Exploring the complexity of neural dynamics…

FunSy seminars are open to everybody and hybrid, on Zoom or in person at LNCA (University of Strasbourg). They cover a large range of topics (systems neuroscience, learning and memory, cognition and behavior, brain function and dysfunction…) and approaches (electrophysiology, imaging, computational modelling and theory…).

All presentations take place on Wednesdays at 14h30 (Strasbourg time) and are followed by ample time for questions and discussions. We will also publish some of the talk videos for offline viewing.

Where? At College Doctoral Europeen (CDE) building, 46 boulevard de la Victoire – 67000 Strasbourg

Also on Zoom! Registration compulsory at this page (to get a personal link valid for all talks)

Fall 2023 FunSy seminars series … coming soon!

Organizer: Dr. Samy Castro

Spring 2023 (past) FunSy seminars (& videos !)

July 5th 2023 – Ingrid Bethus

Université de la Côte d’Azur / NeuroMod, Nice

Coding dynamics of the striatal networks during learning

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During learning process, it is commonly believed that the goal directed behaviour, is sustained by the activity of the dorsomedial portion of the striatum – DMS, whereas the activation of the dorsolateral striatum – DLS – sustains inflexible motor routines, stimulus-response learning and more generally habit behaviour. However, this DMS-DLS functional dissociation is mainly observed in instrumental conditioning, but it is less straightforward in non-instrumental learning. In this study we aimed at investigating this issue using a spontaneous alternation task with no cue-guided instruction, thus limiting experimentally-defined discrete actions that possibly influence ‘task bracketing’ activity. DMS and DLS single neuron activity was recorded from the first day rats 81 were exposed to the task until they reached and maintained stable performance. To decode animal behaviour from neural activity we used classical analyses based on either firing rate or neural synchronization, but we also combined the two measures using Hawkes process to reconstruct directed connectivity graphs of neurons. This approach enabled us to better unravel the coding capacity of both regions in the course of learning. We showed that DMS and DLS display different task-related activity throughout learning stages. The proportion of DMS coding neurons decreases whereas the number of DLS coding neurons increases over time, but this changes do not influence the capacity to decode animal behaviour from DMS and DLS neural networks. These results suggest that both DMS and DLS neural networks are engaged during all learning stages but they gradually reorganize in different ways, in contrast with the common assumption of a gradual shift from DMS to DLS across learning stages.

Video

Speaker in person!
Come since 13h00 to eat pizza (or your food) with the speaker
!

June 14th 2023 – Gabrielle Girardeau

Sorbonne University, France

Neural mechanisms for memory and emotional processing during sleep

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The hippocampus and the amygdala are two structures required for emotional memory. While the hippocampus encodes the contextual part of the memory, the amygdala processes its emotional valence. During Non-REM sleep, the hippocampus displays high frequency oscillations called “ripples”. Our early work shows that the suppression of ripples during sleep impairs performance on a spatial task, underlying their crucial role in memory consolidation. We more recently showed that the joint amygdala-hippocampus activity linked to aversive learning is reinstated during the following Non-REM sleep epochs, specifically during ripples. This mechanism potentially sustains the consolidation of aversive associative memories during Non REM sleep. On the other hand, REM sleep is associated with regular 8 Hz theta oscillations, and is believed to play a role in the regulation of emotional reactivity and the consolidation of emotional memories. In particular, the activity of the amygdala during REM sleep is important for emotional regulation, but the underlying physiology is relatively unknown. Unraveling the fine neuronal dynamics related to REM sleep, Non-REM sleep and the transitions between states in the amygdala will further our understanding of the implication of these sleep stages and related brain patterns in emotional processing.

Speaker in person!
Come since 13h00 to eat pizza (or your food) with the speaker!

June 7th 2023 – Antoine Adamantidis

University of Bern, Switzerland

Neural circuits underlying sleep structure and functions

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Brain activity during sleep is characterized by circuit-specific oscillations, including slow waves, spindles, sharp-wave ripples or theta, that are nested in thalamocortical or hippocampus networks, respectively. However, the activity of other brain circuits is strongly modulated during sleep states. A major challenge is to determine the neural mechanisms underlying these activities and their functional implications. In this lecture, I will summarize our work on the dissection of the neural circuits underlying sleep-wake control, sleep oscillations and their relevance to brain plasticity associated with REM sleep, and discuss their relevance to the elaboration of goal-directed behaviors including feeding and emotional processing.

Video

Speaker in person!
Come since 13h00 to eat pizza (or your food) with the speaker!

May 31st 2023 – Tim Buschman

Princeton University, USA

Multiplexed Subspaces Route Neural Activity Across Brain-wide Networks

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Cognition is flexible. Behaviors can change on a moment-by-moment basis. Such flexibility is thought to rely on the brain’s ability to route information through different networks of brain regions in order to support different cognitive computations. However, the mechanisms that determine which network of brain regions is engaged are unknown. To address this, we combined cortex-wide calcium imaging with high-density electrophysiological recordings in eight cortical and subcortical regions of mice. Different dimensions within the population activity of each brain region were functionally connected with different cortex-wide ‘subspace networks’ of regions. These subspace networks were multiplexed, allowing a brain region to simultaneously interact with multiple independent, yet overlapping, networks. Alignment of neural activity within a region to a specific subspace network dimension predicted how neural activity propagated between regions. Thus, changing the geometry of the neural representation within a brain region could be a mechanism to selectively engage different brain-wide networks to support cognitive flexibility.

