anatomy of cerebrum is important for any supratentorial surgical procedures and assessing signs associated with different lobes

1. CEREBRUM
LOBAR ANATOMY

2. CEREBRUM
Main functions:
1. Seat of intelligence
– It provides the ability to
• read, write and speak;
• Make calculations
• Compose music
• To remember the past
• Plan for the future
• Imagine things that have never existed before
2. Centre of sensory perception
3. Initiate and coordinate skeletal muscle contraction

3. Cerebral cortex and it’s structures:
• Consists of cerebral cortex (gray matter), internal
region of cerebral white matter and gray matter
nuclei deep within the white matter.
• Thick : 2 – 4 mm, contains billions of neurons.
• This gray matter is made of cell bodies of neurons.
• During embryonic development, when brain size
increases rapidly, the gray matter of the cortex
enlarges much faster than the deeper white matter.
• As a result, cerebral cortex rolls and folds upon itself
so that it could fit into the cranial Cavity.

4. • The folds called gyri / gyrus or convolutions.
• The deeper grooves between folds are
known as fissures.
• The shallow grooves between folds are
termed as sulci / sulcus.
• The most prominent fissure, is the
longitudinal fissure which separates the
cerebrum into right and left halves called
cerebral hemisphere.

6. Within the longitudinal fissure between the
cerebral hemispheres is the falx cerebri.
• The hemispheres are connected internally by the
corpus callosum. (broad band of white matter
containing axons that extend between the
hemispheres)

7. • Each hemisphere is further subdivided into five
lobes.
• The lobes are named after the bones that cover
them:
–Frontal lobes.
–Parietal lobes.
–Temporal lobes.
–Occipital lobes.
– Insula
A fifth part of the cerebrum, the insula,
cannot be seen at the surface of the brain
because it lies within the lateral cerebral sulcus,
deep to the parietal,frontal and temporal lobes.

8. Main boundaries in cerebrum
Sulcus and fissures:
• Central sulcus
– Separates the frontal and parietal lobes.
• Longitudinal fissure
– Separates the cerebrum into right and left
hemispheres.
• Lateral cerebral sulcus
– Separates the frontal and temporal lobes.
• Parieto-occipital sulcus
– Separates parietal and occipital lobes.

10. Major Gyrus of
cerebrum:
• Precentral gyrus
– Located immediately
anterior to the central
sulcus.
– It contain primary
motor area.
•Postcentral gyrus
– is located immediately
posterior to the central
sulcus, contains the
primary somatosensory
area of the cerebral
cortex.

12. CEREBRAL WHITE MATTER
• The cerebral white matter consists of
myelinated and unmyelinated axons that
transmit impulses.
• There are 3 types of tracts:-
– Association tracts.
– Commissural tracts
– Projection tracts.

14. • Association tracts: contain axons that conduct
nerve impulses between gyri in the same
hemisphere.
• Commissural tracts: contain axon that
conduct nerve impulses from gyri in one
cerebral hemisphere to corresponding gyri in
the other cerebral hemisphere.
3 important commissural tracts are the:
• Corpus callosum (largest fiber bundle in the
brain – 300 million fibers)
• Anterior commissure
• Posterior commissure

15. • Projection tracts: contain axons that conduct
nerve impulses from the cerebrum to lower
parts of the CNS (thalamus, brainstem, or
spinal cord) or lower parts of the cerebrum to
the cerebellum.
An example; is the internal capsule, which is
the thick band of white matter that contains
both ascending and descending axons.

21. Frontal Lobar Anatomy
• The frontal lobes lie anterior to the central or
rolandic sulcus and superior to the sylvian
fissure.
• It makes up about the anterior one-half of
each hemisphere in man.
• They are larger in humans than in any other
primate .

23. Sulci and Gyri
• On the lateral aspect of frontal lobe 3 sulci are
visible: precentral sulci, superior frontal sulci and
inferior frontal sulci.
• In between these sulci are 4 gyri:
1.precentral gyrus between central and
precentral sulcus.
2.Superior frontal gyrus: superior to superior
frontal sulcus.
3.Middle frontal gyrus: between superior and
inferior frontal sulcus.
4.Inferior frontal gyrus: inferior to inferior frontal
sulcus.

