Abstract
Conflicts in spatial stimulus–response tasks occur when the task-relevant feature of a stimulus implies a response toward a certain location which does not match the location of stimulus presentation. This conflict leads to increased error rates and longer reaction times, which has been termed Simon effect. A model of dual route processing (automatic and intentional) of stimulus features has been proposed, predicting response conflicts if the two routes are incongruent. Although there is evidence that the prefrontal cortex, notably the anterior cingulate cortex (ACC), plays a crucial role in conflict processing, the neuronal basis of dual route architecture is still unknown. In this study, we pursue a novel approach using positron emission tomography (PET) to identify relevant brain areas in a rat model of an auditory Simon task, a neuropsychological interference task, which is commonly used to study conflict processing in humans. For combination with PET we used the metabolic tracer [18F]fluorodeoxyglucose, which accumulates in metabolically active brain cells during the behavioral task. Brain areas involved in conflict processing are supposed to be activated when automatic and intentional route processing lead to different responses (dual route model). Analysis of PET data revealed specific activation patterns for different task settings applicable to the dual route model as established for response conflict processing. The rat motor cortex (M1) may be part of the automatic route or involved in its facilitation, while premotor (M2), prelimbic, and ACC seemed to be essential for inhibiting the incorrect, automatic response, indicating conflict monitoring functions. Our findings and the remarkable similarities to the pattern of activated regions reported during conflict processing in humans demonstrate that our rodent model opens novel opportunities to investigate the anatomical basis of conflict processing and dual route architecture.
Highlights
The limits of cognitive capacity are especially evident during attempts to perform simultaneously several tasks, such as speaking and typing
BEHAVIOR Our study confirmed the results of Courtière et al (2007) that rats performing a Simon task displayed longer reaction times (RTs) and produced more errors in incompatible compared to compatible trials
This was statistically significant in the behavioral block, for both reaction times and error rate (ER), while in the positron emission tomography (PET) block only ERs were significantly elevated in incompatible trials
Summary
The limits of cognitive capacity are especially evident during attempts to perform simultaneously several tasks, such as speaking and typing. This leads to conflicts in the cognitive system and to slower activity and in the worst case, to action slips, as typing errors. While the neuronal bases of automatic and intentional pathways are unknown, human fMRI and EEG studies have suggested that the dorsal anterior cingulate cortex (ACC) monitors conflicts arising during incompatible dual route processing, and signals the dorsomedial prefrontal cortex to improve performance in subsequent conflict trials (conflict resolution; Botvinick et al, 1999, 2001, 2004; Kerns, 2006).
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