The cerebrum is the largest part of the human brain and consists of two hemispheres separated by the longitudinal cerebral fissure. Each hemisphere has an outer layer of grey matter called the cerebral cortex and an inner mass of white matter. The cortex is highly folded to fit within the skull, forming convolutions called gyri separated by sulci. The cortex can be divided into four lobes - frontal, parietal, temporal and occipital - based on sulci and gyri. Within each lobe are functional areas including motor, sensory, and association areas that control voluntary movement, process sensation, and integrate sensory information respectively.

1. CEREBRUM
DR.SREEKALA.C.NAIR
B.SC, BHMS, M.SC
MEDICAL ANATOMY

2. CEREBRUM
• The cerebrum is the largest part of the human brain
• It has two lateral halves called cerebral hemispheres
• The two cerebral hemispheres are incompletely separated by
a median cleft called longitudinal cerebral fissure
• The cleft is complete in the front and behind and in the
middle it extends downwards up to the corpus callosum
• Corpus callosum is the large mass of the white fibres joining
the two cerebral across the median plane

5. Longitudinal cerebral fissure is
occupied by the following structures
1. Falx cerebri
2. Fold of arachnoid that follows the surface of falx cerebri
3. Pia matter covering the medial surface of falx cerebri
4. Anterior cerebral arteries and veins

7. Cerebral hemisphere
1. An outer layer of grey matter called cerebral cortex
2. An inner mass of white matter
3. Large masses of grey matter embedded in the basal part of
the white matter called basal ganglia
4. A cavity within it called lateral ventricle

10. External features
1. Poles
2. Surfaces
3. Borders
4. Sulci
5. Gyri

11. poles
1. Frontal pole
2. Occipital pole
3. Temporal pole

12. surfaces
• Three surfaces
1. Superolateral
2. Medial
3. Inferior
a) Orbital part – small/anterior
b) Tentorial surface – large/posterior

14. Borders
• Superomedial border – separates the superolateral surface
from the medial surface
• Superciliary border is at the junction of superolateral and
orbital surfaces
• Inferolateral border separates the superolateral surface from
the tentorial surface

15. Borders
• The medial orbital border separates the medial surface from
the orbital surface
• Inferomedial /hippocampal border surrounds the cerebral
peduncle
• The medial occipital border separates the medial surface
from the tentorial surface

17. Sulci and gyri
• the cerebral cortex is highly extensive in mam so to
accommodate it within the rigid cranial cavity the surface of
the cerebral hemisphere becomes folded and produce
numerous convolutions separated by fissures
• These convolutions and fissures are termed as gyri and sulci

19. Main cerebral sulci
1. Lateral
2. Central
3. Parieto-occipital
4. Calcarine sulci

20. Lateral sulcus (of
sylvius)
• Lateral sulcus has a stem and three rami
• The stem of the sulcus begins as a deep cleft on the inferior
surface of the cerebral hemisphere at the anterior perforated
substance
• When it reaches the superolateral surface it divides into 3
rami:
1. Anterior horizontal
2. Anterior ascending
3. Posterior

22. Central sulcus
(of Rolando)
• Central sulcus begins by cutting the superomedial border of
the hemisphere 1cm behind the midpoint between the frontal
and occipital poles
• The central sulcus forms the boundary between the motor
area of cerebral hemisphere in front and the sensory area
behind

24. Calacrine sulcus
• It is present on the medial surface of the cerebral hemisphere

26. Parieto-occipital sulcus
• It is present on the medial surface of the hemisphere

27. Lobes of the cerebral
hemisphere
• The superolateral surface is divided into 4 lobes
• Frontal
• Parietal
• Temporal
• Occipital
• Superolateral surface is divided into 4 lobes by three sulci
• Central
• Lateral
• Parieto – occipital
• And two imaginary lines

29. Insula/island of reil
• It is also called the central lobe of the cerebrum
• Insula is the submerged portion of the cerebral cortex in the
floor of the lateral sulcus
• It can be only seen when the lips of the lateral sulcus are
widely pulled apart
• It is triangular in shape and surrounded all around by a sulcus
– circular sulcus except anteroinferiorly at its apex called
limen insulae

