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Cerebral

Cortex

Won Taek Lee, M.D. Ph.D.

Department of Anatomy,

Yonsei University College of Medicine

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The layer of gray matter covering

the entire surface of cerebral hemisphere

  • Migration of neurons from inner mantle layer of

neural tube

  • Accommodates enormous number of neurons

- Large surface area accommodates

more neurons than deep nuclei

- Gyri and sulci also increase surface area

- Laminar organization also accommodates

enormous number of neurons

Cerebral Cortex

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Numerical Data

Total surface area: 2200 cm2 (2.5 ft2)

about 1/3 ------ surface area

about 2/3 ------ hidden in the sulci

Thickness: 1.5 mm (V I) - 4.5 mm (M I)

Generally, thickest over the crest of the convolution

and, thinnest in the depth of sulci

Weight: 600 gm (40 % of total brain weight)

180 gm --------- neurons

420 gm --------- glial cells

Cerebral Cortex

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Numerical Data

Number of neuronal cells in cerebral cortex

neurons ----------- 10-15 billion

glial cells ---------- 50 billion

Estimation of number of cortical neurons

von Economo and Koskinas (1925) 14.0 billion

Shariff (1953) 6.9 billion

Sholl (1956) 5.0 billion

Pakkenberg (1966) 2.6 billion

Cerebral Cortex

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Subdivision of Cerebral Cortex

Allocortex

Archicortex (Archipallium)

Palaeocortex (Paleopallium)

Isocortex

Neocortex (Neopallium)

cf. mesocortex, juxtallocortex, mesallocortex

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Isocortex typical 6 layered cortex

I. Molecular Layer

II. External Granular Layer

III. External Pyramidal Layer

IV. Internal Granular Layer

V. Internal Pyramidal Layer

VI. Polymorphic Layer

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Histological Organization

Cellular Elements

1. Pyramidal Cell - output neuron

giant pyramidal cell of Betz

2. Fusiform Cell --- modified pyramidal cell

3. Granular (Stellate) Cell

basket cell, double bouquet cell, bipolar cell,

chandlier cell, neurogliform cell

4. Horizontal Cell of Cajal (Retzius-Cajal cell)

5. Cells of Martinotti

Cerebral Cortex

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1. Pyramidal Cell

2. Fusiform Cell

3. Granular (Stellate) Cell

4. basket cell

5. double bouquet cell

6. chandlier cell

7. neurogliform cell

8. Horizontal Cell of Cajal

9. Cells of Martinotti

a: axon

Cerebral Cortex

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I. Molecular Layer

II. External Granular Layer

III. External Pyramidal Layer

Line of Kaes-Bechterew

IV. Internal Granular Layer

Outer band of Baillarger

- Line of Gennari in area 17

V. Internal Pyramidal Layer

Giant pyramidal cell of Betz

Inner Band of Baillarger

VI. Polymorphic Layer

Golgi Nissl Weigert

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1. corticocortical fiber

association fiber

commissural fiber

2. thalamocortical fiber - specific and non-specific

3. extrathalamic subcortical fiber

cholinergic fiber - acetylcholine

basal nucleus of Meynert

mesolimbic dopaminergic fiber - dopamine

ventral tegmental area

serotonergic fiber – serotonine - raphe nuclei

norepinephrinergic fiber - norepinephrine

nucleus locus ceruleus

Cortical Afferent Fiber

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Cortical Afferent Fiber

1. association fiber

2. commissural fiber

3. specific

thalamocortical fiber

4. non-specific

thalamocortical fiber

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1. Corticofugal Fiber - Projection Fiber

corticostriate fiber

corticothalamic fiber

corticorubral fiber

corticotectal fiber

corticopontine fiber

cortico-olivary fiber

corticobulbar fiber

corticospinal fiber

2. Corticocortical Fiber

Association fiber

Commissural fiber

Cortical Efferent Fiber

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5. association fiber

6. commissural fiber

7. corticostriate fiber

8. corticorubral fiber

corticopontine fiber

corticobulbar fiber

9. corticospinal fiber

corticotectal fiber

10. corticothalamic fiber

Cortical Efferent Fiber

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A. pyramidal neuron

B. excitatory

granular cell

C. inhibitory

granular cell

1. afferent fiber

2. efferent fiber

3. corticothalamic fiber

Columnar Cortical Unit and Cortical Circuitary

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A. Homotypical isocortex

------- association cortex

B. Heterotypical isocortex

1. granular cortex

--- primary sensory cortex

V I (17), S I (3), A I (41)

