How positive and negative affective stimuli interact in the brain to influence behavioral outcomes remains poorly understood. Here, we show that recall of a positively valenced reward-associated cue (reward-conditioned stimulus, CS+) can prevent or reverse fear generalization in mice. Modification of generalized fear by recall of a CS+ is dependent on the midbrain dopamine system and the regulation of discriminatory fear encoding by the central amygdala (CeA). Precisely timed, transient elevations in dopamine are necessary to reverse fear generalization and nondiscriminatory fear encoding in the CeA. Recall of a positive association is also effective at enhancing the extinction of a conditioned fear response in a dopamine-dependent manner. These data demonstrate that recall of a positive experience can be an effective means to suppress generalized fear and show that dopamine projections to the CeA are an important neural substrate for this phenomenon.

The ventral pallidum (VP) lies at the intersection of basal ganglia and basal forebrain circuitry, possessing attributes of both major subcortical systems. Basal forebrain cholinergic neurons are rapidly recruited by reinforcement feedback and project to cortical and subcortical forebrain targets; in contrast, striatal cholinergic cells are local interneurons exhibiting classical 'pause-burst' responses to rewards. However, VP cholinergic neurons (VPCNs) are less characterized, and it is unclear whether basal forebrain and striatal type cholinergic neurons mix in the VP. Therefore, we performed anterograde and mono-transsynaptic retrograde labeling, in vitro acute slice recordings and bulk calcium recordings of VPCNs in mice of either sex. We found that VPCNs broadly interact with the mesocorticolimbic circuit that processes rewards and punishments, targeting the basolateral amygdala, the medial prefrontal cortex and the lateral habenula, while receiving inputs from the nucleus accumbens, hypothalamus, central amygdala, bed nucleus of stria terminalis and the ventral tegmental area. Bulk calcium recordings revealed that VPCNs responded to rewards, punishments and reward-predicting cues. Acute slice recordings showed that most VPCNs resembled the bursting type of basal forebrain cholinergic neurons (BFCNs), while a few of them were of the regular rhythmic type, which differentiated most VPCNs from striatal cholinergic interneurons. These results were confirmed by in vivo electrophysiological recordings of putative VPCNs. We conclude that VPCNs show burst firing and specialized connectivity to relay aversive and appetitive stimuli to the reinforcement circuitry, possibly implicated in mood disorders and addiction. The ventral pallidum is a special brain area, being part of both the basal ganglia system implicated in goal-directed behavior and the basal forebrain system implicated in learning and attention. It houses, among others, neurons that release the neurotransmitter acetylcholine. While these cholinergic neurons have distinct characteristics in other regions of the basal ganglia and basal forebrain, it is unclear whether those in the ventral pallidum resemble one or the other or both. Here we demonstrate that they are closer to basal forebrain cholinergic neurons both anatomically and functionally, especially resembling a burst-firing subtype thereof. In accordance, we found that they convey information about aversive and appetitive stimuli to the reinforcement circuitry, possibly implicated in mood disorders and addiction.

Knowledge of how vocal communication signals are represented in the auditory system is crucial for understanding the perceptual basis of vocal communication. Using male and female zebra finches, we identified a series of differentially expressed markers that helped define distinct (caudal, rostral, dorsal and ventral) domains within the caudomedial nidopallium (NCM), a high-order cortical auditory area known for its song-selective responses. Using expression analysis of the activity-inducible gene , we found that the number of activated neurons is more stimulus dependent in NCM than in the auditory midbrain or the caudomedial mesopallium, and that information on the density and spatial distribution of responsive neurons in NCM is sufficient to discriminate responses to conspecific song from other stimuli. We observed stronger activation of dorsal NCM, higher selectivity of caudal NCM towards conspecific song, and strong activation of the inhibitory network of rostral NCM by non-conspecific song stimuli. Song auditory representation in NCM was dependent on acoustic features, with the spatial organization of responsive cells particularly sensitive to both spectral and temporal components. We also obtained evidence of broadly distributed song-selective neuronal ensembles and that individual NCM neurons participate in the representation of conspecific songs, implying independent activation and molecular induction responses. We conclude that some basic aspects of the cortical response to complex auditory stimuli are topographically organized, a finding that has been elusive in other systems. These findings advance our knowledge of the functional organization of a key song-processing cortical area, providing novel insights into the auditory representation of conspecific vocal communication signals. Understanding how vocal signals are processed and represented in the brain is fundamental to the study of animal communication. Songbirds provide a powerful model for investigating these processes due to their rich vocal behavior and well-characterized neural circuits. Through analysis of differentially expressed markers and mapping of activity-induced gene expression, we have uncovered how different domains and neuronal populations within a high-order auditory cortical area respond to acoustic features of song and other stimuli. Besides providing in-depth knowledge of the functional organization of a key avian brain area, these findings provide insights into how acoustic features of complex learned vocal signals are processed and represented in cortical circuits, including evidence of how basic aspects of this representation can be topographically organized.

