The Frontal Lobes and Executive Function

Question 1

What % of brain volume is made up by the frontal lobe?

Answer 1

30%

Question 2

Name 3 ways the brain can be subdivided

Answer 2

Cytoarchitecture
Thalamic connections
Functional properties (e.g. primary, secondary, association areas)

Question 3

What is “executive function”?

Answer 3

Inter-related processes responsible for goal directed, purposeful behaviour
Includes emotional and social behaviour as well as cognition

Question 4

What kind of functions is the dorsolateral pre-frontal cortex responsible for?

Answer 4

Traditional "executive" functions:
Working memory
Response selection
Planning and organising
Hypothesis generation
Flexibly maintaining or shifting set
Insight
Moral judgment

Question 5

Which artery supplies the dorsolateral pre-frontal cortex?

Answer 5

Middle cerebral

Question 6

Which artery supplies the medial pre-frontal cortex?

Answer 6

Anterior cerebral

Question 7

Which arteries supply the orbitofrontal pre-frontal cortex?

Answer 7

Anterior cerebral, middle cerebral

Question 8

What kind of functions is the medial pre-frontal cortex responsible for?

Answer 8

Emotional-motivational interface:
Akinetic mutism (at most extreme)
Apathy
Initiative
Indifference

Question 9

What kind of functions is the orbitofrontal pre-frontal cortex responsible for?

Answer 9

Highly connected to limbic areas

Responsible for emotional, cognitive, social inhibition

Question 10

What kind of defects may occur in a lesion of the orbitofrontal pre-frontal cortex?

Answer 10

Impulsivity (making decisions faster, making more errors)

Question 11

How are dorsolateral, medial, and orbitofrontal lesions formally assessed?

Answer 11

Neuropsychological testing is more sensitive to dorsolateral lesions
Clinical judgment and history traking are more useful for medial and orbitofrontal lesions

Question 12

List some common causes of executive dysfunction

Answer 12

Closed head injury
Stroke (middle and anterior cerebral arteries, anterior communicating artery)
Psychiatric conditions (schizophrenia, mania)
Dementias (fronto-temporal, AD, HD)
Focal lesions
Inflammatory conditions (MS, encephalitis)
Developmental (autism)

Question 13

Describe the development of the frontal lobe

Answer 13

Last area of the brain to develop
One of the first to degenerate in the aging process
Dynamic process (involving positive and negative processes, i.e. neuronal proliferation and pruning)

Question 14

List 6 positive symptoms of executive dysfunction

Answer 14

Distractability
Social disinhibition
Emotional instability
Perseveration
Impulsivity
Hypergraphia

Question 15

List 6 negative symptoms of executive dysfunction

Answer 15

Lack of concern
Restricted emotion
Deficient empathy
Failure to complete tasks
Lack of initiation

Question 16

Distinguish between frontal lobe dysfunction and executive dysfunction

Answer 16

The prefrontal cortex acts as a “coordinator” of executive functioning
Executive function involves an entire executive system and dysfunction may occur due to disruption at any level (e.g. subcortical)