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

Motor cortex 1.Primary level of motor control 2.Direct connections with the cranial nerves and spinal motor neurons 3.Focal lesions result in a loss of voluntary motor control over a specific area of the body 4.Chronic deficits of fine motor control 5.Reduction of the speed and strength of limb movements

Penfield & Graziano

Premotor Cortex

Premotor cortex 1.Secondary level of motor control 2.Influences motor movements through connections to subcortical centers (e.g., basal ganglia & thalamus). 3.Deficits are subtle because subcortical centers still exert some control over movements.

Premotor Cortex II 4.Damage impairs the integration of separate movements into fluid sequences of action. 5.Reflex changes: a. “Counter-pull” b. Involuntary grasp reflex c. Clumsy, rapid, short steps

Prefrontal Cortex

Working memory Refers to the capacity to keep track of and update information at the moment E.g., 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 Brown Blue Red 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” Property of 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-Making Reinforcement Value of Sensory Stimuli

Orbitofrontal Cortex 1.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

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 cortex 1.Impairs the integration of sequences into fluid actions 2.Reflex changes (i.e., grasp reflex)

Summary II Prefrontal cortex 1.Working memory problems (superior—where; inferior—what) 2.Difficulty generating new items or hypotheses 3.Lack of inhibition 4.Perseveration 5.Difficulty planning sequences or organizing strategies 6.Eye movement deficits

Summary III Orbitofrontal & Ventromedial prefrontal cortex 1.Personality & emotional changes 2.Disregard for rules 3.Imitation 4.No IQ or dorsolateral problems Anterior cingulate 1.Problems with initiating movements 2.Apathy 3.No emotional response to pain