Frontal lobe and its functions

 Anatomy

 Circuits

 Physiology

 Normal functioning and Assesment

 Syndromes

 Largest of all lobes
◦ SA: ~1/3 / hemisphere

 3 major areas in each lobe
◦ Dorsolateral aspect
◦ Medial aspect
◦ Inferior orbital aspect

Premotor area Primary motor area
B6 B4

Central sulcus
Supplementary
motor area
(medially)

Frontal eye field
B8

Prefrontal area
B 9, 10, 11, 12
Lateral sulcus/
Sylvian fissure
Motor speech
area of Broca
B 44, 45

 MOTOR CORTEX • PREFRONTAL CORTEX

• Primary • Dorsolateral Area
• Premotor • Medial
• Supplementary • Orbitofrontal
• Frontal eye field
• Broca‟s speech area

 PRIMARY MOTOR CORTEX (4)

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

 PREMOTOR CORTEX (6)

◦ Input: thalamus, BG, sensory cortex
◦ Output: primary motor cortex
◦ Function: stores motor programs; controls coarse
postural movements
◦ Lesions: moderate weakness in proximal muscles
on contralateral side

 SUPPLEMENTARY MOTOR (Med 6)

◦ Input: cingulate gyrus, thalamus, sensory &
prefrontal cortex
◦ Output: premotor, primary motor
◦ Function: intentional preparation for movement;
procedural memory
◦ Lesions: mutism, akinesis; speech returns but it
is non-spontaneous

 FRONTAL EYE FIELDS (8)

◦ Input: parietal / temporal (what is target);
posterior / parietal cortex (where is target)
◦ Output: caudate; superior colliculus;
paramedian pontine reticular formation
◦ Function: executive: selects target and
commands movement (saccades)
◦ Lesion: eyes deviate ipsilaterally with
destructive lesion and contralaterally with
irritating lesions

 BROCA‟S SPEECH AREA

◦ Input: Wernicke‟s
◦ Output: primary motor cortex
◦ Function: speech production (dominant
hemisphere); emotional, melodic component of
speech (non-dominant)
◦ Lesions: motor aphasia; monotone speech

 ORBITAL PREFRONTAL CORTEX (10,11)

◦ 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,
distractibility, „hyperkinesis‟

 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

 DORSOLATERAL PREFRONTAL CORTEX (9,10,46)

◦ 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

 DOPAMINERGIC TRACTS

◦ Origin: ventral tegmental area in midbrain
◦ Projections: prefrontal cortex (mesocortical tract)
and to limbic system (mesolimbic tract)
◦ Function: reward; motivation; spontaneity; arousal

 NOREPINEPHRINE TRACTS

◦ Origin: locus ceruleus in brainstem and lateral
brainstem tegmentum
◦ Projections: anterior cortex
◦ Functions: alertness, arousal, cognitive
processing of somatosensory info

 SEROTONIN TRACTS

◦ Origin: raphe nuclei in brainstem
◦ Projections: number of forebrain structures
◦ Function: minor role in prefrontal cortex;
sleep, mood, anxiety, feeding

 Brodmann area 4

◦ Bedside tests:
 Motor strength of hand grip.
 The patient is asked to grip the examiners fingers.
 Strength should be roughly equal, with greater strength on the
dominant side.
 It should be difficult for the examiner to free her/his fingers.
 Diagnostically, poor performances suggest local lesions such as
vascular or neoplastic pathology, or a generalized lesion such as
a degenerative disease. (Peripheral nerve lesion must, of
course, be excluded.)

 Brodmann area 6
 It is involved in sensorimotor integration.
 Lesions cause inability to make use of sensory
feedback in the performance of smooth movements
and apraxia.
 Apraxia may also be a result of lesions of other
areas (parietal lobe).
 Bedside tests:
◦ 1. Sensorimotor abilities are tested by asking the patient
touch each finger to the thumb in succession as rapidly as
possible.
 Watch for speed and dexterity.
◦ 2. Apraxia can be tested by asking the patient to "blow a
kiss" and to demonstrate the use of an object.
◦ Poor performance carries the diagnostic implications as for
the motor cortex above.

