Post on 17-Aug-2015
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
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)
Functional 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
Functional Anatomy of Frontal Lobe
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
Heteromodal Prefrontal - dorsolateral
10 Inferior prefrontal cortex
Heteromodal Prefrontal - dorsolateral
Functional Anatomy of Frontal Lobe
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)
Functional Anatomy of Frontal Lobe
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
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).
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
Frontal Lobe Syndromes
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
Frontal Lobe Syndromes
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
Frontal Lobe Syndromes
Attention and memory– Inattentiveness– Defect in working memory– Defect in sequencing, perseverance
Frontal Lobe Syndromes
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)
Frontal Lobe Syndromes - Tests
Language– Broca’s / non-fluent aphasia– Prefrontal/ transcortical motor aphasia– Language-motor dissociation– Akinetic mutism
Frontal Lobe Syndromes - Tests
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”
Frontal Lobe Syndromes - Tests
Frontal Lobe Syndromes - Tests
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)
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
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
Diseases Commonly Associated With Frontal Lobe Lesions
Degenerative diseases– Pick’s disease– Huntington’s disease
Infectious diseases– Neurosyphilis– Herpes simplex encephalitis
Diseases Commonly Associated With Frontal Lobe Lesions
Psychiatric Illness – proposed associations
– Depression
– Schizophrenia– OCD– PTSD– ADHD
Diseases Commonly Associated With Frontal Lobe Lesions
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