• The frontal lobes lie anterior to the central or rolandic
sulcus and superior to the sylvian fissure.
makes up about the anterior one-half of each
hemisphere in man.
• They are larger in humans than in any other primate .
Sulci and Gyri
• On the lateral aspect of frontal lobe 3 sulci are visible:
precentral sulci, superior frontal sulci and inferior frontal
In between these sulci are 4 gyri: precentral gyrus
between central and precentral sulcus.
Superior frontal gyrus: superior to superior frontal sulcus.
Middle frontal gyrus: between superior and inferior frontal
Inferior frontal gyrus: inferior to inferior frontal sulcus.
• On the medial surface, the frontal lobe extends down to
the cingulate sulcus.
• The paracentral lobule consists of the extensions of the
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.
Orbital surface Frontal lobe
• Divided into four orbital gyri by
a well-marked H-shaped
• The medial, anterior, lateral,
and posterior orbital gyri.
• The medial orbital gyrus
presents a well-marked
antero-posterior sulcus, the
olfactory sulcus, for the
• the portion medial to this is
named the gyrus rectus
Functional Frontal Lobe Anatomy
Clinically important areas of the frontal lobe include
•The primary motor area.
•The premotor Area.
•Supplementary motor areas.
•The prefrontal region.
•The frontal eye fields.
•The motor speech areas.
Primary motor cortex
• Primary motor area, or Brodmann area 4, occupies the
precentral gyrus extending over the superior border into
the paracentral lobule.
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
Primary motor cortex
• Input: Thalamus, Basal ganglia, sensory, premotor areas
• Output: Motor fibers to brainstem and spinal cord
• Function: Executes design into movement.
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
Pre motor cortex
• Input: Thalamus, Basal ganglia, sensory cortex
• Output: Primary motor cortex
• Lesions: Inability to make use of sensory feedback in
performance of smooth movements and apraxia
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.
Supplementary motor area
• Input: Cingulate gyrus, Thalamus, sensory & prefrontal
• Output: Premotor, primary motor cortex
• Lesions: Mutism, contralateral motor neglect, impairment
of bi brachial coordination.
Frontal eye field
• It is Broadmann area 8.
• It is located in the middle frontal gyrus.
• Input: Parietal / temporal (what is target & where is
• Output: caudate; superior colliculus; paramedian pontine
• Function: it is considered to control voluntary scanning
movements of the eye.
• Lesion: Eyes deviate ipsilaterally with destructive lesion
and contralaterally with irritating lesions.
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
Input: Wernicke’s area
Output: primary motor cortex
Function: speech production (dominant hemisphere);
emotional, melodic component of speech (non-dominant)
Lesions: motor aphasia.
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
• Clinically, the prefrontal region can be divided into the
dorsolateral prefrontal cortex (DLPFC), the medial
prefrontal cortex (MPC), and the orbitofrontal cortex
•The Case of Phineas Gage (Harlow 1848)
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, became erratic
• The DLPFC is important in the organization of self•
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.
Frontal lobe executive function is the ability to plan, carry
out, and monitor a series of actions intended to
accomplish a goal.
Lesions: executive function deficit; disinterest apathy,
decresed attention to relevant stimuli.
OFC and MPC
• The OFC has important connections with the limbic
system, including the amygdala.
• Disinhibition syndromes, ranging from mildly inappropriate
social behavior to full-blown mania, may occur with
dysfunction of the OFC, particularly of the right
• Lesion of MPC causes Paucity of spontaneous
movements, sparse verbal output, lower extremity
weakness and incontinence.
• Medial parts of frontal lobe: Anterior cerebral artery
• Convexity and deep regions: Superior (rolandic) division
• Underlying deep white matter: series of small penetrating
arteries (lenticulostriate) directly from stem of MCA
Frontal subcortical circuits
• The connections of the frontal lobes were described in
details by Goldman Rakic.
• Five FSCs have been described:
• 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.
• 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.
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
• 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.
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
FSC: Oculomotor circuit
•Voluntary scanning eye movement
FSC: Dorso-lateral circuit
This circuit is responsible for executive functions.
•motor planning, deciding which stimuli to attend to, shifting cognitive
•Attention span and working memory
•Lesion: difficulty focusing and sustaining attention as well as
reduced verbal fluency and motor programming
FSC: Orbito-frontal circuit
circuit mediates empathic, civil and
• Lesion: Disinhibition and emotional liability.
FSC: Anterior Cingulate Circuit
• This circuit is involved in motivational mechanisms.
• Lesions: Abulia, akinetic mutism.
Frontal lobe: Neuro-imaging
• The central sulcus is a useful landmark for identifying
• 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
• 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
• 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
• The precentral gyrus contains an area at its superior
lateral part, which resembles an upside-down omega, an
area of cortex that represents the motor-hand area.
difficulty in controlling their emotions, lacking in judgment
and are easily distracted
• Many patients are incorrectly diagnosed with a personality
Frontal Convexity syndrome
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.
Medial Frontal syndrome
• Characterized by mutism and akinesia.
indifference to thirst or hunger.
• Loss of sensation and weakness of lower extremities
along with urinary incontinence.
Right and left functional lobes lesional Deficits
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
Sucking reflex (pout, snout, rooting)
Glabellar tap reflex
Clinical assessment contd..
To assess the following functions:
Emotional make-up and personality
Abstraction and judgment
Attention and memory
Emotional make-up and personality is 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.
Attention and memory
• Attention is the patient’s ability to attend to a specific
stimulus without being distracted by external, internal or
• Attention can be tested by alternative sequence
• Luria’s ‘fist-edge-palm’ test
”tap once if I tap twice, don’t tap if I tap once”
“tap for A” read 60 letters at 1/sec
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
• Spontaneous speech
• Reading and writing.
• Wisconsin Card Sorting Test
• Trail Making
• Stroop Color & Word Test
Wisconsin Card Sorting Test
• Used primarily to assess perseveration and abstract
• The WCST is also considered a measure of executive
function because of its reported sensitivity to frontal lobe
• The WCST consists of four key cards and 128 response
• The task requires subjects to find the correct classification
principle by trial and error and examiner feedback.
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
• 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.).
A frontal assessment battery at bedside:
• 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)
“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
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
• > 9 words: 3, 6 -9 words: 2, 3 -5 words: 1, < 3 words: 0
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
•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
• 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: 1-1-2-12-2-2-1-1-2.
Score No errors: 3, 1 -2 errors: 2, > 2 errors: 1
• “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
• “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
• 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.
• 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
Anterior cingulate circuit: Abulia
Frontal Assessment battery is a useful bedside test to
differentiate frontal lobe syndromes with other causes of