Functional anatomy of Frontal lobe

Functional Anatomy of Frontal Lobe

PresenterDr. Anusa A M

First year MD PG 1st August 2012

Hon. Chairperson

Dr. KUMANAN MD DPM, Professor

Dr. KARTHIKEYAN MD, DPM, Assistant Professor

Outline

Anatomy & Functional anatomy of frontal lobes

Neurotransmitters in the frontal lobes

Circuits of the frontal lobe and deficits

Testing prefrontal cortical function

Common causes of frontal lobe syndromes

References

Increased with Evolution……

Frontal Lobe

Largest of all lobes

Sagitally : ~1/3 / hemisphere

3 major areas in each lobe

Dorsolateral aspect

Medial aspect

Inferior orbital aspect

1, 2, 3 = primary sensory cortex4 = motor cortex5, 7 = secondary sensory cortex6 = supplementary motor area (medial) and premotor cortex (lateral)8 = frontal eye fields9/46 = dorsolateral prefrontal cortex10 = frontopolar cortex11, 12 = orbitofrontal areas17 = primary visual cortex18, 19, 20, 21, 37 = secondary visual cortex24, 32 = anterior cingulate cortex41 = primary auditory cortex22, 42 = secondary auditory cortex39 = angular gyrus, part of Wernicke's area40 = supramarginal gyrus, part of Wernicke's area44/45 = Broca's Area47 Ventrolateral prefrontal cortex(13, 14, 15, 16, 27, 49, 50, 51 - monkey only)

Frontal Lobe - Sulci & Gyri

Surface Division Separated by & B Number

Superolateral PrefrontalSuperior frontal gyrus (4l, 6l, 8l) · Middle frontal gyrus (9l, 10l, 46)Inferior frontal gyrus: 11l · 47-Pars orbitalis · Broca's area (44-Pars opercularis, 45-Pars triangularis)

Superior frontal sulcus · Inferior frontal sulcus

Precentral Precentral gyrus · Precentral sulcus

Medial/inferior PrefrontalSuperior frontal gyrus (4m, 6m) · Medial frontal gyrus (8m, 9m)Paraterminal gyrus/Paraolfactory area (12) · Straight gyrus (11m) · Orbital gyri/Orbitofrontal cortex (10m, 11m, 12) · Ventromedial prefrontal cortex (10m) ·Subcallosal area (25)

Olfactory sulcus · Orbital sulci

Precentral Paracentral lobule (4) · Paracentral sulcus

BothPrimary motor cortex (4) · Premotor cortex (6) · Supplementary motor area (6) · Frontal eye fields (8)

Anatomy of Frontal Lobe


Lateral sulcus/Sylvian fissure

Central sulcus

Motor speech area of Broca

Frontal eye field

B 44, 45

B 9, 10, 11, 12

B 8

Primary motor areaPremotor area

Prefrontal area

B6 B4

Supplementarymotor area(medially)

Brodmann area

Frontal Lobe

Primary Motor area Premotor area

Anterior Premotor Ventral anterior Premotor

Orbital frontal cortex Lateral Prefrontal cortex

▪ Dorsolateral Venteromedial prefrontal cortex

▪ Lateral frontopolar▪ Venterolateral


Broadman's area

Anatomical descriptions

Cortical type Functional region

4 Primary Motor Cortex

Primary Motor Motor

6 Premotor Primary Motor (caudal); Unimodal motor (Roustral)

Premotor

44 Pars opercularis Unimodal motor Premotor8 Motor

association cortex

Unimodal motor (caudal); heteromodal (rostral)

Premotor

46 Dorsolateral Prefrontal cortex

Heteromodal Prefrontal - dorsolateral

9 Superior Prefrontal cortex


10 Inferior prefrontal cortex



Broadman's area

Anatomical descriptions Cortical type Functional region

45 Pars triangularis Heteromodal Prefrontal - ventrolateral

47 Pars orbitalis Heteromodal Prefrontal - ventrolateral

11 Lateral orbitofrontal cortex

Heteromodal Prefrontal - orbitofrontal

12 Medial orbitofrontal cortex

Heteromodal (Rostral); Paralimbic (Caudal)

Prefrontal - orbitofrontal

32 Medial frontal cortex Heteromodal (Rostral); Paralimbic (Caudal)

Paralimbic (medial, frontal)