2. agranular cortex

--- motor cortex

M I (4), PM (6)

Regional Variation of Cortical Lamination

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Von Economo’s classification of cortical types

1. agranular, 2. frontal, 3. parietal, 4. polar, 5. granular

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1. agranular, 2. frontal, 3. parietal, 4. polar, 5. granular

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Phrenology of Gall and Spurzheim

Clinical evidences

Broca’s area (1861)

Jacksonian epilepsy (1864)

Experimental evidences

Fritsch and Hitzig (1870) --- motor cortex

von Gudden (1870) ---- visual cortex

Ferrier (1873) ---- auditory cortex

Functional Localization of Cerebral Cortex

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Albertus Magnus

(1206-1280)

Phrenology of Gall (1758-1828)

and Spurzheim (1776-1832)

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PET (positron emission tomography) scan

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based on cytoarchitectonic studies

Campbell (1905) -------- about 20 areas

Brodmann (1909) ------ 47 areas

- most popular

Vogt and Vogt (1919) - over 200 areas

von Economo (1929) -- 109 areas

Morphological Classification of Cortical Areas

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Brodmann’s cytoarchitectorial map (Lateral surface)

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Brodmann’s cytoarchitectorial map (Lateral surface)

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Sensory area

primary sensory area

secondary sensory area

Motor area

primary motor area

secondary motor area

supplementary motor area

Association area

parietal, occipital and temporal cortex

- conceptual elaboration of sensory data

prefrontal (frontal) cortex

- judgement, foresight

Functional Localization of Cerebral Cortex

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Somesthetic Area (Somesthesia) S I, S II

Visual Area (vision) V I, V II

Auditory Area (Hearing) A I, A II

Vestibular Area (Equilibrium)

Gustatory Area (Taste)

Olfactory Area (Smell)

Sensory Areas

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S I ----- 3, 1, 2 (postcentral gyrus)

afferernts: ventrobasal complex (VPLc, VPM)

discrimination of position and intensity of sensation

S II ---- superior bank of lateral fissure

no clinical disorders

Somesthetic Association Cortex

------- 5, 7 (parietal lobule, precuneus)

afferents: S I, LP of thalamus

integration of geneal sensation with past experience

tactile agnosia, astereognosis

Somesthetic Area

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Sensory Homunculus

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Thalmocortical

connection

(VPLc S I)

Central region

--- cutaneous (3b, 1)

Peripheral region

--- deep (3a, 2)

Primary

Somesthetic

Area

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Secondary

Somesthetic

Area (SII)

superior bank of

lateral fissure

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V I ----- 17 (striate cortex - line of Gennari)

greatly thickened outer band of Baillarger

heterotypical isocortex

afferent: LGd of thalamus

visual field defect:

homonymous quadranopsia and macular sparing

V II ---- 18, 19 (visual association area)

afferents: V I, pulvinar of thalamus

integration of vision with past experience

visual agnosia

cf. occipital eye field

Visual Cortex

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Visual

Areas

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V4

(color)

Face

recognition

Perceive

Facial Expression

Visual

association

areas

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A I ----- 41, 42 (trannsverse temporal gyrus of Heschl)

heterotypical isocortex

afferents: MGv of thalamus - core projection

slight diminution in auditory acuity

A II ---- 22 (Wernike's area of original connotaion)

not well-defined

afferents: non-laminar part (MGm, MGd) – belt projection

A I

auditory agnosia - sensory aphasia

Auditory Cortex

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Auditory

Areas

Planum

temporale

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Auditory

Areas

A I ----- 41, 42

A II ---- 22

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Vestibular Area

Area 3a and 2v of S I

afferents: VPLo

[superior temporal gyrus anterior to A I]

