Selective updating of working memory content modulates meso-cortico-striatal activity

Abstract

Accumulating evidence from non-human primates and computational modeling suggests that dopaminergic signals arising from the midbrain (substantia nigra/ventral tegmental area) mediate striatal gating of the prefrontal cortex during the selective updating of working memory. Using event-related functional magnetic resonance imaging, we explored the neural mechanisms underlying the selective updating of information stored in working memory. Participants were scanned during a novel working memory task that parses the neurophysiology underlying working memory maintenance, overwriting, and selective updating. Analyses revealed a functionally coupled network consisting of a midbrain region encompassing the substantia nigra/ventral tegmental area, caudate, and dorsolateral prefrontal cortex that was selectively engaged during working memory updating compared to the overwriting and maintenance of working memory content. Further analysis revealed differential midbrain-dorsolateral prefrontal interactions during selective updating between low-performing and high-performing individuals. These findings highlight the role of this meso-cortico-striatal circuitry during the selective updating of working memory in humans, which complements previous research in behavioral neuroscience and computational modelin

Chunking improves symbolic sequence processing and relies on working memory gating mechanisms

“…While the overlap between the neural correlates of chunking and WM gating (Graybiel 1998;Bor et al 2003;Gruber et al 2006;Tremblay et al 2010;Murty et al 2011;D'Ardenne et al 2012;Wymbs et al 2012;Jin et al 2014) was considered as indirect evidence of their possible interactions, in accordance with the computational models (O'Reilly and Frank 2006; Grossberg and Kazerounian 2011), we provide here, for the first time, behavioral evidence that chunking is linked to WM gating processes. This suggests that, in accordance with our prediction, chunking during sequence performance relies on the same mechanisms as in WM updating tasks, i.e., presumably the capacity to gate the access of information to WM while filtering irrelevant distractors (Gruber et al 2006;O'Reilly and Frank 2006;D'Ardenne et al 2012).…”

“…In order to address these issues experimentally, we correlated individual estimates of chunking strategy in a sequence-learning task with general task performance, cognitive workload (as indexed by pupil size), and performance in a WM updating task (Murty et al 2011). Since motor sequence learning appears to depend less on attentional and central executive resources than nonmotor sequence learning (Hikosaka et al 2002;Keele et al 2003;Song et al 2008), we opted in the present experiment for a symbolic sequence-learning task.…”

“…The sequence (3 2 3 2 2 3 2 3 4 1 4 1 1 4 1 4) was repeated six times per block and the task comprised of eight block repetitions. The WM task (Murty et al 2011;Podell et al 2012), administered prior to the sequence-learning task, consisted of a WM updating (16 trials) and a WM maintenance task (24 trials). Every trial started with the encoding phase, during which subjects had to remember a set of digits, and ended with the retrieval phase, during which they had to compare a currently remembered set of digits to the one displayed on the screen.…”

“…The subject's performance was determined by computing the proportion of correct responses in each of these conditions. In nonmatching trials, a single digit was changed from the correct digit combination (Murty et al 2011). The tasks were implemented using Psychtoolbox 3.0.9 (Brainard 1997) with Matlab 7.5 (The MathWorks).…”

Functional imaging of brain responses to different outcomes of hypothesis testing: revealed in a category induction task

“…Error bars reflect standard deviation of the mean. correlate with consequent WM manipulation (Cohen et al, 1997;Honey et al, 2000;Murty et al, 2011). Recently, human neuroimaging studies have revealed the parietal cortex activity during WM tasks that require selective WM updating (Bledowski et al, 2009;Montojo and Courtney, 2008;Murty et al, 2011).…”