Biology subjects

Ritchey, M.

Publications and source records attributed to Ritchey, M..

10 recordsLinked to original sources

bioRxiv2026

Remembered event features shape default mode network engagement during emotional memory recall

Episodic memory involves reconstruction of past events through integration of multiple types of information, including perceptual details, narrative content, and emotional tone. The default mode network (DMN) is a set of regions thought to support episodic retrieval, yet it remains unclear how distinct subnetworks contribute to recall of these different memory features. Here, we examined how DMN subnetworks support and represent memory for naturalistic emotional events. Male and female human participants encoded short news videos that varied in emotional valence and recalled them in response to neutral cues during functional MRI scanning. Videos were again recalled one day later and memories were scored for perceptual and narrative details. Activity in the dorsomedial subnetwork was related to the emotional valence of the memory, while activity in the medial temporal subnetwork was associated with the number of perceptual details recalled. Multivariate pattern analyses further revealed that the medial temporal subnetwork exhibited greater pattern stability across recalls when recalling more perceptual details, while stability in the dorsomedial and core subnetworks was tied to emotional remembering. Our findings suggest that the dorsomedial subnetwork provides an affective frame for a memory, while the medial temporal subnetwork contributes perceptual specificity. These results demonstrate that the contents of memory retrieval shape network engagement during emotional recall, providing insight into how the brain reconstructs complex real-world experiences. Significance StatementHow do we remember the emotional tone of an event versus its visual details? This study examines how distinct subnetworks within the brains default mode network (DMN) contribute to remembering different features of memory. While the medial temporal subnetwork is connected to retrieving the perceptual details of past events, the dorsomedial subnetwork supports recall of the emotional tone. Furthermore, patterns of activity in the medial temporal subnetwork are more stable when recalling more perceptually rich memories, while stability in the dorsomedial subnetwork is tied to emotional remembering. These findings suggest that the default mode network flexibly responds to different kinds of memory features, supporting the reconstruction of rich emotional memories from complex real-world experiences.

neuroscience↗

bioRxiv2025

Neural signatures of recollection are sensitive to memory quality and specific event features

Episodic memories reflect a bound representation of multimodal features that can be recollected with varying levels of precision. Recent fMRI investigations have demonstrated that the precision and content of information retrieved from memory engage a network of posterior medial temporal and parietal regions co-activated with the hippocampus. Yet, comparatively little is known about how memory content and precision affect common neural signatures of memory captured by electroencephalography (EEG), where recollection has been associated with changes in event-related potential (ERP) and oscillatory measures of neural activity. Here, we used a multi-feature paradigm previously reported in Cooper & Ritchey (2019) with continuous measures of memory, in conjunction with scalp EEG, to characterize the content and quality of information that drives ERP and oscillatory markers of episodic memory. A common signature of memory retrieval in left posterior regions, called the late positive component (LPC), was sensitive to overall memory quality and also to precision of recollection for spatial features. Analysis of oscillatory markers during recollection revealed that alpha/beta desynchronization was modulated by overall memory quality and also by individual features in memory. Importantly, we found evidence of a relationship between these two neural markers of memory retrieval, suggesting that they may represent complementary aspects of the recollection experience. These findings demonstrate how time-sensitive and dynamic processes identified with EEG correspond to overall episodic recollection, and also to the retrieval of precise features in memory.

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bioRxiv2023

Intrinsic functional connectivity among memory networks does not predict individual differences in narrative recall

Individuals differ greatly in their ability to remember the details of past events, yet little is known about the brain processes that explain such individual differences in a healthy young population. Previous research suggests that episodic memory relies on functional communication among ventral regions of the default mode network ("DMN-C") that are strongly interconnected with the medial temporal lobes. In this study, we investigated whether the intrinsic functional connectivity of the DMN-C subnetwork is related to individual differences in memory ability, examining this relationship across 243 individuals (ages 18-50 years) from the openly available Cambridge Center for Aging and Neuroscience (Cam-CAN) dataset. We first estimated each participants whole-brain intrinsic functional brain connectivity by combining data from resting-state, movie-watching, and sensorimotor task scans to increase statistical power. We then examined whether intrinsic functional connectivity predicted performance on a narrative recall task. We found no evidence that functional connectivity of the DMN-C, with itself, with other related DMN subnetworks, or with the rest of the brain, was related to narrative recall. Exploratory connectome-based predictive modeling (CBPM) analyses of the entire connectome revealed a whole-brain multivariate pattern that predicted performance, although these changes were largely outside of known memory networks. These results add to emerging evidence suggesting that individual differences in memory cannot be easily explained by brain differences in areas typically associated with episodic memory function.

