Zach Reagh awarded Holcomb Scholarship

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Congratulations to Zach Reagh for being awarded the coveted Dr. William F. Holcomb Scholarship by the School of Biological Sciences! This award supports a graduate student in biomedical sciences and is in the amount of $2000. Zach is pictured here at the award ceremony with Dr. Mike Mulligan, Associate Dean for Graduate Studies, on the left and Dr. Frank LaFerla, Dean of the School of Biological Sciences, on the right.

New paper: Temporal discrimination in older adults

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New paper by graduate student Jared Roberts. Here he is with the paper pony!

Roberts J.M., Ly, M., Murray, E., Yassa, M.A. (2014) Temporal discrimination deficits as a function of lag interference in older adultsHippocampus DOI:10.1002/hipo.22303

Abstract

A vital component of episodic memory is the ability to determine the temporal order of remembered events. Although it has been demonstrated that the hippocampus plays a crucial role in this ability, the details of its contributions are not yet fully understood. One proposed contribution of the hippocampus is the reduction of mnemonic interference through pattern separation. Prior studies have used behavioral paradigms designed to assess this function in the temporal domain by evaluating the ability to determine the order of remembered events as a function of proximity in time. Results from these paradigms in older adults (OA) have been mixed, possibly due to limitations in controlling elapsed time and narrow range of temporal lags. Here, we introduce a novel behavioral paradigm designed to overcome these limitations. We report that OAs are impaired relative to younger adults at moderate and high temporal lags but not at low lags (where performance approached floor). We evaluated OAs’ ability to benefit from primacy (enhanced order judgment on the first few items of any given sequence) and found two distinct subgroups: one group was on par with young adults [aged-unimpaired (AU)] and the other group was two standard deviations below the mean of young adults [aged-impaired (AI)]. Temporal discrimination performance in AU adults was consistent with a pattern separation deficit, while performance in AI adults was consistent with a generalized temporal processing deficit. We propose that the task introduced is a sensitive marker for episodic memory deficits with age, and may have diagnostic value for early detection of age-related pathology.

New paper: Pattern separation and emotional information

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New paper by graduate student Stephanie Leal. Here she is holding the paper pony!

Leal, S.L., Tighe, S.K., Jones, C.K., Yassa, M.A. (2014) Pattern separation of emotional information in  hippocampal dentate and CA3.Hippocampus DOI:10.1002/hipo.22298.

Abstract:

Emotional arousal, mediated by the amygdala, is known to modulate episodic memories stored by the hippocampus, a region involved in pattern separation (the process by which similar representations are independently stored). While emotional modulation and pattern separation have been examined independently, this study attempts to link the two areas of research to propose an alternative account for how emotion modulates episodic memory. We used an emotional discrimination task designed to tax pattern separation of emotional information by concurrently varying emotional valence and similarity of stimuli. To examine emotional modulation of memory at the level of hippocampal subfields, we used high-resolution fMRI (1.5 mm isotropic) of the medial temporal lobe. Consistent with prior reports, we observed engagement of the hippocampal dentate gyrus (DG) and CA3 during accurate discrimination of highly similar items (behavioral correlate of pattern separation). Furthermore, we observed an emotional modulation of this signal (negative > neutral) specific to trials on which participants accurately discriminated similar emotional items. The amygdala was also modulated by emotion, regardless of the accuracy of discrimination. Additionally, we found aberrant amygdala-hippocampal network activity in a sample of adults with depressive symptoms. In this sample, amygdala activation was enhanced and DG/CA3 activation was diminished during emotional discrimination compared to those without depressive symptoms. Depressive symptom severity was also negatively correlated with DG/CA3 activity. This study suggests a novel mechanistic account for how emotional information is processed by hippocampal subfields as well as how this network may be altered in mood disorders.

Jared Roberts awarded Haycock Memorial Travel Award

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Congratulations to Jared Roberts who was just awarded the John Haycock Memorial Travel Award. The award was established to honor John W. Haycock; friend and mentor to many, and an influential scientist.

