Decision speed and bias after unilateral stroke

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neurology

Background:

• Stroke can affect cognitive functions, including visual memory and decision-making processes.
• Hemispheric lateralization suggests distinct roles for the left and right brain in cognitive tasks.

Purpose of the Study:

• To compare nonverbal visual memory, response speed, and decision bias in patients with left-hemisphere versus right-hemisphere stroke lesions.
• To investigate the relationship between verbal impairment and response speed in aphasic patients.
• To analyze decision-making strategies in stroke patients using Signal Detection Theory.

Main Methods:

• Two experiments were conducted comparing left-stroke, right-stroke patients, and healthy volunteers.
• Experiment 1 assessed vocal recognition response times in aphasic patients.
• Experiment 2 used a recurrent recognition task with complex nonverbal art designs, measuring discriminability and decision bias via Signal Detection Theory.

Main Results:

• Left-stroke patients showed a high negative decision bias, making fewer correct and false recognitions.
• Right-stroke patients had the lowest recognition scores but normal decision criteria.
• Both stroke groups were slower than controls; right-stroke patients had fewer long-latency decisions.
• Left-stroke patients exhibited deficiencies in decision-making speed and bias, independent of verbal deficits.

Conclusions:

• Cognitive deficits after stroke are lateralized, affecting different aspects of nonverbal visual memory and decision-making.
• Left-hemisphere stroke primarily impacts decision-making speed and bias, with relatively preserved recognition ability.
• Right-hemisphere stroke significantly impairs nonverbal recognition accuracy.