.

275
00:18:34,050 --> 00:18:36,880
Then, as they grow larger,
the largest structures

276
00:18:36,880 --> 00:18:38,320
become more connected.

277
00:18:38,320 --> 00:18:41,800
There's a general rule
in comparative anatomy--

278
00:18:41,800 --> 00:18:45,054
larger is more connected.

279
00:18:45,054 --> 00:18:46,845
So we have these huge
cerebral hemispheres.

280
00:18:46,845 --> 00:18:51,800
It's got connections to all
parts of the spinal cord,

281
00:18:51,800 --> 00:18:56,370
hindbrain, midbrain,
diencephalon, as well

282
00:18:56,370 --> 00:18:59,920
as many connections
within the hemisphere.

283
00:18:59,920 --> 00:19:04,860
But animals who are very
small, cerebral hemispheres

284
00:19:04,860 --> 00:19:06,800
do not have these
long connections.

285
00:19:09,820 --> 00:19:13,560
They also added controlled
by motivational states,

286
00:19:13,560 --> 00:19:16,820
and we will see,
the midbrain can

287
00:19:16,820 --> 00:19:19,430
include structures
that are involved

288
00:19:19,430 --> 00:19:20,670
in motivational control.

289
00:19:20,670 --> 00:19:23,280
It's not only the
hypothalamus that does it.

290
00:19:23,280 --> 00:19:27,750
Remember, we talked about
the hierarchy of control,

291
00:19:27,750 --> 00:19:31,610
or autonomic functions
like temperature.

292
00:19:31,610 --> 00:19:35,880
So it's not just the
hypothalamus that does that.

293
00:19:35,880 --> 00:19:37,720
The midbrain does it,
the hindbrain does it,

294
00:19:37,720 --> 00:19:39,940
the spinal cord does it.

295
00:19:39,940 --> 00:19:44,080
So we'll look at
that in the midbrain.

296
00:19:44,080 --> 00:19:46,565
And then this is just
about those structures.

297
00:19:46,565 --> 00:19:50,710
There had to be visual
and olfactory pathways

298
00:19:50,710 --> 00:19:57,770
from those systems, from the
tweenbrain and endbrain, as

299
00:19:57,770 --> 00:20:00,440
well of inputs, of course,
from more caudal structures,

300
00:20:00,440 --> 00:20:03,730
including the cerebellum
that come into the midbrain.

301
00:20:03,730 --> 00:20:05,580
So first of all, what
are the two inputs

302
00:20:05,580 --> 00:20:08,560
carrying information
about light levels

303
00:20:08,560 --> 00:20:11,554
into the central nervous system?

304
00:20:11,554 --> 00:20:13,970
So we're going to talk a little
bit about primitive vision

305
00:20:13,970 --> 00:20:16,550
here, and then about
primitive olfaction.

306
00:20:16,550 --> 00:20:18,903
So for vision, what
are the two inputs?

307
00:20:29,770 --> 00:20:33,280
Lateral eyes,
that's one of them.

308
00:20:33,280 --> 00:20:36,430
What's the other one?

309
00:20:36,430 --> 00:20:38,850
What's it called-- the
eye on top of the head.

310
00:20:38,850 --> 00:20:41,426
Yeah, you don't have it, I know.

311
00:20:41,426 --> 00:20:44,340
The pineal eye.

312
00:20:44,340 --> 00:20:47,870
It's an actual eye
in many creatures.

313
00:20:47,870 --> 00:20:50,060
Many amphibians
have a pineal eye.

314
00:20:56,440 --> 00:21:02,210
An early role of that
optic input-- no doubt,

315
00:21:02,210 --> 00:21:07,130
before even their image
forming eyes were present,

316
00:21:07,130 --> 00:21:10,400
just detection of
light levels-- was

317
00:21:10,400 --> 00:21:15,290
control of the rhythm of
activity, which was different

318
00:21:15,290 --> 00:21:16,950
in day and night,
because it made

319
00:21:16,950 --> 00:21:18,600
a big difference in efficiency.

320
00:21:18,600 --> 00:21:21,170
It made a big difference
in survival of the animals.

321
00:21:21,170 --> 00:21:23,460
They were active during
certain periods of the day.

322
00:21:26,430 --> 00:21:29,860
And we know now that
cells developed there

323
00:21:29,860 --> 00:21:35,840
that had an endogenous
rhythm, a circadian rhythm,

324
00:21:35,840 --> 00:21:37,870
but it was affected
by light levels.

325
00:21:37,870 --> 00:21:42,255
They were active either during
the day or during the night.

326
00:21:42,255 --> 00:21:49,840
So here are the two inputs,
pineal eye and retinal input,

327
00:21:49,840 --> 00:21:54,000
from lateral eyes coming right
into the hypothalamus, the most

328
00:21:54,000 --> 00:21:55,350
primitive visual connection.

