Biology subjects

Samide, R.

Publications and source records attributed to Samide, R..

3 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↗

bioRxiv2018

Parietal representations of stimulus features are amplified during memory retrieval and flexibly aligned with top-down goals

In studies of human episodic memory, the phenomenon of reactivation has traditionally been observed in regions of occipitotemporal cortex (OTC) involved in sensory experience. However, reactivation also occurs in lateral parietal cortex (LPC), and recent evidence indicates that reactivation of stimulus-specific information may be stronger in LPC than in OTC. These observations raise a number of questions about the nature of memory representations in LPC and their relation to representations in OTC. Here, we report two fMRI experiments that quantify stimulus feature information (color and object category) within LPC and OTC, separately during perception and memory retrieval, in male and female human subjects. Across both experiments, we show a clear dissociation between OTC and LPC: while feature information in OTC is relatively stronger during perception than memory, feature information in LPC is relatively stronger during memory than perception. Thus, while OTC and LPC represent common stimulus features, they preferentially represent this information during different stages. We show that this transformation of feature information across regions co-occurs with stimulus-level reinstatement within LPC and high-level OTC. In Experiment 2, we consider whether feature information in LPC during memory retrieval is flexibly and dynamically shaped by top-down goals. Indeed, we find that dorsal LPC preferentially represents retrieved feature information that addresses current goals. In contrast, ventral LPC represents retrieved features independent of current goals. Collectively, these findings provide insight into the nature and significance of mnemonic representations in LPC and constitute an important bridge between putative mnemonic and control functions of parietal cortex.

neuroscience↗

bioRxiv2017

Decomposing parietal memory reactivation to predict consequences of remembering

Memory retrieval can strengthen, but also distort memories. Parietal cortex is a candidate region involved in retrieval-induced memory changes as it reflects retrieval success and represents retrieved content. Here, we conducted an fMRI experiment to test whether different forms of parietal reactivation predict distinct consequences of retrieval. Subjects studied associations between words and pictures of faces, scenes, or objects, and then repeatedly retrieved half of the pictures, reporting the vividness of the retrieved pictures ( retrieval practice). On the following day, subjects completed a recognition memory test for individual pictures. Critically, the test included lures highly similar to studied pictures. Behaviorally, retrieval practice increased both hit and false alarm rates to similar lures, confirming a causal influence of retrieval on subsequent memory. Using pattern similarity analyses, we measured two different levels of reactivation during retrieval practice: generic category-level reactivation and idiosyncratic item-level reactivation. Vivid remembering during retrieval practice was associated with stronger category- and item-level reactivation in parietal cortex. However, these measures differentially predicted subsequent recognition memory performance: whereas higher category-level reactivation tended to predict false alarms to lures, item-level reactivation predicted correct rejections. These findings indicate that parietal reactivation can be decomposed to tease apart distinct consequences of memory retrieval.

neuroscience↗