Question

1. Prefrontal cortex exercises cognitive control. What does this mean?

2. What causes the "Stroop Effect" among persons with prefrontal cortex damage?

Answer 1

1. The prefrontal cortex is the cortex of association of the frontal lobes. It plays a major role in the temporal organization of behavior, reasoning and language.Each of the three principal prefrontal regions has its own set of reciprocal fiber connections which is topologically arranged with the other two prefrontal regions, and cortical & subcortical structures. The three prefrontal regions are connected well with the thalamus, limbic structures, the basal ganglia, and other parts of the cortex. This has very important functional implications. The orbital and medial prefrontal regions are well connected with the medial and anterior nuclei of the thalamus, the piriform cortex, the hippocampus, the amygdala, and the hypothalamus.The main function of the dorsolateral prefrontal cortex is the temporal organization of behavior, language and reasoning. This cortical region secures the orderly and timely execution of all new goal-directed sequences in those three domains of activity. The dorsolateral prefrontal cortex also orchestrates the functions of many other parts of the brain. The end-result of this is structuring of behavior and cognition in time, and of forming temporal gestalts toward the attainment of biological and cognitive goals. Medial frontal cortex is involved in performance monitoring: evaluating outcome vis-à-vis expectancy, and detecting performance errors or conflicting response tendencies. Lateral and orbitofrontal divisions of prefrontal cortex are involved in subsequently implementing appropriate adjustments. Hence the construct of 'cognitive control' which is the process that allow to adaptively vary information processing to meet the moment to moment goal , can be said to be governed by prefrontal cortex.

2 The Stroop interference effect is the observed fact of increased amount of time it takes to name the color of a word when the ink color and the word are incongruent, in comparison to the choice when the ink color and the word are congruent. The anterior cingulate cortex and the dorsolateral prefrontal cortex are active during the stroop task. Both of these areas are responsible for conflict monitoring and resolution. When there is competing information, ACC selects an appropriate response and allocate attentional resources. The Stroop task requires the inhibition of the dominant, overlearned response of reading to make the required color-naming response. Response inhibition of this kind depends on the functioning of the frontal lobes of the brain as mentioned through the action of ACC and DLPC. People with poorly functioning frontal lobes can read the color words written in black and name the color rectangles normally. But they are slower than normal people in naming the ink color in which color words are printed. So in essence when the inhibitory processes are compromised in a patient with prefrontal cortex damage, that is reflected in the stroop task .