 Brodmann area 8, with some area 9 and 6.
 Voluntary eye movements are of two types.
 Pursuit movement occurs when the eyes to follow
moving objects.
 Saccadic eye movements are used to follow
imaginary points.
 Bedside test:
◦ 1. Ask the patient to follow the movement of a finger
from left to right and up and down.
◦ 2. Ask the patient to look from left to right, up and down
(with no finger to follow).
◦ Note inability to move or jerky movement.

 Brodmann area 9 and the lateral aspect of 10 and most of
area 46.
 The executive functions include
◦ the integration of sensory information,
◦ the generation of a range of response alternatives to
environmental challenges,
◦ the selection of the most appropriate response,
◦ maintenance of task set, sequential ordering of data,
◦ self-evaluation of performance
◦ the selection of a replacement responses if the first applied
response fails.
 The executive functions largely determine the ability of the
individual to cope with the continuous, but ever changing
challenges of the environment.
 Thus, the patient‟s ability to make an appointment and to
arrive on time is valuable information.
 So too, is the ability of the patient to give a comprehensive
account of her/himself and the reasons for the
consultation.

 Bedside tests:
 1. Is the patient able to make an appointment and
arrive on time?
 2. Is the patient able to give a coherent account of
current problems and the reason for the interview?
◦ Is there evidence of thought disorder?
 3. Digit span, days of the week or months of the year
backwards.
 4. Controlled oral word association test (COWAT):
◦ the patient is asked to produce as many words as possible,
in one minute, starting with F, then A, then S.
◦ Proper nouns and be previously used words with a different
suffix are prohibited (Benton, 1968).
◦ Other categorical fluency tests include naming animals,
fruits and vegetables (Monsch et al, 1992)

 Normal provide more than ten items for each of these
categories, while a patient score less than eight.
 Common errors include perseveration (repeating
words which have already been given either during
the task at hand or an earlier task).
 There may also be inappropriate utterances. (These
also suggest disinhibition which is discussed under
orbitofrontal cortex, below.)
 5. Alternating hand sequences.
◦ One example is that one hand is placed palm upwards and
the other is place palm downwards, and the patient is then
asked to reverse these positions as rapidly as possible.
◦ Another example is that the backs of the hands are both
placed downwards, but one hand is clenched and the other
is open, then the patients is asked to close the open hand
and open the closed hand, and keep reversing the posture
of the hands as rapidly as possible

 A final example is that the patient taps twice with one fist and once with
the other, then after the rhythm is established, the patient is asked to
change over the number of beats (the fist which first tapped twice now
taps only once).
 Patients with frontal lobe deficits usually perform poorly on these tests,
often being unable to follow the relatively simple instructions.
 6. Formal neuropsychological may be necessary where uncertainty
remains.
◦ Commonly employed tests include Controlled Oral Word Association Test (Benton,
1968) and the Wisconsin Card Sorting Tests (Heaton, 1985).
 Head injury and dementing illnesses may result in severe impairment of
the executive functions.
 Schizophrenia often has thought disorder as a major feature and the
executive functions tests are usually also at least mildly affected.
 Depressive disorder may be associated with poor performance on verbal
fluency tests during the acute phase, which normalizes with remission
(Trichard, et al., 1995).

 Brodmann areas 10 and 11
 It mediates empathic, civil and socially appropriate behavior
(Mega and Cummings, 1994).
 Much of the personality change described in cases of frontal
lobe injury (Phineas Gage being the most famous) is due to
lesions in this area.
 Patients may become irritable, labile, disinhibited and fail to
respond to the conventions of acceptable social behavior.
 Similar changes may occur with lesions of subcortical element of
the frontal-subcortical circuit, as with caudate damage in
Huntington's disease.
 Increased concern about social behavior and contamination has
been associated with increased orbitofrontal and caudate
metabolism.
 This has been reported with lesions of the globus pallidus and in
obsessive compulsive disorder.

