2 Ocak 2012 Pazartesi

Short Notes from Conflict and Cogntive Control in the Brain

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Conflict and Cogntive Control in the brain
Vincent van Veen1 and Cameron S. Carter2
1Department of Psychology, University of Pittsburgh, and 2Departments of Psychology and Psychiatry, University of California, Davis

ABSTRACT—Recent research from cognitive psychology and cognitive neuroscience has suggested that the control mechanisms by which people are able to regulate task performance can be dissociated into evaluative and executive components.
One process, implemented in the anterior cingulate cortex of the brain, monitors the amount of conflict that occurs during information processing; another process, implemented in the dorsolateral prefrontal cortex, is involved with maintaining the requirements of the task at hand and with biasing information processing in favor of appropriate responses.
Whenever one performs a task, one has to make sure that one selects the relevant information (stimuli, actions) and not get distracted by stimuli or thoughts that are irrelevant to the task. Such distraction might lead to inappropriate actions, such as errors. How the brain manages to do this is the central question in this paper: specifically, how people manage to pay more attention after they have either made an error or almost made an error.

One of the key aspects of cognitive control is how flexible it is.
The issue of how people monitor and correct for errors has become a popular topic of inquiry in cognitive research;
Many phenomena from cognitive and social psychology are thought to depend on automatic processes. Processes can be automatic when they are innate or highly practiced, because they are part of a strongly activated schema, or because they are imposed by a powerful social context or a strong motivational or emotional state, among other reasons.

Of all the stimuli that one encounters, only a limited set is relevant to what one is trying to accomplish; nevertheless, both relevant and irrelevant stimuli compete for access to the response system. Such competition can be difficult to overcome when the processing of irrelevant information is relatively automatic. When the irrelevant information is associated with a response, reliance on automatic processing might facilitate the task if this response is desirable. However, when the irrelevant, automatically processed information is associated with an inappropriate response, the resulting conflict between appropriate and inappropriate responses might be difficult to overcome.
This is thought to occur because word reading is relatively more automatic than color naming; therefore the word is hard to ignore, and it activates the associated response. During incongruent trials, the responses associated with the color compete with those associated with the word. When conflicts occur, attentional control is needed to overcome the conflict by selecting the relevant information and suppressing the processing of irrelevant information. Control is often conceptualized as the ability to represent and maintain the task requirements, to support the processing of information relevant to the goals of the current task, and to suppress irrelevant information. Many neuropsychological and neuroimaging studies have shown that an important brain structure that supports this ability is the prefrontal cortex (PFC ).
The PFC is also involved in the control of other forms of higher-order cognition. For instance, many neurophysiological and neuroimaging studies have shown that
this region is able to maintain task-relevant information for brief periods of time, which has supported the notion that this region constitutes a neural basis for working memory. Also, the PFC is involved in task preparation and switching between different tasks. Therefore, it is thought to be involved in many aspects of the executive control over our thoughts and actions.
The notion that control regulates other types of information processing begs the question, how is control itself regulated? Without a clear answer to this question, the notion of attentional control becomes homuncular, posing the same questions as it is supposed to answer. Therefore, an answer to this question is fundamental to understanding the flexible nature of attentional control.

We and other researchers have argued that
the amount of conflict occurring in the information-processing system plays a central role in regulating how much control is exerted and when control is withdrawn. The anterior cingulate cortex (ACC) of the brain, located on the medial surface of the frontal lobe, has (possibly among other functions) the role of detecting situations in which there are conflicts within the information-processing stream and which therefore require attention to be resolved
This activation of the incorrect response is followed by activation of the correct response. If the initial incorrect activation does not manage to reach response threshold and the correct response manages to override the incorrect response, the response to the trial ends up being correct. Errors in speeded-response tasks are typically fast, impulsive responses based on incomplete stimulus evaluation. The timing of response activation during error trials does not differ much from that during correct trials, the main exception being that during error trials the initial activation of the incorrect response does reach response threshold. The subsequent activation of the correct response is manifested as the tendency to ‘‘correct’’ the error
Many studies, including subliminal-priming studies, have suggested that conflict can occur in the absence of awareness; however, studies have not been conclusive as to whether this conflict also engages the ACC or whether such conflict is associated with a subsequent increase in attention.
Similarly, these areas have also been suggested to play a role in cognitive dissonance; Harmon-Jones (2004) has hypothesized that the ACC detects conflicts (dissonance) between actions and attitudes and alerts the PFC to reduce this dissonance.