cerebrum

1. Cerebrum
By
Dr.Anoop.V.Nair
Dept of Cons Dentistry &
Endodontics
KVG Dental College, Sullia

2. The brainThe dental pulp

3. CONTENTS
• Anatomical and functional relationships
• Functions of specific cortical areas
• The association areas
• Functions of the brain in communication
• Function of corpus callosum
• Thoughts, consciousness and memory
• Immediate memory
• Short term and long term memory

4. • Consists of two cerebral hemispheres,
separated- in upper part falx cerebri invaginates
- in lower part two hemispheres connected by
white commissure, corpus callosum
Each hemisphere,
3 poles-
Frontal pole anteriorly
Occipital pole posteriorly
Temporal pole
Surfaces-
Superolateral surface
Medial surface
Inferior surface
Borders-
Superomedial border
Inferolateral border
Medial border
Surface of a hemisphere-
Covered by thin grey matter (2-4mm)
Folded with intervening grooves of
fissures,
Folds or convolutions- gyri
Intervening fissures- sulci
As a result of folding, cerebral cortex
surface area, much larger

5. General Appearance
of
cerebral hemispheres:
 Separated by a deep
midline
sagittal fissure
– longitudinal cerebral
fissure
 The fissure contains
falx cerebri and the
anterior cerebral arteries
 In the depth of the
fissure, the
corpus callosum
connects the
hemispheres across
the midline

6. Lobes-
• Each hemisphere- 4 lobes,
• Boundaries separating one lobe from another on the superolateral
surface are formed by three prominent sulci and two imaginary
lines
• Sulci, separating lobes are-
- Central sulcus or fissure of Rolando
- Posterior ramus of lateral or Sylvian sulcus
- Parieto-occipital sulcus
• Imaginary lines-
- First line- connects upper end of parieto-occipital sulcus to
parieto-occipital notch
- Second line- backward continuation of the posterior ramus of
lateral sulcus to meet the first imaginary line

7. Parieto-occipital
sulcus
Central sulcus/
Fissure of Rolando
Posterior ramus
of lateral sulcus
(Sylvian sulcus)
Frontal
pole
Temporal pole
Inferolateral
border
Occipital
pole
Second
imaginary line
First
imaginary
line
Motor
functions
Sensory
functions
Hearing
Vision

8. The Occipital Lobe-posterior end of cortex
Contains primary visual cortex
The Parietal Lobe-between occipital lobe & the central sulcus
Contains the primary somatosensory cortex-receiving touch
sensation, muscle-stretch information and joint position
information
The Temporal Lobe-lateral portion of each hemisphere, near the
temples
Contains targets for audition, essential for understanding
spoken language, complex visual processes, emotional and
motivational behaviors
The Frontal Lobe-extends from the central sulcus to the anterior
limit of the brain
Contains Primary Motor Cortex-fine movements
Contributes to shifting attention, planning of action, delayed
response tasks as examples

9. Layers of the Cerebrum
Gray matter
Outer layer
Composed mostly
of neuron cell
bodies
White matter
Fiber tracts inside the
gray matter
Example: corpus callosum
connects hemispheres

10. Any man who can drive safely while kissing a pretty girl is simply not
giving the kiss the attention it deserves.
Albert Einstein

11. Why do women multitask better than men?
• The inferior-parietal lobe is larger in men than in women.
• This area of the brain is thought to control characteristics that
make a person more prone to mechanical and
analytical thought.
• The corpus callosum, the space between the right and left
hemispheres of the brain is larger in women than in men and
contains more neural pathways. This is thought to make
women superior in processing language, information,
emotion and cognition.
• Hence, women are superior in
understanding the subtleties of
relationships, emotional overtones,
and artistic expressions.

