In this episode, we’re joined by Dr. Niels Niethard from the University of Tübingen to explore what sleep looks like at the level of cortical microcircuits — and how excitation and inhibition are dynamically reconfigured across brain states.

Niels walks us through how excitatory pyramidal neurons interact with distinct inhibitory interneuron populations, including somatostatin (SST) and parvalbumin (PV) cells. We discuss how these cell-type-specific interactions shift from wakefulness to non-REM sleep and into REM, creating fundamentally different circuit configurations across sleep stages.

We discuss how sleep spindles, slow oscillations, and REM sleep each create distinct configurations of dendritic and somatic inhibition. Niels explains how spindle timing relative to slow oscillation peaks influences synaptic plasticity and how these processes support selective memory consolidation.

The conversation also touches on his work on synaptic downscaling in cortical and hypothalamic networks, the potential link between AMPA receptor regulation and sleep pressure, and how sleep interacts with feeding-related circuits and metabolic state in mice.

This episode offers a detailed, cell-type-specific perspective on how excitation and inhibition are balanced across sleep stages, revealing the microcircuit mechanisms underlying memory, synaptic downscaling, and brain homeostasis.

Find out more about Dr. Niethard’s lab and see relevant publications below:

• Cortical circuit activity underlying sleep slow oscillations and spindles. PNAS, 2018
• Slow-wave sleep drives sleep-dependent renormalization of synaptic AMPA receptor levels in the hypothalamus. PLOS Biolology, 2024
• Cell-type specific dynamics of calcium activity in cortical circuits over the course of slow wave sleep and rapid eye movement sleep. Journal of Neuroscience, 2021

Check out our NaPS website to find out more about the podcast, our research and events.

This recording is the property of the Sleep Science Podcast and not for resale.

We've gathered the NaPS lab to answer all your fascinating questions on all things sleep! A perfect bitesize episode to get stuck into the marvellous world of sleep.

1. How does sleep deprivation affect mental health? - Answered by Martha Wawrzuta

• Bunney, B. G. , Bunney, W. E. (2013). Mechanisms of Rapid Antidepressant Effects of Sleep Deprivation Therapy: Clock Genes and Circadian Rhythms. Biological Psychiatry
• Fang, H., Tu, S., Sheng, J., Shao, A. (2018). Depression in sleep disturbance: A review on a bidirectional relationship, mechanisms and treatment. Journal of Cellular and Molecular Medicine

2. What is narcolepsy? - Answered by Kyrillos Meshreky

• Leschziner G., Narcolepsy: a clinical review, Practical Neurology 2014;14:323-331

3. Does the full moon affect sleep? - Answered by Al Saqib Majumder

• Casiraghi, L. et al. (2021). Moonstruck sleep: Synchronization of human sleep with the moon cycle under field conditions.
• Chaput, J. P. et al. (2016). Are Children Like Werewolves? Full Moon and Its Association with Sleep and Activity Behaviors in an International Sample of Children. Sleep Medicine

4. How does a smart watch track sleep? - Answered by Yan Wang

5. What is orthosomnia? - Answered by Sophie Smith

• Baron, K.G., et al. (2017) Orthosomnia: Are some patients taking the quantified self too far? J Clin Sleep Med

6. What is sleep regression and how long does it last? - Answered by Mo Abdellahi

• Weinraub, M. et al. (2012). Patterns of developmental change in infants' nighttime sleep awakenings from 6 through 36 months of age. Developmental Psychology
• Bruni O. et al. (2014) Longitudinal study of sleep behavior in normal infants during the first year of life. J Clin Sleep Med

7. Does Magnesium Citrate help you sleep? - Answered by Dulni Peramunugamage

• Magnesium for sleep, Sleep Foundation, 2025

8. Does dark chocolate help you sleep? - Answered by Martha Nguyen

• Abdoli, E. et al. (2024). A clinical trial of the effects of cocoa rich chocolate on depression and sleep quality in menopausal women. Scientific reports,
• Garbarino, S., Garbarino, E., & Lanteri, P. (2022). Circadian Rhythm, Mood, and Temporal Patterns of Eating Chocolate: A Scoping Review of Physiology, Findings, and Future Directions. Nutrients

Music by Sergio Prosvirini from Pixabay

Check out our NaPS website to find out more about the podcast, our research and events.

