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

Green

Yellow

Red

Purple

Blue

Red

Black

Yellow

Orange

Blue

Purple

Red

Green

Black

Blue

Yellow

Green

Red

Purple

Blue

Blue

Brown

Blue

Red

Green

Green

Yellow

Red

Yellow

Orange

Blue

Red

Green

Yellow

Black

Yellow

Orange

Red

Purple

Blue

Purple

Red

Green

Black

Blue

Yellow

Green

Red

Purple

Blue

Green

Yellow

Red

Yellow

Orange

Blue

Brown

Blue

Red

Green

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