The document describes the structure and function of the different areas of the cerebral cortex. It discusses the six layers of the cortex and how areas are classified as homotypical or heterotypical. It then outlines the major cortical areas including their Brodmann areas, functions, and implications of damage. The primary areas are involved in motor control, sensory perception, and language comprehension and expression. Surrounding association areas integrate information from different sources.

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7. Structure of the cerebral cortex
grey matter outside, white matter inside
consists of approx. 10 billion neurons
thickness : 1.5 – 4.5mm
surface has been increased by gyri
which are separated by sulci
contains a mixture of nerve cells,
nerve fibers, neuroglia and blood cells
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8. Layers of the cerebral cortex
i. Molecular /plexiform layer
ii. External granular layer
iii. External pyramidal layer
iv. Internal granular layer
v. Internal pyramidal layer
vi. Multiform layer
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9. Variations in cortical structure
• The areas in the cortex which contain all the 6 layers
are called homotypical
• The areas in which the basic 6 layers cannot be
identified are heterotypical
• Heterotypical areas are further described as
granular and agranular type
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11. CORTICAL AREAS
Different areas of the cerebral
cortex area functionally specialized
The primary sensory areas (with granular cortex) and
the primary motor areas (with agranular cortex) are
heterotypical and form only a small part of the total
cortical surface
The remaining areas have all 6 layers and are known
as homotypical or association areas
Brodmann’s areas8/9/2013 11

