The Frontal Lobes

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Bryan Kolb Ian Q. Whishaws
Fundamentals of Human Neuropsychology, Sixth
Edition Chapter 15 Lecture PPT
Prepared by Gina Mollet, Adams State College
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The Frontal Lobes
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Portrait Losing Frontal-Lobe Functions

• E.L.
• Highly organized college professor
• Became disorganized, showed little emotion, and
  began to miss deadlines
• Scores on intelligence and memory tests were
  superior
• Showed impairment on frontal lobe tests

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Anatomy of the Frontal Lobes

• Constitute 20 of the neocortex
• Subdivisions
• Motor Area 4
• Premotor Areas 6 and 8
• Can be divided into
• Lateral area 6 Premotor cortex
• Medial area 6 Supplementary motor cortex
• Area 8 Frontal eye field
• Area 8A Supplementary eye field

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Anatomy of the Frontal Lobes

• Prefrontal Cortex
• Area of the frontal lobe that receives input from
  the dorsomedial nucleus of the thalamus
• Divisions
• Dorsolateral Prefrontal Cortex
• Inferior Frontal Cortex
• Also called Orbitofrontal cortex
• Medial Frontal Cortex
• Sometimes considered part of the cingulate
• Many areas of the frontal lobe are multimodal

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Connections of the Motor and Premotor Areas

• Motor Cortex
• Projects to spinal motor neurons, cranial nerves
  that control the face
• Projects to the basal ganglia and the red nucleus
• Premotor
• Projections to the spinal cord
• Projections to the motor cortex

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Connections of the Motor and Premotor Areas

• Premotor
• Receives projections from parietal areas PE and
  PF
• Receives projections from dorsolateral prefrontal
  area
• Eye fields
• Receive from PG and the superior colliculus

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Connections of the Prefrontal Areas

• End of dorsal and ventral streams of visual input
• Dorsolateral Prefrontal Area
• Reciprocal connections with the posterior
  parietal and STS
• Extensive connections with the cingulate cortex,
  basal ganglia, and superior colliculus
• Receives input from dopaminergic cells in
  tegmentum

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Connections of the Prefrontal Areas

• Orbital Frontal Cortex
• Receives from the temporal lobe, amygdala,
  gustatory cortex, somatosensory cortex, olfactory
  cortex, dopaminergic cells in tegmentum
• Projects to hypothalamus and amygdala

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A Theory of Frontal-Lobe Function

• Planning and selection
• Persistence and ignoring distracting stimuli
• Memory for what you have already done
• Executive Functions
• Responds to both internal, external, and context
  cues

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Functions of the Premotor Cortex

• Selects movements to be executed
• Functions to choose behavior in response to
  external cues
• An increase in activity in the premotor cortex is
  seen when cues become associated with movement

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Functions of the Prefrontal Cortex

• Controls cognitive processes so that appropriate
  movements are selected at the correct time
• Internal Cues
• Temporal memory Memory for what has just
  happened
• External Cues
• Feedback about rewarding properties of stimuli
• Orbital Frontal Cortex - Learning by association

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Functions of the Prefrontal Cortex

• Context Cues
• Orbital Frontal - Social Interactions
• Autonoetic Awareness
• Self knowledge
• Binding together the awareness of oneself as
  continuous through time

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Asymmetry of the Frontal Lobes

• Left
• Language
• Encoding memories
• Right
• Nonverbal movements, facial expression
• Retrieving memories

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Heterogeneity of Frontal-Lobe Function

• Frontal lobes perform a variety of functions
• Frontal damage is unlikely to produce impairment
  to all functions

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Snapshot Heterogeneity of Function in the
Orbitofrontal Cortex

• Stephen Frey and Michael Petrides
• Examined functions of the orbital region using
  PET
• Increased activity in area 13 to unpleasant
  auditory stimuli
• Increased activity in area 11 when learning new
  visual information
• Functional dissociation between the two areas
• Area 13 Responds to affective qualities
• Area 11 Processes new visual information

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Symptoms of Frontal Lobe Lesions