Speaker over Zoom

May 10th 2023 – Luca Mazzucato

University of Oregon, USA

Predicting the effect of micro-stimulation on macaque prefrontal activity based on spontaneous circuit dynamics

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A crucial challenge in targeted manipulation of neural activity is to identify perturbation sites whose stimulation exerts significant effects downstream (high efficacy), a procedure currently achieved by labor-intensive and potentially harmful trial-and-error. Targeted perturbations will be greatly facilitated by understanding causal interactions within neural ensembles to guide the design of intervention protocols. Can one predict the effects of electrical stimulation on neural activity solely based on the properties of circuit dynamics during spontaneous periods? Here, we show that the effects of single-site microstimulation on ensemble activity in an alert monkey’s prefrontal cortex can be predicted solely based on the ensemble spontaneous activity. 

We infer the ensemble’s functional causal flow (FCF) based on the functional interactions inferred at rest. We compare the performance of alternative classes of models based on information theory, such as transfer entropy and granger causality, or deterministic dynamical systems, such as convergent cross-mapping (CCM). We find that FCF, inferred via CCM, successfully predicts intervention effects, outperforming all information-based methods and it reveals a causal hierarchy between the array electrodes. We elucidate the computational features underlying FCF using ground truth data from recurrent neural network models, showing that FCF is robust to noise and common inputs. Our results provide the foundation for using targeted circuit manipulations to develop targeted interventions suitable for brain-machine interfaces and ameliorating cognitive dysfunctions in the human brain.

Video

Speaker over Zoom

May 3rd 2023 – Rodrigo Cofre

Paris-Saclay University, France

Novel perspectives on the structure-function dynamics of the primate and human brain under diverse consciousness states

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The analysis of brain network dynamics provides an insightful perspective to analyze the dynamic reconfiguration in brain network structure across species to investigate its role during the loss of consciousness. Recent work has highlighted the importance of the dynamical aspect in understanding the functional relevance of alterations in this network structure to investigate how the brain supports consciousness. In this talk, my idea is to fly over a set of ideas and recent results in order to discuss the problems associated with data analysis in the temporal dimension. I will show convergent and complementary results between different methods of investigating the dynamical aspects of the structure-function relationship during the loss of consciousness in the primate and human brain.

Video

Speaker in person!
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April 12th 2023 – Anna Levina

University of Tübingen, Germany

Timescales in neuronal activity (and how to find them)

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Ongoing neural activity unfolds across different timescales, reflecting networks´ specialization for task-relevant computations. However, it is unknown whether these timescales can be flexibly modulated during trial-to-trial alternations of cognitive states (e.g., attention state) and what mechanisms can cause such modulations. We analyzed autocorrelations of population spiking activity recorded from individual cortical columns of the primate area V4 during a spatial attention task and a fixation task. We developed a method to correctly estimate timescales from short trials and rigorously determine the number of timescales in neural activity. We found at least two distinct timescales in spontaneous and stimulus-driven activity. The slower timescale was significantly longer on trials when monkeys attended to the location of the receptive field of the recorded neurons than on control trials when monkeys attended to a different location. Interestingly, under the attention condition, the timescale predicted the reaction time. Using computational models, we show that the observed timescales emerge from the recurrent network dynamics shaped by the spatial connectivity structure. Finally, we discuss how the timescales could reflect optimization to perform the information processing tasks.

Video

Speaker in person!
Come since 13h00 to eat pizza (or your food) with the speaker!

March 22nd 2023 – Yuval Nir

Tel Aviv University, Israel

Sleep: sensory disconnection and memory consolidation

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A fundamental feature of sleep is that a sensory stimulus does not reliably affect behavior or subjective experience. What mediates such “sensory disconnection”? Do similar processes occur during anesthesia, cognitive lapses, and some neuropsychiatric disorders? In a series of studies in humans and rodents, we compared neuronal responses to identical auditory stimuli across wakefulness and sleep. In A1, early single-neuron spiking responses are largely comparable across wakefulness, natural sleep, and light anesthesia. However, robust differences emerge in downstream high-level regions and late-responding neurons, and in signatures of feedback processing, suggesting that sleep impairs effective cortical connectivity. Next, we show that reduced locus coeruleus-noradrenaline (LC-NE) activity during sleep mediates sensory disconnection. In rodents, the level of ongoing tonic LC activity during sleep anticipates sound-evoked awakenings, while minimal optogenetic LC activation or silencing increases and decreases such awakenings, respectively. In humans, pharmacological manipulation of NE levels modulates sensory perception and late sensory responses, suggesting that NE links sensory awareness to external world events. We are exploring novel methods such as transcutaneous vagal nerve stimulation to modulate LC-NE non-invasively in humans. Finally, I will present recent results on sleep and memory consolidation. In epilepsy patients implanted with depth electrodes we investigate the effects of intracranial electrical closed loop stimulation during sleep on memory and hippocampal-neocortical dialogue at single-neuron resolution.

Video
Recorded with the permission of the speaker

Speaker over zoom

March 8th 2023 – Luiz Pessoa

University of Maryland, USA

The entangled brain: the integration of emotion, motivation, and cognition

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Research on the “emotional brain” often focuses on specific structures, such as the amygdala and the ventral striatum. In this presentation, I will discuss research that embraces a distributed view of both emotion- and motivation-related processing, as well as efforts to unravel the impact of emotion and motivation across large-scale cortical-subcortical brain networks. In this context, I will discuss experimental paradigms used to study the dynamics of threat- and reward-related processes, as well as their interactions. Taken together, these studies support a framework where emotion and motivation have broad effects on brain and behavior, such that brain parts dynamically assemble together into functional circuits to support complex cognitive-emotional behaviors.

Video
Recorded with the permission of the speaker

Speaker over zoom