12. Cortical functional areas
• Brodmann divided cortex into 47 areas, based on
cytoarchitecture(number & thickness of cortical lamellae & cell type)
Motor areas-
• Primary motor area( Brodmann’s area 4)
• Premotor area(area 6)
• Frontal eye field(area 8)
• Supplementary motor area
Sensory areas-
• Primary somaesthetic areas ( area 3,1 and 2)
• Secondary (supplementary) somaesthetic area
• Somaesthetic association areas (area 5,7 and higher association area
40)

13. Auditory areas-
• Primary auditory area (area 41) or auditory area I
• Auditory association area (area 42) or auditory area II
• Higher auditory association area (area 22)
Visual areas-
• Primary visual area (area 17) or visuostriate area of visual area I
• Visual association area 18 (peristriate area)
• Visual association area 19 ( parastriate area)
Speech areas-
- Motor speech area-
• Anterior area (Broca’s area) or
areas 44,45
• Superior area
- Sensory speech areas-
• Area 39 (reading centre)
• Area 40
• Area 22 (Wernicke’s area)
Smell area- area 28
Gustatory area- area 43

14. Phylogenetical divisions of cerebral
cortex
• Cerebral cortex- ‘Pallium’, divided into three-
1. Allocortex- old cortex
• Forms 10% of entire cortex
• Divided into-
Archipallium (ancient cortex)- hippocampus & dentate gyrus
Paleopallium (old cortex)- uncus, part of parahippocampal gyrus-
belong to piriform area of olfactory cortex
• Allocortex- also called limbic cortex, as most of allocortex located
around peripheral margin of the diencephalon in the form of a ring.
• Ring of limbic cortex functions as a two way communication linkage
between neocortex and lower limbic structures.
• Along with thalamus & hypothalamus, limbic cortex is concerned
with emotional & instinctive behaviour.

15. 2. Mesocortex- transitional zone between allocortex and neocortex
and comprises the cingulate gyrus, part of parahippocampal gyrus
and subiculum.
3. Neocortex-
• Isocortex
• 90% of cerebral cortex
• With evolution of mammals the extent of neocortex has increased

16. Areas, connections, functions
and applied aspects of different
lobes

17. I. Frontal lobe
• Lies in front of central sulcus and above posterior ramus of lateral
sulcus
• 1/3rd of cortical surface.
• On basis of function, subdivided into-
a. Precentral cortex
b. Prefrontal cortex

18. a. Precentral cortex-
• Posterior part of frontal lobe
• Includes lip of central sulcus, precentral gyrus and posterior part
of superior, middle and inferior frontal gyri.
• Stimulation at different points- activity of discrete skeletal muscles
• Excitomotor area of cortex
• Stimulation causes some sensory perception- ‘Sensorimotor
cortex’
Areas-
i. Primary motor area-
Brodmann’s area 44, 45
ii. Premotor area-
Brodmann’s area 6,8,44
and 45
iii. Supplementary motor
area

19. i. Primary motor area-
- Area 4
- Presence of giant pyramidal
cells called Betz cells in
ganglionic layer and a thin
granular layer.
- Area is centre for volition
i.e, it is concerned with
initiation of voluntary
movements of the contra-
lateral half of the body
and initiation of speech
area 45 also called suppressor
area, forms a narrow strip
anterior to area 4.
- It inhibits movements
initiated by area 4.

20. ii. Premotor area-
• Lies anterior to primary
motor area
• Includes Brodmann’s area
6,8,44 and 45
• Absence of giant pyramidal
cells in ganglionic layer
• Involved in integration of
voluntary movements
• Thus, skilled movements
are accurate and smooth.