32. Insula/island of reil
• The insula is divided into two regions –anterior and posterior by a
central sulcus
• The anterior region presents 3-4 short gyri called gyri brevia
• Posterior region presents 1-2 long gyri called gyri longa
• The insula is hidden from the surface by the overgrown cortical
areas of frontal , parietal and temporal lobes
• These areas are termed as frontal , frontoparital and temporal
opercula
• The superior surface of the temporal operculum presents anterior
and posterior transverse temporal gyri
• The middle cerebral artery and deep middle cerebral vein lie on
the surface of the insula

34. Sulci and gyri on the superolateral
surface of the cerebral hemisphere
• In the frontal lobe
The prefrontal sulcus
• The area between the central and precentral sulci is called
precentral gyrus
Anterior to the precentral sulcus there are two sulci called
superior and inferior frontal sulci
• These divide the frontal lobe into suprerior , middle and
inferior frontal gyri

36. Sulci and gyri on the superolateral
surface of the cerebral hemisphere
• In frontal lobe
• The anterior and ascending rami of lateral sulcus divide the
inferior frontal gyrus into 3 parts
• The part below the anterior ramus is called pars orbitalis
• The part between anterior and ascending rami is the pars
triangularis
• The upper part posterior to the ascending ramus – pars
opercularis

38. Sulci gyri in parietal
lobe
• Postcentral sulcus
• The area between the postcentral and central sulci is called
postcentral gyrus
• The rest of the parietal lobe is divided into a superior and
inferior parietal lobules by an intra-parietal sulcus

40. Sulci gyri in parietal lobe
• The posterior ramus of lateral sulcus and the posterior ends of
the superior and inferior temporal sulci extends into the
inferior parietal lobule and divide it into 3 parts
1. Supramarginal gyrus – surrounds the posterior ramus of the
lateral sulcus
2. Angular gyrus – surrounds the superior temporal sulcus
3. Temporo-occipitalis – surrounds the inferior temporal
sulcus

43. Sulci gyri in temporal
lobe
1. Superior temporal sulcus
2. Inferior temporal sulcus
• These divide the temporal lobe into superior , middle and
inferior temporal gyri
• The superior surface of superior temporal gyrus presents two
transverse temporal gyri.
• The anterior transverse temporal gyrus also called
HESCHL’S GYRUS forms the primary auditory areas of the
cortex

45. Sulci gyri in the occipital
lobe
• Occipital lobe posses three short sulci
1. Lateral occipital sulcus runs horizontally and divides the
lobe into superior and inferior occipital gyri
2. Transverse occipital
3. Lunate sulcus is C shaped sulcus

54. Cerebral cortex
• Cerebral cortex is an intricate blend of nerve cells and fibres
,neuroglia and blood vessels
• Microscopically the cortex consists of six layers or laminae
lying parallel to the surface
• Molecular (plexiform) layer
1. External granular layer
2. External pyramidal layer
3. Internal granular layer
4. Internal pyramidal (ganglionic) layer
5. Multiform layer (layer of polymorphic cells)

55. Types of neurons in the
cerebral cortex
1. Pyramidal cells
2. Stellate/granule cells
3. Horizontal cells of Cajal
4. Cells of Martinotti
5. Fusiform cells

57. Types of neurons in
cerebral cortex
1. Pyramidal cells
• They are pyramidal in shape with their apices directed
towards the surface. The axon arise from the base of the cell
body and dendrites arise from its apex and basal angles. The
axons enter the white matter as projection fibres
2. Stellate/granule cells
• They have star shaped body and are smaller than the
pyramidal cells. They have short axons and many dendrites
• Koniocortex – in certain areas of cerebral cortex these cell
are so numerous they resemble a cloud of dust particle.