• Disturbances of Motor Function
• Loss of fine movements, speed, and strength
• Typically appears after damage to the primary
  motor cortex
• Loss of movement programming
• Damage to the premotor or dorsolateral cortex
• Changes in voluntary gaze
• Damage to the frontal eye fields

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Symptoms of Frontal Lobe Lesions

• Disturbances of Motor Function
• Corollary discharge or reafference
• Internal neural signal that movement will occur
• Frontal lobe damage disrupts corollary discharge
• Speech Problems
• Damage to Brocas area
• Agrammatism
• Damage to the supplementary motor cortex
• Mute

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Symptoms of Frontal Lobe Lesions

• Convergent vs. Divergent Thinking
• Convergent thinking Only one answer to the
  question
• Divergent thinking Questions that ask for a
  variety of responses
• Frontal lobe patients are impaired on divergent
  thinking
• Loss of behavioral spontaneity
• Decreased verbal fluency
• Decreased design fluency
• Reduction in general behaviors

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Symptoms of Frontal Lobe Lesions

• Increased perseveration
• Inability to form a strategy
• Larger deficit when completing novel tasks
• Loss of response inhibition
• The Wisconsin Card Sorting Task
• The Stroop Test

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The Wisconsin Card Sorting Test
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The Stroop Test
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Symptoms of Frontal Lobe Lesions

• Take more risks
• Iowa Gambling Task
• Appears after damage to
• the orbitofrontal cortex
• Deficits in self-regulation
• Loss of associative learning
• Inability to select from
• competing responses

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Testing Associative Learning
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Symptoms of Frontal Lobe Lesions

• Poor Temporal Memory
• Five animal experiments indicate a role for the
  frontal lobe in temporal memory
• Area 46
• Role in providing an internal representation of
  spatial information
• Active during delayed response test
• Medial regions
• Role in object recognition

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Experiments Showing Deficits of Temporal Memory
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Symptoms of Frontal Lobe Lesions

• Poor Temporal Memory
• Studying Temporal Memory in Humans
• Recency memory
• Tests memory for the order in which things have
  occurred
• Frontal lobe patients show impairment on this
  task
• Recent Findings on Temporal Memory
• Critical role for the prefrontal cortex
• Fuster and colleagues
• Single cell recording of sensory associations
  across time

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Symptoms of Frontal Lobe Lesions

• Impaired social and sexual behavior
• Example Phineas Gage

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Symptoms of Frontal Lobe Lesions

• Impaired social and sexual behavior
• Changes in personality
• Pseudodepression
• Appears after lesions of the left frontal lobe
• Outward apathy, indifference, loss of initiative
• Reduced sexual interest, Little or no verbal
  output
• Pseudopsychopathy
• Appears after lesions of the right frontal lobe
• Immature behavior, lack of tact and restraint
• Promiscuous sexual behavior
• Coarse language, lack of social graces, increased
  motor activity

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Symptoms of Frontal Lobe Lesions

• Impaired social and sexual behavior
• Deficits in Social and sexual behavior
• Orbitofrontal lesions
• Reduce inhibitions and may introduce abnormal
  sexual behavior
• Leads to deficits in identifying facial
  expressions
• Dorsolateral lesions
• Reduce interest in sexual behavior

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Symptoms of Frontal Lobe Lesions

• Spatial Deficits?
• May be a role for the frontal lobe in selecting
  visual locations
• Symptoms Associated with Damage to the Frontal
  Facial Area
• Sensory and motor functions of the face are
  preserved after damage
• Left Loss of verbal fluency
• Right Loss of design fluency

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Clinical Neuropsychological Assessment of Frontal
Lobe Damage
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Imaging Frontal Lobe Function
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Diseases Affecting the Frontal Lobe

• Schizophrenia
• Abnormality in the mesocortical dopaminergic
  projection
• Decrease in blood flow to the frontal lobes, and
  frontal lobe atrophy
• Parkinsons Disease
• Loss of dopamine cells in the substantia nigra
  that project to the prefrontal cortex
• Korsakoffs
• Alcohol-induced damage to the dorsomedial
  thalamus and a deficiency in frontal lobe
  catecholamines