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Frontal Lobe Functions

Fredric E. Rose, Ph.D.Winter 2006

Pivotal Case:Phineas Gage

9/13/1848 25 yo construction foreman for Rutland

and Burlington RR in New England Used a tamping iron to fill holes in

stones with sand over explosive powderin order to level the terrain

Once forgot to put in sand…

What did change? What didwe learn from this?

Pre-accident personality Responsible, intelligent, honest, well-liked by peers

and elders, “the most efficient and capable man”according to employers

Post-accident personality Disinhibited, irreverent, capricious, disrespectful of

social conventions, unable to hold a job Equipotentiality v. Localization of Function

Harlow (1868): some portion of the brain that wasremoved by the tamping rod was responsible for therestraint and well-mannered behavior that mostpeople possess, and that Gage lost in the accident.

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Gage Revisited (Science,1994) Damasio & Damasio Computer graphics to plot

trajectory Ventromedial OFC region,

sparing of Broca’s and otherFL motor regions

Region is responsible fordecision-making regardingpersonal and socialmatters,as well as emotionprocessing

Anatomy of the Frontal Lobes

3 prefrontal regions:DorsolateralOrbitofrontalMesial

Frontal Lobe Circuitry

Oculomotor Motor Dorsolateral Orbitofrontal Anterior Cingulate

Alexander, DeLong, & Strick (1986). Parallelorganization of functionally segregated circuitslinking basal ganglia and cortex. Annual Review ofNeuroscience, 9, 357-381.

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Neurotransmitters Glutamate (corticostriatal, thalamocortical) GABA (basal ganglia) Dopamine (cortical, subcortical)

Modulates all 3 circuits Acetylcholine (striatal)

Open circuit influence) Serotonin (cortical, subcortical)

Core Frontal Circuitry

Thalamus

Subthalamic

Internal External

Striatum

Frontal Cortex

Globus Pallidus

Glutamate (+)Glutamate (+)

Glutamate (+)

GABA (-)

GABA (-)

GABA (-)

Feifel (1999)

Dorsolateral Circuit Functions

Subserves executive function Behavioral responses to complex

problems Activation of remote memories Environmental independence Shifting/maintaining cognitive sets Generating motor programs Verbal mediation of behavior

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Executive Functions

Planning

Decision making

Self-directed goal selection

Monitoring, guiding, and directing behaviorto achieve a goal

Dorsolateral CircuitDysfunction

Poor organizational behavior Poor memory search strategies Environmental dependency Poor set shifting

(perseveration) Verbal/manual dissociations

Orbitofrontal Circuit Functions

2 parallel circuits: Lateral and Medial Personality Characteristics

Empathy Civility Social appropriateness

Environmental independence Emotional continence

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Orbitofrontal CircuitDysfunction

Personality Changes Tactlessness Impulsivity Irritability Antisocial behavior

Utilization/imitation behavior Mood disorders Obsessive-Compulsive disorder

Orbitofrontal Syndrome

Emotional lability (mood swings) Disinhibition Criminal behavior Unusual/impulsive sexual behavior Often lack awareness Anosmia Environmental Dependency Pseudopsychopathic

Anterior Cingulate Functions

Motivated Behavior Drive Spontaneity “Personhood” Creativity

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Anterior CingulateDysfunction

Akinetic mutism Indifference to pain Apathy Poverty of speech Psychic emptiness Excessive conformity Poor response inhibition

Personality Changes

Impairments in social skills inappropriate or bizarre social behavior “loosening" of normal social restraints

Change in motivation apathy, withdrawal, lack of interest, and

initiative Pseudodepression / pseudoretarded

Summary of Personality/BehavioralSymptoms

POSITIVE Disinhibition Impulsivity Vulgarity Irritability Emotional lability Inappropriate

laughter, crying Bizarre behavior

NEGATIVE Apathy Reduced initiative

(Abulia) Reduced interest in

daily activities/self-care

Akinetic mutism Social withdrawal

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Personality/BehavioralAssessment

Observation Impulsive, disinhibited, environmentally

dependent… Questionnaires

Self-report Caregiver/family member

Interviews Patient Family

Secondary Motor Cortex

Supplementary Motor Area Sequencing, timing, and proper initiation

of voluntary movements. PET studies

Specific vs random motor sequence magining this movement.

