Subtly distinct dysexecutive deficits after frontal versus parietal brain damage

Cognitive flexibility, the ability to adjust behavior to changing task demands, is critically dependent on distinct control processes supported by a multiple demand frontoparietal cortical network. While behavioral deficits following focal frontal lesions are well documented, most past studies relied on global indices of accuracy or reaction time, without a detailed analysis of specific error types. Here, we investigated task-switching behavior in patients with focal frontal (n = 18) and parietal (n = 8) brain lesions—and in their age-matched healthy controls—by employing a fine-grained taxonomy of error subtypes. Group differences were tested separately for each of the first three target trials following switch and repeat cues using Kruskal–Wallis tests, followed by Dunn’s post-hoc pairwise comparisons when appropriate.Distinct error profiles emerged, with subtle differences across clinical groups: perseverative errors denoted failures in task-setting or rule updating mostly in frontal patients, distraction errors reflected deficits in monitoring or working memory maintenance mainly in parietal patients, whereas omission errors were linked to impaired energization or alerting in both clinical groups. Crucially, patients’ correct responses to target trials were paradoxically preserved most of the time, underscoring that their impairments reflect time-varying fluctuations in the efficiency of cognitive control rather than permanent cognitive deficits or global motor slowing. Complementary machine learning analyses confirmed that multivariate patterns of post-cue errors provided sensitive markers of brain injury, although they did not neatly distinguish between frontal and parietal damage. Together, these findings support evidence for a novel mechanistic account of dysexecutive deficits, suggesting that both frontal and parietal nodes of the frontoparietal network jointly contribute to task-setting, monitoring, and energization subcomponents of cognitive control, although selective damage to different frontoparietal nodes gives rise to subtly distinct behavioral error profiles.