329
00:21:59,610 --> 00:22:04,990
And in that hypothalamus that
we see those two visual inputs,

330
00:22:04,990 --> 00:22:08,446
there was mechanisms
for controlling

331
00:22:08,446 --> 00:22:12,100
the sleep-waking cycle,
altering physiology

332
00:22:12,100 --> 00:22:16,940
and behavior, involved both the
epithalamus or the pineal eye

333
00:22:16,940 --> 00:22:22,430
connected, and the anterior
parts of the hypothalamus.

334
00:22:22,430 --> 00:22:27,710
And in a modern mammal, if
you damage that anterior part

335
00:22:27,710 --> 00:22:31,330
of the hypothalamus, as Nauta
did many years ago-- before he

336
00:22:31,330 --> 00:22:35,350
even was a neuroanatomist
and doing a PhD thesis,

337
00:22:35,350 --> 00:22:39,760
he made lesions in hypothalamus,
because he studied and he

338
00:22:39,760 --> 00:22:46,050
realized, these must be
crucial for important controls

339
00:22:46,050 --> 00:22:47,480
of the animal's life.

340
00:22:47,480 --> 00:22:54,460
And he found major centers
for controlling wakefulness

341
00:22:54,460 --> 00:22:56,950
and sleep.

342
00:22:59,490 --> 00:23:03,820
He's still cited
for those findings.

343
00:23:03,820 --> 00:23:08,300
But other, we could say, the
cyclical motivational states

344
00:23:08,300 --> 00:23:10,860
are influenced by
this biological clock.

345
00:23:10,860 --> 00:23:13,540
They're regulated by
mostly the hypothalamus.

346
00:23:16,520 --> 00:23:19,960
Cyclical forging, feeding,
drinking, nesting,

347
00:23:19,960 --> 00:23:20,924
and other things.

348
00:23:24,780 --> 00:23:26,860
But in order for
the visual inputs,

349
00:23:26,860 --> 00:23:29,420
we just deal with vision now.

350
00:23:29,420 --> 00:23:32,680
In order for those inputs to
control local mode responses

351
00:23:32,680 --> 00:23:35,810
more directly-- that is,
not just through controlling

352
00:23:35,810 --> 00:23:39,360
the circadian
rhythm-- then they had

353
00:23:39,360 --> 00:23:42,930
to have links to the midbrain.

354
00:23:42,930 --> 00:23:46,290
Now, when it comes
to olfaction, it

355
00:23:46,290 --> 00:23:50,520
was and remains an important
control of behavioral state.

356
00:23:50,520 --> 00:23:52,080
And these are the
two main things

357
00:23:52,080 --> 00:23:59,530
olfaction did for animals--
learning object identities,

358
00:23:59,530 --> 00:24:02,620
remembering them,
altering behavior

359
00:24:02,620 --> 00:24:05,140
according to what
those objects were,

360
00:24:05,140 --> 00:24:09,100
so they could detect sexual
identity and individual

361
00:24:09,100 --> 00:24:11,030
differences.

362
00:24:11,030 --> 00:24:13,105
They could discriminate
what was good to eat

363
00:24:13,105 --> 00:24:15,790
and what was bad to eat--
they learned that just

364
00:24:15,790 --> 00:24:16,540
through olfaction.

365
00:24:20,010 --> 00:24:23,470
Why was it so important to do it
through olfaction and not just

366
00:24:23,470 --> 00:24:25,770
with taste?

367
00:24:25,770 --> 00:24:28,740
Well, to identify food,
if you had to taste it,

368
00:24:28,740 --> 00:24:32,124
well, you'd have to come
right up and touch it.

369
00:24:32,124 --> 00:24:35,150
But with olfaction, you might
be able to do it at a distance,

370
00:24:35,150 --> 00:24:41,940
so there was a big
advantage-- no doubt

371
00:24:41,940 --> 00:24:45,075
promoted the evolution of the
olfaction, olfactory system.

372
00:24:49,840 --> 00:24:52,970
For the olfaction
to control behavior

373
00:24:52,970 --> 00:24:55,810
on the basis of those
object identifications,

374
00:24:55,810 --> 00:25:01,765
you needed pathways going
down to the motor system.

375
00:25:01,765 --> 00:25:04,680
And I point that out
here at the bottom,

376
00:25:04,680 --> 00:25:07,170
and I point out the
structures that were involved.

377
00:25:07,170 --> 00:25:10,196
We call them ventral
striatum and the amygdala,

378
00:25:10,196 --> 00:25:12,085
are the precursors
to those structures.

379
00:25:14,600 --> 00:25:19,180
Their main outputs were
to the hypothalamus.

380
00:25:19,180 --> 00:25:22,290
But the hypothalamus likewise,
to influence movement,

381
00:25:22,290 --> 00:25:25,160
most of the pathways went
through the midbrain.

382
00:25:25,160 --> 00:25:27,960
And then, of course, it
was important for detecting

383
00:25:27,960 --> 00:25:31,120
places too-- good
places, bad places.

384
00:25:31,120 --> 00:25:35,650
They had to learn them, remember
them, direct their behavior,

385
00:25:35,650 --> 00:25:41,670
according to whether they were
something desirable or not.

386
00:25:41,670 --> 00:25:43,540
And that led to the
evolution of what

387
00:25:43,540 --> 00:25:46,050
we call the medial
pallium, which

388
00:25:46,050 --> 00:25:50,590
became the hippocampus
in mammals.