58. Types of neurons in cerebral
cortex
3. Fusiform cells
• They have a fusiform cell body .they are concentrated in the
deep cortical layers
4. The horizontal cells of Cajal
• They are fusiform and present horizontally. They are found in
the most superficial layer of the cortex
5. Cells of Martinotti are small multipolar cells that are present
throughout the layers of cerebral cortex

59. Layers of cerebral cortex
1. Molecular layer – it is made up of predominantly of nerve
fibres and a few horizontal cells of Cajal
2. External granular layer is made up of mainly densely
packed stellate cells
3. External pyramidal cells is made up of small and medium
sized pyramidal cells

60. Layers of cerebral cortex
4. Internal granular layer –it is made up of stellate cells. In the
middle of this layer there is a band of horizontally arranged
white fibres called white stria or external band of
Baillarger.The white stria is the most marked in the visual
cortex – so it is also called striate cortex
5. Internal pyramidal layer- It is made up of large pyramidal
cells (of betz).the basal part of this layer contains a thin band
of horizontally arranged fibres called inner band of Baillarger .
6. Multiform layer – it is made up of cells of multiple forms.
This layer fuses with the white matter.

62. Functional areas of the
cerebral cortex
• Brodmann has divided the cerebral cortex into 47 areas.
• Types of cortical areas:
1. Motor area
2. Sensory area
3. Association areas

64. Functional area in the
frontal lobe
Primary motor area(area 4 of brodmann)
• Location
• Precentral gyrus on superolateral surface
• Anterior part of the paracentral lobule on the medial surface
• It contains large number of pyramidal cells including the
large pyramidal cells of Betz

65. Functional area in the frontal
lobe
Primary motor area(area 4 of brodmann)
Representation of the body
• The body is represented upside down (inverted homunculus) in the
primary motor area.
• The sequence of representation of body parts from above downwards is
leg , thigh , trunk , upper limb , face , larynx , lips , jaws ,tongue and
pharynx
• The area of the cortex representing a part of the body is not proportional
to its size of that part , but to the skill movements performed by that
part. Thus the movements of the hand , lips, tongue and larynx are
represented by relatively larger areas of the cortex

67. Functional area in the frontal
lobe
• Functions
1. It controls the voluntary movements of the opposite side of
the body
2. It also controls the acts of micturition and defecation
• Applied anatomy
1. A lesion of this area gives rise to upper motor neuron type
of paralysis on the opposite side if the body

68. Premotor area(area 6 of
brodmann)
• Location
• Anterior to the primary motor area and Extends on to the
medial surface of the hemisphere.
• It is responsible for performance of voluntary motor activity
• Lesion of premotor area produce difficulty in the
performance of skilled movements

70. Supplementary motor
area
• It is located in the medial frontal gyrus
• The body is represented from before backwards in craniocaudal
order
• Stimulation of this area produces – assumption of posture –
turning the head , assuming position of trunk and lower limb etc.
• Lesion of supplementary area produce bilateral flexor Hypotonia
with no paralysis

71. Frontal eye field (area 8 of
brodmann)
• Location
• Posterior part of the middle frontal gyrus
• The frontal eye field controls voluntary scanning movements of
the eyes and is independent of the visual stimuli
• The frontal eye field is connected to the visual area of occipital
cortex by association fibres
• Lesion of frontal eye field of one hemisphere cause the two eyes
to deviate to the side of lesion and in ability to turn the eyes to the
opposite sides

72. Motor speech area
• Motor speech area of Broca is located in the pars triangularis
(area450 and pars opercularis (area 44) of the inferior gyrus of
frontal lobe of the left hemisphere(dominant) in most of the
individuals and 30% cases it is present in the right hemisphere
(left handed persons).
• Function
• It is essential for production of expressive speech
• If the motor speech area is damaged the individual will suffer
from motor aphasia

73. Prefrontal area
• The part of the frontal lobe rostral to the motor and premotor
area is referred to as prefrontal area
• This area is concerned with individuals personality
• It is also concerned with depth of emotions , social , moral
and ethical awareness , concentration ,orientation and
foresightedness .
• Bilateral destruction of this area results in change in
personality of the individual
• He/she depicts inappropriate social behavior e.g. use of
obscene language , urinating in public ,becomes careless
about his/her dress and appearance.