 Bedside tests:
 1. Does the patient dress or behave in a way which
suggests lack of concern with the feelings of others
or without concern to accepted social customs.
 2. Test sense of smell - coffee, cloves etc.
 3. Go/no-go Test.
◦ The patient is asked to make a response to one signal (the
Go signal) and not to respond to another signal (the no-go
signal). The most basic is to ask the patient to tap their
knee when the examiner says, “Go” and to make no
response when the examiner says, “Stop”.
◦ The task may be made more demanding by reversing the
customary meaning of signals.
◦ An example is to ask the patient to tap the knee when the
examiner says "Stop" and not to tap when the examiner
says "Go" (Malloy and Richardson, 1994).

 4. The Stroop Test (Stroop, 1935)
 Failure of inhibition may complicate head
injury, other destructive lesions (including dementing
processes) and schizophrenia.
 Failure of inhibition is found in impulse control and
personality disorder (particularly of the antisocial
type).
 Depressive disorder may manifest irritability, and has
been associated with poor performance on the Stroop
Test (Trichard et al, 1995).
 Obsessive compulsive disorder in which there is
excessive concern and caution is associated with
increased metabolism in the orbitofrontal cortex
(which may result from subcortical pathology)

 The supplementary motor area is the medial aspect of Brodmann area 6
(Barker & Barasi, 1999) and the anterior cingulate gyrus is Brodmann
area 24.
 These areas are involved in motivated behavior (Mega and
Cummings, 1994), initiation and goaldirected behavior (Devinsky et
al, 1995).
 At present there are no office or neuropsychological tests to measure
the functional status of these areas
 Akinetic mutism occurs with gross lesions (e.g., meningioma) of the
anterior cingulate.
 Such patients are profoundly apathetic, generally mute and eat and drink
only when assisted.
 They do not respond to pain and are indifferent to their circumstances.
Lesions of the supplementary motor area are associated with the alien
hand syndrome (Goldberg & Bloom, 1990).
 The apathy of schizophrenia and the immobility of depressive disorder
may be associated with defects in associated circuits

 As the CNS matures, frontal lobe cells develop and begin to inhibit the
primitive reflexes which are present in normal babies.
 These may reappear with brain damage or disease.
 However, they may also reappear with normal aging.
 Their significance is greater when they appear unilaterally and in young
individuals (Ross, 1985).
 Grasp
◦ The hand is stroked across the palm toward the thumb by the examiners fingers or
the handle of the patella hammer.
◦ When the reflex is present the fingers grasp or the thumb strongly adducts.
◦ The patient may be unable to release the grip. Presence suggests contralateral frontal
lobe disease.
 Sucking (pout, snout, rooting)
◦ The sucking reflex is elicited by stroking the lips of the patient with a finger or a
spatula from side to middle and back again.
◦ The pouting reflex is elicited by the examiner placing the index finger of the
patient‟s closed lips and tapping the finger with a patella hammer.
◦ Sucking or pouting movements of the lips suggest frontal lobe damage or bilateral
lesions above the mid-pons.

 Palmar-mental
◦ The palm is scratched firmly with a key or the handle of the
patella hammer, from the fingers, toward the wrist.
◦ The positive response is a flicker in the skin on the ipsilateral
side of the point of the chin.
◦ Presence suggests contralateral frontal lobe damage, however, the
true value of the reflex is yet to be clearly determined.
 Glabella Tap
◦ The patient is asked to close the eyes and the examiner repeatedly
taps (finger tip or patella hammer) the supraorbital ridge.
◦ In the normal individual the orbicularis oris contracts in response
to the first two or three taps and then ceases.
◦ In pathological conditions the orbicularis oris continues to
contract with every tap.
◦ This reflex is used in the diagnosis of Parkinson's disease, but it
may also occur with frontal damage of other etiologies

Frontal Lobe Syndromes
 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

Wisconsin Card Sorting Test

“Please sort the 60 cards under the 4 samples.
I won‟t tell you the rule, but I will announce every mistake.
The rule will change after 10 correct placements.”