389
00:25:50,590 --> 00:25:53,740
Outputs went through the ventral
striatum and hypothalamus,

390
00:25:53,740 --> 00:25:57,450
and then of course
to the midbrain.

391
00:25:57,450 --> 00:25:59,480
And this just expands
on that a little bit.

392
00:25:59,480 --> 00:26:05,890
I talk about the approach
avoidance movements

393
00:26:05,890 --> 00:26:10,740
that involves both of
these kinds of control.

394
00:26:10,740 --> 00:26:19,540
And so for odors to
influence locomotion,

395
00:26:19,540 --> 00:26:23,830
the projections went to specific
places in the hypothalamus

396
00:26:23,830 --> 00:26:27,225
and the midbrain that had
been studied, especially

397
00:26:27,225 --> 00:26:29,400
by the electrophysiologist,
and I'm

398
00:26:29,400 --> 00:26:33,250
going to identify those areas
for you in a minute here,

399
00:26:33,250 --> 00:26:34,840
and we'll come
back to it when we

400
00:26:34,840 --> 00:26:39,850
start talking about the motor
system, locomotor control.

401
00:26:39,850 --> 00:26:43,550
So escape from predator threat
we've talked about before.

402
00:26:46,160 --> 00:26:52,480
Now we'll see what that's
led to in locomotor

403
00:26:52,480 --> 00:26:54,570
areas of the brain.

404
00:26:54,570 --> 00:26:59,100
And then the other function
for controlling orienting,

405
00:26:59,100 --> 00:27:00,970
how is olfaction
involved in orienting?

406
00:27:00,970 --> 00:27:02,720
Olfaction doesn't
really give you

407
00:27:02,720 --> 00:27:07,920
a sense of place except if
you're near a good place

408
00:27:07,920 --> 00:27:12,510
or near a bad place and
they smell different.

409
00:27:12,510 --> 00:27:16,130
It certainly will affect the
motivation of the animal.

410
00:27:16,130 --> 00:27:18,560
And that will affect the
response of the animal

411
00:27:18,560 --> 00:27:21,860
to visual, auditory, and
somatosensory inputs.

412
00:27:21,860 --> 00:27:23,670
So that's how it
affects orienting.

413
00:27:23,670 --> 00:27:26,050
You can trace those pathways.

414
00:27:26,050 --> 00:27:28,110
So here's the midbrain.

415
00:27:28,110 --> 00:27:32,180
This is the structure
we're talking about.

416
00:27:32,180 --> 00:27:37,650
And now some more
specific questions--

417
00:27:37,650 --> 00:27:48,080
what are the three major types
of multipurpose movements

418
00:27:48,080 --> 00:27:49,870
controlled by
descending pathways that

419
00:27:49,870 --> 00:27:52,390
originate in the midbrain?

420
00:27:52,390 --> 00:27:55,340
Multipurpose movements
you have to separate

421
00:27:55,340 --> 00:27:58,110
from specialized movements.

422
00:27:58,110 --> 00:28:01,410
Give me an example of each.

423
00:28:01,410 --> 00:28:09,690
A multipurpose movement is used
in various motivational states.

424
00:28:09,690 --> 00:28:11,670
We use it when we want food.

425
00:28:11,670 --> 00:28:13,500
We use it when we want sex.

426
00:28:13,500 --> 00:28:15,660
We use it when we
want to do this

427
00:28:15,660 --> 00:28:17,480
or that or the other thing.

428
00:28:17,480 --> 00:28:19,620
There are certain
kinds of movements

429
00:28:19,620 --> 00:28:22,890
that are used for many
different purposes.

430
00:28:22,890 --> 00:28:26,150
There's other movements that
are very specialized-- courtship

431
00:28:26,150 --> 00:28:28,480
movements, for example,
sexual movements.

432
00:28:28,480 --> 00:28:31,770
They're very particular.

433
00:28:31,770 --> 00:28:35,210
And there are many
movements like that.

434
00:28:35,210 --> 00:28:38,070
In an evolution,
fixed action patterns,

435
00:28:38,070 --> 00:28:41,740
meaning genetically controlled
patterns of behavior,

436
00:28:41,740 --> 00:28:49,850
evolve both types, multipurpose
and special purpose.

437
00:28:49,850 --> 00:28:52,640
So there's three major types
of multipurpose movements

438
00:28:52,640 --> 00:28:58,295
controlled by the midbrain
and pathways from it.

439
00:28:58,295 --> 00:29:00,420
We want to know what the
structures in the midbrain

440
00:29:00,420 --> 00:29:05,500
are that gave rise
to those pathways.

441
00:29:05,500 --> 00:29:09,700
Can anybody name one of
them, either the structure

442
00:29:09,700 --> 00:29:10,790
or the type of movement?

443
00:29:13,930 --> 00:29:17,010
Orienting, turning
movements-- that's

444
00:29:17,010 --> 00:29:18,300
a general purpose movement.

445
00:29:18,300 --> 00:29:22,570
We use it for all
kinds of behaviors.

