Observations on Frontal Lobe Function

1. Observations on Frontal Lobe Function • Restlessness – animals with bilateral frontal lobe lesions move about consistently and aimlessly • Indifference – such animals show suppression of curiosity and interest • Decreased affect – bifrontal animals show little interest or concern toward other animals • Emotionality – these animals suffer a strong fear of noise, other animals, stimuli which does not disturb them in the natural habitat • Abnormal mental state – such animals show defective reflection, judgment, memory, inability to adapt • Instincts – certain instincts have been weakened • Activity – tendency toward stereotypic and automatic activities

2. Observations on Frontal Lobe Function • Restlessness – animals with bilateral frontal lobe lesions move about consistently and aimlessly • Indifference – such animals show suppression of curiosity and interest • Decreased affect – bifrontal animals show little interest or concern toward other animals • Emotionality – these animals suffer a strong fear of noise, other animals, stimuli which does not disturb them in the natural habitat • Abnormal mental state – such animals show defective reflection, judgment, memory, inability to adapt • Instincts – certain instincts have been weakened • Activity – tendency toward stereotypic and automatic activities Bianchi (1895)

3. Anatomical Subdivisions of Frontal Cortex

4. Frontal Subcortical Circuits • Circuits unite functional regions of the frontal cortex with the basal ganglia and thalamus in networks mediating motor activity, eye movements, and behavior. • Five circuits have been identified and named according to their function or cortical site of origin.

5. Frontal Lobes and Executive Dysfunction • About 1/3 of cortex is contained in the frontal lobes • Area of the brain that is most “developed” in humans compared to other primates • Damage tends to affect cognitive/behavioral functions typically regarded as uniquely human • Damage to similar areas in different individuals can produce strikingly different impairment

6. The Frontal Lobes and Executive Dysfunction • Executive functions: Highest order cognitive functions • Capacity for autonomous behavior without external guidance • Directed behavior when goal is remote or absent • Self-direction, self-monitoring, self-regulation • Ability to organize a behavioral response to a novel or complex situation / problem • Planning and regulation of adaptive and goal-directed behavior • Problem solving / reasoning / generating solutions to problems • Spontaneity and fluency of thought and action • Cognitive flexibility • Strategic use of memory • Ability to shift cognitive set • Ability to inhibit or withhold responses as appropriate • Ability to focus or sustain attention (inhibit attentional capture by nonrelevant stimuli)

7. Two Broad Frontal Syndromes • Dorsolateral prefrontal syndrome • Lowered general arrousal • Impaired attention/distractable • Apathy, depressed mood • Perseverative behavior • Working memory deficits • Diminished spontaneous behavior • Difficulty with goal-directed behavior • “Stimulus Boundedness”

8. Two Broad Frontal Syndromes 2. Ventromedial prefrontal syndrome • Disinhibition of drives • Impulsivity • Elevated mood • Hyperactive • Impaired attention

9. Executive Dysfunction: • Working memory deficits • Temporal memory / Source memory • Perseveration • Loss of spontaneous behavior • Apathy • Planning deficits/impaired goal-directed behavior • Disinhibition/impulsive behavior • Impaired attention • Depression • Elevated mood

10. Executive Dysfunction Associated with: • Frontal lobe brain damage (TBI, CHI, lesions, etc.) • Dementia • Major depression • Parkinson’s/Huntington’s disease • HIV-Related Dementia • Subcortical strokes • Schizophrenia • Alcoholic Dementia (Wernicke-Korsakoff syndrome)

11. Memory-related deficits • Working memory: delayed response tasks • Temporal memory: when did the event occur? • Source memory: where did I get this information from? • Confabulation: production of fabricated accounts of past events • Momentary – plausible but incorrect memories which fill the gap • Fantastic – unnecessary and implausible memories (e.g., story is a wild concoction of past events)

12. Inhibition-Related Deficits • Perseveration • Inability to inhibit a dominant response set • Social Disinhibition/Impulsivity • Loss of spontaneous behavior • Poor planning/goal-directed behavior? • Attentional deficits?

13. Mood/Affect/Emotion Symptoms • Depression • Mood elevation • Apathy/Indifference • Agitation • Disinhibition/Impulsivity • “Personality Change”

14. Phineous Gage • Railroad foreman • Well-respected, hard-working • 1848: tamping iron accident • He never lost consciousness, and had no obvious neurological symptoms • But he was “no longer Gage”

15. Phineous Gage Gage’s Doctor described Gage’s post accident personality as Fitful, irreverent, indulging at times in the greatest profanity which was not previously his custom, manifesting but little deference for his fellows, impatient of restraint and advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operation, which are no sooner arranged than they are abandoned … a child in his intellectual capacity and manifestations, he has the animal passions of a strong man.