scholarly journals Functional magnetic resonance imaging of a parametric working memory task in schizophrenia: relationship with performance and effects of antipsychotic treatment

2011 ◽  
Vol 216 (1) ◽  
pp. 17-27 ◽  
Author(s):  
Ulrich Ettinger ◽  
Steven C. R. Williams ◽  
Dominic Fannon ◽  
Preethi Premkumar ◽  
Elizabeth Kuipers ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Working Memory ◽  
Magnetic Resonance ◽  
Functional Magnetic Resonance Imaging ◽  
Memory Task ◽  
Antipsychotic Treatment ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging

When less is more: a functional magnetic resonance imaging study of verbal working memory in remitted depressed patients

2013 ◽  
Vol 44 (6) ◽  
pp. 1197-1203 ◽  
Author(s):  
R. Norbury ◽  
B. Godlewska ◽  
P. J. Cowen
Keyword(s):  
Magnetic Resonance Imaging ◽  
Working Memory ◽  
Magnetic Resonance ◽  
Functional Magnetic Resonance Imaging ◽  
Memory Task ◽  
Verbal Working Memory ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Less Is More ◽  
Depressed Patients

BackgroundPatients with depression show abnormalities in the neural circuitry supporting working memory. However, it is unclear if these abnormalities are present in unmedicated remitted depressed patients. To address this question, the current study employed functional magnetic resonance imaging (fMRI), in combination with a simple verbal n-back task, in a cohort of unmedicated remitted depressed patients.MethodWe studied 15 healthy control subjects (HC) and 15 unmedicated remitted depressed patients (rMDD). Participants performed a verbal working memory task of varying cognitive load (n-back) while undergoing fMRI. We used multiple regression analyses to assess overall capacity (1-, 2-, 3-back versus 0-back) as well as quadratic modulation of cognitive demand.ResultsPerformance accuracy and response latency did not differ between groups, and overall capacity was similar. However, rMDD showed a positive quadratic load response in the bilateral hippocampus; the converse was true for HC.ConclusionsOur data suggest that remitted depression was associated with a perturbed pattern of activation in the bilateral hippocampus during a verbal working memory task. We propose that a reduced ability to dampen task-irrelevant activity may reflect a neurobiological risk factor for recurrent depression.

Not-so-working Memory: Drift in Functional Magnetic Resonance Imaging Pattern Representations during Maintenance Predicts Errors in a Visual Working Memory Task

2019 ◽  
Vol 31 (10) ◽  
pp. 1520-1534 ◽  
Author(s):  
Phui Cheng Lim ◽  
Emily J. Ward ◽  
Timothy J. Vickery ◽  
Matthew R. Johnson
Keyword(s):  
Magnetic Resonance Imaging ◽  
Working Memory ◽  
Magnetic Resonance ◽  
Functional Magnetic Resonance Imaging ◽  
Activity Patterns ◽  
Memory Task ◽  
Recognition Task ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Neural Noise

Working memory (WM) is critical to many aspects of cognition, but it frequently fails. Much WM research has focused on capacity limits, but even for single, simple features, the fidelity of individual representations is limited. Why is this? One possibility is that, because of neural noise and interference, neural representations do not remain stable across a WM delay, nor do they simply decay, but instead, they may “drift” over time to a new, less accurate state. We tested this hypothesis in a functional magnetic resonance imaging study of a match/nonmatch WM recognition task for a single item with a single critical feature: orientation. We developed a novel pattern-based index of “representational drift” to characterize ongoing changes in brain activity patterns throughout the WM maintenance period, and we were successfully able to predict performance on the match/nonmatch recognition task using this representational drift index. Specifically, in trials where the target and probe stimuli matched, participants incorrectly reported more nonmatches when their activity patterns drifted away from the target. In trials where the target and probe did not match, participants incorrectly reported more matches when their activity patterns drifted toward the probe. On the basis of these results, we contend that neural noise does not cause WM errors merely by degrading representations and increasing random guessing; instead, one means by which noise introduces errors is by pushing WM representations away from the target and toward other meaningful (yet incorrect) configurations. Thus, we demonstrate that behaviorally meaningful drift within representation space can be indexed by neuroimaging.

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