446
00:29:22,570 --> 00:29:26,900
We need to be able
to orient our senses,

447
00:29:26,900 --> 00:29:30,290
orient our heads and
eyes towards something.

448
00:29:30,290 --> 00:29:32,170
That's one of the general
purpose movements.

449
00:29:32,170 --> 00:29:35,137
And what's the structure so
important for controlling that?

450
00:29:37,819 --> 00:29:40,430
You say, well,
the visual cortex.

451
00:29:40,430 --> 00:29:42,670
Well, that came much later.

452
00:29:42,670 --> 00:29:45,520
Let's talk about the midbrain.

453
00:29:45,520 --> 00:29:49,510
What was the midbrain structure
so important in orienting?

454
00:29:49,510 --> 00:29:52,460
And most animals, even if
they have a large cortex,

455
00:29:52,460 --> 00:29:54,070
still use that structure.

456
00:29:54,070 --> 00:29:57,025
The pathway simply goes from
the cortex down to the structure

457
00:29:57,025 --> 00:29:59,780
to control orienting.

458
00:29:59,780 --> 00:30:05,180
It's the surface of the superior
colliculus, or midbrain tectum.

459
00:30:05,180 --> 00:30:10,240
We saw a picture a while
back of a predatory fish

460
00:30:10,240 --> 00:30:12,860
with enormous optic tectum.

461
00:30:12,860 --> 00:30:15,230
Remember the barracuda
I showed you?

462
00:30:15,230 --> 00:30:19,930
Enormous tectum, bigger than
any structure in the brain.

463
00:30:26,250 --> 00:30:29,990
Well, we're very
visual animals too.

464
00:30:29,990 --> 00:30:33,360
Why isn't it so big in
us in relative terms?

465
00:30:36,610 --> 00:30:41,080
Because some animals, the
types of orienting they do

466
00:30:41,080 --> 00:30:46,840
are much more under the
control of learning.

467
00:30:46,840 --> 00:30:50,120
And the midbrain is only good
for very short-term kinds

468
00:30:50,120 --> 00:30:52,890
of learning.

469
00:30:52,890 --> 00:30:56,920
And we'll talk about
that again in a minute.

470
00:30:56,920 --> 00:31:00,140
I want you to be able to name
two pathways that originate

471
00:31:00,140 --> 00:31:02,310
in the midbrain and
descend to the spinal cord.

472
00:31:02,310 --> 00:31:03,625
Why aren't there three?

473
00:31:03,625 --> 00:31:06,210
Because the third one
we don't know as much

474
00:31:06,210 --> 00:31:07,220
about anatomically.

475
00:31:07,220 --> 00:31:09,064
We know about it
from physiology.

476
00:31:09,064 --> 00:31:10,355
It's some very nice physiology.

477
00:31:13,500 --> 00:31:17,290
And I use the physiology data
as well as anatomical data

478
00:31:17,290 --> 00:31:20,695
in coming to these descriptions.

479
00:31:23,390 --> 00:31:27,020
So here's a typical
picture of a midbrain

480
00:31:27,020 --> 00:31:30,915
of an animal like a rat
or a mouse or a hamster.

481
00:31:33,860 --> 00:31:35,920
When I first drew these,
I drew them from memory.

482
00:31:35,920 --> 00:31:38,720
And the animal I'd use
the most was the hamster.

483
00:31:38,720 --> 00:31:42,710
I had also done work
with rats and mice

484
00:31:42,710 --> 00:31:44,025
and a number of other animals.

485
00:31:47,350 --> 00:31:51,812
So here is that optic
tectum, except we usually

486
00:31:51,812 --> 00:31:56,360
call it the superior
colliculus in a mammal.

487
00:31:56,360 --> 00:32:00,050
We think of it as
a visual structure,

488
00:32:00,050 --> 00:32:05,460
but the visual layers are
just these superficial layers.

489
00:32:05,460 --> 00:32:07,780
What are the axons down below?

490
00:32:10,710 --> 00:32:12,580
Well, it must be
the input coming

491
00:32:12,580 --> 00:32:19,887
in from the eye, the retina,
and from posterior visual areas

492
00:32:19,887 --> 00:32:20,470
of the cortex.

493
00:32:24,050 --> 00:32:28,350
This is all superior
colliculus down here too.

494
00:32:28,350 --> 00:32:30,700
You don't need that
much colliculus just

495
00:32:30,700 --> 00:32:35,670
to get output to
the lower brain stem

496
00:32:35,670 --> 00:32:41,390
and to the upper spinal cord to
control head and eye movements.

497
00:32:41,390 --> 00:32:43,755
Other sensory inputs
come in there too,

498
00:32:43,755 --> 00:32:47,630
and they tend to match
the visual inputs.

499
00:32:47,630 --> 00:32:52,620
They match them in representing
the same parts of space.

500
00:32:52,620 --> 00:32:56,450
So auditory and somatosensory
inputs come out of here.

