FRONTAL LOBE- Dr. Sriram.R

INTRODUCTION• The frontal lobe is one of the four major lobes of

the cerebral cortex.

• Located at the front of each cerebral hemisphere and positioned anterior to parietal lobe.

• Superior and anterior to the Temporal lobes.

• Separated from the parietal lobe by a space between tissues called the central sulcus.

• Separated from the temporal lobe by a deep fold called the lateral (Sylvian) sulcus.

• The precentral gyrus, forming the posterior border of the frontal lobe, contains the primary motor cortex, which controls voluntary movements of specific body parts.

• In humans, the frontal lobe reaches full maturity around the late 20s (Giedd et al., 1999)

• A small amount of atrophy, however, is normal in the aging person’s frontal lobe.

• A decline in frontal lobe volume of approximately .5% every year seemed to be average. (Fjell, 2009)

• These findings corroborate those of Coffey, who in 1992 indicated that the frontal lobe decreases in volume approximately 0.5%-1% per year.

Leukotomy and lobotomy (1935 – Egas Moniz)

STRUCTURE OF FRONTAL LOBE

• On the lateral surface of the human brain, the central sulcus separates the frontal lobe from the parietal lobe.

• The lateral sulcus separates the frontal lobe from the temporal lobe.

• The frontal lobe bottom can be divided into a • lateral, • polar, • orbital (above the orbit; also called basal or ventral), and • medial part.

• Each of these parts consists of particular gyri and the gyri are separated by sulci

• Lateral part: Precentral gyrus, lateral part of the superior frontal gyrus, middle frontal gyrus, inferior frontal gyrus.

• Polar part: Transverse frontopolar gyri, frontomarginal gyrus.

• Orbital part: Lateral orbital gyrus, anterior orbital gyrus, posterior orbital gyrus, medial orbital gyrus, gyrus rectus.

• Medial part: Medial part of the superior frontal gyrus, cingulate gyrus.

LATERAL SURFACEORBITAL (VENRAL SURFACE)

MEDIAL SURFACE

The orbitofrontal cortex is divided into ventromedial (reddish in the anterior view: above and yellow in the convex-lateral and median-sagittal view) and the lateral orbitofrontal cortex (green)

BLOOD SUPPLY of FL – MCA and ACA

• The middle cerebral artery (MCA) is one of the three major paired arteries that supply blood to the cerebrum.

• The MCA arises from the internal carotid and continues into the lateral sulcus where it then branches and projects to many parts of the lateral cerebral cortex.

• To the frontal lobe, it gives off 4 branches - • Lateral frontobasal (orbitiofrontal)• Prefrontal arteries• Pre-Rolandic artery (precentral)• Rolandic arteries (central)

• The anterior cerebral artery (ACA) is one of a pair of arteries on the brain that supplies oxygenated blood to most medial portions of the frontal lobes and superior medial parietal lobes.

• The two anterior cerebral arteries arise from the internal carotid artery and are part of the Circle of Willis.

• The ACA supplies the frontal lobe in the following areas –

- The medial surface of the frontal lobe by the medial orbito-frontal artery.

- Approximately 1 inch of the lateral surfaces of FL

ACA – MEDIAL SURFACE OF BRAIN

LATERAL SURFACE OF THE BRAIN PINK - REGION SUPPLIED BY MIDDLE CEREBRAL ARTERYBLUE – REGION SUPPLIED BY ANTERIOR CERBRAL ARTERY

CYTOARCHITECTURE, FUNCTIONS and

TESTS of FRONTAL LOBE

• Cytoarchitecture (Greek κύτος= "cell" + αρχιτεκτονική= "architecture"), also known as cytoarchitectonics, is the study of the cellular composition of the body's tissues under the microscope.

• Refers to the arrangement and characteristic organization of neuronal cell bodies in the brain and spinal cord.

• The birth of the cytoarchitectonics of the human cerebral cortex is credited to the Viennese psychiatrist Theodor Meynert (1833-1892)

• Korbinian Brodmann (1868-1918) in Berlin, working on the brains of diverse mammalian species, developed a division of the cerebral cortex into 52 discrete areas (of which 44 in the human, and the remaining 8 in non-human primate brain.

BROCA’S AREA • Broca's area or the Broca area is a region in the frontal lobe of one 

hemisphere (usually the left), named after Pierre Paul Broca.

• Broca's area in the left hemisphere and its homologue in the right hemisphere are designations usually used to refer to pars triangularis (PTr) and pars opercularis (POp) of the inferior frontal gyrus.

• Represented in Brodmann's cytoarchitectonic map as areas 44 and 45 of the dominant hemisphere.

• Leborgne was a patient of Broca's. Almost completely unable to produce any words or phrases, he was able to repetitively produce only the word tan. Lelong was another patient of Broca's. He also exhibited reduced productive speech. He could only say five words, 'yes,' 'no,' 'three,' 'always,' and 'lelo'

FUNCTIONS OF BROCA’s area• Language production and language comprehension/use syntax to determine

meaning of sentences.

