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Sang Ah Lee
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Journal Articles
Publisher: Journals Gateway
Journal of Cognitive Neuroscience 1–16.
Published: 05 August 2024
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Crossing a spatial boundary such as a doorway plays an important role in the temporal organization of episodic memory. However, despite the wealth of evidence showing that visual boundary structures in scenes affect our representation of space, no studies have tested the possibility that they also function as event boundaries even without active navigation. In this study, we used a nonnavigational scene-based memory task that required participants to remember a sequence of objects moving to various baskets in a scene. In the boundary condition, there was a freestanding boundary in the middle of the room, low enough to see the rest of the room beyond it. We found that the additional boundary within the scene was sufficient to trigger a larger response in the cortical visual scene network, the hippocampus, and their coordinated activity. These results suggest that active navigation across a spatial boundary such as a doorway into another room is not necessary to form an event boundary and that a visual representation of boundaries is sufficient to influence the organization of a hippocampal episodic memory.
Journal Articles
Publisher: Journals Gateway
Journal of Cognitive Neuroscience (2023) 35 (11): 1773–1787.
Published: 01 November 2023
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Despite distinct neural representation of what , where , and when information, studies of individual differences in episodic memory have neglected to test the three components separately. Here, we used a componential episodic memory task to measure cognitive profiles across a wide age range and in Alzheimer disease (AD) and to examine the role of theta oscillations in explaining performance. In Experiment 1, we tested a group of 47 young adults (age 21–30 years, 21 women) while recording their scalp EEG. A separate behavioral experiment (Experiment 2) was performed in 42 older adults (age 66–85 years, 29 women) and in a group of 16 AD patients (age 80–90 years, 12 women). In Experiment 1, K-means clustering based on behavioral data resulted in three “cognotypes” whose memory profiles showed corresponding differences in their EEG markers: What and where memory depended on frontal theta power and when memory depended on theta modulation by temporal distance between retrieved items. In Experiment 2, healthy older adults showed three cognotypes similar to those found in younger adults; moreover, AD patients had an overlapping profile with one specific cognotype, characterized by marked difficulties in when memory. These findings highlight the utility of componential episodic memory tests and cognotyping in understanding individual strengths and vulnerabilities in age-related neurocognitive decline.