Marco Pompili
@mnpompili.bsky.social
Pretending to be a behavior/systems neuroscientist
🌐 Overall, our results show how distinct hippocampal subregions encode complementary aspects of associative learning — learning and expression — and how population-level coordination across the HPC dorsoventral axis integrates these signals to support adaptive behavior.
12/12
12/12
February 9, 2026 at 2:59 PM
🌐 Overall, our results show how distinct hippocampal subregions encode complementary aspects of associative learning — learning and expression — and how population-level coordination across the HPC dorsoventral axis integrates these signals to support adaptive behavior.
12/12
12/12
🧠✨ These multifactorial engrams, distributed across the dorsoventral axis of the hippocampus, provide a population-level substrate for integrating emotional learning with its associated behavioral response — offering a mechanism for coordinating associative learning.
11/12
11/12
February 9, 2026 at 2:59 PM
🧠✨ These multifactorial engrams, distributed across the dorsoventral axis of the hippocampus, provide a population-level substrate for integrating emotional learning with its associated behavioral response — offering a mechanism for coordinating associative learning.
11/12
11/12
🔗 These mixed assemblies combined neurons encoding fear expression with neurons encoding fear learning — effectively binding behavior and associative value at the population level.
10/12
10/12
February 9, 2026 at 2:59 PM
🔗 These mixed assemblies combined neurons encoding fear expression with neurons encoding fear learning — effectively binding behavior and associative value at the population level.
10/12
10/12
🧩 Crucially, these signals did not remain segregated and converged in cell assemblies composed of both dHPC and vHPC neurons that emerged during conditioning.
9/12
9/12
February 9, 2026 at 2:59 PM
🧩 Crucially, these signals did not remain segregated and converged in cell assemblies composed of both dHPC and vHPC neurons that emerged during conditioning.
9/12
9/12
🧭 Population activity revealed a dorsoventral division of labor in the hippocampus:
• dHPC → fear expression
• vHPC → fear learning / cue valence
with representations mapped onto complementary components of the emotional experience.
This raised a key question: how are these signals combined?
8/12
• dHPC → fear expression
• vHPC → fear learning / cue valence
with representations mapped onto complementary components of the emotional experience.
This raised a key question: how are these signals combined?
8/12
February 9, 2026 at 2:59 PM
🧭 Population activity revealed a dorsoventral division of labor in the hippocampus:
• dHPC → fear expression
• vHPC → fear learning / cue valence
with representations mapped onto complementary components of the emotional experience.
This raised a key question: how are these signals combined?
8/12
• dHPC → fear expression
• vHPC → fear learning / cue valence
with representations mapped onto complementary components of the emotional experience.
This raised a key question: how are these signals combined?
8/12
🔔 In contrast, vHPC neurons developed robust excitatory responses to the conditioned stimulus, independent of freezing behavior — tracking the acquisition of conditioned fear rather than its expression.
7/12
7/12
February 9, 2026 at 2:59 PM
🔔 In contrast, vHPC neurons developed robust excitatory responses to the conditioned stimulus, independent of freezing behavior — tracking the acquisition of conditioned fear rather than its expression.
7/12
7/12
🧊 Importantly, dHPC responses were specific to fearful freezing — not immobility or motor confounds — and were context-dependent, pointing to a role for dHPC (but not vHPC) in encoding contextual aspects of learned fear expression.
6/12
6/12
February 9, 2026 at 2:59 PM
🧊 Importantly, dHPC responses were specific to fearful freezing — not immobility or motor confounds — and were context-dependent, pointing to a role for dHPC (but not vHPC) in encoding contextual aspects of learned fear expression.
6/12
6/12
⚠️➡️ Unexpectedly, neuronal correlates of fear expression (freezing) were more prominent in the dorsal hippocampus than in the ventral hippocampus — challenging the long-standing view that vHPC is the main locus of fear regulation.
5/12
5/12
February 9, 2026 at 2:59 PM
⚠️➡️ Unexpectedly, neuronal correlates of fear expression (freezing) were more prominent in the dorsal hippocampus than in the ventral hippocampus — challenging the long-standing view that vHPC is the main locus of fear regulation.
5/12
5/12
📈 As expected, fear conditioning induced large-scale shifts in firing rates in both regions, with neurons increasing or decreasing their activity following acquisition of the CS–US association.
4/12
4/12
February 9, 2026 at 2:59 PM
📈 As expected, fear conditioning induced large-scale shifts in firing rates in both regions, with neurons increasing or decreasing their activity following acquisition of the CS–US association.
4/12
4/12
🔬 Here, we performed simultaneous single-unit recordings in dorsal and ventral hippocampus during fear conditioning — to our knowledge, the first time this has been done.
This let us directly compare population dynamics as fear is learned and expressed.
3/12
This let us directly compare population dynamics as fear is learned and expressed.
3/12
February 9, 2026 at 2:59 PM
🔬 Here, we performed simultaneous single-unit recordings in dorsal and ventral hippocampus during fear conditioning — to our knowledge, the first time this has been done.