This recording is the property of the Sleep Science Podcast and not for resale.

In this episode, we welcome neuroscientist Michele Bellesi from the University of Camerino to explore the fascinating world of glial cells and their dynamic role in sleep.

Michele guides us through the four types of glial cells:

• Astrocytes: Regulators of synaptic function and help form the blood brain barrier (BBB)
• Oligodendrocytes: Crucial for myelination and fast signal transmission
• Microglia: The brain's immune sentinels, important for responding to infection and injury as well as shaping the synaptic landscape
• Ependymal Cells: Involved in cerebrospinal fluid (CSF) production and CFS movement around the brain

We dive into how each of these cells types behaves differently across wake, sleep and sleep deprivation and the impacts on each cell types function.

Find out more about Michele's work here and see relevant papers below.

• The role of sleep and wakefulness in myelin plasticity, 2019, Glia
• Sleep loss promotes astrocytic phagocytosis and microglial activation in mouse cerebral cortex, 2017, Journal of Neuroscience
• Effects of sleep and wake on astrocytes: clues from molecular and ultrastructural studies, 2015, BMC Biology

Check out our NaPS website to find out more about the podcast, our research and events.

This recording is the property of the Sleep Science Podcast and not for resale.

Can sleep help us unlearn biases and make our memories more positive?

Implicit biases are unconscious stereotypes that influence our judgments and decisions - like assuming a particular gender for a specific job role. But what if we could change these biases?

In this episode, we explore how manipulations of sleep might help reshape our implicit attitudes. We speak with Professor Xiaoqing Hu, a leading researcher in the use of Targeted Memory Reactivation (TMR) during sleep to alter implicit bias and make memories more positive. Xiaoqing shares his journey of applying Implicit Association Tasks (IATs) to sleep research, and how conflict biases, congruent vs. incongruent data, and task design play a role in measuring and modifying bias.

We also dive into the nitty gritty of memory consolidation in sleep — examining how REM and NREM stages contribute to emotional memory consolidation, and how recency vs. saliency affects which memories get updated.

Prof. Hu discusses his groundbreaking study demonstrating the ability to update unwanted emotional memories during sleep, and we explore the potential for applying this research to clinical populations. We also consider how individual schemas might influence the effectiveness of TMR across different people.

If you would like to find out more about Prof. Hu's work, please see the lab website here. You can find relevant papers below:

• Unlearning implicit social biases during sleep, 2015
• Updating memories of unwanted emotions during human sleep, 2022
• Targeted memory reactivation during sleep influences social bias as a function of slow-oscillation phase and delta power, 2023
• Reactivating cue approached positive personality traits during sleep promotes positive self-referential processing, 2024
• Aversive memories can be weakened during human sleep via the reactivation of positive interfering memories. 2024
• Disarming emotional memories using Targeted Memory Reactivation during Rapid Eye Movement sleep, 2024
• Targeted memory reactivation in REM but not SWS selectively reduces arousal responses, 2021

Glossary

IAT - Implicit Association Task - a test used to measure the strength of automatic associations between our concepts that we may not be consciously aware of.

TMR - Targeted Memory Reactivation - A technique used to modify memory processing, through the use of presenting cues (audio or smell) that were associated with learning, whilst a person sleeps. These cues can modify select memories and in recent research is being used in emotional memory.

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Host Professor Penny Lewis

Produced by Sophie Smith

Check out our NaPS website to find out more about the podcast, our research and events.

This recording is the property of the Sleep Science Podcast and not for resale.

We're joined by Hongi Ngo, who developed a revolutionary technique for manipulating sleep oscillations during his PhD. Closed-loop Auditory Stimulation (CLAS), which uses bursts of pink noise which are carefully timed to a particular phase of an existing brain oscillation to either boost or dampen the target oscillation. It has been used to selectively strengthen or weaken memories, improve the immune response, reduce epileptic seizures, and even potentially to slow down age related cognitive decline.