John’s family has established a memorial graduate student award named for John in the Center for the Neurobiology of Learning and Memory at UC Irvine. John was a graduate student and received his Ph.D. from UC Irvine before going on to do research and teach at several universities, including The Rockefeller University. The purpose of the John W. Haycock Memorial Graduate Student Travel Award is to provide funding to outstanding graduate students in neuroscience to travel to the annual Society for Neuroscience meeting. This is the most important and informative annual meeting for neuroscientists world-wide, and one that John, himself, greatly enjoyed attending.

Jared will be able to use the award to cover expenses for travel to Washington DC to present his research at the Society for Neuroscience meeting this year. Congrats Jared!

 

Zach Reagh presents his research to Congress!

zach_capitolhillGraduate student Zach Reagh presented his NSF-supported research on Alzheimer’s disease biomarkers to members of Congress at Capitol Hill as part of an effort to increase awareness of the science supported by the National Science Foundation.

New paper: emotion and interference

New paper by Stephanie Leal just published in Neurobiology of Learning and Memory.

Leal, S.L., Tighe, S.K., Yassa, M.A. (2014) Asymmetric effects of emotion on mnemonic interference. Neurobiology of Learning and Memory DOI:10.1016/j.nlm.2014.02.013

Abstract

Emotional experiences can strengthen memories so that they can be used to guide future behavior. Emotional arousal, mediated by the amygdala, is thought to modulate storage by the hippocampus, which may encode unique episodic memories via pattern separation – the process by which similar memories are stored using non-overlapping representations. While prior work has examined mnemonic interference due to similarity and emotional modulation of memory independently, examining the mechanisms by which emotion influences mnemonic interference has not been previously accomplished in humans. To this end, we developed an emotional memory task where emotional content and stimulus similarity were varied to examine the effect of emotion on fine mnemonic discrimination (a putative behavioral correlate of hippocampal pattern separation). When tested immediately after encoding, discrimination was reduced for similar emotional items compared to similar neutral items, consistent with a reduced bias towards pattern separation. After 24 hours, recognition of emotional target items was preserved compared to neutral items, whereas similar emotional item discrimination was further diminished. This suggests a potential mechanism for the emotional modulation of memory with a selective remembering of gist, as well as a selective forgetting of detail, indicating an emotion-induced reduction in pattern separation. This can potentially increase the effective signal-to-noise ratio in any given situation to promote survival. Furthermore, we found that individuals with depressive symptoms hyper-discriminate negative items, which correlated with their symptom severity. This suggests that utilizing mnemonic discrimination paradigms allows us to tease apart the nuances of disorders with aberrant emotional mnemonic processing.

News and Views: Ground Zero in Alzheimer’s Disease, Nature Neuroscience

Our News and Views piece covering the fantastic work by Khan and colleagues in Nature Neuroscience is out in the current issue.

Abstract: New findings in preclinical Alzheimer’s disease patients and mouse models of the disease suggest that it is the lateral, rather than the medial, entorhinal cortex that is most susceptible to tau pathology early in Alzheimer’s disease. Aberrations begin here and spread to other cortical sites. Read the full News and Views here | Original paper

 

Caffeine stimulates memory consolidation: a possible BDNF link

Serra Favila and Brice Kuhl write in Nature Neuroscience News and Views about a possible link between caffeine’s enhancement of memory consolidation and a BDNF-mediated mechanism. Very nice summary and review of our paper. Read their N&V piece here.

 

This is your brain on coffee!

brain_on_coffeeFor lovers of latte art. Enjoy! Thanks to the awesome Michael Richardson of Kéan Coffee in Newport Beach for the latte art, to my wife Manuella Yassa for photography and Craig Stark for editing and post-processing. Framing this one for the lab to celebrate the caffeine paper 🙂

New paper: Post-study caffeine administration enhances memory consolidation in humans – Nature Neuroscience

Our latest work has just been published in Nature Neuroscience. Advance online publication here. Congratulations to Daniel Borota, Liz Murray, Allen Chang, Gizem Keceli, Maria Ly, Joe Watabe and John Toscano for their hard work and collaborative spirit that made this work possible. Read more here.