Multiple effects of prefrontal lesions on task-switching

Shallice · 2007 · OpenAlex-citations

DOI: 10.3389/neuro.09.002.2007

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Summary

This study investigates the specific cognitive processes involved in task-switching and their neural substrates within the prefrontal cortex. While previous research established that prefrontal lesions impair task-switching, it remained unclear which specific regions support distinct components of the process, such as task-set reconfiguration versus inhibition of previous sets. To address this, the authors examined 41 patients with focal prefrontal lesions and 38 healthy controls using a cued task-switching paradigm. The design included three conditions: single-task blocks (no switching), and two switching blocks where the relevant task was signaled either 1500 ms (Long Cue) or 200 ms (Short Cue) before stimulus presentation. This manipulation allowed the authors to distinguish between processes that could occur during preparation time and those requiring immediate processing. Patients were categorized into four groups based on lesion location: left lateral, right lateral, inferior medial, and superior medial. The results demonstrated that task-switching relies on multiple, dissociable processes localized to specific prefrontal regions. Patients with superior medial lesions exhibited both a general slowing of reaction times and a significantly increased switch cost, indicating a deficit in the reconfiguration of task sets. In contrast, patients with inferior medial lesions showed increased error rates during switching conditions, suggesting a role in maintaining task accuracy or inhibiting interference. Patients with left dorsolateral lesions (specifically area 9/46v) displayed slower learning of the task, evidenced by high error rates early in the experiment. No other prefrontal groups showed significant increases in reaction time switch costs. These findings indicate that different frontal areas support distinct aspects of switching: superior medial regions for reconfiguration speed, inferior medial regions for error control, and left dorsolateral regions for task learning. The significance of this work lies in its refinement of the understanding of prefrontal function in executive control. By using a paradigm that separates preparation time from stimulus processing, the study challenges the view that switch costs solely reflect task-set reconfiguration time. Instead, it supports a multi-component model where different prefrontal structures contribute to different stages of switching, such as preparation, inhibition, and learning. This dissociation helps resolve conflicting results from previous functional imaging and neuropsychological studies, providing a more precise map of how the frontal lobes support cognitive flexibility. The findings underscore the importance of considering specific lesion locations and distinct performance metrics (reaction time vs. errors) when interpreting prefrontal contributions to executive function.

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• task switching