21. • Area 6- 6a (upper) and 6b (lower)
• (Electrical) Stimulation of area 6a causes generalized pattern of
movements like rotation of head, eyes and trunk towards opposite
side
• Stimulation of area 6b produces rhythmic, complex coordinated
movements involving muscles of face, buccal cavity, larynx and
pharynx
• Lesions lead to loss of skilled movements, recovery may occur but
movements become awkward- grasping reflex
• Lesion of area 6 with area 4- hemiplegia with spastic paralysis

22. Area 8-
• Frontal eyelid
• Lies anterior to area 6
• Concerned with control of eye movements
• Electrical stimulation causes conjugate movements of eyeball to the
opposite side, opening and closure of eyelids, pupillary dilatation
and lacrimation
• Lesions of this area turns eye towards the affected side.
Area 44 and 45 or BROCA’s motor speech area-
• Movements of structures responsible for the production of voice
and articulation of speech, activation of vocal cords simultaneously
with movements of mouth and tongue during speech
• Lesions of this area causes motor aphasia i.e, inability to speak the
word although vocalization is possible

23. iii. Supplementary motor area-
In association with premotor area provides attitudinal movements,
fixation movement of different segments of the body and positional
movements of head and eyes

24. b. Prefrontalcortex
• Prefrontal lobe or orbitofrontal cortex’
• Anterior part of frontal lobe lying anterior to area 8 and 44

25. • Major areas- Brodmann’s areas 9-14, 23, 24,29, 32, 44-47
• Centre for planned actions
• Centre for higher functions- emotions, learning, memory and
social behaviour
• Responsible for various autonomic changes during emotional
conditions because of connections with hypothalamus and brain
stem
• Seat of intelligence/organ of mind- short term memories
registered here
• Can keep track of many bits of information and ability to recall this
information bit by bit for subsequent thoughts.
• Control of intellectual activities like prognosticate, plan future,
allows to concentrate on central theme of thought- helps in depth
and abstractness of thought and thereby in elaboration of
thought.
• Allows to delay action in response to incoming sensory signals so
sensory signals can be weighed until best response is obtained.

26. • Allows to consider the consequence of motor activites before their
performance
• Plays role in solution of complicated mathematical, legal and
philosophical problems
• Allows to correct avenues of information in diagnosis of rare
diseases
• Allows to control ones activity according to the moral laws

27. Frontal lobe syndrome
• Symptom complex occurring due to injury or ablation of prefrontal cortex
• Prefrontal leucotomy- cutting the connection between thalamus and
prefrontal lobe also results in frontal lobe syndrome.
• Flight of ideas- difficulty in planning
• Emotional instability
• Euphoria- false sense of well being, failure to realize or indifference to
seriousness of others feelings or emotions
• Impairment of memory- recent memory only
• Loss of moral and social sense
• Lack of attention and power of concentration
• Lack of initiative following marked depression of intellectual activity
• Functional abnormalities like hyperphagia, loss of control over urinary or
rectal sphincters
• Disturbances in orientation
• Slight tremor

28. Further Investigation
Phineas Gage: Phineas Gage was a railroad worker in the 19th century living in
Cavendish, Vermont. One of his jobs was to set off explosive charges in large rock in
order to break them into smaller pieces. On one of these instances, the detonation
occurred prior to his expectations, resulting in a 42 inch long, 1.2 inch wide, metal
rod to be blown right up through his skull and out the top. The rod entered his skull
below his left cheek bone and exited after passing through the anterior frontal lobe
of his brain.

29. Remarkably, Gage never lost consciousness, or quickly regained it (there is
still some debate), suffered little to no pain, and was awake and alert when
he reached a doctor approximately 45 minutes later. He had a normal pulse
and normal vision, and following a short period of rest, returned to work
several days later. However, he was not unaffected by this accident.
Learn more about Phineas Gage: http://en.wikipedia.org/wiki/Phineas_Gage

30. Gage’s personality, reasoning, and capacity to understand and follow social
norms had been diminished or destroyed. He illustrated little to no interest in
hobbies or other involvements that at one time he cared for greatly. ‘After the
accident, Gage became a nasty, vulgar, irresponsible vagrant. His former
employer, who regarded him as "the most efficient and capable foreman in their
employ previous to his injury," refused to rehire him because he was so
different.’
The first identified (2009) portrait of Gage,
shown here with his "constant companion for
the remainder of his life"—his inscribed
tamping iron

31. Gage is a fixture in the curricula of neurology, psychology and related
disciplines, and is frequently mentioned in books and academic papers; he
even has a minor place in popular culture. Despite this celebrity the body of
established fact about Gage and what he was like (whether before or after
his accident) is remarkably small, which has allowed "the fitting of almost
any theory to the small number of facts we have"—Gage having been cited,
over the years, by proponents of various theories of the brain wholly contra-
dictory to one another.

