1. Evolution of Brain and Language
I: Introduction
(1) How Evolution Works
(2) The Human Brain

2. Course website

3. Outline of Topics for the Course
Introduction: What we are up against
How evolution works
The human brain
2. Linguistic structure
The system that had to evolve to make
it possible for us to speak
3. Evolution of the human brain
How/why it grew so large
4. Early stages of language evolution:
      From 3,000,000 BP to 100,000 BP
5. Later stages: From 100,000 BP to 1,000 BP
Language spread and diversification
The Indo-European family and other families
6. The last few hundred years
The exponential progress of evolution

4. Outline of Topics for the Course
Introduction: What we are up against
How evolution works
The human brain
2. Linguistic structure
The system that had to evolve to make
it possible for us to speak
3. Evolution of the human brain
How/why it grew so large
4. Early stages of language evolution:
      From 3,000,000 BP to 100,000 BP
5. Later stages: From 100,000 BP to 1,000 BP
Language spread and diversification
The Indo-European family and other families
6. The last few hundred years
The exponential progress of evolution

5. How Evolution Works
Darwinian evolution: a process of long-range learning
It works by trial-and-error
Variety is always present
And is continually produced
The more able varieties have survival value
Better chance of surviving
Better chance of reproducing
Consequence: Changes in the genome over multiple generations
Case in point: Human evolution

6. How evolution works: I
Starting point

7. How evolution works: II
Variation

8. How evolution works: III
Variation

9. How evolution works: IV
Less successful variants
perish or fail to reproduce

10. How evolution works: V Less successful variants
perish or fail to reproduce

11. How evolution works: VI
More successful variants
thrive and reproduce more

12. How evolution works: VII
Most successful variants
thrive and reproduce more

13. How evolution works: VIII
Variation continues

14. How evolution works: IX
Variation continues

15. How evolution works: X Less successful variants
perish or fail to reproduce

16. How evolution works: XI
Less successful variants
perish or fail to reproduce

17. How evolution works: XI
More successful variants
thrive and reproduce more

18. How evolution works: XII
More successful variants
thrive and reproduce more

19. How evolution works: XIII
Variation continues

20. How evolution works: XIV
More successful variants thrive

21. How evolution works: XV
Less successful variants
perish or fail to reproduce

22. How evolution works: XVI
Less successful variants
perish or fail to reproduce

23. How evolution works: XVI
More successful variants
thrive and reproduce more

24. How evolution works: XVII
More successful variants
thrive and reproduce more

25. How evolution works: XVIII
Variation continues

26. How evolution works: XIX
More successful variants
thrive and reproduce more

27. How evolution works: XX
Less successful variants
perish or fail to reproduce

28. How evolution works: XXI
Less successful variants
perish or fail to reproduce

29. How evolution works: XXII
Variation continues

30. How evolution works: XXIII
More successful variants
thrive and reproduce more

31. How evolution works: XXIV
Less successful variants
perish or fail to reproduce

32. How evolution works: XXV
Less successful variants
perish or fail to reproduce

33. How evolution works: XXVI
Variation continues

34. How evolution works: XXVII
Variation continues

35. How evolution works: XXVIII
More successful variants
thrive and reproduce more

36. How evolution works: XXIX
Less successful variants
perish or fail to reproduce

37. How evolution works: XXX
Less successful variants
perish or fail to reproduce

38. How evolution works: XXXI
Variation continues

39. How evolution works: XXXII
More successful variants
thrive and reproduce more

40. How evolution works: XXXIII
Less successful variants
perish or fail to reproduce

41. How evolution works: XXXIV
Less successful variants
perish or fail to reproduce

42. How evolution works: XXXV

43. How evolution works: XXXVI
Starting point

44. The Human Brain Components of the Brain The cerebral cortex
Neurons, axons, dendrites
Synapses
Transmission of neural activity
Left brain and right brain

45. The nervous system Central nervous system Peripheral nervous system
Spinal cord
Brain
Peripheral nervous system
Motor and sensory neurons connected to the spinal cord

46. The brain Medulla oblongata – Myelencephalon
Pons and Cerebellum – Metencephalon
Midbrain – Mesencephalon
Thalamus and hypothalamus – Diencephalon
Cerebral hemispheres – Telencephalon
Cerebral cortex
Basal ganglia
Basal forebrain nuclei
Amygdaloid nucleus
More..

