ICLM Journal Club
This Week - 23 March 2018 (9:30 a.m., Gonda 2nd Floor Conference Room)
Speaker: Jiannis Taxidis
Title: Hippocampal Spiking Sequences encoding odors and time during working-memory activation
Abstract: Neuronal spiking sequences are a candidate mechanism for the brain to retain information in memory for short time periods. Studies suggest that the hippocampus is involved in working-memory tasks by encoding time through such temporal sequences. But the circuit mechanisms underlying these population dynamics are not well understood. What type of information do these sequences encode? How do they adjust to increasing memory load and how stable are they across multiple days? Are they causally linked to working-memomory? I will be presenting our work which addresses these questions through in vivo two-photon calcium imaging and optogenetic manipulation of hippocampal area CA1 in head-fixed mice while they are performing an olfactory working-memory task. We have observed ‘odor-cells’ that were active during the presentation of specific odor stimuli and ‘delay- cells’ that were active during specific time points of the delay following odor stimuli. These neurons were spatially intermingled and, collectively, formed odor-specific temporal spiking sequences encoding both time and odor-identity while working-memory is activated. By tracking the same cells over days or by extending the memory load within a recording session, we found that these sequences were partly reshaped. Odor-representation remained stable whereas delay-cells remapped their activity shifting their fields backward or forward in time, revealing a dynamic time-representation. Finally, disrupting these sequences optogenetically during learning of the task, revealed the importance of entorhinal inputs that shape such dynamics. This work indicates that two different neural codes coexist in CA1. A stable stimulus-driven one and an internally-generated unstable one encoding task-relevant time. Untangling the properties and mechanisms that generate and sustain these two representations is crucial for understanding the emergence of any population encoding in the hippocampus and its role in memory formation.
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:
Shonali Dhingra & Helen Motanis
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)
v) Walt Babiec (O'Dell Lab) (2013-2014)
vi) Walt Babiec (O'Dell Lab) & Helen Motanis (Buonomano Lab) (2014-2017)
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