25. • On the medial surface, the frontal lobe extends
down to the cingulate sulcus.
• The paracentral lobule consists of the extensions
of the precentral and postcentral gyri onto the
medial hemispheric surface above the cingulate
sulcus; it is important in bladder control.
• The inferior frontal gyrus is divided into the pars
orbitalis, pars triangularis, and the pars
opercularis.
• On the inferior surface lies the olfactory sulcus,
olfactory bulb and tract overlies this sulcus.

27. Orbital surface Frontal lobe
• Divided into four orbital gyri
by a well-marked H-shaped
orbital sulcus.
• The medial, anterior, lateral,
and posterior orbital gyri.
• The medial orbital gyrus
presents a well-marked
antero-posterior sulcus, the
olfactory sulcus, for the
olfactory tract; the portion
medial to this is
named the gyrus rectus

28. Functional Frontal Lobe Anatomy
• Motor cortex
Primary
Premotor
Supplementary
Frontal eye field
Broca’s speech area
• Prefrontal cortex
– Dorsolateral
– Medial
– Orbitofrontal

31. Primary motor cortex
• Primary motor area, or Brodmann area 4,
occupies the precentral gyrus extending over the
superior border into the paracentral lobule.
• The primary motor area, if electrically stimulated,
produces isolated movements on the opposite
side of the body as well as contraction of muscle
groups concerned with the performance of a
specific movement.
• The movement areas of the body are represented
in inverted form in the precentral gyrus.

33. Primary motor cortex
• Input : thalamus, BG, sensory, premotor
• Output : motor fibers to brainstem and spinal
cord
• Function : executes design into movement
• Lesions : increase/decrease tone; decrease
power; decrease fine motor function on
contra lateral side.

34. Pre motor area
• The premotor area (Area 6), is wider superiorly
than below and narrows down to be confined to
the anterior part of the precentral gyrus.
• It has no giant pyramidal cells of Betz.
• Electrical stimulation of the premotor area
produces muscular movements similar to those
obtained by stimulation of the primary motor
area; however, stronger stimulation is necessary
to produce the same degree of movement.

35. Pre motor area
• Input : Thalamus, BG, sensory cortex
• Output : Primary motor cortex
• Function : Stores motor programs; controls
coarse postural movements, sensorimotor
integration
• Lesions : Moderate weakness in proximal
muscles on contralateral side, Inability to
make use of sensory feedback in performance
of smooth movements and apraxia

36. Supplementary motor area
• The supplementary motor area ( area 6) is
situated in the medial frontal gyrus on the
medial surface of the hemisphere and anterior
to the paracentral lobule.
• Stimulation of this area results in movements
of the contralateral limbs, but a stronger
stimulus is necessary than when the primary
motor area is stimulated.

37. Supplementary motor area
• Input : Cingulate gyrus, thalamus, sensory &
Prefrontal cortex
• Output : Premotor, primary motor
• Function : Intentional preparation for movement,
Procedural memory, recall of memorized motor
sequences
• Lesions : Mutism, akinesis, speech returns but it
is non-spontaneous, contralateral motor neglect,
impairment of bi brachial coordination.

38. Frontal eye field
• It is Broadmann area 8.
• It is located in the middle frontal gyrus.
• Input : Parietal / temporal (what is target);
posterior / parietal cortex (where is target)
• Output : Caudate; superior colliculus; paramedian
pontine reticular formation
• Function : Executive: selects target & commands
movement (saccades), it is considered to control
voluntary scanning movements of the eye.
• Lesion : Eyes deviate ipsilaterally with destructive
lesion & contralaterally with irritating lesions

39. Broca’s speech area
• Brodmann area 44
• It is located in the inferior frontal gyrus.
• In the majority of individuals, this area lies on
the left or dominant hemisphere.
• Input : Wernicke’s
• Output : Primary motor cortex
• Function : Speech production (dominant
hemisphere); emotional, melodic component
of speech (non-dominant)
• Lesions: motor aphasia; monotone speech

40. Pre frontal area
• The most anterior parts of the frontal lobes
(areas 9 to 12 and 45 to 47), sometimes referred
to as the prefrontal areas, are particularly well
developed in human beings.
• Is also called as organ of civilization.
• These areas are connected with the somesthetic,
visual, auditory, and other cortical areas by long
association bundles, and with the thalamus and
the hypothalamus by projection fibers.
• Clinically, the prefrontal region can be divided
into the dorsolateral prefrontal cortex (DLPFC),
the medial prefrontal cortex (MPC), and the
orbitofrontal cortex (OFC).