Basal Ganglia Advances is a collection highlighting research on the structure, function, and disorders of the basal ganglia. It features studies spanning neuroscience, clinical insights, and computational models, serving as a hub for advances in movement, cognition, and behavior.

Recent advances in the field of Voltage Imaging, with a special focus on new constructs and novel implementations.

Work related to place tuning, spatial navigation, orientation and direction. Mainly includes articles on connectivity in the hippocampus, retrosplenial cortex, and related areas.

Striatal dopamine (DA) release regulates reward-related learning and motivation and is believed to consist of a short-lived and continuous component. Here, we build a large-scale three-dimensional model of extracellular DA dynamics in dorsal (DS) and ventral striatum (VS). The model predicts rapid dynamics in DS with little to no basal DA and slower dynamics in the VS enabling build-up of DA levels. These regional differences do not reflect release-related phenomena but rather differential dopamine transporter (DAT) activity. Interestingly, our simulations posit DAT nanoclustering as a possible regulator of this activity. Receptor binding simulations show that D1 receptor occupancy follows extracellular DA concentration with milliseconds delay, while D2 receptors do not respond to brief pauses in firing but rather integrate DA signal over seconds. Summarised, our model distills recent experimental observations into a computational framework that challenges prevailing paradigms of striatal DA signalling.

Striatal output is dynamically modulated by cholinergic interneurons (CINs), the primary source of acetylcholine in the striatum. CINs have been classically viewed as a random and homogeneous population, but recent evidence suggests heterogeneity in their anatomical and functional organization. Here, using systematic mapping and quantitative spatial analyses, we found that-contrary to current dogma-CINs exhibited striking enrichment and nonrandom clustering in the striosome compartment, particularly in the lateral striatum. Similar analyses carried out for parvalbumin- and somatostatin-expressing interneurons revealed that compartmental organization is interneuron specific. The strong "striosome preference" exhibited by CINs was confined within striosome borders, not extending to the surrounding matrix. We further found that striosome and matrix CINs differed in their expression levels of phospho-S6 ribosomal protein-Ser240/244 and choline acetyltransferase, suggesting functional differences, and clustered CINs differed from unclustered CINs in their intrinsic membrane properties. Finally, CINs expressing Lhx6, which defines a distinct γ-aminobutyric acid (GABA) coreleasing population, were notably absent from regions where highly clustered striosomal CINs appeared. Collectively, our findings uncover important dimensions of CIN organization, suggesting that modulation of regional and compartmental striatal output may depend upon the spatial-functional heterogeneity of CINs.

Mitochondrial dysfunction and abnormalities in mitochondrial quality control contribute to the development of neurodegenerative diseases. Parkinson's disease is a neurodegenerative disease that causes motor problems mainly due to the loss of dopaminergic neurons in the substantia nigra pars compacta. Axonal mitochondria in neurons reportedly differ in properties and morphologies from mitochondria in somata or dendrites. However, the function and morphology of axonal mitochondria in human dopaminergic neurons remain poorly understood. To define the function and morphology of axonal mitochondria in human dopaminergic neurons, we newly generated tyrosine hydroxylase (TH) reporter (TH-GFP) induced pluripotent stem cell (iPSC) lines from one control and one PRKN-mutant patient iPSC lines and differentiated these iPSC lines into dopaminergic neurons in two-dimensional monolayer cultures or three-dimensional midbrain organoids. Immunostainings with antibodies against axonal and dendritic markers showed that axons could be better distinguished from dendrites of dopaminergic neurons in the peripheral area of three-dimensional midbrain organoids than in two-dimensional monolayers. Live-cell imaging and correlative light-electron microscopy in peripheral areas of midbrain organoids derived from control TH-GFP iPSCs demonstrated that axonal mitochondria in dopaminergic neurons had lower membrane potential and were shorter in length than those in non-dopaminergic neurons. Although the mitochondrial membrane potential did not significantly differ between dopaminergic and non-dopaminergic neurons derived from PRKN-mutant patient lines, these differences tended to be similar to those in control lines. These results were also largely consistent with those of our previous study on somatic mitochondria. The findings of the present study indicate that midbrain organoids are an effective tool to distinguish axonal from dendritic mitochondria in dopaminergic neurons. This may facilitate the analysis of axonal mitochondria to provide further insights into the mechanisms of dopaminergic neuron degeneration in patients with Parkinson's disease.