Biology subjects

Dimsdale-Zucker, H. R.

Publications and source records attributed to Dimsdale-Zucker, H. R..

6 recordsLinked to original sources

bioRxiv2026

The role of contextual similarity on brain activity patterns for associated events

Our everyday lives are characterized by repeated contexts, such as returning to work in the same office every day. Although the physical office may be identical, other features vary--e.g., time of day, light conditions, one's internal state--leading to differing degrees of similarity, even among putatively identical contexts. Alternatively, contexts can change abruptly, such as leaving the office to go home for dinner. Despite the prevalence of various levels of contextual overlap in everyday life, prior experimental work has largely ignored their influence on related experiences. To address this gap, we took a novel approach in which participants viewed real-world audiovisual stimuli (commercials [events], TV shows [contexts]) while undergoing functional magnetic resonance imaging scans (fMRI) to examine whether the degree of contextual overlap influenced brain activity patterns for related events. Representational similarity analyses revealed sensitivity to global context--greater similarity for commercials seen within the same versus different show--in ventromedial prefrontal cortex, posterior medial cortex, perirhinal cortex, and parahippocampal cortex. Additionally, parahippocampal cortex was uniquely sensitive to local context--greater similarity for commercials seen in the same versus different episode of the same show--and showed reduced activity to repetition of event-specific information, suggesting representation of event-level conceptual information. Thus, even with no explicit demand to retrieve contextual associations, event representations changed based on the degree of contextual similarity, suggesting that contextual information is an inherent part of how experiences are represented.

neuroscience↗

bioRxiv2025

Aging and false memories: Comparing effects of item-relatedness and list position

Evidence from classic serial position curves suggests that semantic false memories traditionally arise from presumed long-term memory stores whereas phonological false memories arise from presumed short-term memory stores. However, recent research with younger adults challenges this distinction, finding semantic and phonological false memories across memory stores and list positions (Atkins & Reuter-Lorenz, 2008; Dimsdale-Zucker et al., 2018; Flegal et al., 2010). The present study tested whether semantic and phonological false memories reflect distinct or shared underlying mechanisms and whether these patterns differ with age. Younger (YAs) and older (OAs) adults completed a modified Deese-Roediger-McDermott paradigm that manipulated semantic and phonological similarity across list position. Although OAs recalled fewer items than YAs, both groups generated more phonological than semantic false memories. Notably, list position did not influence false memories in either YAs or OAs, suggesting false memory generation is driven by list composition rather than putative memory store. These findings challenge traditional views of memory organization by revealing shared cognitive processes, which transcend traditional memory system distinctions that underlie semantic and phonological false memories.

neuroscience↗

bioRxiv2023

Proximity to Boundaries Reveals Spatial Context Representation in Human Hippocampal CA1

Recollection of real-world events is often accompanied by a sense of being in the place where the event transpired. Convergent evidence suggests the hippocampus plays a key role in supporting episodic memory by associating information with the time and place it was originally encountered. This representation is reinstated during memory retrieval. However, little is known about the roles of different subfields of the human hippocampus in this process. Research in humans and non-human animal models have suggested that spatial environmental boundaries have a powerful influence on spatial and episodic memory, as well as hippocampal representations of contexts and events. Here, we used high-resolution fMRI to investigate how boundaries influence hippocampal activity patterns during the recollection of objects encountered in different spatial contexts. During the encoding phase, participants viewed objects once in a naturalistic virtual reality task, in which they passively explored two rooms in one of two houses. Following the encoding phase, participants were scanned while they recollected items in the absence of any spatial contextual information. Our behavioral results demonstrated that spatial context memory was enhanced for objects encountered near a boundary. Activity patterns in CA1 carried information about the spatial context associated with each of these boundary items. Exploratory analyses revealed that memory for the room in which each object was studied was correlated with the fidelity of retrieved spatial context representations in anterior parahippocampal cortex and subiculum. Our results highlight the privileged role of boundaries in CA1 and suggest more generally a close relationship between memory for spatial contexts and representations in the hippocampus and parahippocampal region.

neuroscience↗

bioRxiv2021

Relationships between individual differences in dual process and electrophysiological signatures of familiarity and recollection during retrieval

Our everyday memories can vary in terms of accuracy and phenomenology. According to one theoretical account, these differences hinge on whether the memories contain information about both an item itself as well as associated details (remember) versus those that are devoid of these associated contextual details (familiar). This distinction has been supported by computational modeling of behavior, studies in patients, and neuroimaging work including differences both in electrophysiological and functional magnetic resonance imaging. At present, however, little evidence has emerged to suggest that neurophysiological measures track individual differences in estimates of recollection and familiarity. Here, we conducted electrophysiological recordings of brain activity during a recognition memory task designed to differentiate between behavioral indices of recollection and familiarity. Non-parametric cluster-based permutation analyses revealed associations between electrophysiological signatures of familiarity and recollection with their respective behavioral estimates. These results support the idea that recollection and familiarity are distinct phenomena and is the first, to our knowledge, to identify distinct electrophysiological signatures that track individual differences in these processes.

neuroscience↗

bioRxiv2019

Hippocampal subfields integrate information about past temporal and cognitive contexts

The hippocampus plays a critical role in supporting episodic memory, in large part by binding together experiences and items with surrounding contextual information. At present, however, little is known about the roles of different hippocampal subfields in supporting this item-context binding. To address this question, we constructed a task in which items were affiliated with differing types of context - cognitive associations that vary at the local, item level and membership in temporally organized lists that linked items together at a global level. Participants made item recognition judgments while undergoing high-resolution fMRI imaging. We performed voxel pattern similarity analyses to answer the question of how human hippocampal subfields represent retrieved information about cognitive states and the time at which a past event took place. As participants recollected previously presented items, activity patterns in the CA23DG subregion carried information about prior cognitive states associated with these items. We found no evidence to suggest reinstatement of information about temporal context at the level of list membership, but exploratory analyses revealed representations of temporal context at a coarse level in conjunction with representations of cognitive contexts. Results are consistent with characterizations of CA23DG as a critical site for binding together items and contexts in the service of memory retrieval.

neuroscience↗

bioRxiv2017

CA1 And CA3 Differentially Support Spontaneous Retrieval Of Episodic Contexts Within Human Hippocampal Subfields

The hippocampus plays a critical role in spatial and episodic memory. Mechanistic models predict that hippocampal subfields have computational specializations that differentially support memory. However, there is little empirical evidence suggesting differences between the subfields, particularly in humans. To clarify how hippocampal subfields support human spatial and episodic memory, we developed a virtual reality paradigm where participants passively navigated through houses (spatial contexts) across a series of videos (episodic contexts). We then used multivariate analyses of high-resolution fMRI data to identify neural representations of contextual information during recollection. Multi-voxel pattern similarity analyses revealed that CA1 represented objects that shared an episodic context as more similar than those from different episodic contexts. CA23DG showed the opposite pattern, differentiating between objects encountered in the same episodic context. The complementary characteristics of these subfields explain how we can parse our experiences into cohesive episodes while retaining the specific details that support vivid recollection.

neuroscience↗