41. Dorsolateral Prefrontal Cortex
• The DLPFC is important in the organization of
selfordered tasks.
• It plays a critical role in the neural network subserving
working memory .
• The responsibility for executive function largely resides
with the DLPFC and its connections.
• Connections: Motor / sensory convergence areas,
thalamus, GP, caudate, SN
• Functions: Monitors and adjusts behavior using
‘working memory’
• Lesions: Executive function deficit; disinterest /
emotional reactivity; attention to relevant stimuli.

42. Orbital prefrontal cortex
• The OFC has important connections with the
limbic system, including the amygdala
• Connections: temporal,parietal, thalamus, GP,
caudate, SN, insula, amygdala Part of limbic
system
• Function: Emotional input, arousal, suppression
of distracting signals
• Lesions: emotional lability, disinhibition
syndrome ranging from mildly inappropriate
social behavior to full-blown maniaparticularly of
the right hemisphere, distractibility, hyperkinesis.

43. Dorsomedial prefrontal cortex
• Connections: temporal,parietal, thalamus,
caudate, GP, substantia nigra, cingulate
• Functions: motivation, initiation of activity
• Lesions: Apathy; decreased drive/ awareness/
spontaneous movements; akinetic-abulic
syndrome & mutism.

44. Neurotransmitters
Dopaminergic tracts
• Origin: ventral tegmental area in midbrain
• Projections: Prefrontal cortex (mesocortical
tract) and to limbic system (mesolimbic tract)
• Function: Reward; motivation; spontaneity;
arousal

45. Neurotransmitters
Norepinephrine tracts
• Origin: Locus ceruleus in brainstem and lateral
brainstem tegmentum
• Projections: Anterior cortex
• Functions: Alertness, arousal, cognitive
processing of somatosensory info

46. Neurotransmitters
Serotonin tracts
• Origin: Raphe nuclei in brainstem
• Projections: Number of forebrain structures
• Function: Minor role in prefrontal cortex;
sleep, mood, anxiety, feeding

47. Vascular supply
• Medial parts of frontal lobe: Anterior cerebral
artery
• Convexity and deep regions: Superior
(rolandic) division of MCA
• Underlying deep white matter: series of small
penetrating arteries (lenticulostriate) directly
from stem of MCA

49. Frontal subcortical circuits
• The connections of the frontal lobes were
described in details by Goldman Rakic.
• Five FSCs have been described:
1.Motor
2.Oculomotor
3.Dorsolateral prefrontal
4.Lateral orbitofrontal
5.Anterior cingulate

50. Frontal subcortical circuits
• These circuits share a general structure
consisting of the cortex, basal ganglia and
thalamus.
• Information originates from the cerebral
cortex, travels first to the basal ganglia then
on to the thalamus, and finally returns to
numerous areas of the cortex.
• All FSC circuits have both a direct and an
indirect pathway, which have “opposite” or
reciprocal functions.

52. Direct FSC
• The basal ganglia can be characterized as either
“input” or “output” nuclei.
• The caudate, putamen, and ventral striatum
make up the input nuclei and receive excitatory
glutamate projections from multiple areas of the
cortex.
• The input nuclei then connect by way of
inhibitory GABA fibers to the major output nuclei,
which consist of the internal segment of the
globus pallidus and the pars reticulata of the
substantia nigra.
• The output nuclei send inhibitory GABA efferents
to thalamic nuclei that project back to the cortex
by way of excitatory glutamate fibers.