47. The brain Medulla oblongata – Myelencephalon
Pons and Cerebellum – Metencephalon
Midbrain – Mesencephalon
Thalamus and hypothalamus – Diencephalon
Cerebral hemispheres – Telencephalon
*Brain Stem
Alternative partition:
Brain stem*
Cerebellum
Thalamus & hypothalamus
Cerebral hemispheres

48. The brain Medulla oblongata – Myelencephalon
Pons and Cerebellum – Metencephalon
Midbrain – Mesencephalon
Thalamus and hypothalamus – Diencephalon
Cerebral hemispheres – Telencephalon
Cerebral cortex
Basal ganglia
Basal forebrain nuclei
Amygdaloid nucleus

49. Thalamus and Cortex The cortex is the area for
High-level information processing
Language
But the thalamus is also very important for
Timing and coordination of cortical activity
Details not yet well understood
Metaphor:
The cortex is the orchestra
A very large orchestra
The thalamus is the conductor

50. Two hemispheres Right Left
Interhemispheric fissure (a.k.a. longitudinal fissure)

51. Corpus Callosum Connects Hemispheres

52. Major Left Hemisphere landmarks
Central Sulcus
Sylvian fissure

53. The Sylvian Fissure opened up (it’s huge) (shown with arteries)

54. Major landmarks and the four lobes
Central Sulcus
Parietal
Lobe
Frontal
Lobe
Occipital
Lobe
Temporal
Lobe
Sylvian fissure

55. Primary motor and somatosensory areas
Central Sulcus
Primary Somato-
sensory Area
Primary
Motor Area
Sylvian fissure

56. Some terms.. Fissures and sulci (the “grooves”) Gyri
Singular: sulcus – Plural: sulci
The major sulci are usually called fissures
Interhemispheric fissure
Sylvian fissure
Sometimes the term Rolandic fissure is used for the central sulcus
Gyri
Singular: gyrus – Plural: gyri

57. Alternatives terms for some fissures
Interhemispheric fissure
Also known as Longitudinal fissure
Sylvian fissure
Also known as Lateral sulcus
Central sulcus
Also known as Rolandic fissure

58. Primary Areas Primary Somato- sensory Area Primary Motor Area
Primary Auditory
Area
Primary
Visual Area

59. Divisions of Primary Motor and Somatic Areas
Primary Somato-
sensory Area
Leg
Primary
Motor Area
Trunk
Arm
Hand
Fingers
Mouth
Primary Auditory
Area
Primary
Visual Area

60. Higher level motor areas
Primary Somato-
sensory Area
Actions per-
Formed by leg
Leg
Actions
performed
by hand
Trunk
Arm
Hand
Actions
performed
by mouth
Fingers
Mouth
Primary Auditory
Area
Primary
Visual Area

61. Video of basic cortical anatomy
From Medical Legal Art (2009)

62. The brain operates by means of connections
It is not a computer
Despite what you may have heard
Neurons do not store information
Rather, they operate by emitting activation
To other neurons to which they connect
Via synapses
Proportionate to activation being received
From other neurons via synapses
Therefore, a neuron does what it does by virtue of its connections to other neurons
The first big step in understanding how the brain operates

63. The cerebral cortex is a large network
Made up of interconnected neurons
A very large network
Dynamic
Changes take place in connection strengths
All of the information in it has the form of a network
The information is in the connectivity
(stay tuned for further details)
Every neuron is connected (directly or indirectly) to every other neuron

64. Some brain quantities
The cortex accounts for 60-65% of the volume of the brain
But has only a minority of the total neurons of the brain
Surface of the cortex – about 2600 sq cm
That is, about 400 sq inches
Weight of cortex –
Range: 1,130 – 1,610 grams
Average: 1,370 grams
Brain mass nears adult size by age six yrs
Female brain grows faster than male during 1st 4 yrs
Thickness of cortex – (inf. from Mountcastle 1998)
Range: 1.4 – 4.0 mm
Average: 2.87 mm

