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Functional anatomy of Frontal lobe
1. Presenter
Dr. Anusa A M
First year MD PG
1st August 2012
Hon. Chairperson
Dr. KUMANAN MD DPM,
Professor
Dr. KARTHIKEYAN MD, DPM,
Assistant Professor
2. 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
3.
4. Largest of all lobes
Sagitally : ~1/3 / hemisphere
3 major areas in each lobe
Dorsolateral aspect
Medial aspect
Inferior orbital aspect
5. 1, 2, 3 = primary sensory cortex
4 = motor cortex
5, 7 = secondary sensory cortex
6 = supplementary motor area (medial) and premotor cortex (lateral)
8 = frontal eye fields
9/46 = dorsolateral prefrontal cortex
10 = frontopolar cortex
11, 12 = orbitofrontal areas
17 = primary visual cortex
18, 19, 20, 21, 37 = secondary visual cortex
24, 32 = anterior cingulate cortex
41 = primary auditory cortex
22, 42 = secondary auditory cortex
39 = angular gyrus, part of Wernicke's area
40 = supramarginal gyrus, part of Wernicke's area
44/45 = Broca's Area
47 Ventrolateral prefrontal cortex
(13, 14, 15, 16, 27, 49, 50, 51 - monkey only)
6. Surface Division Separated by & B Number
Superolateral Prefrontal
Superior 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 Prefrontal
Superior 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
Both
Primary motor cortex (4) · Premotor cortex (6) · Supplementary motor
area (6) · Frontal eye fields (8)
7.
8. 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
Supplementary
motor area
(medially)
Brodmann area
9.
10.
11. Primary Motor area
Premotor area
Anterior Premotor
Ventral anterior Premotor
Orbital frontal cortex
Lateral Prefrontal cortex
▪ Dorsolateral
Venteromedial prefrontal cortex
▪ Lateral frontopolar
▪ Venterolateral
12. 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 Premotor
8 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
13. 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)
14. Motor cortex
Primary
Premotor
Supplementary
Frontal eye field
Broca’s speech area
Prefrontal cortex
– Dorsolateral
– Medial
– Orbitofrontal
15. Executive function
Thinking
Judgment
Social
Curiosity
Motivation
Attention
Sequencing
16. 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
17.
18. 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
19. 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
20. 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
21. 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
22. 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
23. 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
24. 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’
25. 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
28. 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
29.
30. Dopaminergic tracts
Origin:
▪ ventral tegmental area in midbrain
Projections:
▪ Prefrontal cortex (mesocortical tract) and to limbic
system (mesolimbic tract)
Function:
▪ Reward; motivation; spontaneity; arousal
31. Norepinephrine tracts
Origin:
▪ Locus ceruleus in brainstem and lateral brainstem tegmentum
Projections:
▪ Anterior cortex
Functions:
▪ Alertness, arousal, cognitive processing of somatosensory info
32. Serotonin tracts
Origin:
▪ Raphe nuclei in brainstem
Projections:
▪ Number of forebrain structures
Function
▪ Minor role in prefrontal cortex; sleep, mood, anxiety,
feeding
38. 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, CM
Thalamus
Hypo-
thalamus
39. Voluntary scanning eye movement
Independent of visual stimuli
Frontal
Eye Field
Central
Caudate
DM Globus
Pallidus
Substantia
Nigra
VA, MD
Thalamus
40. Executive functions: motor planning, deciding which stimuli to
attend to, shifting cognitive sets
Attention span and working memory
Lateral
Prefrontal
DL
Caudate
DM Globus
Pallidus
Substantia
Nigra
VA, MD
Thalamus
41. Emotional life and personality structure
Arousal, motivation, affect
Orbitofrontal cortex: consciousness
VM
Caudate
DM Globus
Pallidus
Substantia
Nigra
VA, MD
Thalamus
Infero-
lateral
prefrontal
Orbito-
frontal
44. Frontal Lobe Syndromes
The 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
45. 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
46. 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
47. Frontal Lobe Syndromes
Emotional make-up and personality
Abstraction and judgment
Attention and memory
Language
48. 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
49. Frontal Lobe Syndromes
Abstraction and judgment
– Cognitive functions undisturbed
– Concrete thinking
– Diminished insight
– Defect in planning / executive control
50. 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
51. Attention and memory
– Inattentiveness
– Defect in working memory
– Defect in sequencing, perseverance
52.
53. 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
54. 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)
55. Language
– Broca’s / non-fluent aphasia
– Prefrontal/ transcortical motor aphasia
– Language-motor dissociation
– Akinetic mutism
56. 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”
57. 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
58. “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.”
59. Trail Making Test
A
C1
2
7
3 D
5 B
4
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”
60. 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”
61. 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”
62. 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
63. 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
64. 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
65. 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