• Plays a role in interpreting action of others – Action recognition and production.

• Speech-associated gestures could possibly reduce lexical or sentential ambiguity, comprehension should improve in the presence of speech-associated gestures. As a result of improved comprehension, the involvement of Broca's area should be reduced

FRONTAL-SUBCORTICAL CIRCUITS

• There are 5 parallel, separate circuits (Alexander et al, 1986)

1. a motor circuit originating in the motor cortex and pre-motor cortex

2. an oculomotor unit originating in the frontal eye fields

3. the dorsolateral prefrontal circuit, which underpins executive functions

4. the anterior cingulate circuit which underpins motivation

5. the orbitofrontal circuit which underpins impulse control and social behavior.

Neurology

Psychiatry

Frontal lobes: Subcortical connections -Thalamus

dorsomedial

Dorsolateral prefrontal

Dorsolateralcaudate

Lateral dorsomedial

Globus Pallidus

VA & MDThalamus

Ventromedialcaudate

MedialGlobus pallidus

Anterior Cingulate

Nucleusaccumbens

RostrolateralGlobus Pallidus

MDThalamus

Orbital prefrontal

VA & MDThalamus

Frontal lobes: Subcortical connectionsThalamus

Frontal lobes: Subcortical connectionsWhite matter

uncinate fasciculuslong tracts to posterior association areas

cortical u-fibers

Frontal lobes: Cortical connections

Functional regions of the frontal lobes

I. Primary motor area

II. Premotor area

III. Frontal eye fields

IV. Dorsolateral prefrontal cortex

V. Orbital and basal areas

VI. Supplementary motor area and anterior cingulate gyrus area

I. Primary motor area• Brodmann area 4• Input from ventral lateral

thalamic nucleus, primary somatosensory area in parietal lobe

• Output to internal capsule• Pyramidal motor functions• Although designated a

“motor” cortex, this area is also involved with somatosensory perception

CORTICAL HOMUNCULUS (Primary motor)• A cortical homunculus is a pictorial representation of

the anatomical divisions of the primary motor cortex.

Primary motor dysfunction

• Initially flacid hemiparesis or hemiplegia on contralateral side

• Later spastic hemiparesis or hemiplegia

Bedside tests for Primary motor cortex:

1. 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.

2. Motor speed as in finger tapping has also been listed as a useful test (Malloy & Richardson, 1994) but such tests do not discriminate from the premotor cortex.

• 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.)

II. Premotor area

• Brodmann area 6• Input from ventral anterior

thalamic nucleus and secondary somatosensory area

• Output to motor area and connections via corpus callosum to contralateral premotor area

• Integration of sensory and motor information

• Praxis

Premotor dysfunction

• Apraxia• Preserved postural praxis via

basal ganglia• Contralateral fine motor

deficits• Difficulty using sensory

feedback

Bedside tests for premotor cortex:

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" / demonstrate the use of a shovel / draw a cube / draw a star / light a cigarette etc.

Poor performance carries the diagnostic implications as for the motor cortex above. (i.e. the area is affected by vascular insult/neoplasm)

EFFECTS of LESIONS AFFECTING BOTH Primary motor and Premotor cortex

• Motor – Contralateral spastic paresis; loss of fine motor control

• Reduced verbal fluency• Impaired spelling• Others effects – (GROUPS)

1. Gegenhalten/Paratonia

2. Primitive reflexes (grasp/sucking/palmar-mental/glabellar tap)

3. Optic atrophy (Ipsilateral)

4. Urinary incontinence

5. Perseveration

6. Seizures (Jacksonian)

III. Frontal eye field• Brodmann area 8 (posterior

portion of middle frontal gyrus), with some area 9 and 6

• Volitional eye movement in contralateral visual field

• Active visual search• 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.

Frontal eye field dysfunction

• Failure to move eyes volitionally to contralateral visual field

• Intact passive eye movement

• Poor visual search

Bedside test for frontal eye field:

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.

IV. Dorsolateral PFC

• Brodmann areas 46,45,47,8,9,10. A compromise position is that the DLPFC is composed of Brodmann area 9 and the lateral aspect of 10 and most of area 46.

• Executive functions - (“Executive” in frontal lobe means cognitive system that controls and manages other cognitive processes. )• Integration of multimodal sensory information• Generation of multiple reponse alternatives to environmental

challenges• Selection of most appropriate response, self evaluation of

responses and selection of a replacement response if first response fails

• Maintenance of task set, persistence• Sequential ordering of data• Set shifting, flexibility• Spatial working memory

FUNCTIONS OF DLPFC

• 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.

• It is believed by some authors that formal thought disorder arises from a lack of executive planning and editing (McGrath, 1991).

• In thought disorder there are frequent examples of failure to maintain set (distractibility), sequentially order information, and to ensure that the listener is comprehending.