65. Cortical Neurons Cells, but quite different from other cells
Multiple fibers, branching in tree-like structures
Input fibers: Dendrites
Output fibers: Axons
Great variation in length of fibers
Short ones — less than one millimeter
Long ones — several centimeters
Only the pyramidal cells have such long ones

66. Cellular Communication: How to communicate with other cells
Method One (Nervous System):
Fibers projecting from cell body
Branching into multiple fibers
Input fibers – dendrites
Allow cell to receive from multiple sources
Output fiber – axon
Allows cell to send to multiple destinations
Method Two:
Circulation
Circulatory system
Endocrine system
Lymphatic system

67. Santiago Ramon y Cajal 1852-1934 Spanish neuroscientist
“The father of modern neuroscience”
Used microscope to examine brain tissue
Was skilled at drawing
Many of his drawings are still used today in teaching neuroscience
Nobel Prize in Medicine, 1906

68. View of the cortex by Ramon y Cahal

69. Some quantities relating to neurons
Number of neurons
In cortex: ca. 27 billion (Mountcastle)
Beneath 1 sq mm of cortical surface: 113,000
Synapses
440 million synaptic terminals/mm3 in visual area
Each neuron receives avg 3,400 synaptic terminals

70. Gray matter and white matter (coronal section)

71. Coronal section magnified
Grey matter, about 3 mm
from top to bottom,
Has 6 layers

72. Further magnification: Layers of the Cortex
From top to bottom, about 3 mm

73. Connecting fibers of pyramidal neurons
Apical dendrite
Basal dendrites
Axon

74. Types of cortical neurons
Cells with excitatory output connections (spiny)
Pyramidal cells (about 70% of all cortical neurons)
Spiny stellate cells (in layer IV)
Cells with inhibitory output connections (non-spiny)
Large basket cells (two subtypes)
Columnar basket cells
Double bouquet cells
Chandelier cells
Others

75. Types of cortical neurons

76. Pyramidal neurons About 70% of cortical neurons are of this type
Microelectronic probe
About 70% of cortical neurons are of this type

77. Structure of pyramidal neuron
Apical dendrite
Cell body
Axon
Myelin

78. Neuronal Structure and Function: Connectivity
White matter: it’s all connections
Far more voluminous than gray matter
Cortico-cortical connections
The fibers are axons of pyramidal neurons
They are all excitatory
White since the fibers are coated with myelin
Myelin: glial cells
There are also grey matter connections
Unmyelinated
Local
Horizontal, through gray matter
Excitatory and inhibitory

79. Pyramidal neurons and their connections
Connecting fibers
Dendrites (input): length 2mm or less
Axons (output): length up to 10 cm
Synapses
Afferent synapses: up to 50,000
From distant and nearby sources
Distant – to apical dendrite
Local – to basal dendrites or cell body
Efferent synapses: up to 50,000
On distant and nearby destinations
Distant – main axon, through white matter
Local – collateral axons, through gray matter

80. Interconnections of pyramidal neurons
Input from distant cells
Input from neighboring columns
Output to distant cells

81. Neuronal fibers Estimated average 10 cm of fibers per neuron
A conservative estimate
Times 27 billion neurons in cortex
Amounts to 2.7 billion meters of neural fibers in cortex (27 billion times 10 cm)
Or 2.7 million kilometers – about 1.68 million miles
Enough to encircle the world 68 times
Seven times the distance from the Earth to the moon
Big lesson: Connectivity rules!

