Abstract
Cognitive tasks are used to probe neuronal activity during functional magnetic resonance imaging (fMRI) to detect signs of aberrant cognitive functioning in patients diagnosed with schizophrenia (SZ). However, nonlinear (inverted-U-shaped) associations between neuronal activity and task difficulty can lead to misinterpretation of group differences between patients and healthy comparison subjects (HCs). In this paper, we evaluated a novel method for correcting these misinterpretations based on conditional performance analysis. Participants included 25 HCs and 27 SZs who performed a working memory (WM) task (N-back) with 5 load conditions while undergoing fMRI. Neuronal activity was regressed onto: 1) task load (i.e., parametric task levels), 2) marginal task performance (i.e., performance averaged over all load conditions), or 3) conditional task performance (i.e., performance within each load condition). In most regions of interest, conditional performance analysis uniquely revealed inverted-U-shaped neuronal activity in both SZs and HCs. After accounting for conditional performance differences between groups, we observed few difference in both the pattern and level of neuronal activity between SZs and HCs within regions that are classically associated with WM functioning (e.g., posterior dorsolateral prefrontal and parietal association cortices). However, SZs did show aberrant activity within the anterior dorsolateral prefrontal cortex. Interpretations of differences in neuronal activity between groups, and of associations between neuronal activity and performance, should be considered within the context of task performance. Whether conditional performance-based differences reflect compensation, dedifferentiation, or other processes is not a question that is easily resolved by examining activation and performance data alone.
Highlights
Cognitive tasks are used during functional magnetic resonance imaging to probe for signs of aberrant neuronal functioning in patients diagnosed with schizophrenia (SZs)
Since brain responses vary with task performance, and because performance differs between patients and healthy control subjects (HCs), it is often unclear whether different patterns of neuronal response between groups should be attributed to intrinsic differences in brain function, differences in performance, or both (Brown & Eyler, 2006; Callicott et al, 2003; Manoach, 2003)
Analyses based on task difficulty alone revealed one Regions of Interest (ROIs) with inverted-U-shaped neuronal activity for HCs, results suggested the oppositive pattern for SZs
Summary
Cognitive tasks are used during functional magnetic resonance imaging (fMRI) to probe for signs of aberrant neuronal functioning in patients diagnosed with schizophrenia (SZs). Since brain responses vary with task performance, and because performance differs between patients and healthy control subjects (HCs), it is often unclear whether different patterns of neuronal response between groups should be attributed to intrinsic differences in brain function, differences in performance, or both (Brown & Eyler, 2006; Callicott et al, 2003; Manoach, 2003). Working memory (WM) is defined as the “ : : : mechanisms or processes that are involved in the control, regulation and active maintenance of task-relevant information in the service of complex cognition : : : ” In the attempt to better understand WM deficits, researchers often rely on neuroimaging methods, especially fMRI (Brown & Eyler, 2006)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Journal of the International Neuropsychological Society
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
