ICLM Journal Club
This Week
06 February 2015 YOUNG INVESTIGATOR SEMINAR
Time: 09:30 am
Place : Gonda 2nd Floor Conference Room
Title: Dissociable profiles of generalization/discrimination in human hippocampus during visual associative memory retrieval
Speaker: Natalie De Shetler (Rissman Lab)
A number of recent high-resolution functional magnetic resonance imaging (hr-fMRI) studies have identified differential discrimination and generalization responses in hippocampal subfields. The combined CA3 / dentate gyrus (CA3DG) region responds similarly to novel stimuli and close lure images of previously viewed stimuli, a discrimination sometimes equated to pattern separation processes. Conversely, activity in CA1 to these same lure images tends to be comparable with that elicited by repeated stimuli. In a parallel line of research into hippocampal subfield functions, several studies have found that the CA1 region is particularly sensitive to whether events match or mismatch one’s memory-based expectations (e.g., associative novelty). However, the expression of these effects may differ according to whether subjects are explicitly oriented towards the goal of detecting mnemonic targets or whether the detection is incidental. We conducted a hr-fMRI study to determine if the previously described profile of mnemonic discrimination in CA3DG and generalization in CA1 persist in an explicit associative memory recall task. Each trial of our task required subjects to retrieve a previously learned visual associate in response to an arbitrarily paired verbal cue stimulus, hold the retrieved memory in mind for a brief interval, and then evaluate whether a visual probe stimulus was the same, similar, or dissimilar from the studied associate. In both CA3DG and CA1 we found match enhancement effects (same > novel). Consistent with prior work, CA3DG responded comparably to lures and novels (discrimination), and CA1 responded comparably to lures and repeated targets (generalization). Importantly, our results reflect dissociable profiles to task conditions. CA3DG discriminated old from new irrespective of the task relevance context, showing the same degree of match enhancement to all repeated images, regardless of whether they were correctly or incorrectly paired; in contrast, CA1 generalized only for repeated stimuli with correct item pairings, while responding to incorrectly paired repeats as if they were novel stimuli.
About Us
Introduction
The Integrative Center for Learning and Memory (ICLM) is a multidisciplinary center of UCLA labs devoted to understanding the neural basis of learning and memory and its disorders. This will require a unified approach across different levels of analysis, including;
1. Elucidating the molecular cellular and systems mechanisms that allow neurons and synapses to undergo the long-term changes that ultimately correspond to 'neural memories'.
2. Understanding how functional dynamics and computations emerge from complex circuits of neurons, and how plasticity governs these processes.
3. Describing the neural systems in which different forms of learning and memory take place, and how these systems interact to ultimately generate behavior and cognition.
History of ICLM
The Integrative Center for Learning and Memory formally LMP started in its current form in 1998, and has served as a platform for many interactions and collaborations within UCLA. A key event organized by the group is the weekly ICLM Journal Club. For more than 10 years, graduate students, postdocs, principal investigators, and invited speakers have presented on topics ranging from the molecular mechanisms of synaptic plasticity, through computational models of learning, to behavior and cognition. Dean Buonomano oversees the ICLM journal club with help of student/post doctoral organizers. For other events organized by ICLM go to http://www.iclm.ucla.edu/Events.html.
Current Organizers:
Walt Babiec (O'Dell Lab) & Helen Motanis (Buonomano Lab)
Current Faculty Advisor:
Past Organizers:
i) Anna Matynia(Aug 2004 - Jun 2008) (Silva Lab)
ii) Robert Brown (Aug 2008 - Jun 2009) (Balleine Lab)
iii) Balaji Jayaprakash (Aug 2008 - Nov 2011) (Silva Lab)
iv) Justin Shobe & Thomas Rogerson (Dec 2011 - June 2013) (Silva Lab)
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