501
00:32:56,450 --> 00:33:01,040
If I am working with
a rat, say, and I'm

502
00:33:01,040 --> 00:33:06,050
looking at the part of
that optic layer that's

503
00:33:06,050 --> 00:33:09,110
responding to this visual field
right out here-- remember,

504
00:33:09,110 --> 00:33:13,560
the rat's eyes are looking up
here this way, 60 degrees out,

505
00:33:13,560 --> 00:33:16,330
30 degrees up, at least for
the hamster, very similar

506
00:33:16,330 --> 00:33:17,250
for the mouse.

507
00:33:17,250 --> 00:33:18,970
So here's the two
eyes looking up.

508
00:33:18,970 --> 00:33:22,930
And I show him
something up here,

509
00:33:22,930 --> 00:33:25,450
and I get a response
from the colliculus

510
00:33:25,450 --> 00:33:32,900
in the upper temporal
field, somewhere in here,

511
00:33:32,900 --> 00:33:36,270
fairly far back from the tectum.

512
00:33:36,270 --> 00:33:40,630
Now, if I come close to
him, what am I going to do?

513
00:33:40,630 --> 00:33:42,876
I'm going to touch
whiskers here.

514
00:33:42,876 --> 00:33:48,280
If I stimulate those whiskers,
this activates the same region

515
00:33:48,280 --> 00:33:51,590
but in the deeper layers.

516
00:33:51,590 --> 00:33:54,780
And in the middle,
there's auditory input.

517
00:33:54,780 --> 00:33:57,410
And the auditory
input in many animals

518
00:33:57,410 --> 00:34:02,280
also gives you a pretty
good map of space.

519
00:34:02,280 --> 00:34:06,570
Like the cat, the owl--
very, very good at auditory

520
00:34:06,570 --> 00:34:07,963
localization too.

521
00:34:07,963 --> 00:34:13,630
The owl can hear rustling on
the forest floor below his tree

522
00:34:13,630 --> 00:34:16,685
and know where that mouse is
even though he never sees it.

523
00:34:16,685 --> 00:34:17,810
He just hears the rustling.

524
00:34:20,449 --> 00:34:26,586
And the cat is pretty similar
in localized sounds really well.

525
00:34:26,586 --> 00:34:30,540
I'll try to go a
little faster here.

526
00:34:30,540 --> 00:34:35,909
So the three output systems,
I list them structurally here,

527
00:34:35,909 --> 00:34:37,699
functionally here.

528
00:34:37,699 --> 00:34:40,839
Descending axons from the
midbrain locomotor area

529
00:34:40,839 --> 00:34:42,985
is the first output system.

530
00:34:42,985 --> 00:34:47,245
It controls locomotion involved
in approach, avoidance,

531
00:34:47,245 --> 00:34:52,460
in exploring, foraging, seeking
behavior or various types.

532
00:34:52,460 --> 00:34:54,179
It's a general purpose movement.

533
00:34:54,179 --> 00:34:57,430
That's the axon system,
studied physiologically

534
00:34:57,430 --> 00:34:59,620
in some beautiful
experiments by a number

535
00:34:59,620 --> 00:35:01,060
of different investigators.

536
00:35:01,060 --> 00:35:05,490
Then the tectospinal
tract from the deep layers

537
00:35:05,490 --> 00:35:08,400
of the superior colliculus
or optic tectum.

538
00:35:08,400 --> 00:35:10,090
It's controlling
orienting movements--

539
00:35:10,090 --> 00:35:14,150
that means turning
of the eyes and head.

540
00:35:14,150 --> 00:35:17,790
And finally, rubrospinal tract.

541
00:35:17,790 --> 00:35:22,020
Rubro in Latin means red.

542
00:35:22,020 --> 00:35:26,290
So rubrospinal means a
pathway from the red nucleus

543
00:35:26,290 --> 00:35:31,210
to the spinal cord, and that's
controlling limb movements

544
00:35:31,210 --> 00:35:33,740
involved in exploring or
reaching and grasping.

545
00:35:36,820 --> 00:35:38,835
Those are the three
multipurpose movements

546
00:35:38,835 --> 00:35:43,270
we're talking about--
locomotion, orienting,

547
00:35:43,270 --> 00:35:46,195
and we'll just use
that term, grasping.

548
00:35:52,960 --> 00:35:54,612
We'll come back to
those again when

549
00:35:54,612 --> 00:35:56,250
we talk about motor system.

550
00:35:56,250 --> 00:35:59,510
Now, this is from a
physiological study

551
00:35:59,510 --> 00:36:02,950
using electrical
stimulation to define

552
00:36:02,950 --> 00:36:05,290
locomotor areas in the brain.

553
00:36:05,290 --> 00:36:08,830
This was done in the cat by
the Russian, Orlovsky, who

554
00:36:08,830 --> 00:36:11,310
did some very nice work on this.

555
00:36:11,310 --> 00:36:15,950
And what I did is I
traced two of his drawings

556
00:36:15,950 --> 00:36:19,000
where he was showing
the stimulation sites.

557
00:36:19,000 --> 00:36:23,820
And he outlined the most areas
where he most easily elicited

558
00:36:23,820 --> 00:36:26,320
locomotion from
the hypothalamus,

559
00:36:26,320 --> 00:36:29,150
and that was called the
hypothalamic locomotor area.