Blue Purple Green
Red Red Yellow
Green Green Red
Yellow Black Yellow
Black Blue Orange
Yellow Yellow Blue
Orange
Green Brown
Red
Red Blue
Purple
Blue Purple Red
Blue Green

Trail Making Test

5 B
A 4

6
1 C
2

3 D
7

Various levels of difficulty:
1. “Please connect the letters in alphabetical order as fast as you can.”
2. “Repeat, as in „1‟ but alternate with numbers in increasing order”

Tower of London Tests

Various levels of difficulty:
e.g. “Please rearrange the balls on the pegs, so that each peg has
one ball only. Use as few movements as possible”


 Emotional make-up and personality
 Abstraction and judgment
 Attention and memory
 Language


 Tests of abstraction and judgment
– 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

 Tests of attention and memory
– Digit repetition test
– A random letter 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; N: < 2 errors


 Tests of attention and memory cont‟
– Digit span
– “repeat 3-52; 3-52-8; 3-52-8-67..”
– Recency test
–“recall sequence of stimuli / events”
– Imitation (of examiner) / utilization (of
objects presented)


 Language
– Broca‟s / non-fluent aphasia
– Prefrontal/ transcortical motor aphasia
– Akinetic mutism


 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”

 Three Frontal Lobe syndromes
 Orbitofrontal syndrome (lacks inhibition)
 Frontal Convexity syndrome (apathetic)
 Medial Frontal syndrome (akinetic)

 Answer lab assessments correctly but make
poor choices in real situations
 Tests of perception, construction, language, and
spatial attention are unharmed

 Orbitalfrontal syndrome
 Commonly caused by closed-head injury
 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
 Possible link between violent offenders and traumatic
brain injury

 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

 Medial Frontal syndrome
 Characterized by occasional mutism, inability to
control sexual appetite and akinesia
 Loss of sensation in lower extremities as well as
weakness also occur

 Many patients experience symptoms from
each syndrome

 I. Effects of unilateral frontal disease, either left or right
◦ A. Contralateral spastic hemiplegia
◦ B. Slight elevation of mood, increased talkativeness, tendency to joke
inappropriately (Witzelsucht), difficulty in adaptation, loss of initiative
◦ C. If entirely prefrontal, no hemiplegia; grasp and suck reflexes or
instinctive grasping may be released
◦ D. Anosmia with involvement of orbital parts

 II. Effects of right frontal disease
◦ A. Left hemiplegia
◦ B. Changes as in I.B, C, and D

 III. Effects of left frontal disease
◦ A. Right hemiplegia
◦ B. Motor speech disorder with agraphia, with or without apraxia of the lips
and tongue

◦ C. Sympathetic apraxia of left hand
◦ D. Loss of verbal associative fluency; perseveration
◦ E. Changes as in I.B, C, and D

 IV. Effects of bifrontal disease
◦ A. Bilateral hemiplegia
◦ B. Spastic bulbar (pseudobulbar) palsy
◦ C. If prefrontal,
 abulia or akinetic mutism,
 lack of ability to sustain attention and solve complex problems,
 rigidity of thinking,
 bland affect,
 social ineptitude,
 behavioral disinhibition,
 inability to anticipate,
 labile mood, and varying combinations of grasping,
 sucking,
 obligate imitative movements,
 utilization behavior.
◦ D. Decomposition of gait and sphincter incontinence

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

with Frontal Lobe Lesions

 Frontal Lobe seizures
– Usually secondary to trauma
– Difficult to diagnose: can be odd (laughter, crying, verbal
automatism, complex gestures)


 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


 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


 Degenerative diseases
– Pick‟s disease
– Huntington‟s disease

 Infectious diseases
– Neurosyphilis
– Herpes simplex encephalitis

with Frontal Lobe Lesions

 Psychiatric Illness – proposed associations
– Depression
– Schizophrenia
– OCD
– PTSD
– ADHD

 Schizophrenia
◦ Abnormality in the mesocortical dopaminergic
projection
◦ Decrease in blood flow to the frontal lobes, and
frontal lobe atrophy
 Parkinson‟s Disease
◦ Loss of dopamine cells in the substantia nigra
that project to the prefrontal cortex
 Korsakoff‟s
◦ Alcohol-induced damage to the dorsomedial
thalamus and a deficiency in frontal lobe
catecholamines

Frontal lobe and its functions

Frontal lobe and its functions

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Frontal lobe and its functions