24 Anterior cingulate Paralimbic Paralimbic (medial, frontal)

25 Paraolfactory region Paralimbic Paralimbic (medial, frontal)


Motor cortex Primary Premotor Supplementary Frontal eye field Broca’s speech

area

Prefrontal cortex– Dorsolateral – Medial – Orbitofrontal

Functions Associated with Prefrontal Cortex

Executive function

Thinking

Judgment

Social

Curiosity

Motivation

Attention

Sequencing

Functions Associated with Lateral Prefrontal cortex

Selective attention

Working memory

Preparatory set

Monitoring

Temporal organization of behavior, speech, and reasoning

Distractibility, Perseveration, Dis-inhibition

Novelty, Uncertainty, Choice

Emotional Coloring of Action, Experience, and Decision

Making

Significance, Context and Ambiguity

Switching Perspectives and Mental Relativism

Memory & Frontal Lobe

Theories of Frontal Lobe Function Single-process theories

Damage to a single process or system is responsible for a number of different dysexecutive symptoms

Multi-process theories Frontal lobe executive system consists of a number of

components that typically work together in everyday actions (heterogeneity of function)

Construct-led theories: Most,if not all, frontal functions can be explained by one

construct (homogeneity of function) such as working memory or inhibition”

Single-symptom theories A specific dysexecutive symptom (e.g., confabulation) is

related to the processes and construct of the underlying structures

Motor Cortex

Primary motor cortex

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

Motor Cortex Supplementary motor

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

Motor Cortex Premotor cortex

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

Motor Cortex

Frontal eye fields

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)

Lesion : Eyes deviate ipsilaterally with destructive

lesion & contralaterally with irritating

lesions

Motor Cortex

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

Prefrontal Cortex Orbital prefrontal cortex

Connections: ▪ temporal,parietal, thalamus, GP, caudate, SN,

insula, amygdala ▪ Part of limbic system

Function▪ Emotional imput, arousal, suppression of distracting

signals Lesions

▪ emotional lability, disinhibition, distractibility, ‘hyperkinesis’

Schematic illustrating the connections of the VS. Blue arrows=inputs; gray arrows=outputs; Amy=amygdala; BNST=bed nucleus stria terminalis; dACC=dorsal anterior cingulate cortex; Hipp=hippocampus; hypo=hypothalamus; MD=medio-dorsal nucleus of the thalamus; OFC=orbital frontal cortex; PPT=pedunculopontine nucleus; S=shell; SNc=substantia nigra, pars compacta; STN=subthalamic nucleus; Thal=thalamus; VP=ventral pallidum; VS=ventral striatum; VTA=ventral tegmental area; vmPFC=ventral medial prefrontal cortex

Prefrontal Cortex 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

Prefrontal Cortex

Dorsolateral prefrontal cortex 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

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

Neurotransmitters

Norepinephrine tracts

Origin:

▪ Locus ceruleus in brainstem and lateral brainstem

tegmentum

Projections:

▪ Anterior cortex

Functions:

▪ Alertness, arousal, cognitive processing of

somatosensory info

Neurotransmitters

Serotonin tracts

Origin:

▪ Raphe nuclei in brainstem

Projections:

▪ Number of forebrain structures

Function

▪ Minor role in prefrontal cortex; sleep, mood,

anxiety, feeding

Neurotransmitter connection

BS-ACh, brain stem cholinergic cell groups; DRN, dorsal raphe nuclei; MRN, median raphe nuclei; NBM, nucleus basalis of Meynert; VTA; ventraltegmental area; 5HT, 5-hydroxytrytamine (serotonin).

Functional Frontal Lobe Anatomy

Five ‘frontal subcortical circuits’ (Cummings,‘93)

1. Motor2. Oculomotor3. Dorsolateral prefrontal4. Lateral orbitofrontal5. Anterior cingulate

Functional Frontal Lobe Anatomy

‘Frontal subcortical circuits’

ThalamusDM & CM

nuclei

Frontal cortex

StriatumCaudate & Putamen

Globus Pallidus &Substantia

Nigra

Frontal subcortical Circuits: 1. Motor Circuit

Supplementary Motor & Premotor: planning, initiation & storage of motor programs; fine-tuning of movements