32. II. Parietal lobe
• Lies between central sulcus and parieto-occipital sulcus and upper
part of first imaginary line
• Divided into three parts functionally,
• Primary sensory area(corresponds to Brodmann’s area 3,1 & 2),
also called primary somatosensory area or first somatosensory
area, SI
• Secondary sensory area or second somatic sensory area SII
• Sensory association areas (Brodmann’s area 5,7)

33. i. Primary sensory area/ first somatic sensory area/SI
• Occupies posterior wall of central sulcus, postcentral gyrus and
postcentral part of paracentral lobule
• Includes Brodmann’s area 3,1 and 2
• Granular cortex densely packed with stellate cells, with few small
and medium sized pyramidal cells
• Recieves sensory inputs from opposite half of the body
• Sensations derived from skin are appreciated in anterior part of the
area and proprioceptive sensations in posterior part of the area
• Electrical stimulation of area produces vague sensations like
numbness and tingling
• If lesions occur without involving thalamus, sensations are
perceived but discriminative functions are lost. If thalamus also
affected, loss of sensations in opposite side of body

34. ii. Secondary sensory area/ SII
• Situated in post central gyrus below first somatic sensory area,
most of it buried in the superior wall of the sylvian fissure
• Recieves sensory impulses from primary sensory area as well as
thalamus
• Neurons in anterior part respond to touch whereas neurons in
posterior part can be excited by touch, auditory, visual and
nociceptive stimuli
• Lesions produce deficits in discriminative power whereas sensory
processing in SI not affected.

35. iii. Sensory association areas
• Include area 5 and 7, also area 40- higher association area
• Area 5- lies posterior to area SI in parietal lobe and contains
neurons which react to passive or active rotation of a joint or joints
• Area 7- concerned with more elaborate process of discrimination
between stimuli
• Area 40- higher association area, concerned with stereognosis i.e,
recognition of common objects placed in the hand without looking
at them.
• Lesion affecting this area produces tactile agnosia

36. Functions of parietal lobe
• SI localizes, analyzes and discriminates different cutaneous and
proprioceptive senses
• Area 3- receives cutaneous sensations of touch, pressure, position
and vibratory senses
• Area 1- receives projections from cutaneous and joint senses
• Area 2- primarily concerned with deep senses from muscles and
joints
• SII receives sensory impulses from SI and thalamus, concerned
with perception of sensation. Thus sensory parts of the body have
two representation in area SI and SII.
• Sensory assoc. areas (5,7)- assoc. with more elaborate process of
discrimination between the stimuli, thus helps in differentiating
the relative intensity of different stimuli. Eg:- warm objects from
warmer, cold from colder etc
• Higher association areas (40)- stereognosis- recognition of
common familiar objects placed in hand without looking at them

37. III. Temporal lobe
• Lies below posterior ramus of lateral sulcus and its continuation,
the second imaginary line.

38. Areas of temporal lobe-
Major areas-
• Primary auditory area- area 41, 42
• Auditory association area- area 22,21,20

39. i. Primary auditory area
• Audiosensory area- Brodmann’s area 41, 42 and forms centre for
hearing
• Situated in middle of superior temporal gyrus on the upper margin
and on its deep or insular aspect (Heschl’s or transverse temporal
gyrus).
ii. Auditory association area
• Corresponds to Brodmann’s area 22, 21, 20
• Area 22- Wernicke’s area, sensory speech centre
• Functions are interpretation of the meaning of what is heard and
comprehension of spoken languages and the formation of ideas
that are articulated in speech
• Area 21, 20- located in the middle and inferior temporal gyrus
respectively
• Receive impulses from primary area and are concerned with
interpretation and integration of auditory impulses
• Lesions of these areas impair auditory, short term memory without
impairing visual memory.

