Biology subjects

Hjort, M. M.

Publications and source records attributed to Hjort, M. M..

3 recordsLinked to original sources

bioRxiv2025

Lateral Hypothalamic Glutamate and GABA Neurons Cooperatively Shape Striatum-Wide Dopamine Dynamics During Consumption

The lateral hypothalamic area (LHA) contains GABAergic and glutamatergic neurons that converge on the midbrain dopamine system and exert opposing influences on consummatory feeding behavior. However, the activity dynamics of these populations during consumption and their impact on striatal dopamine release remain poorly understood. Here, we show that LHA GABAergic and glutamatergic neurons independently scale their activity during the consumption of rewarding and aversive solutions while cooperatively regulating dopamine release along the anterior-posterior axis of the striatum in mice. Dopamine release exhibited widespread modulation during consumption, with anterior striatal regions showing stronger representation of solution value and its recent history--an effect dependent on LHA activity. These findings suggest that the LHA acts as a central regulator of striatal dopamine release during consumption, providing a mechanism through which hypothalamic circuits influence motivational and consummatory behaviors.

neuroscience↗

bioRxiv2022

Medial accumbens shell spiny projection neurons encode relative reward preference

Medial nucleus accumbens shell (mNAcSh) is a critical brain region for driving motivated behaviors. Despite this well-established role, the underlying reward processing of individual neurons, circuits and cell-types within mNAcSh remains largely unknown. Here, we leverage deep brain 2-photon calcium imaging through endoscopic lenses to record mNAcSh spiny projection neuron (SPN) ensemble responses to rewards of different concentrations and to reward-predictive cues across cue-reward learning. Reward responses were found to be heterogeneous and particularly differentiated based on reward concentration and cell type. A large subpopulation of reward-excited enkephalinergic SPNs were found to be specifically recruited during consumption of high concentration, unpreferred reward. A major enkephalinergic efferent projection from mNAcSh to ventral pallidum (VP) was also found to be recruited to high concentration but unpreferred reward and to causally drive low positive reward preference. Enkephalin and dynorphinergic SPNs in mNAcSh distinctly represent rewards of different preference and propagate distinct signals through efferent projections to drive consummatory behavior.

neuroscience↗

bioRxiv2022

A stable, distributed code for cue value in mouse cortex during reward learning

The ability to associate reward-predicting stimuli with adaptive behavior is frequently attributed to the prefrontal cortex, but the stimulus-specificity, spatial distribution, and stability of pre-frontal cue-reward associations are unresolved. We trained headfixed mice on an olfactory Pavlovian conditioning task and measured the coding properties of individual neurons across space (prefrontal, olfactory, and motor cortices) and time (multiple days). Neurons encoding cues or licks were most common in olfactory and motor cortex, respectively. By quantifying the responses of cue-encoding neurons to six cues with varying probabilities of reward, we unexpectedly found value coding in all regions we sampled, with some enrichment in prefrontal cortex. We further found that prefrontal cue and lick codes were preserved across days. Our results demonstrate that individual prefrontal neurons stably encode components of cue-reward learning within a larger spatial gradient of coding properties.

neuroscience↗