Biology subjects

Jungmann, R. M.

Publications and source records attributed to Jungmann, R. M..

3 recordsLinked to original sources

bioRxiv2026

Hippocampal astrocytes contribute to encoding context-specific aversive stimuli to regulate fear-related behavior

In contextual fear conditioning, subjects learn to associate a neutral environment with an aversive stimulus and exhibit fear responses to that context, signaling danger. Neuronal activity in hippocampal-amygdala circuits has been shown extensively to underlie the conditioning and recall of contextual fear memories, yet the direct contribution of astrocytes to integrating stimulus and contextual information in this task remains unknown. In this study, we monitor astrocyte activity in real time in the hippocampus and simultaneously during performance in the contextual fear conditioning task. We find that shock-evoked astrocyte responses during conditioning predict the magnitude of freezing during recall in a context-specific manner. Importantly, astrocytic Ca2+ activity progressively precedes freezing onset specifically in the shock-associated context, indicating that hippocampal astrocytes contribute to encoding context-specific shock information. This work reveals an unprecedented contribution of astrocytes to the encoding of context-related information about aversive stimuli in fear-related behavior.

neuroscience↗

bioRxiv2026

Valence-specific ensembles in the laterodorsal tegmentum encode salient stimuli and modulate motivated behavior

The laterodorsal tegmentum (LDT) is a brainstem hub that integrates sensory and motivational signals to regulate adaptive behavior. While LDT neurons are known to modulate reward and aversion, whether salient stimuli recruit distinct neuronal ensembles within this structure remains unknown. Here, combined cell-type-specific calcium imaging, activity-dependent genetic tagging (TRAP2), and optogenetic reactivation to investigate how rewarding and aversive stimuli recruit and functionally define LDT neurons. Notably, single exposures to cocaine or shock in TRAP2;Ai14 mice labeled spatially and neurochemically distinct ensembles, with minimal overlap. We used fiber photometry and TRAP2 system to tag active neuronal ensembles in the LDT during cocaine (coca-LDT) and foot shock (shock-LDT) exposure, expressing GCaMP8m (green) in these neurons and, simultaneously, sRGECO (red) in the whole LDT. Our results demonstrate coca-LDT activation by physical aversive events and valenced odours, with reduced activity in response to rewarding liquids. Shock-LDT showed activation by physical aversive events, odours, and shock-predictive cues. Additionally, optogenetic reactivation of cocaine-TRAPed ensembles in a two-choice operant task biased action selection toward stimulation-paired responses, whereas shock-TRAPed ensemble activation did not drive avoidance. These findings identify functionally segregated LDT ensembles recruited by opposing motivational stimuli and reveal a causal role for reward-activated brainstem ensembles in shaping behavior. This functional segregation may contribute to the brains ability to differentiate stimulus types and, to some extent, valence experiences. Our results may provide evidence on how the LDT influences decision-making processes in addiction and anxiety disorders, potentially paving the way for novel therapeutic approaches.

neuroscience↗

bioRxiv2026

Dissociable neuronal substrates for positive and negative valence stimuli in the nucleus accumbens

The nucleus accumbens (NAc) responds to both natural and artificial rewards and to aversive stimuli; however, it remains unclear whether these opposing valence signals engage distinct neuronal ensembles. Here we used Fos-CreERT2-based activity-dependent tagging to label NAc neuronal ensembles activated by cocaine or foot shock. We found that cocaine ensemble consisted predominantly of dopamine D1 receptor-expressing medium spiny neurons (D1-MSNs), whereas foot shock ensemble similarly recruited D1- and D2-MSNs. One-photon calcium imaging in freely moving mice revealed that acute cocaine primarily excited D1-MSNs while inhibiting the majority of D2-MSNs, whereas foot shock induced excitatory responses in both types of MSNs. Optogenetic reactivation of the cocaine-ensemble elicited a strong behavioural preference, whereas reactivation of the shock-ensemble produced no significant behavioural effect. Together, these findings demonstrate that cocaine recruits a functionally specific NAc ensemble distinct from that recruited by shock, providing mechanistic insight into the valence-specific neuronal substrates underlying reward and aversion processing.

neuroscience↗