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Nabavi Group


Nabavi group - Memory formation and consolidation at the synaptic and circuit levels

The Nabavi group is focusing on how plasticity at the synaptic and circuit levels in the brain relates to behavioral plasticity (learning and memory formation) and how the newly formed memories are integrated into the existing network (cellular and systems consolidation) using rodents as model organism.

Research focus

The idea that changes in synaptic strength (synaptic plasticity) is the foundation of memory and learning has a long history. For this reason long term potentiation (LTP) and long term depression (LTD), the electrophysiological manifestations of synaptic plasticity, have been intensely studied. However, the proof of causality, that by changing synaptic strength one can remove and reinstate a memory, had been missing.

In our recent paper we provided the most direct evidence showing a cause-effect relation between synaptic plasticity and memory formation (Nabavi et al., 2014, Nature). With the use of optogenetics fortified by in vitro/in vivo recording and behavioral assays we generated an associative memory and showed that we could repeatedly turn off and on this associative memory simply by inducing LTD and LTP (see the figure).

An immediate question following this study is how these newly formed memories are integrated into the existing network. This is a vital concern for any system that aims to store and retrieve information. Our brain is continuously exposed to external sensory inputs. This amount of information can overwhelm any storage device no matter how large its capacity. Therefore, a challenge for our brain is to decide which information is worthy of permanent storage. The storage process itself, however, poses another challenge: how to integrate new information into a network of pre-existing memories without “catastrophic interference” (forgetting).

The first challenge is commonly known as synaptic consolidation, which takes place within the first minutes to hours after memory formation. The second challenge, known as systems consolidation, is a slower process that takes weeks, months or even years. The major focus of my research is to understand how our brain tackles these challenges. To this end we will use a combination of tools such as molecular biology, in vitro and in vivo electrophysiology, two-photon laser scanning microscopy, optogenetics, behavioral analysis (i.e. whatever it takes) to move forward.

These studies may lead us to better understand and treat better neuropsychological diseases thought to be related to aberrations in synaptic plasticity, such as posttraumatic stress disorder, schizophrenia, substance abuse disorders and dementia.

a) Fear conditioning with optogenetics. Diagram of rat’s fear memory circuit receiving optogenetically driven input stimulation (laser) paired with a shock (left). Animal is tested one day later (right) by optical activation of the input (blue). Time plot shows normalized number of lever presses (1 min bins) to a previously learned cued lever-press task. b) LTD inactivates memory. In vivo field response in lateral amygdala to single optical stimulus (left) before and after LTD induction (1Hz). Animal is tested one day later (right). c) LTP reactivates memory. Same as b) except animal receives an LTP protocol (100Hz).

News

Previous news from the research group

News

2019.09.20 | People

Randi Hald Melsen continues in Sadegh Nabavi's group as laboratory assistent

Randi Hald Melson continues as laboratory assistant in Sadegh Nabavi's research group, being the maternity cover for laboratory technician Kathrine M. Christensen from mid September 2019 until Kathrine is back.

2019.08.21 | SadeghNabavi

The latest 'Behind the Scenes' profile features Dr Sadegh Nabavi, Group Leader at DANDRITE

Nabavi’s group focuses on memory formation and consolidation at the synaptic and circuit levels. Recently, Dr. Sadegh Nabavi had his group leader position extended for a further four years. In our latest Behind the Scenes article, Dr Nabavi discusses his research and his curiosity and passion for neuroscience.

2019.08.20 | SadeghNabavi

João Lima is prolonged as Postdoc in Sadegh Nabavis group

João Lima will be staying at DANDRITE in Sadegh Nabavis group. He has been prolonged as Postdoc starting the 20th of August on Sadegh Nabavis DFF Grant.

Group Leader Sadegh Nabavi

2019.07.05 | Research news

Congratulations to Sadegh Nabavi, who has had his Group Leader extension approved

The Executive Board of DANDRITE has approved the recommendations from Sadegh’s Assessment Committee to extend his employment at DANDRITE for additional four-year period until 2024.

2019.02.04 | People

Welcome to new PhD student Valentina Khalil

Valentina Khalil has been accepted as PhD student starting 1. February 2019 in Group Leader Sadegh Nabavi's group. Valentina will be investigating the neural circuits implicated in the visual-evoked innate fear.

2018.08.23 | People

João Lima is new Postdoc in Nabavi Group

João will investigate the plasticity rules that underlie attention-dependent forms of associative learning at the cellular and circuit levels, in mice. The project is multidisciplinary and will involve extracellular and intracellular recordings, calcium imaging, optogenetics, and behavioural training of animals. Furthermore than working in Nabavi…

2018.06.21 | People

Emma Johannsen is new shared Student Assistant in Yonehara, Denham and Nabavi Group

Emma is a new student assistant shared between Mark Denham, Keisuke Yonehara and Sadegh Nabavi. She will mainly be handling autoclavation in connection to class2 labs. Emma is studying Molecular Medicine on her 4th semester. 

2018.04.03 | Research news

Official Inauguration of PROMEMO on 4 April 2018

The official inauguration of PROMEMO - Center for Proteins in Memory - a Danish National Research Foundation Center of Excellence will take place on 4 April 2018. The research center PROMEMO started on 1 December 2017 and aims to identify and understand the function of memory associated proteins that determines the persistence of a memory.

2018.03.15 | People

Nehal Hassan is new Research Assistant in Nabavi Group

Nehal is new Research Assistant in Sadegh Nabavi's group from March 10th. She will join the investigation of neural circuits in aversive memories and will be supporting various lab members in their projects.

2018.03.02 | Awards

Nabavi lab received 2,000,000 DKK from Lundbeckfonden & NIH BRAIN Initiative for the project “Independent optical excitation of overlapping neural populations in behaving animals”.

In the last decade, optogenetic techniques, particularly light-gated ion channels, have been a transformational tool. They are powerful enough to manipulate a single neuron in behaving animals, and yet simple enough to be adapted by laboratories of diverse expertise. Light-gated ion channels come in different varieties, with blue and red-shifted…

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