54. Indirect FSC pathway
• The indirect pathway tends to inhibit the
thalamus and decreases excitatory drive to the
cortex.
• This circuit involves GABA projections, first from
the striatum to the globus pallidus externa, then
on to the subthalamic nucleus.
• Projections then connect with the globus pallidus
interna and substantia nigra by way of glutamate
neurons.
• This reciprocity of the direct versus indirect
pathways is believed be involved in the initiation
and cessation of behaviors required for adaptive
functioning.

55. FSC: Motor circuit
• Supplementary Motor & Premotor: Planning, initiation & storage
of motor programs; fine-tuning of movements
• Motor: final station for execution of the movement according to
the design

56. FSC: Oculomotor circuit
•Voluntary scanning eye movement

57. FSC: Dorso-lateral circuit
• This circuit is responsible for executive functions.
-motor planning, deciding which stimuli to attend to,
shifting cognitive sets
-Attention span and working memory
-Lesion: difficulty focusing and sustaining attention as
well as reduced verbal fluency and motor programming

58. FSC: Orbito-frontal circuit
• This circuit mediates empathic, civil and socially
appropriate behavior.
• Lesion: Disinhibition and emotional liability.

59. FSC: Anterior Cingulate Circuit
• This circuit is involved in motivational mechanisms.
• Lesions: Abulia, akinetic mutism.

60. Frontal lobe: Neuro-imaging
• The central sulcus is a useful landmark for
identifying frontal lobe.
• But identifying it with certainty can present
some difficulty on CT and MR images.
• On axial scans, follow the superior frontal
sulcus from anterior to posterior until it meets
and forms an angle with the precentral sulcus
– the central sulcus is the next one behind.

61. • On lateral sagittal images note the Y-shaped
sulcus of the pars triangularis at the anterior end
of the Sylvian fissure. The next major fissure
posterior to the Y is the precentral sulcus
• On medial sagittal images follow the cingulate
sulcus as it ascends superiorly and posteriorly
towards the vertex as the pars marginalis, the
central sulcus lies just in front of pars marginalis.
• The precentral gyrus contains an area at its
superior lateral part, which resembles an upsid
down omega, an area of cortex that represents
the motor-hand area.

64. Frontal lobe syndromes
• Three Frontal Lobe syndromes
•Orbitofrontal syndrome (lacks inhibition)
•Frontal Convexity syndrome (apathetic)
•Medial Frontal syndrome (akinetic)

65. Orbito-frontal syndrome
• Characterized by disinhibited, impulsive
behavior, difficulty in controlling their
emotions, lacking in judgment and are easily
distracted
• Many patients are incorrectly diagnosed with
a personality disorder

66. Frontal Convexity syndrome
• Characterized by disinterest, slowing of the
motor functions and apathy.
• Inability to regulate behavior according to
personal goals.
• Inability to plan ahead, lack of motivation and
concern.
• Generally not caring about the world around
them.

67. Medial Frontal syndrome
• Characterized by mutism and akinesia.
• profound apathy, motor and verbal inactivity
and indifference to thirst or hunger.
• Loss of sensation and weakness of lower
extremities along with urinary incontinence.

68. The Case of Phineas Gage (Harlow
1868)
• Tamping iron blown through
skull: L frontal brain injury
• Excellent physical recovery
• Dramatic personality change:
‘no longer Gage’:stubborn,
lacked in consideration for
others, had profane speech,
failed to execute his plans

69. Right and left functional lobes lesional Deficits

70. Clinical Assessment of frontal lobe
• History, Examination and formal tests :
Abnormal behavior, speech disorder, urinary
incontinence, Frontal gait(magnetic gait) ,
weakness of limbs
• Test sense of smell.
• Frontal release reflexes
Grasp reflex
Sucking reflex (pout, snout, rooting)
Palmo-mental reflex
Glabellar tap reflex

71. Clinical Assessment of frontal lobe
• To assess the following functions:
• Emotional make-up and personality
• Abstraction and judgment
• Attention and memory
• Language

72. Emotional make-up and personality
• best assessed by history from family / friends &
observation.
• Abstraction and judgment are assessed by
proverb interpretation and similarities.
• E.g explain in your own words the meaning of
• Don’t cry over spilled milk
• Rome was not built in a day.
• Similarity between mango and orange, turnip and
cauliflower, car and airplane.