Gustatory Area

Area 43 (inferior end of postcentral gyrus)

afferents: VPMpc

Olfactory Area

Piriform Lobe - Limbic System

Other Primary Sensory Areas

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primary Motor Area (M I)

Premotor Area (PM)

Supplementary Motor Area (SMA)

Frontal Eye Field

Motor Areas

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Motor Homunculus

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M I ------- 4

precentral gyrus of lateral surface

anterior part of paracentral lobule

heterotypical agranular cortex

giant pyramidal cell of Betz

afferents: premotor area, SMA, S I

VLc, VPLo of thalamus

Motor Homunculus

Upper Motor Neuron (UMN) syndrome

Primary Motor Area

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Premotor Area (PM) ------ lateral surface of 6

afferents: VLc, VPLo of thalamus from cerebellum

Supplementary Motor Area (SMA)

-------------------------- medial surface of 6

afferents: VLo, Vapc of thalamus from basal ganglia

Frontal Eye Field ---------- 8

voluntary tracking movement

Other Motor Areas

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Brodman’s Map of Motor and Sensory Areas

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Language Areas ----- 22, 39, 40, 44, 45

Posterior Parietal Association Area

------ 5, 7 (39, 40)

body image

Temporal Association Area

------ 20, 21, 37, 38 (22)

multisensory integration, conceptual ideation

Prefrontal Association Area

----- 9, 10, 11, 12, 46, 47 (44, 45)

judgement, foresight, personality

Association Areas

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Order of Cortical Maturation

1

2

3

3

3

2

1

1

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Agnosia

Tactile agnosia

Visual agnosia

Alexia

Auditory agnosia

Apraxia

Aphasia

Wernicke’s (receptive) aphasia

Broca’s (Motor) aphasia

conduction aphasia

global aphasia

Disorders of Association Cortex

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Apraxia

The inability to execute a voluntary motor movement despite being able to demonstrate normal muscle function.

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Sensory Language Area (Wernike's area) ---- 22, 39, 40

Receptive Aphasia - area 22

defect in comprehension, good spontaneous speech

Anomic Aphasia - word finding difficulty

Jargon aphasia - fluent, but unintelligiable jargon

39 (supramarginal gyrus), 40 (angular gyrus)

Superior Longitudinal Fasciculus

Conduction Aphasia

good comprehension, good spontaneous speech

poor repetition, poor response

Motor Language Area (Broca’s area) --- 44, 45

Motor Apahsia

good comprehension, no speech

Language Areas

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Language Areas (Geschwind Model)

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Photograph of the brain of Paul Broca’s patient called “Tan” (real name is Leborgne).

Broca’s Area

Pars triangularis and pars opercularis of the inferior frontal gyrus of dominant hemisphere.

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Paul Broca (1824-1880) Carl Wernicke (1848-1905)

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PET (positron emission tomography) scan

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Composite radioisotope brain scan

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Cerebral Dominance (Lateralization, Asymmetry)

Dominant Hemisphere

Language

– speech, writing

Calculation

Non-dominant Hemisphere

Spatial Perception (3D subject)

Singing

Playing musical instrument

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Language

Speech

Writing

Calculation

3D perception

Singing

Playing Musical

instrument

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Roger Sperry (1913-1994)

1981 Nobel Laureate

                                           

Split Brain

Commissuratomy

(split corpus callosum)

Two minds in one brain?

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  • Frontal Granular Cortex

Lateral Prefrontal Association Area

------ 9, 10, 46

judgement, foresight, problem solving

Orbitofrontal Cortex

------ 11, 12, 47

emotion, olfaction, personality

Case of Phineas Gage

Prefrontal Leucotomy of Moniz and Freeman

Prefrontal Association Areas

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Phineas Gage

(1823-1861, accident in 1848)

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Phineas Gage’s lesion reconstructed

(H. Damasio and R. Frank, 1992)

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Prefrontal Leucotomy

(Frontal Lobotomy)

Antonio Egas Moniz

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Conceptual Framework of Cerebral Function