Injury – disorder of motor planning,organization, and initiation

Premotor Area Sequencing, timing, and proper initiation of

voluntary movements. BUT… more in external cue readiness,

such as the interval between CUE and GO. Cingulate Motor Area

Emotional or motivational impetus formovement (when reward is involved)

Injury – lack of spontaneous motor activity,reduced speech output

Secondary Motor Cortex (cont.)

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Measures of SMC Functioning

Written Alternating Sequences

Perseveration: the inability to stopbehaviors once they have started

•Motor Impersistence: a form of distractibility in whichpatients only briefly sustain a motor action in response to acommand such as "Raise your arms" or "Look to the right."

Measures of SMC Functioning(cont.)

Luria 3-Step Fist, Edge, Palm

Go-No Go (also Orbital-PFC –disinhibition)

Multiple Loops

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Apraxia Inability to execute purposeful, complex

motor acts, despite physical ability,comprehension, and willingness.

Ideomotor Apraxia: Gestures tocommand

Motor representations in Parietal Lobe,but Premotor Cortex (including SMA)translates into movements

Frontal Release Signs

FL lesions (nonlocalized; dementia)can produce a return of primitivereflexes: Grasp Sucking/”Snout” Groping Utilization behavior

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Summary of Motor Symptoms ofFL Disorder

Poor motor sequencing Poor initiation of movements Dysarthria Apraxia Frontal release signs

Assessing ExecutiveFunctions

Anatomy of the Frontal Lobes

3 prefrontal regions:DorsolateralOrbitofrontalMesial

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Divide these 6 stimuli into 2 groupsbased on a shared characteristic.

Now do it again based on anothershared characteristic.

Stroop Color-Word Test

RedRedRedGreen

GreenBlueGreenRed

BlueGreenBlueGreen

RedBlueRedBlue

BlueRedGreenGreen

GreenBlueRedBlue

RedGreenBlueRed

XXXXXXXXXXXX

XXXXXXXXXXXX

XXXXXXXXXXXX

XXXXXXXXXXXX

XXXXXXXXXXXX

XXXXXXXXXXXX

XXXXXXXXXXXX

Stroop Color-Word Test

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Stroop Color-Word Test

RedRedRedGreen

GreenBlueGreenRed

BlueGreenBlueGreen

RedBlueRedBlue

BlueRedGreenGreen

GreenBlueRedBlue

RedGreenBlueRed

Wisconsin Card Sorting Test

Deck of cards with differentstimuli on each

Patient sorts the deck into 4piles according to “key”cards

Told only if right or wrong oneach sort

Letter Fluency

60

45

30

15

0

SecLipsF*ck!Cat

FlowerCabbageFiddleCrayonFeverFudgeCaterpillar

LemonFudgeCatchingListFeverCatchFudgeLeverCar

LFC

SPEED FACTORS-poor initiation-poor maintenance

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Trail Making Test A

E

B

D

G

H

A

CF

Trail Making Test B

1

2

B

4

C

3

AD

Rey-Osterrieth Complex Figure

copy

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So, what are“Executive Functions”?

Generate a list and identify the theme.

Planning Organizing Selective attention Problem-solving Initiating Inhibiting Self-monitoring Abstract thinking Mental flexibility

Executive functions are complex functions that allow one to engage in effective and efficientgoal-directed behavior.

What’s the common thread?

FL Memory Functions

Working MemoryRetrieval

Source Memory

Working Memory

Serial 7’s Put this in order with letters first, then numbers:

“L-4-C-2-M-8”. Spell “WORLD” backwards. What does these have in common? Define

‘working memory.’ What are the 2 maincomponents? an active system for temporarily storing and

manipulating information needed in the execution ofcomplex cognitive tasks

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Working Memory (pp. 169-170)

Baddeley (1986): WM has 3 components Central executive Articulatory phonological loop Visual-spatial sketch pad

Goldman-Rakic (1988) Dorsolateral prefrontal cortex holds

information “on line” while it is processed(monkey research).

Confirmed by PET and fMRI

Paced Auditory Serial AdditionTask (PASAT)

4382378

“7”

“11”

“10”

“5”

“10”

“15”

EXAMINER PATIENT

TIME Phonological Loop

orVisual-spatial Sketchpad

N-back

1-Backtarget

2-Backtarget

0-Backtarget

Cn

AN

qQ

Xc

Time

Phonological Loopor

Visual-spatial Sketchpad

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Spatial Span Task

Phonological Loopor

Visual-spatial Sketchpad