This let us directly compare population dynamics as fear is learned and expressed.
3/12
This let us directly compare population dynamics as fear is learned and expressed.
3/12
📚 Classically, the dorsal hippocampus (dHPC) is linked to contextual/spatial processing, while the ventral hippocampus (vHPC) is associated with emotion and anxiety.
Both are required for fear conditioning — but how their contributions are integrated remained unknown.
2/12
Both are required for fear conditioning — but how their contributions are integrated remained unknown.
2/12
February 9, 2026 at 2:59 PM
📚 Classically, the dorsal hippocampus (dHPC) is linked to contextual/spatial processing, while the ventral hippocampus (vHPC) is associated with emotion and anxiety.
Both are required for fear conditioning — but how their contributions are integrated remained unknown.
2/12
Both are required for fear conditioning — but how their contributions are integrated remained unknown.
2/12
…and we have another work coming where we propose a way to study cell assemblies without binning or z-scoring. Stay tuned!
December 8, 2025 at 10:06 PM
…and we have another work coming where we propose a way to study cell assemblies without binning or z-scoring. Stay tuned!
Binning is necessary for the most common method of cell assembly detection that we also used in this study (ICA), but we agree this does have its limitations, which we discuss here: doi.org/10.1007/978-...
Detection of Cell Assemblies in High-Density Extracellular Electrophysiological Recordings
Cell assemblies, i.e., concurrently active groups of neurons, likely underlie neural processing for higher brain functions. Recent technological progress has enabled large-scale recording of neuronal ...
doi.org
December 8, 2025 at 10:06 PM
Binning is necessary for the most common method of cell assembly detection that we also used in this study (ICA), but we agree this does have its limitations, which we discuss here: doi.org/10.1007/978-...
It remains unclear whether such co-firing truly matters for brain function. Here, we show that in the prefronto-amygdalar circuit, “cell assemblies” matter on timescales of up to ~40 ms: synchronous activity over longer windows fails to trigger a supralinear downstream response.
December 8, 2025 at 10:06 PM
It remains unclear whether such co-firing truly matters for brain function. Here, we show that in the prefronto-amygdalar circuit, “cell assemblies” matter on timescales of up to ~40 ms: synchronous activity over longer windows fails to trigger a supralinear downstream response.
What cell assemblies are — and what they do for the brain — is a profound question and the central motivation behind this work! Most people define an assembly as a set of neurons that fire together (thereby enabling the plasticity associated with synchrony).
December 8, 2025 at 10:06 PM
What cell assemblies are — and what they do for the brain — is a profound question and the central motivation behind this work! Most people define an assembly as a set of neurons that fire together (thereby enabling the plasticity associated with synchrony).
In sum: (1) this is, to our knowledge, the first experimental support for the “reader-centric” framework of cell assemblies; (2) assembly reading implements both pattern completion and pattern separation; and (3) assembly–reader relationships can be flexibly modified by learning. 10/10
December 6, 2025 at 9:26 PM
In sum: (1) this is, to our knowledge, the first experimental support for the “reader-centric” framework of cell assemblies; (2) assembly reading implements both pattern completion and pattern separation; and (3) assembly–reader relationships can be flexibly modified by learning. 10/10
Finally, we expected that assembly–reader relationships could flexibly change to reflect learning processes. Indeed, fear conditioning induced changes in AMY assembly → mPFC reader couplings, and conversely, changes in mPFC → AMY reading followed fear extinction. 9/10
December 6, 2025 at 9:26 PM
Finally, we expected that assembly–reader relationships could flexibly change to reflect learning processes. Indeed, fear conditioning induced changes in AMY assembly → mPFC reader couplings, and conversely, changes in mPFC → AMY reading followed fear extinction. 9/10
The assembly–reader mechanism implements both pattern completion (responses did not simply increase proportionally with the number of active members) and pattern separation (responses were selective for specific assemblies and discriminated between overlapping assemblies). 8/10
December 6, 2025 at 9:26 PM
The assembly–reader mechanism implements both pattern completion (responses did not simply increase proportionally with the number of active members) and pattern separation (responses were selective for specific assemblies and discriminated between overlapping assemblies). 8/10
Assembly activations exerted synergistic effects on reader neurons (not just a linear summation of responses to individual assembly members), and the identity of participating members mattered beyond their compound activity (spikes from neurons A and B > two spikes from A alone). 7/10
December 6, 2025 at 9:26 PM
Assembly activations exerted synergistic effects on reader neurons (not just a linear summation of responses to individual assembly members), and the identity of participating members mattered beyond their compound activity (spikes from neurons A and B > two spikes from A alone). 7/10
We recorded large neural ensembles from the medial prefrontal cortex (mPFC) and the amygdala (AMY), which are reciprocally interconnected, and showed that assembly activation could trigger firing responses in downstream neurons. 6/10
December 6, 2025 at 9:26 PM
We recorded large neural ensembles from the medial prefrontal cortex (mPFC) and the amygdala (AMY), which are reciprocally interconnected, and showed that assembly activation could trigger firing responses in downstream neurons. 6/10