82. Synapses The connections between neurons
Neurotransmitters cross from pre-synaptic terminal to post-synaptic terminal
Synaptic cleft – about 20 nanometers

83. Diagram of synaptic structure

84. Release of neurotransmitter
Presynaptic terminal releases neurotransmitter

85. Video of Synaptic Transmission
By Jokerwe

86. Quantity of synapses in the cortex
Synapses of a typical pyramidal neuron:
Incoming (afferent) – 50,000 (5 x 104)
Outgoing (efferent) – 50,000
Number of synapses in cortex:
28 billion neurons (Mountcastle’s estimate)
i.e., 28 x 109
Synapses in the cortex (do the math)
5 x 104 x 28 x 109 = 140 x 1013 = 1.4 x 1015
Approximately 1,400,000,000,000,000
i.e., over 1 quadrillion

87. Connections to other neurons
Excitatory
Pyramidal cells and spiny stellate cells
Output terminals are on dendrites or cell bodies of other neurons
Neurotransmitter: Glutamate
Inhibitory
All other cortical neurons
Output terminals are on cell bodies or axons of other neurons
Neurotransmitter: GABA
GABA: gamma-aminobutyric acid

88. Inhibitory connections
Axosomatic
Axoaxonal

89. Another kind of neurotransmitter
Released into interneural space, has global effect – e.g. serotonin, dopamine

90. Integration of neural inputs
Takes place at the axon hillock
Excitatory inputs are summed
Inhibitory inputs are subtracted
This summation is the amount of incoming activation
Determines how much activation will be transmitted along the axon (and its branches), hence to other neurons
Degree of activation is implemented as frequency of spikes

91. Transmission of activation (sensory neuron)
Kandel 28

92. Spread of activation Activation moves across links At the small scale
from neuron to neuron
At larger scale, across multiple links
In vision
From retina to conceptual area of cortex
In speech production,
from meanings to their expression
For a listener,
From expression to meaning

93. Frequencies relating to neural transmission
Duration of one action potential: about 1 ms
Frequency of action potentials: 1–100 per sec
Rate of transmission of action potential:
1–100 mm per ms
Faster for myelinated axons
Faster for thicker axons
Synaptic delay: ½ – 1 ms

94. Traveling the pathways of the brain
Neuron-to-neuron time in a chain (rough estimate)
Neuron 1 fires 100 Hz)
Time for activation to reach ends of axon
10 10 mm/ms = 1 ms
Time to activate post-synaptic receptor – 1 ms
Neuron 2
Activation reaches firing threshold – 4 ms (??)
Hence, overall neuron-to-neuron time – ca. 6 ms
Time required for spoken identification of picture
Subject is alert and attentive
Instructions: say what animal you see as soon as you see the picture
Picture of horse is shown to subject
Subject says “horse”
This process takes about 600 ms

95. Long-distance cortico-cortical connections
White matter –
Long-distance inter-column connections
Example: the arcuate fasciculus
A bundle of fibers very important for language
Connects Wernicke’s area to Broca’s area

96. Gray matter and white matter (coronal section)
Grey
matter
White

97. The White Matter
Provides long-distance connections between cortical columns
Consists of axons of pyramidal neurons
The cell bodies of those neurons are in the gray matter
Each such axon is surrounded by a myelin sheath, which..
Provides insulation
Enhances conduction of nerve impulses
The white matter is white because that is the color of myelin

98. Myelin (and other features)
Dendrite
Axon terminal
Node of Ranvier
Soma
Schwann cell
Myelin sheath
Nucleus

99. Functional layout of the gray matter
Primary areas:
Visual (occipital)
Auditory (temporal)
Somatosensory (parietal)
Motor (frontal)
Secondary areas
Association areas
Executive area, in prefrontal lobe

100. Hierarchy in cortical structure
Primary Somato-
sensory Area
Primary
Motor Area
All other areas are secondary, association,
or executive areas
Primary Auditory
Area
Primary
Visual Area

101. The cortical network has a hierarchical structure
At ‘bottom’, the primary systems
Somatosensory, visual, auditory, motor
In ‘middle layers’ the association areas and ‘higher-level’ motor areas
At ‘top’ (prefrontal cortex) the supra-modal association area
Frontal lobe comprises 1/3 of the area of the cortex
Prefrontal cortex is nearly 1/4 of the whole cortex
Prefrontal functions
Planning, anticipation, mental rehearsal, prediction, judgment, problem solving

102. Sequence of development in the cortex

103. T h a t ’ s i t f o r t o d a y