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bioRxiv2022

Integrating region- and network-level contributions to episodic recollection using multilevel structural equation modeling

The brain is composed of networks of interacting brain regions that support higher order cognition. For instance, a posterior medial (PM) network appears to support recollection and other forms of episodic construction. Past research has focused largely on the roles of individual brain regions in recollection or on their mutual engagement as part of an integrated network. Yet the relationship between these region- and network-level contributions remains poorly understood. Here we applied multilevel structural equation modeling (SEM) to examine the functional organization of the PM network and its relationship to episodic memory outcomes. We evaluated two aspects of functional heterogeneity in the PM network: first, the organization of individual regions into subnetworks, and second, the presence of regionally-specific contributions while accounting for network-level effects. The results suggest that the PM network is composed of ventral and dorsal subnetworks, with the ventral subnetwork making a unique contribution to recollection, and that memory-related activity in individual regions is well accounted for by these network-level effects. These findings highlight the importance of considering both region and network levels of analysis when studying brain-behavior relationships.

neuroscience↗

bioRxiv2020

Mapping the organization and dynamics of the posterior medial network during movie watching

Brain regions within a posterior medial network (PMN) are characterized by sensitivity to episodic tasks, and they also demonstrate strong functional connectivity as part of the default network. Despite its cohesive structure, delineating the intranetwork organization and functional diversity of the PMN is crucial for understanding its contributions to multidimensional event cognition. Here, we probed functional connectivity of the PMN during movie watching to identify its pattern of connections and subnetwork functions in a split-sample replication of 136 participants. Consistent with prior findings of default network fractionation, we identified distinct PMN subsystems: a Ventral PM subsystem (retrosplenial cortex, parahippocampal cortex, posterior angular gyrus) and a Dorsal PM subsystem (medial prefrontal cortex, hippocampus, precuneus, posterior cingulate cortex, anterior angular gyrus). Ventral and Dorsal PM subsystems were differentiated by functional connectivity with parahippocampal cortex and precuneus and integrated by retrosplenial cortex and posterior cingulate cortex, respectively. Finally, the distinction between PMN subsystems is functionally relevant: whereas both Dorsal and Ventral PM connectivity tracked the movie content, only Ventral PM connections increased in strength at event transitions and appeared sensitive to episodic memory. Overall, these findings reveal PMN functional pathways and the distinct functional roles of intranetwork subsystems during event cognition.

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bioRxiv2019

Dissociable brain mechanisms for long-term memory of disgust- and fear- related associations

Remembering events that evoke emotions such as disgust or fear is critical to our survival. However, previous studies investigating the interplay between emotion and memory disregarded the effects of specific emotions, leading to inconsistent results. Also, the role of amygdala throughout memory stages has been poorly understood. Here, we show that after 3 weeks delay, word pairs evoking disgust were remembered better than pairs evoking fear. These two emotions distinctly modulated neural mechanisms of memory. Successful encoding of disgust-evoking information was mediated by univariate activation in amygdala and perirhinal cortex, in contrast to fear-evoking memories that engaged hippocampus and parahippocampal gyrus. Critically, univariate activation in the amygdala during encoding was correlated with memory reinstatement of individual word pairs, and more so for disgust than for fear. Together, these findings shed a new light on the role of the amygdala and medial temporal lobe regions in encoding and reinstatement of specific emotional memories.