12. FRONTAL LOBE
i. PRIMARY MOTOR AREA
ii. PRE MOTOR AREA / SECONDARY MOTOR AREA
iii. SUPPLEMENTARY MOTOR AREA
iv. MOTOR SPEECH AREA OF BROCA
v. FRONTAL EYE FIELD
vi. PRE FRONTAL CORTEX
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13. i. PRIMARY MOTOR AREA
• Brodmann’s area 4
• produces isolated movements of the opposite side of
the body
• Origin of 40% of pyramidal fibers
• Specific regions within the area are responsible for
movements in the specific parts of the body
• Only movements are represented in this area and not the
muscles
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15. ii. PRE MOTOR AREA
• Brodmann’s area 6
• Main site for cortical origin of extra pyramidal fibers
• Receives inputs from the sensory cortex , thalamus &
basal ganglia
• Function: to store programs of motor activity
assembled as a result of past experience
• It programs the intended activity of the primary
motor cortex & controls the movements in progress
• It is responsible for voluntary motor activities
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16. iii. SUPPLEMENTARY MOTOR AREA
• It is located at the medial extension of area 6, onto
the midline surface of the hemisphere
• Possible functions:
 postural stabilization of the body
 the coordination of both sides of the body such as
during bimanual action
 the control of movements that are internally
generated rather than triggered by sensory events,
 control of sequences of movements
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17. iv. MOTOR SPEECH AREA OF BROCA
• Brodmann’s area 44 & 45
• Present on the pars opercularis (44) and the pars
triangularis (45) of the IFG on the dominant
hemisphere
• It is responsible for expressive speech &
vocalization
• It brings about formation of words by its
connections to adjacent primary motor cortex
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18. v. FRONTAL EYE FIELD
• Brodmann’s areas 6,8 & 9
• The frontal eye field is reported to be activated
during the initiation of eye movements such as
voluntary saccades and pursuit eye movements
• It is one the most important brain areas in generation
& control of eye movements especially in the
direction contralateral to the FEF’s location
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19. vi. PRE FRONTAL CORTEX
• Brodmann’s area 9,10,11 & 12
• Concerned with planning complex cognitive behavior,
personality expression, decision making, and
moderating social/moral/ethical behavior, insight,
foresight etc.
• Regulates a person’s depth of feeling, concentration,
orientation
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20. PARIETAL LOBE
i. PRIMARY SOMESTHETHIC AREA
ii. SECONDARY SOMESTHETIC AREA
iii. SOMESTHETIC ASSOCIATION AREA
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21. i. PRIMARY SOMESTHETHIC AREA
• Brodmann’s areas 3,1,2
• These areas receive sensory information
from thalamic nerve projections
• They are concerned with the perception of
exteroceptive ( pain, touch & temperature) and
proprioceptive (vibration, muscle & joint sense)
sensations from the opposite half of the body
• Sensory homunculus
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23. ii. SECONDARY SOMESTHETIC AREA
• Brodmann's area 43
• Smaller and less important than primary sensory area
• Functional significance is not known (lesions to this
area may impair some elements of sensory
discrimination)
• Neurons responds to sensory stimuli bilaterally,
although with much less precision than the primary
cortex
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24. iii. SOMESTHETIC ASSOCIATION AREA
• Brodmann’s area 5 & 7
• This receives synthesized connections from the
primary and secondary sensory cortices
• Main function: to receive & integrate different
sensory modalities e.g. stereognosis
• relates to past sensory experiences so that
information may be interpreted and recognition
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25. TEMPORAL LOBE
i. PRIMARY AUDITORY AREA
ii. SECONDARY AUDITORY AREA
iii. SENSORY SPEECH AREA OF WERNICKE
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26. i. PRIMARY AUDITORY AREA
• Brodmann’s area 41 & 42
• Located in the inferior wall of the lateral sulcus and
on the superior surface of the STG
• Anterior part of the primary auditory area is
concerned with the reception of sounds of low
frequency and posterior part of the area is
concerned with high frequency
• Unilateral lesion of the auditory area produces
partial deafness in both ears (greater loss is on
contralateral side)
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27. ii. SECONDARY AUDITORY AREA
• Area 22
• situated on the lateral surface of the STG slightly
posterior to the primary auditory area
• Receives impulses from primary auditory area &
thalamus & correlates with past auditory
experiences
• Responsible for interpretation of sounds & for
association of auditory input with other sensory
information
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28. iii. WERNICKE’S SENSORY SPEECH AREA
• Brodmann’s area 39 & 40
• Located in the dominant hemisphere
• Occupies the posterior part of the STG of the
temporal gyrus and angular (area 39) & supra marginal
(area 40) gyri of the parietal lobule
• Permits understanding of the written and spoken
language and enables a person to read a sentence,
understand it and say it aloud
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29. OCCIPITAL LOBE
i. PRIMARY VISUAL AREA
ii. SECONDARY VISUAL AREA
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30. i. PRIMARY VISUAL AREA
• Brodmann’s area 17
• It contains white stria hence also called of as striate area
• It receives afferents from the temporal half of the
ipsilateral retina & nasal half of the contralateral retina
• It is concerned with reception & perception of isolated
visual impressions like color, size, form, motion, illumination
& transparency
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31. ii. SECONDARY VISUAL AREAS
• Brodmann’s area 18 & 19
• Receives information from the primary visual area
• relate the visual information to past experiences to enable
the individual to identify and appreciate what he/she is
seeing
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32. OTHER CORTICAL AREAS
TASTE AREA
• situated in lower end of post central gyrus in superior
wall of lateral sulcus near the insula
• Brodmann’s area 43
VESTIBULAR AREA
• Located opposite the auditory area in the superior
temporal gyrus
• This area along with the vestibular apparatus of the
middle ear are concerned with appreciation of the
positions and movements of head in space.
• The movements of eyes & muscles of the trunk and
limbs are influenced in maintenance of balance
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36. WHITE MATTER OF THE CEREBRAL
HEMISPHERES
• It is composed of myelinated nerve
fibers of different diameters
supported by the neuroglia
• It lies deep in the greater part of
each cerebral hemisphere
• According to their connections they
are classified as-
Association fibers
Projection fibers
Commissural fibers
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37. CEREBRAL DOMINANCE
Dominant hemisphere refers to the side concerned
with the perception and production of
language/speech
90% of have left hemispherical dominance so
consequently over 90% of adult population is right
handed
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39. Implications of damage to the following areas
PRIMARY MOTOR AREA (4):
 paralysis of the contralateral extremities with the
finer & skilled movements suffering the most
PREMOTOR AREA (6):
 little loss of strength, more difficulty in performing
skilled movements
PRIMARY MOTOR + PREMOTOR AREA:
 most complete form of paralysis
 Jacksonian seizure – due to irritative lesion of area 4
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CLINICAL ASPECTS

40. PRIMARY SOMESTHETIC AREA
 Contralateral sensory disturbances
SECONDARY SOMESTHETIC AREA
 No recognizable sensory defects
SOMESTHETIC ASSOCIATION AREA
 Astereognosis
PREFRONTAL CORTEX
 Personality changes, Euphoric
tendencies
 Loss of initiative & judgment
 Socially/morally unacceptable behavior
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41. MOTOR SPEECH AREA OF BROCA (44 & 45)
(dominant side)
 Expressive aphasia/ motor aphasia/ non fluent
aphasia
SENSORY SPEECH AREA OF WERNICKE (39 & 40)
(dominant side)
 Receptive aphasia/ sensory aphasia/ fluent aphasia
MOTOR + SENSORY SPEECH AREAS
(dominant side)
 Global aphasia
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42. References:
• Textbook of Clinical neuro-anatomy: edition 6
Richard Snell
• Inder bir Singh
• BD chaurasia
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44. • Damage to area 39 & 40 of dominant
side?
• Sensory homunculus lies on the.. ?
• How many layers are there in the cortex ?
• Damage to area 44 & 45 of dominant side?
• Motor homunculus lies on the.. ?
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