Assistant Professor, Department of Psychology
Ph.D. Stanford University
Postdoctoral Fellowship, Yale University
Research Interests: Cognitive Neuroscience, Memory, Cognitive Control, fMRI Methods
Overview: I am interested in how our perceptual experiences are transformed into memories and how we recreate and selectively recall these experiences. Research in my lab makes use of behavioral and neuroimaging methods (primarily fMRI) with an emphasis on applying machine learning algorithms and multivariate pattern analyses to neuroimaging data in order to understand how memories are represented and transformed in distributed patterns of brain activity.
Some of the specific topics my lab addresses include: What are the cognitive and neural mechanisms that cause forgetting? How is competition between memories signaled and resolved in the brain during retrieval? How do we reduce interference between memories during encoding? Addressing these questions involves understanding the interactions and relative contributions of fronto-parietal cortex and medial temporal lobe structures.
Decomposing Parietal Memory Reactivation to Predict Consequences of Remembering.
Cereb Cortex. 2018 Aug 23;:
Authors: Lee H, Samide R, Richter FR, Kuhl BA
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 (FA) 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 FAs 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.
PMID: 30137255 [PubMed - as supplied by publisher]
Parietal representations of stimulus features are amplified during memory retrieval and flexibly aligned with top-down goals.
J Neurosci. 2018 Jul 27;:
Authors: Favila SE, Samide R, Sweigart SC, Kuhl BA
In studies of human episodic memory, the phenomenon of reactivation has traditionally been observed in regions of occipitotemporal cortex (OTC) involved in visual perception. However, reactivation also occurs in lateral parietal cortex (LPC), and recent evidence suggests that stimulus-specific reactivation may be stronger in LPC than in OTC. These observations raise important questions about the nature of memory representations in LPC and their relationship to representations in OTC. Here, we report two fMRI experiments that quantified 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 observed a clear dissociation between OTC and LPC: while feature information in OTC was relatively stronger during perception than memory, feature information in LPC was relatively stronger during memory than perception. Thus, while OTC and LPC represented common stimulus features in our experiments, they preferentially represented this information during different stages. In LPC, this bias toward mnemonic information co-occured with stimulus-level reinstatement during memory retrieval. In Experiment 2, we considered whether mnemonic feature information in LPC was flexibly and dynamically shaped by top-down retrieval goals. Indeed, we found that dorsal LPC preferentially represented retrieved feature information that addressed the current goal. In contrast, ventral LPC represented retrieved features independent of the current goal. 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.SIGNIFICANCE STATEMENTWhen humans remember an event from the past, patterns of sensory activity that were present during the initial event are thought to be reactivated. Here, we investigated the role of lateral parietal cortex (LPC), a high-level region of association cortex, in representing prior visual experiences. We find that LPC contained stronger information about stimulus features during memory retrieval than during perception. We also found that current task goals influenced the strength of stimulus feature information in LPC during memory. These findings suggest that, in addition to early sensory areas, high-level areas of cortex like LPC represent visual information during memory retrieval, and that these areas may play a special role in flexibly aligning memories with current goals.
PMID: 30054390 [PubMed - as supplied by publisher]