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bioRxiv2019

Progression from feature-specific brain activity to hippocampal spatial binding during episodic encoding

The hallmark of episodic memory is recollecting multiple perceptual details tied to a specific spatial-temporal context. To remember an event, it is therefore necessary to integrate such details into a coherent representation during initial encoding. Here we tested how the brain encodes and binds multiple, distinct kinds of features in parallel, and how this process evolves over time during the event itself. We analyzed data from 27 human subjects (16 females, 11 males) who learned a series of objects uniquely associated with a color, a panoramic scene location, and an emotional sound while functional magnetic resonance imaging data were collected. By modeling how brain activity relates to memory for upcoming or just-viewed information, we were able to test how the neural signatures of individual features as well as the integrated event changed over the course of encoding. We observed a striking dissociation between early and late encoding processes: left inferior frontal and visuo-perceptual signals at the onset of an event tracked the amount of detail subsequently recalled and were dissociable based on distinct remembered features. In contrast, memory-related brain activity shifted to the left hippocampus toward the end of an event, which was particularly sensitive to binding item color and sound associations with spatial information. These results provide evidence of early, simultaneous feature-specific neural responses during episodic encoding that predict later remembering and suggest that the hippocampus integrates these features into a coherent experience at an event transition. SIGNIFICANCE STATEMENTUnderstanding and remembering complex experiences is crucial for many socio-cognitive abilities, including being able to navigate our environment, predict the future, and share experiences with others. Probing the neural mechanisms by which features become bound into meaningful episodes is a vital part of understanding how we view and reconstruct the rich detail of our environment. By testing memory for multimodal events, our findings show a functional dissociation between early encoding processes that engage lateral frontal and sensory regions to successfully encode event features, and later encoding processes that recruit hippocampus to bind these features together. These results highlight the importance of considering the temporal dynamics of encoding processes supporting multimodal event representations.

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bioRxiv2019

Cortico-hippocampal network connections support the multidimensional quality of episodic memory

Episodic memories reflect a bound representation of multimodal features that can be reinstated with varying levels of precision. Yet little is known about how brain networks involved in memory, including the hippocampus and posterior-medial (PM) and anterior-temporal (AT) cortical systems, functionally interact to support the quality and the content of recollection. Participants learned color, spatial, and emotion associations of objects, later reconstructing the visual features using a continuous color spectrum and 360-degree panorama scenes. Behaviorally, dependencies in memory were observed for the gist but not precision of these event associations. Supporting this integration, hippocampus, AT, and PM regions showed increased inter-network connectivity and reduced modularity during retrieval compared to encoding. These network connections, particularly to hippocampus, tracked a multidimensional, continuous measure of objective memory quality. Moreover, distinct patterns of connectivity tracked item color precision and spatial memory precision. These findings demonstrate not only how hippocampal-cortical connections reconfigure during episodic retrieval, but how such dynamic interactions might flexibly support the multidimensional quality of remembered events.

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bioRxiv2018

Dissociable medial temporal pathways for encoding emotional item and context information

Emotional experiences are typically remembered with a greater sense of recollection than neutral experiences, but memory benefits for emotional items do not typically extend to their source contexts. Item and source memory have been attributed to different subregions of the medial temporal lobes (MTL), but it is unclear how emotional item recollection fits into existing models of MTL function and, in particular, what is the role of the hippocampus. To address these issues, we used high-resolution functional magnetic resonance imaging (fMRI) to examine MTL contributions to successful emotional item and context encoding. The results showed that emotional items were recollected more often than neutral items. Whereas amygdala and perirhinal cortex (PRC) activity supported the recollection advantage for emotional items, hippocampal and parahippocampal cortex activity predicted subsequent source memory for both types of items, reflecting a double dissociation between anterior and posterior MTL regions. In addition, amygdala activity during encoding modulated the relationships of PRC activity and hippocampal activity to subsequent item recollection and source memory, respectively. Specifically, whereas PRC activity best predicted subsequent item recollection when amygdala activity was relatively low, hippocampal activity best predicted source memory when amygdala activity was relatively high. We interpret these findings in terms of complementary compared to synergistic amygdala-MTL interactions. The results suggest that emotion-related enhancements in item recollection are supported by an amygdala-PRC pathway, which is separable from the hippocampal pathway that binds items to their source context.

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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.

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