frontal cortex. frontal lobes traditionally considered to be the seat of intelligence. this is...

Frontal Cortex

Frontal Lobes

• Traditionally considered to be the seat of intelligence.

• This is probably because:– The frontal cortex is the most recent to evolve.– Humans have particularly large frontal lobes

compared to other animals.

• The frontal cortex is the brain lobe least amenable to quantitative testing.

Divisions of the Frontal Cortex

1. Motor cortex

2. Premotor cortex

3. Prefrontal cortex

4. Orbitofrontal & Ventromedial prefrontal cortex

5. Anterior cingulate gyrus

6. Broca’s area

Divisions of the Frontal Cortex

Primary Motor Cortex

Prefrontal Cortex

Working memory

• Refers to the capacity to keep track of and update information at the moment

• E.g., 7 + - 2•  Patricia Goldman-Rakic•  ODR paradigm (oculomotor delayed-response)•  Electrodes record activity from monkey neurons

during the task.•  Different neurons respond to different task

characteristics.

Regional Specialization:

1. Superior prefrontal convexity (dorsal)— spatial location

2. Inferior prefrontal convexity (ventral)—objects, faces

Impaired Response Inhibition

• Stroop

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Perseveration

• Carrie’s timing task with frontals

Shifting Difficulty

• Reduced fluency – Generate animals beginning with “C”

• Difficulty generating hypotheses and flexibly shifting to new task demands

Wisconsin Card Sort Task (WCST)

Test Cards

Wisconsin Card Sorting Task (WCST)

Alternating & Sequencing Deficits

***VIDEO: Pick’s Disease

Alternating & Sequencing Deficits

1. Motor

2. Planning & organizing tasks

3. Developing strategies for learning new tasks

Frontal Eye Fields

Exploratory Eye Movement Deficits

Other Dorsolateral Deficits

1. Pseudo-depression

2. Perceptual deficits

3. Corollary discharge

Mirror Neurons: Characteristic Firing Properties

of Inferior DLPFC

• Motor

• Visual

• Somatosensory

• Body-part centered

(Fadiga et al., 2000)

“Mirror” Propertyof Human DLPFC

(Iacoboni et al., 1999)

Orbitofrontal & Ventromedial Prefrontal Cortex

Phineas Gage

Months later, however, Gage began to have startling changes in personality and in mood.

He became extravagant and anti-social, a fullmouth and a liar with bad manners, and could no longer hold a job or plan his future.  

He was quick to anger and often got into fights.

The Case of Phineas Gage

An explosion projected a tamping rod through his left cheek.Miraculously, he recovered and had “normal intellegence”.

"The equilibrium between his intellectual faculties and animal propensities seems to have been destroyed.” - Harlow

This is hypothesized to occur as a result of impoverished social learning as a result of failure to

make appropriate mappings between events and their

outcomes.

Personality Changes

1. Lack of concern for the future • Consistently poor decision-making • Impulsiveness

2. Failure to obey rules

3. Lack of social graces

4. Disposed to imitation

Personality Changes II

1. Mild euphoria

2. Silliness & facetiousness

3. Pseudo-depression

4. Irritability

Orbitofrontal Cortex

Empathy

Decision-MakingReinforcement Value of Sensory Stimuli

Orbitofrontal Cortex1. Secondary odor & taste cortices

2. Deficits in perceiving auditory or visual emotional cues

– Can be Modality Specific

3. Cells respond to the rewarding or aversive nature of stimuli

– Primary reinforcers

– Learned (secondary) Reinforcers

–Cells respond better to real than to 2-D faces–Cells respond preferentially to specific faces–Cells change their response to objects when reward associations change

Anterior Cingulate

Anterior Cingulate

Bilateral lesions produce:

1. Akinetic mutism—inability to initiate speech

2.  Minimal movement

3.  Incontinence

4.  No emotional display to pain

5.  Profound apathy

6.  Indifference

• ***Striatum Pict – Sagittal?

5 Frontal-Subcortical Circuits

1. Motor

2. Oculomotor

3. Dorsolateral prefrontal

4. Lateral orbitofrontal

5. Anterior cingulate

Frontal-Subcortical Circuits II

Frontal lobe

Striatum (caudate, putamen, ventral striatum)

Globus pallidus & Substantia nigra

Specific thalamic nuclei

Frontal lobe

Summary I

Motor cortex

1. Loss of voluntary control over a specific body area 2. Deficits of fine motor control 3. Reduction of strength & speed

Premotor cortex1. Impairs the integration of sequences into fluid actions2. Reflex changes (i.e., grasp reflex)

Summary II

Prefrontal cortex1. Working memory problems

(superior—where; inferior—what)

2. Difficulty generating new items or hypotheses3. Lack of inhibition4. Perseveration5. Difficulty planning sequences or organizing

strategies6. Eye movement deficits

Summary IIIOrbitofrontal & Ventromedial prefrontal cortex1. Personality & emotional changes2. Disregard for rules3. Imitation 4. No IQ or dorsolateral problems

Anterior cingulate1. Problems with initiating movements2. Apathy3. No emotional response to pain