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