Rajat Saxena
rajatsxn.bsky.social
Rajat Saxena
@rajatsxn.bsky.social
Neural correlates of learning and memory.
Postdoc @ Moser lab, NTNU
PhD @ McNaughton lab, UCIrvine
(Prev: IISc Bangalore, BITS Pilani)
Reposted by Rajat Saxena
Neuroscience projects last several years, and you are usually a bit jaded by the time you wrap it up. Not this one– spending several months on an island in the middle of nowhere, away from all the craziness of the world reminds you how beautiful the world really is.

www.youtube.com/watch?v=46sv...
Bat Island: The New Era of Science
YouTube video by Weizmann Institute of Science
www.youtube.com
October 17, 2025 at 7:07 AM
Reposted by Rajat Saxena
I’m pleased to share our new paper, “Hippocampal ripple diversity organizes neuronal reactivation dynamics in the offline brain”, out in @cp-neuron.bsky.social !

With @vitorlds.bsky.social and David Dupret, we show that diversity in ripple current profiles shapes reactivation dynamics
October 2, 2025 at 3:46 PM
Reposted by Rajat Saxena
1/8
How can the brain create countless unique memories using a single, universal metric of space? We’ve been waiting for the answer to this for two decades!
Read it here:
www.biorxiv.org/content/10.1...
September 25, 2025 at 4:15 AM
Reposted by Rajat Saxena
1/5 How does the brain turn the low-dimensional, universal grid cell metric into the rich, diverse codes needed for memory in hippocampal place cells? 🧵
Preprint link 👇

www.biorxiv.org/content/10.1...
Functional independence of entorhinal grid cell modules enables remapping in hippocampal place cells
A systems-level understanding of cortical computation requires insight into how neural codes are transformed across distinct brain circuits. In the mammalian cortex, one of the few systems where such ...
www.biorxiv.org
September 25, 2025 at 4:06 AM
Reposted by Rajat Saxena
1/
🚨 New preprint! 🚨

Excited and proud (& a little nervous 😅) to share our latest work on the importance of #theta-timescale spiking during #locomotion in #learning. If you care about how organisms learn, buckle up. 🧵👇

📄 www.biorxiv.org/content/10.1...
💻 code + data 🔗 below 🤩

#neuroskyence
September 17, 2025 at 7:33 PM
Reposted by Rajat Saxena
🚨New preprint alert!

The thalamus has long been seen as a relay of sensory signals to cortex.
But could it also generate its own structured activity?
Our study explores this question in the head-direction (HD) system.

Some explanation 🧵👇 1/13

www.biorxiv.org/content/10.1...
Coherent dynamics of thalamic head-direction neurons irrespective of input
While the thalamus is known to relay and modulate sensory signals to the cortex, whether it also participates in active computation and intrinsic signal generation remains unresolved. The anterodorsal...
www.biorxiv.org
September 16, 2025 at 3:56 PM
Reposted by Rajat Saxena
Thrilled to share that our work is now published in Science! ✨

We found a preference for visual objects in the mouse spatial navigation system where they dynamically refine head-direction coding. In short, objects boost our inner compass! 🧭

www.science.org/doi/10.1126/...