73. Emotional make-up and personality
• – May be the only manifestation
• – Apathy / euphoria / labile mood
• – Decreased drive / poor impulse control
• – Abulia; akinetic mutism
• – Pseudobulbar palsy; Opercular syndrome
• – Best assessed with Hx from family / friends
& observation

74. Attention and memory
• Attention is the patient’s ability to attend to a
specific stimulus without being distracted by
external, internal or environmental stimuli.
• Attention can be tested by alternative sequence
(e.g. copying MNMN)
• Luria’s ‘fist-edge-palm’ test
• Go/no-go:
”tap once if I tap twice, don’t tap if I tap once”
“tap for A” read 60 letters at 1/sec

75. Attention and memory
• Digit span test: Measure of short term
memory “repeat 3-5; 7-5-8; 3-9-4-8..” N: >5.
A two year child has a digit span of 2, 3yr- 3,
4yr- 4, 5yr- 5, 6yr-6 and 7yr to adult- 7
• Visual grasp: “look away from stimulus”
• Recency test- recall sequence of stimuli /
events
• Imitation (of examiner) / utilization (of objects
presented)

76. Abstraction and judgment
• Cognitive functions undisturbed
• Concrete thinking
• Diminished insight
• Defect in planning / executive control

77. Abstraction and judgment
Tests:
• Interpret proverbs (e.g.“the golden hammer
opens iron doors”)
• Explain why conceptually linked words are the
same (e.g. coat & skirt)
• Plan & structure a sequential set of activities
(“how would you bake a cake?”)
• Insight / reaction to own illness

78. Language
• Broca’s / non-fluent aphasia
• Prefrontal/ transcortical motor aphasia
• Language-motor dissociation
• Akinetic mutism

79. Language
Language tests:
• Thurstone / word fluency test (“recite as many
words beginning with ‘F’ in 1 min as you can,
then with ‘A’, ‘S’”); N: >15
• Repetition (Broca’s vs transcortical)
– “Ball”
– “Methodist”
– “Methodist episcopal”
– “No if’s end’s or but’s”
– “Around the rugged rock the ragged rascal ran”

80. Formal Tests
• Wisconsin Card Sorting Test
abstract thinking and set shifting; L>R
• Trail Making
visuo-motor track, conceptualization, set shift
• Stroop Color & Word Test
attention, shift sets; L>R
• Tower of London Test
planning

81. Wisconsin Card Sorting Test
• Used primarily to assess perseveration and
abstract thinking.
• The WCST is also considered a measure of
executive function because of its reported
sensitivity to frontal lobe dysfunction.
• The WCST consists of four key cards and 128
response cards.
• The task requires subjects to find the correct
classification principle by trial and error and
examiner feedback.

83. Trail Making Test
• Test for visual attention and task switching.
• Trail Making Test consist of 25 circles distributed over a
sheet of paper.
• In Part A, the circles are numbered 1 – 25, and the
patient should draw lines to connect the numbers in
ascending order.
• In Part B, the circles include both numbers (1 – 13) and
letters (A – L); as in Part A, the patient draws lines to
connect the circles in an ascending pattern, but with
the added task of alternating between the numbers
and letters (i.e., 1-A-2-B-3-C, etc.).

85. Trail making test results

86. Stroop test

88. Test for
perseveration

89. A frontal assessment battery at bedside: FAB
• Similarities (conceptualization)
• Lexical fluency (mental flexibility)
• Motor series “Luria” test (programming)
• Conflicting instructions (sensitivity to
interference)
• Go–No Go (inhibitory control)
• Prehension behaviour (environmental
autonomy)

90. Similarities (conceptualization)
• “In what way are they alike?”
•A banana and an orange
•A table and a chair
•A tulip, a rose and a daisy
• Score (only category responses [fruits,
furniture, flowers] are considered correct)
Three correct: 3 Two correct: 2 One correct: 1
None correct: 0