560
00:36:29,150 --> 00:36:31,780
There is a nearby area
in the subthalamus

561
00:36:31,780 --> 00:36:33,880
where you can also
get locomotion.

562
00:36:33,880 --> 00:36:36,600
People talk much less
about it, but it's there.

563
00:36:36,600 --> 00:36:38,845
And here is the area
in the caudal midbrain.

564
00:36:38,845 --> 00:36:41,770
Now, this is the
sagittal section.

565
00:36:41,770 --> 00:36:44,070
So there's thalamus.

566
00:36:44,070 --> 00:36:48,190
There's the inferior
colliculus, the caudal part

567
00:36:48,190 --> 00:36:50,900
of the colliculus.

568
00:36:50,900 --> 00:36:52,290
And that's the region.

569
00:36:52,290 --> 00:36:56,570
It centers in an area just
in the reticular formation

570
00:36:56,570 --> 00:36:58,595
below the inferior colliculus.

571
00:36:58,595 --> 00:37:01,340
And here it is in a section.

572
00:37:01,340 --> 00:37:05,360
This is a section at this level.

573
00:37:05,360 --> 00:37:08,165
There's the inferior colliculus.

574
00:37:08,165 --> 00:37:10,270
That means lateral
lemniscus, which

575
00:37:10,270 --> 00:37:11,560
we haven't talked about yet.

576
00:37:11,560 --> 00:37:14,155
It's an auditory pathway
carrying auditory information

577
00:37:14,155 --> 00:37:16,970
from the hypothalamus up
to the inferior colliculus.

578
00:37:16,970 --> 00:37:21,580
But there's the area
centered in this area right

579
00:37:21,580 --> 00:37:24,500
below the inferior colliculus--
it's part of the reticular

580
00:37:24,500 --> 00:37:28,445
formation-- that when you
stimulate you get locomotion.

581
00:37:34,090 --> 00:37:34,970
Sorry?

582
00:37:34,970 --> 00:37:37,620
AUDIENCE: [INAUDIBLE].

583
00:37:37,620 --> 00:37:39,670
PROFESSOR: Yes,
it does get input.

584
00:37:39,670 --> 00:37:44,740
If we just draw-- here
are some major pathways--

585
00:37:44,740 --> 00:37:49,700
I'll just sketch them here--
from the hypothalamic locomotor

586
00:37:49,700 --> 00:37:55,900
area to the midbrain
locomotor area,

587
00:37:55,900 --> 00:38:01,480
from superior colliculus to
the midbrain locomotor area.

588
00:38:01,480 --> 00:38:10,640
And from the
striatum way up here,

589
00:38:10,640 --> 00:38:16,370
there are also pathways
that go to that structure.

590
00:38:16,370 --> 00:38:18,380
Remember how I talked
about how olfaction

591
00:38:18,380 --> 00:38:20,150
can affect locomotion,
well, that's

592
00:38:20,150 --> 00:38:21,770
how it does it--
through the striatum.

593
00:38:33,920 --> 00:38:37,040
If you want, I'll put another
slide in and draw those back

594
00:38:37,040 --> 00:38:39,580
when I put this online.

595
00:38:39,580 --> 00:38:41,810
All right, I just
defined the terms

596
00:38:41,810 --> 00:38:43,770
because some people get
very frustrated when

597
00:38:43,770 --> 00:38:46,345
I use abbreviations, and they
don't know what they mean.

598
00:38:46,345 --> 00:38:49,120
But in fact, you can
understand the basic thing here

599
00:38:49,120 --> 00:38:51,460
without knowing what
all these things are.

600
00:38:51,460 --> 00:38:54,190
It doesn't hurt to read them,
because the more you encounter

601
00:38:54,190 --> 00:38:57,380
them, the more likely you
are to remember something

602
00:38:57,380 --> 00:39:00,620
later on when we study
them more specifically.

603
00:39:00,620 --> 00:39:02,455
We didn't talk about the pons.

604
00:39:02,455 --> 00:39:05,730
There it is in the car.

605
00:39:05,730 --> 00:39:08,250
There it is in
the cross-section.

606
00:39:08,250 --> 00:39:11,052
So this is actually rostral
hypothalamus down here.

607
00:39:11,052 --> 00:39:12,260
That's all midbrain up there.

608
00:39:19,670 --> 00:39:22,030
This is just what
we talked about.

609
00:39:22,030 --> 00:39:24,520
Now about the other
two types of movement--

610
00:39:24,520 --> 00:39:29,785
orienting and
reaching and grasping.

611
00:39:29,785 --> 00:39:31,630
Here are the pathways
for orienting.

612
00:39:31,630 --> 00:39:35,580
This is an output cell from
the superior colliculus.

613
00:39:35,580 --> 00:39:36,970
It's a very large cell.

614
00:39:36,970 --> 00:39:41,680
There's many of them in the
intermediate and deep layers

615
00:39:41,680 --> 00:39:42,610
here.