🧵1/
September 11, 2025 at 8:14 PM
Check our new preprint where we examine how enriched experiences alter synaptic connectivity and coding sparsity across the neocortex.
Enriched experience increases reciprocal synaptic connectivity and coding sparsity in higher-order cortex https://www.biorxiv.org/content/10.1101/2025.09.01.673156v1
September 3, 2025 at 2:14 PM
Reposted by Rajat Saxena
This is a super interesting paper from Bruce McNaughton’s lab, showing why we should study behavior in the context of natural/ecological environments. They show that living in enriched complex environments, prior to task performance, affects both behavior and the underlying neural activity.
Environmental enrichment accelerates cortical memory consolidation bioRxivpreprint
Environmental enrichment accelerates cortical memory consolidation
Environmental enrichment is an established strategy to enhance learning and to build resilience against neurodegeneration. In humans, this is known as cognitive reserve. Though the beneficial effects of exposure to a complex environment in animal models have been well-documented by behavioural, immunohistological and morphological observations, its impact on the functional properties of neuronal populations remains poorly understood. This study aimed to compare the functional encoding and offline memory retrieval dynamics of cortical neurons in enriched and control mice performing a virtual spatial foraging task. Thy1-GCaMP6s mice aged 21 days were enriched for 9 weeks by running a complex obstacle course, during which they were gradually exposed to many different types of obstacles requiring climbing, jumping, and/or balancing elements. Control animals were exercise-matched by running a similar track containing only repeating ramps. At the age of 3 months, two-photon calcium imaging was conducted on populations of neurons from the secondary motor cortex in both groups before, during, and after repeated locomotion through a virtual environment with salient visual-tactile cues. We observed an increase in memory reactivation in the enriched group during the first day of exposure. With training, enriched animals exhibited a stronger anticipatory reduction in running speed near the reward location. Moreover, cortical neuron activity representing locations on the track became substantially more stable and precise over days in enriched but not control animals. Altogether, these results indicate that prior environmental enrichment accelerates the consolidation of stable and task-relevant memory representations in the cortex for a novel task, and enables faster and more robust acquisition of new sequence representations.
dlvr.it
August 3, 2025 at 7:55 PM
Reposted by Rajat Saxena
When neurons change, but behavior doesn’t: Excitability changes driving representational drift

New preprint of work with Christian Machens: www.biorxiv.org/content/10.1...
Representational drift without synaptic plasticity
Neural computations support stable behavior despite relying on many dynamically changing biological processes. One such process is representational drift (RD), in which neurons' responses change over ...
www.biorxiv.org
July 29, 2025 at 2:02 PM
Reposted by Rajat Saxena
In many brain areas, neuronal tuning is heterogeneous. But how does this diversity help behavior? We show how tuning diversity shapes representational geometry and boosts coding efficiency for perception in our new preprint: www.biorxiv.org/content/10.1...
(w/ @sueyeonchung.bsky.social&Tony Movshon)
Variations in neuronal selectivity create efficient representational geometries for perception
Our visual capabilities depend on neural response properties in visual areas of our brains. Neurons exhibit a wide variety of selective response properties, but the reasons for this diversity are unkn...
www.biorxiv.org
June 29, 2025 at 12:19 AM
Reposted by Rajat Saxena
A new study led by @timothysit.bsky.social reveals that different layers of mouse V1 integrate visual and non-visual signals differently.

Activity is dominated by vision (or spontaneous fluctuations) in L2/3 and by movement in L5. This leads to different geometries.
www.biorxiv.org/content/10.1...
July 18, 2025 at 4:55 PM
Reposted by Rajat Saxena
I'm pleased to share our new work, “Spatio-temporal organization of network activity patterns in the hippocampus”, out in @cp-cellreports.bsky.social !
With Demi Brizee & David Dupret, we track how oscillations and spiking behaviour map onto hippocampal layers using an LFP-based embedding.

(1/13)
June 5, 2025 at 5:10 PM
Reposted by Rajat Saxena
Our collaboration - from PhD work - examining input-specific (EC L3) contributions to rate and temporal coding in CA1 place cells is now out in @natcomms.nature.com 🔬🧠

rdcu.be/evWtz
Direct entorhinal control of CA1 temporal coding
Nature Communications - Temporal coding in the hippocampus is thought to be key for memory and predictions. Here, the authors show that blocking one entorhinal input affects two aspects of...
rdcu.be
July 12, 2025 at 5:09 PM
Reposted by Rajat Saxena
Super excited to see this paper from Armin Lak & colleagues out! (I've seen @saxelab.bsky.social present it before.)

www.cell.com/cell/fulltex...

tl;dr: The learning trajectories that individual mice take correspond to different saddle points in a deep net's loss landscape.

