Fundamentals of Human Neuropsychology, Sixth Edition Chapter 15 Lecture PPT Prepared by Gina Mollet, Adams State College Bryan Kolb & Ian Q. Whishaw’s.

Fundamentals of Human Neuropsychology,Sixth Edition

Chapter 15 Lecture PPT

Prepared by Gina Mollet, Adams State College

Bryan Kolb & Ian Q. Whishaw’s

Cha

pter

16

The Frontal Lobes

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

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

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

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

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

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

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

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

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

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

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

Asymmetry of the Frontal Lobes

• Left – Language– Encoding memories

• Right – Nonverbal movements, facial expression– Retrieving memories

Heterogeneity of Frontal-Lobe Function

• Frontal lobes perform a variety of functions

• Frontal damage is unlikely to produce impairment to all functions

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

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

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 Broca’s area

– Agrammatism

• Damage to the supplementary motor cortex– Mute

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

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

The Wisconsin Card Sorting Test

The Stroop Test

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

Testing Associative Learning

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

Experiments Showing Deficits of Temporal Memory

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

Symptoms of Frontal Lobe Lesions

• Impaired social and sexual behavior– Example: Phineas Gage

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

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

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

Clinical Neuropsychological Assessment of Frontal Lobe Damage

Imaging Frontal Lobe Function

Diseases Affecting the Frontal Lobe

• Schizophrenia– Abnormality in the mesocortical dopaminergic

projection– Decrease in blood flow to the frontal lobes, and frontal

lobe atrophy

• Parkinson’s Disease– Loss of dopamine cells in the substantia nigra that

project to the prefrontal cortex

• Korsakoff’s – Alcohol-induced damage to the dorsomedial thalamus

and a deficiency in frontal lobe catecholamines