4.3 To link lesions of the frontal lobe to attention and executive disorders Flashcards
Lesions in frontal cortex, 5 categories
Kolb & Wishaw (H16)
- Disturbanes of motor function
- Loss of divergent thinking
- Environmental control of behavior
- Poor temporal memory
- Impaired social and sexual behavior
Disturbances of motor function
Kolb & Wishaw (H16)
Frontal lesions can impair a person’s ability to make a wide variety of movements, to order movement sequences and even to speak.
- Fine movements, speed and strength
- Movement programming
- Voluntary gaze
- Corollary discharge
- Speech
Disturbances of motor function
Fine movements, speed and strength
Kolb & Wishaw (H16)
Damage to primary cortex (M1) is mainly associated with loss to make fine, independent finger movements.
This may be due to a loss of direct corticospinal projections to motor neurons. There is also loss of speed and strength in the hands and limbs.
Disturbances of motor function
Movement programming
Kolb & Wishaw (H16)
Function of the frontal lobe.
Removal of the supplementary motor cortex results in disruption of almost all voluntary movements. The greatest impairments come from dorsolateral injury.
The frontal lobe may be involved in facial control.
Disturbances of motor function
Voluntary gaze
Kolb & Wishaw (H16)
Frontal lobe lesions probduce alterations in voluntary eye gaze.
The eye movement patterns of the patients with large frontal-lobe lesions were quite different from those of controls or those of patients with more posterior lesions.
The voluntary gaze deficits within the frontal lobe seem to stem from interrupted activity in the frontal eye field.
Disturbances of motor function
Corollary discharge
Kolb & Wishaw (H16)
For a voluntary movement, a neural signal must produce both the movement and a signal that the movement is going to take place.
If the eyes are moved mechanically, as when you press on them, there is no such signal and the world moves.
However, when you move your eyes, you generate a neural signal that movement will happen, and the world stays still.
This signal = corollary discharge, or reafference.
Frontal lobe injury: can disrupt movement production and interfere with the signal to the rest of the brain that movement is taking place.
Disturbances of motor function
Speech
Kolb & Wishaw (H16)
Broca: retrieving words on the basis of an object, word, letter, or meaning.
People with stroke in Broca: impaired in using verbs and producing appropriate grammar = agrammatism.
People with strokes in left medial frontal region are often mute. The ability to speack usually returns after a few weeks in people with unilateral lesions but not in those with bilateral lesions.
Loss of divergent thinking
Kolb & Wishaw (H16)
Divergent thinking= the number and variety of responses to a single question rather than a single correct answer.
Frontal lobe injury interferes with the intelligence required by divergent thinking.
- Behavior spontaneity
- Strategy formation
Loss of divergent thinking
Behavioral spontaneity
Kolb & Wishaw (H16)
Patients with frontal lobe lesions= loss of sponteneous speech. And loss of sponteneous behavior.
Defect primarily in left orbitofrontal region, but lesions in the right orbitofrontal region also marked reduction in verbal fluency.
- People with left frontal deletions rarely spoke
- right frontal deletions spoke excessively.
Loss of divergent thinking
Strategy formation
Kolb & Wishaw (H16)
Pat with frontal lobe lesions= impaired at developing novel cognitive plans or strategies for solving problems.
When askes to give reasoning based on general knowledge frontal lobe pat perform poorly and often give bizarre responses.
With simple task pat will not succeed but they do understand the tasks.
Frontal lobe also critical role in coping with novel situations.
Environmental control of behavior
Kolb & Wishaw (H16)
Pat have difficulty in using environmental cues (feedback) to regulate or change their behavior.
- Response inhibition
- Risk taking and rule breaking
- Self-regulation
- Associative learning
Environmental control of behavior
Response inhibition
Kolb & Wishaw (H16)
Pat consistently persevate (volhouden) on responses in a variety of test situations, particularly with changing demands and shifting response strategies is difficult for pat’s.
–> frontal lobe is necessary for behavioral flexibility.
Pat who do the Stroop task and have a left frontal lesion are unable to inhibit reading the words and thus are impaired on this task
Environmental control of behavior
Risk taking and rule breaking
Kolb & Wishaw (H16)
Frontal lobe pat’s = common failure to comply with instructions.
The orbitofrontal cortex (OFC) is part of a neural decision-making circuit that evaluates degrees of uncertainty in the world.
Environmental control of behavior
Self-regulation
Kolb & Wishaw (H16)
Pat’s often have a loss of autobiographical knowledge.
The loss of autobiographical knowledge makes it difficult to put ongoing life events in context and leads to difficulties in regulating behavioral flexibility.
Environmental control of behavior
Associative learning
Kolb & Wishaw (H16)
Pat’s unable to regulate their behavior in response to external stimuli and to learn from experience.
The problem is learning to select, from a set of competing responses, and then choosing the ones appropriate to the various stimuli.
Pat with massive frontal lobe tumors could not be trained to respond consistently with the right hand to a red light and with the left hand to a green light, even though the pat’s could indicate which hand was which and could repeat the instructions.