Hongi tells us how he got got the idea for CLAS, explains how it works, and tells us about some of his existing studies. He talks about combining CLAS with Targeted Memory Reactivation (TMR) and discusses the ideas for future of brain modulation methods with techniques such as transcranial magnetic stimulation (TMS).

Some of the key papers discussed are:

Auditory closed-loop stimulation of the sleep slow oscillation enhances memory (2013)

Auditory closed-loop stimulation of EEG slow oscillations strengthens sleep and signs of its immune-supportive function (2017)

Thalamic spindles promote memory formation during sleep thrugh triple phase-locking of cortical, thalamic and hippocampal rhythms (2017)

Examining the optimal timing for closed-loop auditory stimulation of slow-wave sleep in young and older adults (2019)

Auditory stimulation during sleep suppresses spike activity in benign epilepsy with centrotemporal spikes (2021)

Shaping overnight consolidation via slow-oscillation closed-loop targeted memory reactivation (2022)

Check out our NaPS website to find out more about the podcast, our research and events.

This recording is the property of the Sleep Science Podcast and not for resale.

How are memories represented in the brain and how can we model this?

Professor Anna Schapiro from University of Pennsylvania as we discuss her work on computational modelling of sleep and memory. In this episode, we discuss several kinds of Neural Network models as well as diving into the history of Jay McClleland's Complementary Learning Systems theory and Anna's recent work on combining neural network modeling with EEG.

Find out more about Anna Schapiro and her research group here.

Links to articles discussed in this episode:

• Why there are Complementary Learning Systems in the hippocampus and neocortex
• Methods for reducing interference in the Complementary Learning Systems model
• Self-recovery of memory via generative replay
• A unifying account of reply as context-driven memory reactivation

Host: Penny Lewis
Editor: Sophie Smith

Check out our NaPS website to find out more about the podcast, our research and events.

This recording is the property of the Sleep Science Podcast and not for resale.

How does our sleep change as we age and what could this mean for memory and cognition?

In this episode, we discuss with Professor Rebecca Spencer her research exploring how our sleep patterns evolve over the course of our lives.

We explore the phenomenon of infantile amnesia - why we can't remember our earliest childhood experiences - and unpack the theories behind it. We discuss how hippocampal development changes as we age and how this links to memory consolidation and sleep. We also dive into Rebecca's work on emotional processing in children and how naps and sleeping are able to aid in emotional regulation.

Rebecca runs the Somneuro Lab at the University of Massachusetts Amherst. Find out more about Rebecca and her research group here.

Links to studies in the episode:

• Napping reduces emotional attention bias during early childhood
• Unhealthy diet is associated with poor sleep in preschool-aged children
• Television use and its effects on sleep in early childhood

Host: Professor Penny Lewis

Editor: Sophie Smith

Check out our NaPS website to find out more about the podcast, our research and events.

This recording is the property of the Sleep Science Podcast and not for resale.

In this deep dive episode, we look at how sleep onset can help creativity.

With our amazing guest speakers, Professor Bob Stickgold, Dr Adam Horowitz, Professor Delphine Oudiette and Dr Celia Lacaux, we take a look at their work on creativity, dreams and N1 sleep.

Together, we discuss different definitions of creativity, what defines N1 and what it is about N1 that makes it prime time for creative processing.

Find out more about our guest speakers:

• Professor Bob Stickgold
• Dr Adam Horowitz
• Professor Delphine Oudiette
• Dr Celia Lacaux

Papers from the episode:

• Sleep onset is a creative sweetspot
• Replaying the Game: Hypnagogic Images in Normals and Amnesics
• Dormio: A targeted dream incubation device

Host: Professor Penny Lewis
Editor: Sophie Smith

Check out our NaPS website to find out more about the podcast, our research and events.

This recording is the property of the Sleep Science Podcast and not for resale.