Motor:final station for execution of the the movement according to the design

SMA,Premotor,Motor

Putamen

VL Globus Pallidus

VL, VA, CMThalamus

Hypo-thalamus

Frontal subcortical Circuits: 2. Oculomotor Circuit

Voluntary scanning eye movement Independent of visual stimuli

Frontal Eye Field

CentralCaudate

DM Globus Pallidus

SubstantiaNigra

VA, MDThalamus

Frontal subcortical Circuits: 3. Dorsolateral Prefrontal Circuit

Executive functions: motor planning, deciding which stimuli to attend to, shifting cognitive sets

Attention span and working memory

Lateral Prefrontal

DLCaudate

DM Globus Pallidus

SubstantiaNigra

VA, MDThalamus

Frontal subcortical Circuits: 4. Lateral Orbitofrontal Circuit

Emotional life and personality structure Arousal, motivation, affect Orbitofrontal cortex: consciousness

VMCaudate

DM Globus Pallidus

SubstantiaNigra

VA, MDThalamus

Infero-lateral prefrontal

Orbito-frontal

Frontal subcortical Circuits: 5. Anterior Cingulate Circuit

Abulia, akinetic mutism

AnteriorCingulate Gyrus

VentralStriatum

RL Globus Pallidus

SubstantiaNigra

MDThalamus

Corticostriatal LoopsAlexander, Delong, and Strick, 1986

Corticostriatal LoopsAlexander, Delong, and Strick, 1986

Frontal Lobe SyndromesThe 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

Frontal Lobe when affected cause

Puerile (Childish) Profane (Disrespectful) Slovenly (Sloppy) Facetious (Teasing) Irresponsible Grandiose Irascible (Irritable) Lost spontaneity, curiosity & initiative Apathetic blunting of feeling, drive, attentive power,

behavior. Erosion of foresight, judgment, insight Inability to delay gratification or experience remorse. Impairment of abstract reasoning, hypothesis

generation, creativity, problem solving, and mental flexibility

Frontal Lobe when affected cause

Jumped to premature conclusions Excessively literal Loss of orderly planning and sequencing of complex

behaviors The ability to attend to several components

simultaneously Flexibly alter the focus of concentration Capacity for grasping the context and gist of a complex

situation Resistance to distraction and interference Ability to follow multistep instructions Inhibition of immediate but inappropriate response

tendencies Ability to sustain behavioral output without

perseveration

Frontal Lobe Syndromes

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


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


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

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


Attention and memory– Inattentiveness– Defect in working memory– Defect in sequencing, perseverance


Tests of attention and memory– Alternative sequence (e.g. copying MNMN)– 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

Frontal Lobe Syndromes - Tests

Tests of attention and memory cont’– Digit span

– “repeat 3-52; 3-52-8; 3-52-8-67..” N: >5– Visual grasp: “look away from stimulus”– Recency test

–“recall sequence of stimuli / events”– Imitation (of examiner) / utilization (of objects

presented)


Language– Broca’s / non-fluent aphasia– Prefrontal/ transcortical motor aphasia– Language-motor dissociation– 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”



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

“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.”

Wisconsin Card Sorting Test

Trail Making Test

A

C12

73 D

5 B4

6

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”

Trial making Tests

RED BLUE ORANGE YELLOW

GREEN RED PURPLE RED

GREEN YELLOW BLUE RED

YELLOW ORANGE RED GREEN

BLUE GREEN PURPLE RED

“Please read this as fast as you can”

Stroop Color and Word Tests

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

Tower of London Tests

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)


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


Psychiatric Illness – proposed associations

– Depression

– Schizophrenia– OCD– PTSD– ADHD


Frontal Lobe Syndromes – Summary

Personality and emotional

changes

Reflect prefrontal lesions

Role of Dopamine and

Norepinephrine

Trauma > vascular, tumors

References

Netter’s atlas of Neuroanatomy (Google Images) The Human frontal Lobe – functions and Disorders; Millers BL, Cummings

JL, 2007, 2nd Ed, Guilford Publisher, NY, USA (Google books) Burruss JW, Hurley RA, Taber KH et al. Functional Neuroanatomy of the

frontal lobe circuits. Radiology 2000;214:227-230 (Open access) Stuss DT, Knight RT. Principles of frontal lobe function, 1st Ed, Oxford,

2002, NY, USA

Thank You

Functional anatomy of Frontal lobe

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