Neuropsychological%20Aspects%20of%20Frontal%20Lobe%20Function

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Neuropsychological Aspects of Frontal Lobe
Function

• Russell M. Bauer, Ph.D.
• February 27, 2006

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Important Concepts

• Phylogenetically newest area of cortex
• Exquisite connectivity based on feedback loops
• Inhibitory/excitatory control
• Farthest removed from external environment
  (reflective, not reflexive)
• Highly preprocessed, convergent projections
  (emergent concepts)
• Only neocortical representation of the limbic
  system
• Motivational/emotional interaction
  (goal-direction)

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Symptoms of Frontal Lobe Damage

• Elementary Neurological Defects
• Skilled Movement Disorders
• Language/Speech Disorders
• Memory Disorders
• Executive Deficits
• Neuropsychiatric Disturbances

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Frontal Lobe Cortex

• Functional subdivisions
• Lateral (4, 6, 8-10, 43-47)
• Medial (6, 8-12, 24, 25, 32, 22)
• Inferior (11-15, 25, 47)
• Another division
• Motor (4)
• Premotor (6, 8, 43, 44, 45)
• Prefrontal (9-15, 46, 47)

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Neuropsychological Manifestations of Frontal Lobe
Lesions III Lateral Prefrontal Region
(8,9,46) Lesions in this region produce
impairment in a variety of executive skills
that cut across domains. Some degree of
material-specificity is present, but relatively
weak. A) Fluency impaired verbal fluency
(left) or design fluency (right) B) Memory
impairments defective recency judgment,
metamemory defects, difficulties in memory
monitoring C) Impaired abstract concept
formation and hypothesis testing D) Defective
planning, motor sequencing E) Defective
cognitive judgement and estimation
Tranel, 1992
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Neuropsychological Manifestations of Frontal
Lesions I Frontal Operculum (44,45,47) A) Left
Brocas aphasia B) Right expressive
aprosodia Superior Mesial (mesial 6, 24) A)
Left akinetic mutism B) Right akinetic
mutism Bilateral lesions of mesial SMA (6) and
anterior cingulate (24) produce more severe form
of akinetic mutism
Tranel, 1992
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Neuropsychological Manifestations of Frontal Lobe
Lesions II Inferior Mesial Region A) Orbital
Region (10, 11) Lesions in this region produce
disinhibition, altered social conduct, acquired
sociopathy, and other disturbances due to
impairment in fronto-limbic relationships B)
Basal Forebrain (posterior extension of inferior
mesial region, including diagonal band of Broca,
nucleus accumbens, septal nuclei, substantia
innominata) Lesions here produce prominent
anterograde amnesia with confabulation (material
specificity present, but relatively weak)
Tranel, 1992
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General Organization of Frontal
cortical-striatal-pallidal-thalamic-cortical loops
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Dorsolateral Loop

• Critical for executive function
• Damage produces
• Inflexibility
• Planning
• Problem-solving
• Goal-directed behavior

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Orbitofrontal Loop

• Involved in social and emotional functioning
• Damage produces
• Disinhibition
• Hyperactivity
• Emotional lability
• Aggressiveness
• Reduce self-awareness

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Medial Frontal Loop

• Important in behavioral activation
• Damage results in
• Akinetic mutism
• Abulia
• Impairments in spontaneous initiation of behavior

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Neuropsychological Domains

• motor activity
• attention
• personality/emotion
• perceptual organization
• spatial/visual function
• memory
• cognitive skills
• executive skills

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Elementary Neurological Deficits in Frontal
Syndromes

• Contralesional hemiparesis
• Re-emergence of primitive reflexes
• Gaze abnormalities (spontaneous eye-movements,
  conjugate gaze)

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Frontal Lesions and Personality (overall
emotional tone)

• orbital syndrome
• emotional lability
• disinhibition
• exaggeration of pre-existing personality traits
• medial/lateral syndrome
• abulia/apathy
• depression-like presentation
• defects in self-initiation

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Phineas Gage (Harlow, 1868)
Prior to his accident, he was a religious,
family-loving, honest and hard-working man who
was described after his frontal injury as
fitful, irreverent, indulging at times in the
grossest profanityimpatient of restraint or
advice when it conflicts with his
desiresobstinate, devising many plans of
operation, which are no sooner arranged than they
are abandoned in turn for others appearing more
feasible (Benson, 1994)
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Frontal Lobe Symptoms Relevant to Emotion and
Personality

• NOT independent of cognitive impairments
• Poor self-monitoring and self-reflection
• Defective arousal and orienting responses
• Affective changes
• Witzelsucht and Moria (Oppenheim)
• Depression with lack of concern
• Acquired sociopathy (Damasio) unconcern for
  punishment