74. Functional areas of parietal
lobe

75. Primary sensory area
3, 1 and 2 of brodmann)
• Location
• The primary sensory is located in the postcentral gyrus and
posterior wall of the central sulcus
• Representation of body
• The body is represented upside down similar to the motor
area

77. Primary sensory area
• Function
• It is concerned with perception of exteroceptive (pain, light
touch and temperature) and proprioceptive sensation from
opposite half of the body
• Applied anatomy
• The lesion of primary sensory area lead to loss of
appreciation of extroceptive and proprioceptive sensations in
the opposite half of the body

78. Secondary area
• It is located in the upper lip of the posterior ramus of the
lateral sulcus
• This area relates more to the pain perception
• Ablation of this area may relieve intractable pain

79. Sensory association
• This occupies the superior parietal lobule
• It is concerned with perception of shape , size , roughness and texture of
the objects
• Thus it enables the individual to recognize the object placed in his/her
hand with out seeing them
• Such ability is reffered to as sterognosis
Lesion of this area results in inability to recognize an object by its feel.
This condition is called tactile agnosia or astereognosis

80. Sensory speech area of wernicke
• Location
• Brodmann’s area 22,39 and 40
• Posterior part of the superior temporal gyrus (broadmann area
22) of the dominant cerebral hemisphere
• Parts of the inferior parietal lobule including the
supramarginal and angular gyri corresponding to
BRODMANN AREAS 40 and 39.

81. Sensory speech area of wernicke
• Functions
1. Understanding the written and spoken languages i.e. it is
concerned with the understanding and inter-presentation of
language through visual and auditory input
2. Essential for constant availability of learned word patterns
3. Essential for the process of learning such as reading ,
writing and computing

82. Sensory speech area of wernicke
• Applied anatomy
• If the sensory speech area is damaged the affected individual
will suffer from receptive or sensory aphasia
• Other defects seen in sensory aphasia are :
• Alexia – disability in reading
• Agraphia – disability in writing
• Acalculia – disability in computing
• Anomia – inability in recognition of names of objects

83. Functional areas in
temporal lobe

84. Primary auditory area
brodmann areas 41 and 42
• It occupies the anterior transverse temporal gyrus (Heschl’s
gyrus)
• This area is concerned with reception of isolated impressions
of loudness , quality and pitch of the sound
• Unilateral lesions of the primary auditory area results in
slight loss of hearing but loss will be greater in opposite ear.
• Bilateral lesions of the primary auditory areas cause complete
cortical deafness

85. Secondary auditory area/auditory
association area
(brodmann’s area 22)
• It is situated on the lateral surface of the superior temporal
gyrus slightly posterior to the primary auditory area which it
surrounds
• This area is necessary for the interpretation of the sound
heard
• The lesion of secondary auditory area result in an inability to
interpret the meaning of the sounds heard and patient may
experience word deafness (auditory verbal agnosia)

86. Functional areas in
occipital lobe

87. Primary visual area /striate area
brodmann’s area 17
• It is situated in the walls and floor of the posterior part of the
calcarine sulcus and extends around the occipital pole on to
the superolateral surface of the hemisphere
• The most marked structural feature of the visual cortex is the
presence of white stria (visual stria of gennari) hence the
name striate area
• It is concerned with reception and perception of isolated
visual impression like colour , size , form ,motion
,illumination and transparency

88. Primary visual area /striate area
brodmann’s area 17
• Applied anatomy
• Lesions in the primary visual area result in the loss of vision
in the opposite visual field
• The unilateral lesions of superior wall of postcalacrine sulcus
result in inferior quadrantic hemianopia
• Lesion involving inferior wall of postcalacarine sulcus result
in superior quadrantic hemianopia
• Causes
• Vascular accidents
• Tumours
• Injuries from gunshot wounds

89. Secondary visual area/visual
association area
(brodmann’s areas 18 and 19)
• The secondary visual area surrounds the primary visual area
• It is responsible for recognition of the objects seen
• Lesions of secondary visual area result in loss of ability to
recognize (visual agnosia) seen in opposite field of vision

90. Other functional areas in
cerebral cortex
• Taste area(gustatory area) – located in the inferior part of the
parietal lobe
• Vestibular area – located in the part of the postcentral gyrus
which is concerned with the sensation of the face
• Olfactory area (brodmann area 28) – located in the anterior
part of the parahippocampal gyrus and uncus