616
00:39:42,610 --> 00:39:47,350
And here, the axon crosses
over to this position

617
00:39:47,350 --> 00:39:51,090
and descends to the
caudal hypothalamus

618
00:39:51,090 --> 00:39:54,320
and to the rostral spinal
cord, the cervical spinal cord.

619
00:39:54,320 --> 00:39:57,850
And here is a cell in the
caudal part of the red nucleus,

620
00:39:57,850 --> 00:39:59,420
the output part of
the red nucleus--

621
00:39:59,420 --> 00:40:02,840
large cells that send their
axon across the midline,

622
00:40:02,840 --> 00:40:06,140
they go to a more lateral
position, and as they descend,

623
00:40:06,140 --> 00:40:08,060
they go more and more lateral.

624
00:40:08,060 --> 00:40:11,650
So in the hindbrain, they're
way out at the lateral edge.

625
00:40:11,650 --> 00:40:15,390
From the red nucleus,
descends to where,

626
00:40:15,390 --> 00:40:17,510
if it's going to control
this kind of movement?

627
00:40:17,510 --> 00:40:18,551
Where does it have to go?

628
00:40:20,920 --> 00:40:28,080
From the red nucleus to spinal
cord enlargements, where

629
00:40:28,080 --> 00:40:32,840
the neurons are controlling
those movements.

630
00:40:32,840 --> 00:40:35,260
Movements of the what, too?

631
00:40:35,260 --> 00:40:36,575
To the spinal enlargements.

632
00:40:40,700 --> 00:40:43,490
So I'm not showing the
locomotor area there.

633
00:40:43,490 --> 00:40:46,140
That's defined just
physiologically.

634
00:40:46,140 --> 00:40:51,240
And then I have a slide just
showing all the sensory systems

635
00:40:51,240 --> 00:40:53,360
in or passing
through the midbrain.

636
00:40:53,360 --> 00:40:55,340
So visual inputs up here.

637
00:40:58,180 --> 00:41:00,930
Auditory inputs coming
from inferior colliculus

638
00:41:00,930 --> 00:41:02,890
at this level are
just seen out here.

639
00:41:02,890 --> 00:41:04,874
They're on their
way to the thalamus.

640
00:41:04,874 --> 00:41:10,820
The somatosensory inputs
are passing through,

641
00:41:10,820 --> 00:41:17,430
so the spinothalamic tract
also goes to the tectum there.

642
00:41:17,430 --> 00:41:22,910
These are the medial lemniscus
and trigeminal lemniscus.

643
00:41:22,910 --> 00:41:25,260
They'll stay in
approximately that position.

644
00:41:25,260 --> 00:41:26,950
They'll enter the
caudal thalamus

645
00:41:26,950 --> 00:41:30,208
and terminate in the ventral
part of the caudal thalamus.

646
00:41:33,990 --> 00:41:35,820
Visceral inputs
would be up here.

647
00:41:41,090 --> 00:41:48,120
And then the pathways
descending from the spinal cord

648
00:41:48,120 --> 00:41:49,910
are in blue there.

649
00:41:49,910 --> 00:41:52,780
That's the cerebral peduncle.

650
00:41:52,780 --> 00:41:55,125
I name it here,
cerebral peduncle.

651
00:41:55,125 --> 00:41:57,779
They're fibers from the cortex.

652
00:41:57,779 --> 00:42:00,070
They're going not only to
the spinal cord and hindbrain

653
00:42:00,070 --> 00:42:01,398
but also to the pons.

654
00:42:07,140 --> 00:42:10,490
So we talked about this before,
the roof of the midbrain

655
00:42:10,490 --> 00:42:14,530
with these little
hills, the colliculi.

656
00:42:14,530 --> 00:42:18,200
I said, it shows great
variations in size, remember?

657
00:42:18,200 --> 00:42:20,331
Here was the picture.

658
00:42:20,331 --> 00:42:24,610
If animals are more
specialized for using audition,

659
00:42:24,610 --> 00:42:27,660
they tend to have very
large inferior colliculi,

660
00:42:27,660 --> 00:42:33,610
like in the bat and the dolphin
here, the echolocating bat.

661
00:42:33,610 --> 00:42:36,720
Whereas if they're more
specialized for especially

662
00:42:36,720 --> 00:42:45,380
innate visual reactions, like in
the wild goat or the prosimian

663
00:42:45,380 --> 00:42:50,406
primate, the tarsier, then
the optic tectum is larger.

664
00:42:50,406 --> 00:42:54,480
And as I mentioned, some animals
are specialized in vision.

665
00:42:54,480 --> 00:43:00,660
We've gone huge visual cortex,
as in the higher primates.

666
00:43:00,660 --> 00:43:03,550
The optic tectum is
often well developed

667
00:43:03,550 --> 00:43:04,840
in these primates too.

668
00:43:04,840 --> 00:43:07,820
But in some, like
humans, we're so

669
00:43:07,820 --> 00:43:10,510
dominated by learned
visual reactions

670
00:43:10,510 --> 00:43:13,680
that the colliculus is
still very important,

671
00:43:13,680 --> 00:43:16,360
but it is not as expanded
as it is in these animals.

