Difference between revisions of "ICLM Journal Club"

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(This Week - 11 February 2022 (9:30 a.m., via Zoom))
(This Week - 18 February 2022 (9:30 a.m., via Zoom))
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=<font color="blue">'''This Week - 18 February 2022 (9:30 a.m., via Zoom)'''</font>=
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=<font color="blue">'''This Week - 11 March 2022 (9:30 a.m., via Zoom)'''</font>=
  
<u>Speaker:</u> '''Saray Soldado Magraner '''
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<u>Speaker:</u> '''Ayal Lavi '''
  
<u>Title: </u> ''' “ What is the dynamic regime of the cerebral cortex?  ” '''
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<u>Title: </u> ''' “ A retrograde mechanism coordinates recruitment of memory ensembles across brain regions. ” '''
  
<u>Blurb: </u> In which regime does the cerebral cortex operate? This is a fundamental question for understanding cortical function. Decades of theoretical and experimental studies have converged into a model where strong recurrent excitation--unstable by itself--is balanced by recurrent inhibition. Circuits operating in this regime are known as Inhibition Stabilized Networks (ISN). However, it has been unclear whether the cortex operates as an ISN 'by default' or just under certain circumstances (for example, under strong sensory input). In this talk, I will introduce what ISN are and how we can prove them experimentally. I will then present the most compelling experimental study to date supporting that ISN may be the default dynamic regime of the cortex.
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<u>Summary:</u> Memories are stored in ensembles of neurons in different brain regions. However, it is unclear whether and how the allocation of a memory to these ensembles is coordinated across brain regions. To address this question, we developed a novel approach that uses CREB expression to bias memory allocation in one brain region, and rabies retrograde tracing to study memory allocation in connected presynaptic neurons in other brain regions. Together with mathematical simulations, this approach revealed a universal retrograde mechanism that coordinates the recruitment of memory ensembles across cortical and subcortical regions, and in multiple behavioral paradigms, including conditioned taste aversion and auditory fear conditioning. We leveraged this retrograde mechanism to increase memory ensemble connectivity between brain regions, and show that this enhanced memory. These results uncovered a novel retrograde mechanism that coordinates the recruitment of memory ensembles across brain regions, and demonstrate its importance for memory formation.
  
<u>Summary:</u> Many cortical network models use recurrent coupling strong enough to require inhibition for stabilization. Yet it has been experimentally unclear whether inhibition-stabilized network (ISN) models describe cortical function well across areas and states. Here, we test several ISN predictions, including the counterintuitive (paradoxical) suppression of inhibitory firing in response to optogenetic inhibitory stimulation. We find clear evidence for ISN operation in mouse visual, somatosensory, and motor cortex. Simple two-population ISN models describe the data well and let us quantify coupling strength. Although some models predict a non-ISN to ISN transition with increasingly strong sensory stimuli, we find ISN effects without sensory stimulation and even during light anesthesia. Additionally, average paradoxical effects result only with transgenic, not viral, opsin expression in parvalbumin (PV)-positive neurons; theory and expression data show this is consistent with ISN operation. Taken together, these results show strong coupling and inhibition stabilization are common features of the cortex.
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<u>Relevant papers:</u>  https://www.biorxiv.org/content/10.1101/2021.10.28.466361v1
 
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<u>Relevant papers:</u>  https://elifesciences.org/articles/54875
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https://www.nature.com/articles/s41583-020-00390-z
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https://www.sciencedirect.com/science/article/pii/S0896627321005754
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='''About Us'''=
 
='''About Us'''=

Revision as of 06:58, 9 March 2022

This Week - 11 March 2022 (9:30 a.m., via Zoom)

Speaker: Ayal Lavi

Title: “ A retrograde mechanism coordinates recruitment of memory ensembles across brain regions. ”

Summary: Memories are stored in ensembles of neurons in different brain regions. However, it is unclear whether and how the allocation of a memory to these ensembles is coordinated across brain regions. To address this question, we developed a novel approach that uses CREB expression to bias memory allocation in one brain region, and rabies retrograde tracing to study memory allocation in connected presynaptic neurons in other brain regions. Together with mathematical simulations, this approach revealed a universal retrograde mechanism that coordinates the recruitment of memory ensembles across cortical and subcortical regions, and in multiple behavioral paradigms, including conditioned taste aversion and auditory fear conditioning. We leveraged this retrograde mechanism to increase memory ensemble connectivity between brain regions, and show that this enhanced memory. These results uncovered a novel retrograde mechanism that coordinates the recruitment of memory ensembles across brain regions, and demonstrate its importance for memory formation.

Relevant papers: https://www.biorxiv.org/content/10.1101/2021.10.28.466361v1

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:

Megha Sehgal (Silva Lab) & Giselle Fernandes (Silva Lab). Please email us at iclm.journalclub@gmail.com if you would like to get regular updates regarding our journal club and weekly reminders.

Current Faculty Advisor:

Dean Buonomano


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)

vii) Helen Motanis (Buonomano Lab) & Shonali Dhingra (Mehta Lab) (2017-2018)

viii) Shonali Dhingra (Mehta Lab) (2018-2020)

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