Brain-Behavior Relationships & the Prefrontal Cortex

Solution Preview

Brain-Behavior Relationships

PREFRONTAL CORTEX

Deficits associated with Lesions of the Prefrontal cortex range from minor lesions to more extensive lesions. First, we will look at the deficits associated with the following:
1. With minor
2. With more severe
3. Medial Orbital Lesions
4. Lateral Dorsal Lesions
5. Left Hemisphere Prefrontal Lesions
6. Right Hemisphere Prefrontal Lesions
7. Very severe Lesions.

Next, we will look at the various tests used by neuropsychologists to test the Prefrontal Lobe Function. The references are provided at the end.

Prefrontal Cortex

Prefrontal Cortex is responsible for planning, structuring, and evaluating voluntary (goal directed behavior, i.e., activities requiring the constant comparison of planned acts with the effects achieved.

A. Deficits associated with lesions of the prefrontal cortex

1. With minor lesions

o Inability to prevent rapid extinction of orienting response following verbal instruction (1).
o Disturbances in regulatory role of speech (1).
o Disturbances in complicated gnostic functions (e.g. understanding complicated pictures, thematic pictures, comprehension of written text) (1).
o Problem solving difficulties associated with disturbances in selective organization of mental activity (i.e. serial sevens) (1, 3).
o Deficits in complex tasks requiring inhibition of habitual behavior patterns (2, 8, 10).
o Difficulties with actions requiring a series of movements, less severe when accompanied by external verbalization (Fist, edge, palm) (1, 5).
o Difficulties in task executions when instructions or prompts conflict with what would be expected, although ability to carry out simple instructions is unimpaired (visual or verbal) (3).
o Difficulties tapping at successive groups of rhythms or drawing a series of figures that alternate in pattern (1, 3) (tendency to perseverate).
o Decreased spontaneity, decreased rate of behavior, decreased range of interests, loss of initiative, and impulsiveness without self-corrective action may be early signs (1, 4).
o Deficits in visual tracking and scanning, especially on complex tasks (6).
o Difficulty in constructing mirror-image relationships, especially if complex (3).

2. With more extensive lesions.

· Perseveration: difficulties in making behavioral shifts in attention, movement, and attitude (6, 14).
· Concreteness(7) & decreased creativity(6).
· Inflexibility in cognitive, perceptual and motor modalities (6).
· Poor recall of thematic verbal material (paragraphs) (1).
· Poor recall of verbal & nonverbal series, with contamination of first & subsequent series (1).
· Deficits in comprehension of logical-grammatical (prepositional) constructions (e.g. "place a cross beneath the circle.") (3).
· Difficulties in writing associated with fatigue, progressively smaller characters, perseveration, loss of overall plan (i.e. letter transpositions, etc.) (3).
· Deficits in abstract/categorical intellect(2).
· Take longer to learn go-no go tasks and make more false positive responses (9,3, particularly with medial frontal lesions (15).

· Diminished visual scanning and ...