Dataset Information

Exogenous features versus prior experiences modulate different subregions of the right IPL during episodic memory retrieval.

ABSTRACT: The fractionation view holds that distinct cognitive operations are mediated by subregions of the inferior parietal lobule (IPL). Within IPL, we hypothesised that retrieval-related activity in different parts of the right supramarginal gyrus (rSMG) may be modulated differentially by information acquired via different combinations of attention signals at encoding. We had two groups of participants watch a 42-min TV episode and, after a 24-hr delay, perform a temporal-order judgment task during fMRI. Each retrieval trial comprised three images presented sequentially, requiring participants to judge the temporal order between the first and last images while ignoring the second image ("distractor"). We manipulated the bottom-up factor by presenting distractors that were extracted from either an event-boundary or a non-boundary of the movie. The top-down factor was manipulated by instructing one group perform a segmentation task reporting the event-boundaries at encoding, while the other group watched the movie passively. Across groups, we found that the stimulus-related factor modulated retrieval activation in the anterior rSMG (areas PFt and PFop), whereas the goal-related influence of prior segmentation interacted with this effect in the middle rSMG (area PF), demonstrating IPL segregation during retrieval as a function of prior bottom-up vs. top-down attention signals.

SUBMITTER: Kwok SC

PROVIDER: S-EPMC4460889 | biostudies-other | 2015 Jun

REPOSITORIES: biostudies-other

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Exogenous features versus prior experiences modulate different subregions of the right IPL during episodic memory retrieval.

Kwok Sze Chai SC Macaluso Emiliano E

Scientific reports 20150609

The fractionation view holds that distinct cognitive operations are mediated by subregions of the inferior parietal lobule (IPL). Within IPL, we hypothesised that retrieval-related activity in different parts of the right supramarginal gyrus (rSMG) may be modulated differentially by information acquired via different combinations of attention signals at encoding. We had two groups of participants watch a 42-min TV episode and, after a 24-hr delay, perform a temporal-order judgment task during fM ...[more]

PMID: 26057929

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Project description:BACKGROUND: The objective of this study was to examine differences in episodic memory retrieval between individuals with autism spectrum disorder (ASD) and typically developing (TD) individuals. Previous studies have shown that personality similarities between readers and characters facilitated reading comprehension. Highly extraverted participants read stories featuring extraverted protagonists more easily and judged the outcomes of such stories more rapidly than did less extraverted participants. Similarly, highly neurotic participants judged the outcomes of stories with neurotic protagonists more rapidly than did participants with low levels of neuroticism. However, the impact of the similarity effect on memory retrieval remains unclear. This study tested our 'similarity hypothesis', namely that memory retrieval is enhanced when readers with ASD and TD readers read stories featuring protagonists with ASD and with characteristics associated with TD individuals, respectively. METHODS: Eighteen Japanese individuals (one female) with high-functioning ASD (aged 17 to 40 years) and 17 age- and intelligence quotient (IQ)-matched Japanese (one female) TD participants (aged 22 to 40 years) read 24 stories; 12 stories featured protagonists with ASD characteristics, and the other 12 featured TD protagonists. Participants read a single sentence at a time and pressed a spacebar to advance to the next sentence. After reading all 24 stories, they were asked to complete a recognition task about the target sentence in each story. RESULTS: To investigate episodic memory in ASD, we analyzed encoding based on the reading times for and readability of the stories and retrieval processes based on the accuracy of and response times for sentence recognition. Although the results showed no differences between ASD and TD groups in encoding processes, they did reveal inter-group differences in memory retrieval. Although individuals with ASD demonstrated the same level of accuracy as did TD individuals, their patterns of memory retrieval differed with respect to response times. CONCLUSIONS: Individuals with ASD more effectively retrieved ASD-congruent than ASD-incongruent sentences, and TD individuals retrieved stories with TD more effectively than stories with ASD protagonists. Thus, similarity between reader and story character had different effects on memory retrieval in the ASD and TD groups.

Project description:Most complex cognitive tasks require the coordinated interplay of multiple brain networks, but the act of retrieving an episodic memory may place especially heavy demands for communication between the frontoparietal control network (FPCN) and the default mode network (DMN), two networks that do not strongly interact with one another in many task contexts. We applied graph theoretical analysis to task-related fMRI functional connectivity data from 20 human participants and found that global brain modularity-a measure of network segregation-is markedly reduced during episodic memory retrieval relative to closely matched analogical reasoning and visuospatial perception tasks. Individual differences in modularity were correlated with memory task performance, such that lower modularity levels were associated with a lower false alarm rate. Moreover, the FPCN and DMN showed significantly elevated coupling with each other during the memory task, which correlated with the global reduction in brain modularity. Both networks also strengthened their functional connectivity with the hippocampus during the memory task. Together, these results provide a novel demonstration that reduced modularity is conducive to effective episodic retrieval, which requires close collaboration between goal-directed control processes supported by the FPCN and internally oriented self-referential processing supported by the DMN.SIGNIFICANCE STATEMENT Modularity, an index of the degree to which nodes of a complex system are organized into discrete communities, has emerged as an important construct in the characterization of brain connectivity dynamics. We provide novel evidence that the modularity of the human brain is reduced when individuals engage in episodic memory retrieval, relative to other cognitive tasks, and that this state of lower modularity is associated with improved memory performance. We propose a neural systems mechanism for this finding where the nodes of the frontoparietal control network and default mode network strengthen their interaction with one another during episodic retrieval. Such across-network communication likely facilitates effective access to internally generated representations of past event knowledge.

Dataset Information

Exogenous features versus prior experiences modulate different subregions of the right IPL during episodic memory retrieval.

Publications

Exogenous features versus prior experiences modulate different subregions of the right IPL during episodic memory retrieval.

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