40. Primary Auditory
Cortex
Wernicke’s Area
Primary Olfactory Cortex
(Deep)
Conducted from Olfactory Bulb

41. • Lies behind parieto-occipital sulcus and its continuation down an
imaginary line, concerned with vision
• Mostly formed of sensory and association areas and has only
slight motor function.
Contains visual cortex having three areas-
• Primary visual cortex (area 17)- striate area, receives fibres of
optic radiations which bring impulses from parts of both retinae,
constitutes the centre of vision
• Visual association area (area 18)- peristriate area
• Visual association area or occipital eyefield (area 19)- parastriate
area
IV. Occipital lobe

42. Functions-
• Primary visual area (area 17) is concerned with perception of visual
impulses
• Visual association areas (area 18 and area 19) are concerned with
interpretation of visual impulses. These are involved in the
recognition and identification of objects in the light of past
experience.
• Occipital eyefield area (area 19) is concerned with the movements
of eyeball.

43. White matter of cerebrum
• Passing through, between and around the subcortical masses of
grey matter of cerebrum are tracts of white fibres.
3 types-
• Association fibres
• Commissural fibres
• Projection fibres

44. Association fibres
• Connect different gyri of the same hemisphere.
2 types-
• Short association fibres- connect adjacent gyri
• Long association fibres- connect widely separated gyri-
Five groups-
• Superior longitudinal fasciculus
• Inferior longitudinal fasciculus
• Cingulum
• Fronto-occipital fasciculus
• Uncinate fasciculus

45. Commissural fibres
• Connect corresponding parts of two cerebral hemispheres with
each other. There are five bundles of commissural fibres.
• Corpus callosum
• Anterior commissure
• Posterior commissure
• Habenular commissure
• Hippocampal commissure

46. Projection fibres
• Connect cerebral hemispheres with other parts of CNS eg:-
thalamus, brain stem and spinal cord
• Afferent and efferent
• Corona radiata (fountain of fibres)- refers to that part of projection
fibres that radiates from the upper end of internal capsule to
cerebral cortex. Contains both ascending and descending fibres.
• Internal capsule- thick curved band of projection fibres that occupy
the space between thalamus and caudate nucleus medially and the
lentiform nucleus laterally.

47. Internalcapsule
• Thick curved band of projection fibres that occupy the space
between thalamus and caudate nucleus medially and the lentiform
nucleus laterally.
Subdivisions-
• Anterior limb-
• Genu
• Posterior limb
• Retrolenticular or caudal part
• Sublentiform part

48. Applied aspect-
• Vulnerable to effects of even a pinpoint vascular lesion, as
pyramidal fibres are compressed in a little space
• Damage to internal capsule from infarction and haemorrhage is a
common form of stroke, resulting in loss or decrease in
sensations and movements of the opposite half of the body
• Most common cause of hemiplegia- thrombosis or rupture of one
of the striate branches of middle cerebral artery which passes
through the anterior perforated substance to supply the internal
capsule.
• Charcot’s artery- one of the lateral striate arteries, largest of the
perforating branches, particularly prone to such pathological
conditions
• Heubner artery- thrombosis of recurrent branch of anterior
cerebral artery results in contralateral paralysis of the face and
upper limbs on account of the involvement of corticonuclear
fibres and adjacent pyramidal fibres for the superior extremity.

49. • Think of a number from 1-9
• Multiply by 9
• Add the individual digits
• Subtract the result by 5
• Think of the corresponding english alphabet
• Think of a country that starts with the alphabet
• Think of an animal that starts with the last alphabet of the
country you thought of
• Think of a fruit with the last alphabet of the animal you thought
of
• Did you think of-
• DENMARK
• KANGAROO
• ORANGE…
• Only 2 % of us think different..
• ‘Think different’- Steve Jobs, Apple

50. References
Medical physiology- Guyton
Medical physiology- Indu Khurana
Various internet sources