Download - Why Brains Are Ugly
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Why Brains Are Ugly
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Let’s face it. . . brains are ugly and complicated looking
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And we may be the worst offender!
The problem is that much of the ‘architecture’ of the brain is not
functionally meaningful
FPO
T
F
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Santiago Ramon y Cajal
‘…to extend our understanding of neural function to the most complex human physiological and psychological activities, it is essential that we first generate a clear and accurate view of the structure of the relevant centers, and of the human brain itself, so that the basic plan – the overview – can be grasped in the blink of an eye.’
Histology of the Nervous System of Man and Vertebrates (1909)
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Telencephalon(or ‘Cerebrum’)
Swanson, 1995
Brain
stem
To Begin, Let’s Break the Brain into Two Functional Parts.
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Telencephalon
Cerebellum
Diencephalon
Hindbrain
Spinal Cord
Midbrain Superior Colliculus Inferior Colliculus
CortexLimbic SystemBasal Ganglia
ThalamusHypothalamus
Now add in some sub-divisions
Brain
stem
Brain RegionsYou Should
KNOW
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HumanCNS
Swanson, 1995
Tel: 81Di: 4
Mid: 1Hind: 2
Cblm: 10SC: 2
RatCNS
Tel: 38Di: 6
Mid: 4Hind: 7
Cblm: 10SC: 35
81
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Zebra FinchCNS
Tel: 64Di: 6
Mid: 10Hind: 6
Cblm: 10SC: 4
PigeonCNS
Tel: 38Di: 6
Mid: 12Hind: 7
Cblm: 11SC: 26
64
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Rat Pigeon Finch HumanTelencephalon: 38 38 64 81Diencephalon: 6 6 6 4Midbrain: 4 12 10 1Hindbrain: 7 7 6 2Cerebellum: 10 11 10 10Spinal Cord: 35 26 4 2
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S e n s o r y – D o r s a l
M o t o r – V e n t r a l Hypothalamus
Thalamus
The Brainstem has a simple dorsal/ventral organization
Dorsal
Ventral
When they are sick,Some Dogs
Might Vomit
Note the two sub-divisions of the diencephalon: Thalamus and Hypothalamus
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RatCNS
TelencephalonStimulus (what), motor control
Thalamusrelay, feedback(except olfaction)
Spinal Cordreflexes, input, output
MidbrainStimulus (where) vision and audition only and orienting responses
PrimarySensory Cortex
PrimaryMotor Cortex
Motor output
Sensory input
GENERAL Overview of
Sensory System Organization
(L/R and R/L crossing for vision, touch, audition
only)
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RatCNS
TelencephalonPrimary Auditory Cortex
ThalamusMedial Geniculate
MidbrainInferior Colliculus
HindbrainPons, Medulla
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Basal
Ganglia
AmygdalaHippocampus
Cortex
TELENCEPHALONAND
DIENCEPHALON(some key subregions for S&P)
Cortex
Limbic
Basal Ganglia
Thalamus
Hypothalamus
Thalamus
Hypothalamus
Telencephalon
Diencephalon
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1
2
3
4
5
6
From Thalamus
Back To Thalamus
Output Layer
CORTEX is made of Vertical Columns, each containing 6 layers of neurons
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2D ReceptorArray
Thalamus
Primary Cortex
However…
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Dense 2D Receptor Array
Thalamus
Cortex Is‘Modular’
Means the size and density of cortical columns is fixed
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Because Cortex is Modular, Sensory ‘Maps’ in Primary Cortex are Distorted by Variation in the Density of Sensory Receptors
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A ‘homunculus’ of the USA
Ha-ha! That looks funny!