672
00:43:19,970 --> 00:43:20,470
OK.

673
00:43:22,990 --> 00:43:25,200
I'm going to just show
you this very quickly.

674
00:43:25,200 --> 00:43:26,820
I'd like you to read it.

675
00:43:26,820 --> 00:43:32,660
I divide the midbrain
into two main regions.

676
00:43:32,660 --> 00:43:36,860
First of all, what are the
limbic midbrain regions?

677
00:43:36,860 --> 00:43:41,610
The central gray and the
ventral tegmental area.

678
00:43:41,610 --> 00:43:45,832
If you stimulate these
areas in the central gray,

679
00:43:45,832 --> 00:43:48,070
you can get a lot of
different behaviors.

680
00:43:48,070 --> 00:43:50,620
But it's dominated
by behavior that

681
00:43:50,620 --> 00:43:55,620
indicates they don't like
being stimulated there.

682
00:43:55,620 --> 00:43:59,180
Quite a bit of the central
gray is involved in responses

683
00:43:59,180 --> 00:44:01,810
to pain-- not only, though.

684
00:44:01,810 --> 00:44:04,550
There's other functional
areas in that,

685
00:44:04,550 --> 00:44:07,950
just like there is
in the hypothalamus.

686
00:44:07,950 --> 00:44:10,315
There's an area concerned
with sexual behavior,

687
00:44:10,315 --> 00:44:13,260
there's areas concerned
with temperature regulation,

688
00:44:13,260 --> 00:44:14,660
and so forth.

689
00:44:14,660 --> 00:44:16,820
But a lot of it will
give you, they'll

690
00:44:16,820 --> 00:44:18,760
react like they're in pain.

691
00:44:18,760 --> 00:44:22,080
Whereas down here,
it's the opposite.

692
00:44:22,080 --> 00:44:26,220
They like to be
stimulated down there.

693
00:44:26,220 --> 00:44:33,200
So if they respond to taste,
if it's a very good taste,

694
00:44:33,200 --> 00:44:37,840
taste system projects
directly into that area.

695
00:44:37,840 --> 00:44:40,990
Again, an animal with a very
large cortex, more of the input

696
00:44:40,990 --> 00:44:43,790
comes from above, but there
are direct projections

697
00:44:43,790 --> 00:44:47,300
from the taste nucleus there.

698
00:44:47,300 --> 00:44:49,020
Very bad tastes,
though, are going

699
00:44:49,020 --> 00:44:51,030
to reach the central gray more.

700
00:44:51,030 --> 00:44:52,700
OK.

701
00:44:52,700 --> 00:44:55,050
You can divide the
entire midbrain

702
00:44:55,050 --> 00:44:58,180
into these two systems.

703
00:44:58,180 --> 00:45:02,010
Those two structures I
just talked about we say

704
00:45:02,010 --> 00:45:04,380
are limbic related
areas, because they

705
00:45:04,380 --> 00:45:09,510
get heavy connections from
the fringes of the hemisphere,

706
00:45:09,510 --> 00:45:12,780
the limbic areas
related to hypothalamus.

707
00:45:12,780 --> 00:45:16,200
Remember, I defined
it that way before.

708
00:45:16,200 --> 00:45:19,210
So these are the areas
related to the hypothalamus.

709
00:45:19,210 --> 00:45:22,690
The somatic areas are
all the other areas.

710
00:45:22,690 --> 00:45:25,390
And here they are,
colored for you.

711
00:45:25,390 --> 00:45:29,730
The limbic areas, central gray
and ventral tegmental area--

712
00:45:29,730 --> 00:45:32,010
all the rest are somatic.

713
00:45:32,010 --> 00:45:36,880
Except down here, we look
at the substantia nigra.

714
00:45:36,880 --> 00:45:39,610
I've shown that the medial
area is really limbic.

715
00:45:42,240 --> 00:45:46,123
It should be lumped together
with the ventral tegmental area

716
00:45:46,123 --> 00:45:48,340
in its connections.

717
00:45:48,340 --> 00:45:53,380
And if you follow these regions
forward into the tweenbrain,

718
00:45:53,380 --> 00:45:56,610
you see that the
limbic areas are

719
00:45:56,610 --> 00:45:59,240
interconnected with the
epithalamus-- that's

720
00:45:59,240 --> 00:46:04,910
where the pineal eye comes
in-- and the hypothalamus,

721
00:46:04,910 --> 00:46:08,200
whereas the other regions,
if you follow them forward,

722
00:46:08,200 --> 00:46:10,140
you're in the thalamus
and subthalamus.

723
00:46:12,780 --> 00:46:13,956
Those are the two regions.

724
00:46:17,130 --> 00:46:19,590
So we'll deal with these
questions a little bit

725
00:46:19,590 --> 00:46:25,200
next time and just review
some of these connections,

726
00:46:25,200 --> 00:46:28,458
talk about the variations
across species.

727
00:46:28,458 --> 00:46:31,740
And that's it.

728
00:46:31,740 --> 00:46:34,300
This is just a summary of
all the long connections

729
00:46:34,300 --> 00:46:36,150
going through.