91. Lexical fluency (mental flexibility)
• “Say as many words as you can beginning with
the letter S any words except surnames or
proper nouns.”
• The time allowed is 60 seconds.
• Score (word repetitions or variations [shoe,
shoemaker], surnames, or proper nouns are
not counted as correct responses)
• > 9 words: 3, 6 -9 words: 2, 3 -5 words: 1, < 3
words: 0

92. Motor series “Luria” test
The examiner, seated in front of the patient, performs alone
three times with his left hand the series of fist,edge,palm.
• Now, with your right hand do the same series, first with
me, then alone.
• The examiner performs the series three times with the
patient, then says to him/her:Now, do it on your own.
• Patient performs six correct consecutive series alone: 3
• Patient performs at least three correct consecutive series
alone: 2
• Patient fails alone, but performs three correct
consecutive series with the examiner: 1
• Patient cannot perform three correct consecutive series
even with the examiner: 0

93. Conflicting instructions
• Tap twice when I tap once.
• To ensure that the patient has understood the
instruction, a series of 3 trials is run: 1-1-1.
• Tap once when I tap twice.
• To ensure that the patient has understood the
instruction, a series of 3 trials is run: 2-2-2.
• The examiner then performs the following series:
1-1-2-1-2-2-2-1-1-2.
• Score No errors: 3, 1 -2 errors: 2, > 2 errors: 1

94. Go–No Go
• “Tap once when I tap once.”
• “Do not tap when I tap twice.”
• Score No errors: 3, 1 -2 errors: 2, > 2 errors: 1
• Patient taps like the examiner at least four
consecutive times: 0

95. Prehension behaviour
“Do not take my hands.”
• The examiner is seated in front of the patient. Place the
patient’s hands palm up on his knees.
• Without saying anything or looking at the patient, the
examiner brings his own hands close to the patient’s
hands and touches the palms of both the patient’s
hands, to see if he will spontaneously take them.
• Patient does not take the examiner’s hands: 3
• Patient hesitates and asks what he/she has to do: 2
• Patient takes the hands without hesitation: 1
• Patient takes the examiner’s hand even after he/she
has been told not to do so: 0

96. Interpreting results
• A cut off score of 12 on the FAB has a
sensitivity of 77% and specificity of 87% in
differentiating between frontal dysexecutive
type dementias and AD.

97. Diseases Commonly Associated
With Frontal Lobe Lesions
• Traumatic brain injury
– Gunshot wound
– Closed head injury
Widespread stretching and shearing of fibers
throughout
Frontal lobe more vulnerable
– Contusions and intracerebral hematomas
• Frontal Lobe seizures
– Usually secondary to trauma
– Difficult to diagnose: can be odd (laughter,
crying, verbal automatism, complex gestures)

98. Diseases Commonly Associated
With Frontal Lobe Lesions
• Vascular disease
– Common cause especially in elderly
– ACA territory infarction
Damage to medial frontal area
– MCA territory
Dorsolateral frontal lobe
– ACom aneurysm rupture
Personality change, emotional disturbance

99. Diseases Commonly Associated
With Frontal Lobe Lesions
• Tumors
– Gliomas, meningiomas
– subfrontal and olfactory groove meningiomas:
profound personality changes and dementia
• Multiple Sclerosis
– Frontal lobes 2nd highest number of plaques
– euphoric/depressed mood, Memory problems,
cognitive and behavioral effects

100. Diseases Commonly Associated
With Frontal Lobe Lesions
• Degenerative diseases
– Pick’s disease
– Huntington’s disease
• Infectious diseases
– Neurosyphilis
– Herpes simplex encephalitis

101. Diseases Commonly Associated
With Frontal Lobe Lesions
• Psychiatric Illness – proposed associations
– Depression
– Schizophrenia
– OCD
– PTSD
– ADHD

102. Conclusion
• Frontal lobes besides controlling motor,
oculomotor and language functions also allow
the organism to learn from experience, and
organize current information and choose a course
of action, to summon drive to execute the action,
and remain attentive and resist distraction.
• Lesion of DLPFC or its circuits causes loss of
executive functions.
• Orbito-frontal/circuits: Disinhibition
• Anterior cingulate circuit: Abulia
• Frontal Assessment battery is a useful bedside
test to differentiate frontal lobe syndromes with
other causes of dementia.