Dasa Zeithamova-Demircan

Assistant Professor, Department of Psychology
Member, ION

Ph.D. University of Texas at Austin
M.A. Charles University in Prague

Office:
325 LISB
541-346-6731

 

Research Interests: Cognitive-Neuroscience, Memory

Overview: Memory allows us to use past experiences to navigate novel situations and inform future decisions. Because every event is unique, we need to use memory flexibly, drawing upon multiple relevant experiences to anticipate future judgments. Brain and Memory Lab studies how memories are formed and how they are linked to each other to create internal representations of the world that can guide our behavior. We investigate how different memory systems are implemented in the brain, how they represent information, and how they interact. In the quest for discovery, we rely on computer-based experiments, cognitive models of behavior, and advanced functional MRI methods.

My research focuses on how we build complex knowledge representations—such as schemas, cognitive maps or concepts—from simple learning experiences. Stacking memories as building blocks, we form knowledge that transcend direct experience, allowing us to use the memory for the past to guide behavior in the future. I am especially interested how the hippocampus—a brain structure critical for memory for individual events in our lives—interacts with the prefrontal cortex and other memory systems to support the flexible use of experience. My primary research tools include computer-based experiments, formal models of behavior, and advanced functional MRI methods.

RECENT PUBLICATIONS

Related Articles

Trial timing and pattern-information analyses of fMRI data.

Neuroimage. 2017 Apr 11;:

Authors: Zeithamova D, de Araujo Sanchez MA, Adke A

Abstract
Pattern-information approaches to fMRI data analysis are becoming increasingly popular but few studies to date have investigated experimental design optimization for these analyses. Here, we tested several designs that varied in the number of trials and trial timing within fixed duration scans while participants encoded images of animals and tools. Trial timing conditions with fixed onset-to-onset timing ranged from slow 12-second trials with two repetitions of each item to quick 6-second trials with four repetitions per item. We also tested a jittered version of the quick design with 4-8second trials. We assessed the effect of trial timing on three dependent measures: category-level (animals vs. tools) decoding accuracy using a multivoxel pattern analysis, item-level (e.g., cat vs. dog vs. lion) information estimates using pattern similarity analysis, and memory effects comparing pattern similarity scores across repetitions of individual items subsequently remembered vs. forgotten. For single trial estimates, category decoding was equal across all trial timing conditions while item-level information and memory effects were better detected using slow trial timing. When modeling events on an item-by-item basis across all repetitions of a given item, a larger number of quick, regularly spaced trials provided an advantage over fewer slow trials for category decoding while item-level information was comparable across conditions. Jittered and non-jittered versions of the quick trial timing did not differ significantly in any analysis. These results will help inform experimental design choices in future studies planning to employ pattern-information analyses and demonstrate that design optimization guidelines developed for univariate analyses of a few conditions are not necessarily optimal for pattern-information analyses and condition-rich designs.

PMID: 28411155 [PubMed - as supplied by publisher]

Related Articles

Temporal Proximity Promotes Integration of Overlapping Events.

J Cogn Neurosci. 2017 Mar 02;:1-13

Authors: Zeithamova D, Preston AR

Abstract
Events with overlapping elements can be encoded as two separate representations or linked into an integrated representation; yet, we know little about the conditions that promote one form of representation over the other. Here, we tested the hypothesis that the proximity of overlapping events would increase the probability of integration. Participants first established memories for house-object and face-object pairs; half of the pairs were learned 24 hr before a fMRI session, and the other half 30 min before the session. During scanning, participants encoded object-object pairs that overlapped with the initial pairs acquired on the same or prior day. Participants were also scanned as they made inference judgments about the relationships among overlapping pairs learned on the same or different day. Participants were more accurate and faster when inferring relationships among memories learned on the same day relative to those acquired across days, suggesting that temporal proximity promotes integration. Evidence for reactivation of existing memories-as measured by a visual content classifier-was equivalent during encoding of overlapping pairs from the two temporal conditions. In contrast, evidence for integration-as measured by a mnemonic strategy classifier from an independent study [Richter, F. R., Chanales, A. J. H., & Kuhl, B. A. Predicting the integration of overlapping memories by decoding mnemonic processing states during learning. Neuroimage, 124, 323-335, 2016]-was greater for same-day overlapping events, paralleling the behavioral results. During inference itself, activation patterns further differentiated when participants were making inferences about events acquired on the same day versus across days. These findings indicate that temporal proximity of events promotes integration and further influences the neural mechanisms engaged during inference.

PMID: 28253077 [PubMed - as supplied by publisher]

Related Articles

Repetition suppression in the medial temporal lobe and midbrain is altered by event overlap.

Hippocampus. 2016 Nov;26(11):1464-1477

Authors: Zeithamova D, Manthuruthil C, Preston AR

Abstract
Repeated encounters with the same event typically lead to decreased activation in the medial temporal lobe (MTL) and dopaminergic midbrain, a phenomenon known as repetition suppression. In contrast, encountering an event that overlaps with prior experience leads to increased response in the same regions. Such increased responding is thought to reflect an associative novelty signal that promotes memory updating to resolve differences between current events and stored memories. Here, we married these ideas to test whether event overlap significantly modulates MTL and midbrain responses-even when events are repeated and expected-to promote memory updating through integration. While undergoing high-resolution functional MRI, participants were repeatedly presented with objects pairs, some of which overlapped with other, intervening pairs and some of which contained elements unique from other pairs. MTL and midbrain regions showed widespread repetition suppression for nonoverlapping pairs containing unique elements; however, the degree of repetition suppression was altered for overlapping pairs. Entorhinal cortex, perirhinal cortex (PRc), midbrain, and PRc-midbrain connectivity showed repetition-related increases across overlapping pairs. Notably, increased PRc activation for overlapping pairs tracked individual differences in the ability to reason about the relationships among pairs-our behavioral measure of memory integration. Within the hippocampus, activation increases across overlapping pairs were unique to CA1 , consistent with its hypothesized comparator function. These findings demonstrate that event overlap engages MTL and midbrain functions traditionally implicated in novelty processing, even when overlapping events themselves are repeated. Our findings further suggest that the MTL-midbrain response to event overlap may promote integration of new content into existing memories, leading to the formation of relational memory networks that span experiences. Moreover, the results inform theories about the division of labor within MTL, demonstrating that the role of PRc in episodic encoding extends beyond familiarity processing and item-level recognition. © 2016 Wiley Periodicals, Inc.

PMID: 27479864 [PubMed - in process]