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Dissociable temporo-parietal memory networks revealed by functional connectivity during episodic retrieval.

Hirose S, Kimura HM, Jimura K, Kunimatsu A, Abe O, Ohtomo K, Miyashita Y, Konishi S - PLoS ONE (2013)

Bottom Line: Neuroimaging results revealed several temporal and parietal activations associated with relational/item-based recency judgments.Functional connectivity during task was found to be significant between the parahippocampal region and the parietal region in the RSFC network associated with relational recency judgments.However, out of the four tempo-parietal RSFC networks associated with item-based recency judgments, only one of them (between the left posterior lateral temporal region and the left lateral parietal region) showed significant functional connectivity during task.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, The University of Tokyo School of Medicine, Tokyo, Japan. sahirose@m.u-tokyo.ac.jp

ABSTRACT
Episodic memory retrieval most often recruits multiple separate processes that are thought to involve different temporal regions. Previous studies suggest dissociable regions in the left lateral parietal cortex that are associated with the retrieval processes. Moreover, studies using resting-state functional connectivity (RSFC) have provided evidence for the temporo-parietal memory networks that may support the retrieval processes. In this functional MRI study, we tested functional significance of the memory networks by examining functional connectivity of brain activity during episodic retrieval in the temporal and parietal regions of the memory networks. Recency judgments, judgments of the temporal order of past events, can be achieved by at least two retrieval processes, relational and item-based. Neuroimaging results revealed several temporal and parietal activations associated with relational/item-based recency judgments. Significant RSFC was observed between one parahippocampal region and one left lateral parietal region associated with relational recency judgments, and between four lateral temporal regions and another left lateral parietal region associated with item-based recency judgments. Functional connectivity during task was found to be significant between the parahippocampal region and the parietal region in the RSFC network associated with relational recency judgments. However, out of the four tempo-parietal RSFC networks associated with item-based recency judgments, only one of them (between the left posterior lateral temporal region and the left lateral parietal region) showed significant functional connectivity during task. These results highlight the contrasting roles of the parahippocampal and the lateral temporal regions in recency judgments, and suggest that only a part of the tempo-parietal RSFC networks are recruited to support particular retrieval processes.

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The recency judgment task used in the present study.The task contained three types of trials during the test phase that differed in terms of the presence/absence of presentation of end words and the temporal distance between presented words: End trials, Middle-Long (M-L) trials, and Middle-Short (M-S) trials. W: Word.
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pone-0071210-g001: The recency judgment task used in the present study.The task contained three types of trials during the test phase that differed in terms of the presence/absence of presentation of end words and the temporal distance between presented words: End trials, Middle-Long (M-L) trials, and Middle-Short (M-S) trials. W: Word.

Mentions: Visual stimuli were presented to subjects by projecting them onto a screen. Subjects viewed the screen through prism glasses. A magnet-compatible four-channel button press based on a fiber-optic switch was used to record subjects' performance. The recency judgments task consisted of two main phases, study and test (Fig. 1). During the study phase, twenty words were sequentially presented. Each word was presented for 1 sec, with an inter-stimulus interval (presentation of a white fixation cross) of 1 sec. Subjects were instructed to intentionally encode them for later recency judgments [56], [68]. More specifically, subjects were instructed to make up their own story from the list words, and this instruction is supposed to encourage the subjects to relate sequentially presented words that had otherwise no contexts among them. The words were concrete nouns taken from an object stimulus set [69] and were presented in strings of Japanese characters. To prevent the subjects from rehearsing the words between the study and test phases, the subjects performed a modified Wisconsin card sorting task [70] for approximately 30 seconds as a distracter task [52].


Dissociable temporo-parietal memory networks revealed by functional connectivity during episodic retrieval.

Hirose S, Kimura HM, Jimura K, Kunimatsu A, Abe O, Ohtomo K, Miyashita Y, Konishi S - PLoS ONE (2013)

The recency judgment task used in the present study.The task contained three types of trials during the test phase that differed in terms of the presence/absence of presentation of end words and the temporal distance between presented words: End trials, Middle-Long (M-L) trials, and Middle-Short (M-S) trials. W: Word.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3756987&req=5

pone-0071210-g001: The recency judgment task used in the present study.The task contained three types of trials during the test phase that differed in terms of the presence/absence of presentation of end words and the temporal distance between presented words: End trials, Middle-Long (M-L) trials, and Middle-Short (M-S) trials. W: Word.
Mentions: Visual stimuli were presented to subjects by projecting them onto a screen. Subjects viewed the screen through prism glasses. A magnet-compatible four-channel button press based on a fiber-optic switch was used to record subjects' performance. The recency judgments task consisted of two main phases, study and test (Fig. 1). During the study phase, twenty words were sequentially presented. Each word was presented for 1 sec, with an inter-stimulus interval (presentation of a white fixation cross) of 1 sec. Subjects were instructed to intentionally encode them for later recency judgments [56], [68]. More specifically, subjects were instructed to make up their own story from the list words, and this instruction is supposed to encourage the subjects to relate sequentially presented words that had otherwise no contexts among them. The words were concrete nouns taken from an object stimulus set [69] and were presented in strings of Japanese characters. To prevent the subjects from rehearsing the words between the study and test phases, the subjects performed a modified Wisconsin card sorting task [70] for approximately 30 seconds as a distracter task [52].

Bottom Line: Neuroimaging results revealed several temporal and parietal activations associated with relational/item-based recency judgments.Functional connectivity during task was found to be significant between the parahippocampal region and the parietal region in the RSFC network associated with relational recency judgments.However, out of the four tempo-parietal RSFC networks associated with item-based recency judgments, only one of them (between the left posterior lateral temporal region and the left lateral parietal region) showed significant functional connectivity during task.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, The University of Tokyo School of Medicine, Tokyo, Japan. sahirose@m.u-tokyo.ac.jp

ABSTRACT
Episodic memory retrieval most often recruits multiple separate processes that are thought to involve different temporal regions. Previous studies suggest dissociable regions in the left lateral parietal cortex that are associated with the retrieval processes. Moreover, studies using resting-state functional connectivity (RSFC) have provided evidence for the temporo-parietal memory networks that may support the retrieval processes. In this functional MRI study, we tested functional significance of the memory networks by examining functional connectivity of brain activity during episodic retrieval in the temporal and parietal regions of the memory networks. Recency judgments, judgments of the temporal order of past events, can be achieved by at least two retrieval processes, relational and item-based. Neuroimaging results revealed several temporal and parietal activations associated with relational/item-based recency judgments. Significant RSFC was observed between one parahippocampal region and one left lateral parietal region associated with relational recency judgments, and between four lateral temporal regions and another left lateral parietal region associated with item-based recency judgments. Functional connectivity during task was found to be significant between the parahippocampal region and the parietal region in the RSFC network associated with relational recency judgments. However, out of the four tempo-parietal RSFC networks associated with item-based recency judgments, only one of them (between the left posterior lateral temporal region and the left lateral parietal region) showed significant functional connectivity during task. These results highlight the contrasting roles of the parahippocampal and the lateral temporal regions in recency judgments, and suggest that only a part of the tempo-parietal RSFC networks are recruited to support particular retrieval processes.

Show MeSH
Related in: MedlinePlus