Note - formal thought disorder is also known to involve the left superior temporal sulcus and the left temporal pole (Horn et al, 2010).

Dorsolateral PFC dysfunction

• Difficulty integrating sensory information

• Generation of few, stereotyped response alternatives

• Poor judgement in response selection

• Impersistence• Perseveration

• 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 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).

Bedside tests for DLPFC: 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. Here the patient has to retain the task and simultaneously manipulate information.

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 previously used words with a different suffix are prohibited (Benton, 1968).

5. Other categorical fluency tests include naming animals, fruits and vegetables (Monsch et al, 1992).

6. Alternating hand sequences. These can be devised by the examiner.

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

7. 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).

Dorsolateral testsFigural fluency

Dorsolateral testsLuria’s reciprocal hand movements & graphic designs

Dorsolateral testsPerseverations within and between Lurian tasks

Dysexecutive effects on other tests

Frontal lobesPoor organization of learning and

recall (Ray Osterrieth)

Copy Free recall

V. Orbital and Basal areas• Brodman areas 10,11,12,13,14• Input from limbic and olfactory

systems (amygdala, temporal pole, entorhinal cortex, olfactory nerve); inferotemporal lobe areas, ventral visual pathways

• Output to autonomic musculature and endocrine system (basal forebrain cholinergic system, caudate, and autonomic system)

FUNCTIONS OF OFC• Modulation of affective and social behavior; “...preservation of

behavioral regulation by external stimuli and its dissolution in the absence of external stimulation.”

• It mediates empathic, civil and socially appropriate behavior (Mega and Cummings, 1994).

• Working memory for feature information• Integration of memory and emotional valence• Smell discrimination• 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

Dr. Harlow – SurgeonWho treated Phineas Gage

OFC dysfunction

• Disinhibition, socially inappropriate behavior

• Failure on feature working memory tasks

• Anosmia• Confabulation• 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 for OFC:

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? (Frontal Systems Behavior Scale – FrSBe can be used)

2. Test sense of smell - coffee, cloves etc. (UPSIT can be used)

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”.

Note - 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). This is a neuropsychological test which examines the ability of the patient to inhibit responses. Patients are asked to state the color in which words are printed rather than the words themselves.

Failure of response inhibition is seen in - • Head injury, other destructive lesions (including dementing processes)

and schizophrenia.• 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; Hampson et al, 2012).

Changes in smell with aging - UPSIT

Disinhibition and intrusion in drawing

Prefrontal region and its importance

• Dorsolateral + Basomedial area = Prefrontal region

• Damage to prefrontal region can impair Intelluctual functions (Sequencing, Processing, attention, concentration and execution) as well as cause Personality changes (Pseudosychopathic or Pseudodepressive)

• Connections with thalamus

1. Magnocellular region (medial part of dorsomedial nucleus of thalamus ) to Basomedial/OF region (damage can cause Pseudopsychopathic syndrome)

2. Parvicellular region (lateral part of dorsomedial nucleus of thalamus) to Dorsolateral region of PFC (damage can cause Pseudodepressive syndrome)

• Pseudopsychopathic personality – (CDEFGH)• Childish excitement (Moria)• Disinhibition and promiscuity• Euphoria• Familiarity• Garrulousness (excessive talk)• Humorous punning (Witzelsucht)

• Pseudodepressive personlaity – (RAPID)• Retardation (Psychomotor)• Apathy• Placidity• Indifference (lack of concern)• Diminished drive (lack initiative)

VI. SMA/Cingulate area

• SMA – medial aspect of BA 6 and and Ant. Cingulate gyrus is BA 24, 32

• These areas are involved in drive and motivated behavior (Mega and Cummings, 1994), initiation and goal-directed behavior (Devinsky et al, 1995)

• Connections with older cortical and deep limbic structures

• Environmental exploration• Complex attention

Cingulate/SMA dysfunction

• 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.

• At present there are no office or neuropsychological tests to measure the functional status of these areas.

NEUROLOGICAL DISORDERS AFFECTING FRONTAL LOBE• Neoplasms (90% brain tumor patients with psychiatric

problems have frontal lobe involvement)

• Cerebrovascular diseases

• Multiple sclerosis

• Trauma

• Degenerative diseases – Alzheimer’s, FTD

FRONTAL LOBE SYNDROME• Dysexecutive syndrome consists of a number of symptoms which tend

to occur together (hence it being described as a syndrome). Broadly speaking, these symptoms fall into three main categories; cognitive, emotional and behavioural.

• Cognitive - Short attention span, Poor working memory, Poor short term memory, Difficulty in planning and reasoning, Environmental dependence syndrome

• Emotional - Difficulty in inhibiting emotions, anger, excitement, sadness etc., Depression, Occasionally, difficulty in understanding others' points of view, leading to anger and frustration.

• Behavioural - Utilization behaviour, Perseveration behaviour Inappropriate aggression, Inappropriate sexual behaviour, Inappropriate humour and telling of pointless and boring stories (Witzelsucht)

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