🧠📈 🧪 #NeuroAI
Dopamine encodes deep network teaching signals for individual learning trajectories
Longitudinal tracking of long-term learning behavior and striatal dopamine reveals that dopamine teaching signals shape individually diverse yet systematic learning trajectories, captured mathematical...
www.cell.com
July 10, 2025 at 6:29 PM
Reposted by Rajat Saxena
Our study is out in Nature!
Using wireless Neuropixels we recorded hippocampal activity in freely flying bats and uncovered replay and theta(less) sweeps, revealing striking differences from classic rodent models.

👉 www.nature.com/articles/s41...
Replay and representation dynamics in the hippocampus of freely flying bats - Nature
Nature - Replay and representation dynamics in the hippocampus of freely flying bats
www.nature.com
July 9, 2025 at 3:08 PM
Reposted by Rajat Saxena
Do you do Neuropixel recordings and are you struggling with preprocessing? The Power Pixels pipeline is an easy-to-use pipeline from raw data to neural activity of single neurons in specified brain regions 🧠 Now on bioRxiv!
www.biorxiv.org/content/10.1...
Power Pixels: a turnkey pipeline for processing of Neuropixel recordings
There are many open-source tools available for the processing of neuronal data acquired using Neuropixels probes. Each of these tools, focuses on a part of the process from raw data to single neuron a...
www.biorxiv.org
July 1, 2025 at 9:48 AM
Our work with Maxim Bazhenov's group showing interleaved replay of new and old memories within individual Up states using a combination of biophysical modeling and electrophysiology experiments.
Interleaved Replay of Novel and Familiar Memory Traces During Slow-Wave Sleep Prevents Catastrophic Forgetting https://www.biorxiv.org/content/10.1101/2025.06.25.661579v1
June 30, 2025 at 8:25 AM
Reposted by Rajat Saxena
Your brain doesn’t just passively track time ⏳ - it structures it.
In @Science.org we show that activity in 🧠 memory circuits (LEC) drifts constantly, but makes sharp jumps at key moments, segmenting life into meaningful events. (1/2)

👉 www.science.org/doi/10.1126/...
Event structure sculpts neural population dynamics in the lateral entorhinal cortex
Our experience of the world is a continuous stream of events that must be segmented and organized at multiple timescales. The neural mechanisms underlying this process remain unknown. In this work, we...
www.science.org
June 26, 2025 at 6:06 PM
Reposted by Rajat Saxena
Our new paper out now in Science explores how neural activity in the lateral entorhinal cortex (LEC) *drifts* over time - and *jumps* at key boundaries - to help organize events in memory.

🔗 www.science.org/doi/10.1126/...

Here's a quick summary of what we found 🧵👇
June 26, 2025 at 6:15 PM
Reposted by Rajat Saxena
Your brain learns for you even when you're not actively learning. Maybe. (in mice).
🚶Aimlessly wandering around a city or exploring the new mall may seem unproductive, but new research led by @zh0ng0.bsky.social @marius10p.bsky.social @computingnature.bsky.social suggests it could play an important role in how our brains learn.‬‬ 🧠
🔗 www.janelia.org/news/zoning-...
June 24, 2025 at 12:15 AM
Reposted by Rajat Saxena
Kilosort4 detects a LOT of neurons, I recorded 15k neurons in one year 🤯 Traditionally, one would curate these detected units to see if they are well isolated single neurons. This is not feasible anymore, so today let's look at three options that are out there to automate this process! 🤖👇
March 27, 2025 at 10:38 AM
Reposted by Rajat Saxena
Over the past few years, I’ve shared my personal journey as a sleep scientist living with sleep apnea with other scientists and students to raise awareness and reduce stigma. I’m excited to reach an even broader audience in my recent interview with Parade 🎉

parade.com/health/i-fel...
I Fell Asleep While Driving, Which Led to This Diagnosis
This health condition is often overlooked in women.
parade.com
May 5, 2025 at 9:49 PM
Reposted by Rajat Saxena
As I transition over to Bluesky I have to plug our new #book. If you haven't already, check out the 2nd edition of The #Hippocampus Book!

academic.oup.com/book/59509?s...
The Hippocampus Book
Abstract. The Hippocampus Book investigates the structure, function and pathology of the hippocampus and related cortical areas. It highlights the importan
academic.oup.com
April 26, 2025 at 4:27 AM