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Somatic Marker Hypothesis

• Biasing signals from body are integrated in the
  decision-making and emotional parts of the brain
  (VMPFC) and used to regulate decision-making
  under uncertainty
• Markers signal value and bolster attention and
  working memory
• Case EVR (tumor of VMPFC) became unable to make
  decisions despite good NP performance unsuitable
  choices for business partners, friends, etc.
• EVR impaired in psychophysiological responses to
  positive and threatening information
• Much of the data for SM hypothesis is based on
  the Iowa Gambling Task

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Activation during anticipation (risky decisions
safe decisions) superimposed on T1 image for all
subjects. Overall score on IGT was correlated
with the amount of activity in medial frontal
lobe during risky decisions. Fukui, et al.
(2005). Neuroimage, 24, 253-259.
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Motor Deficits in Frontal Syndromes

• Two dominant behavioral syndromes
• hyperactivity
• apathy/abulia
• Contralesional hemiparesis in less severe form,
  contralateral reduction in speed or dexterity
• Ideomotor apraxia impaired skilled movement in
  nonhemiparetic hand/extremity
• Motor impersistence- failure to maintain motor
  activity test with eye closure, tongue
  protrusion
• Impaired verbal control over conscious motor acts
  - inability to invoke verbal rules(e.g., Go-No
  Go) inability to use verbal intentions to guide
  behavior (e.g., dont drink the water)

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Motor Deficits (contd)

• Defects in motor programming and sequencing -
  recursive writing sequences
• Impaired guidance and error correction
• Poverty of movement without weakness,
  hemiparesis, or abnormality in tone (intentional
  disorder)

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Tests of Frontal Motor Function

• hand-grip strength
• finger tapping speed
• static steadiness
• manual dexterity
• maze coordination
• complex tests of praxis

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Frontal Lobes and Attention

• Inhibition/gating of sensory transmission through
  thalamic interaction

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Attentional Defects in Frontal Disease

• attention-focusing
• attention-maintenance
• attention-selectivity
• interference susceptibility
• Poor goal-dependent filtering of irrelevant
  stimuli
• attention-shifting

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Tests of Attentional Function

• span tests (DS, Sentence Rep)
• cancellation tasks (simple and conditional)
• sustained attention
• PASAT
• Trail Making Test
• Digit Symbol
• qualitative features from other tests

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Frontal Lobes and Memory

• Classic studies of delayed response (DR) and
  delayed alternation (DA)
• Dorsolateral and
• frontal polar lesions
• produce greatest
• deficits
• DR dorsal?
• DA ventral?

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Human Frontal Memory Defects

• Short-term memory
• deficits in working memory
• Learning
• susceptibility to proactive interference
• shallow semantic encoding
• impairment in voluntary memorizing
• impaired directed forgetting
• Long-term memory
• recall deficits relative to recognition
• impaired memory for temporal order
• impaired recency judgments
• Contamination of true memory with inert
  stereotypes

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• Table
• Grill
• Ounce
• Crayon
• Fable
• Pencil
• Grill Fable

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Human Frontal Memory Deficits (contd)

• Impairments in metamemory
• failure of emergent awareness
• poor self-monitoring and self-correction
• poor knowledge of content of memory system (e.g.,
  poor connection between search and FOK)
• deficits in source memory
• poor strategy use
• impaired memory for self-generated responses

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Frontal Executive Skills

• a working definition of executive skill
• relevant skill domains
• planning
• goal establishment
• anticipation
• cognitive estimation
• hypothesis testing (TOTE)

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An MBAs Model of the Brain
Shipping
C.E.O.
Manufacturing
Receiving
Cafeteria/Restrooms
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Cognitive Deficits in Frontal Syndromes

• impaired abstract thinking
• tendency to interpret abstract concepts
  concretely (e.g., proverbs, similarities)
• tendency to be pulled to more immediately
  available sensory information
• impaired verbal reasoning
• impairments in memory
• organizational role
• informational - specific memory capacities of
  frontal lobe (e.g., working memory retrieval)

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Design Fluency
Examiner
Patient
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Utilization Behavior
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Tests Tapping Frontal Cognitive Defects

• Wisconsin Card Sorting Test
• Halstead Category Test
• Shipley-Hartford Analogic Reasoning
• Trail-Making A and B
• Porteus Mazes (planning)
• Constructional Tasks (ROCF, BD)
• practically any other test calling for response
  production and organization!

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Theories of Frontal Lobe Function

• Pribram (1960) Feedback
• Teuber (1964) Corollary discharge
• Nauta (1971) interoceptive (limbic) and
  exteroceptive (sensory, association) connectivity
• Fuster (1980) temporal organization
• Shallice (1978) information processing
• Luria (1973) hierarchical model