The curious case of dopaminergic prediction errors and learning associative information beyond value.
Transient changes in the firing of midbrain dopamine neurons have been closely tied to the unidimensional value-based prediction error contained in temporal difference reinforcement learning models. However, whereas an abundance of work has now shown how well dopamine responses conform to the predictions of this hypothesis, far fewer studies have challenged its implicit assumption that dopamine is not involved in learning value-neutral features of reward. Here, we review studies in rats and humans that put this assumption to the test, and which suggest that dopamine transients provide a much richer signal that incorporates information that goes beyond integrated value.
Are oligodendrocytes bystanders or drivers of Parkinson's disease pathology?
The major pathological feature of Parkinson 's disease (PD), the second most common neurodegenerative disease and most common movement disorder, is the predominant degeneration of dopaminergic neurons in the substantia nigra, a part of the midbrain. Despite decades of research, the molecular mechanisms of the origin of the disease remain unknown. While the disease was initially viewed as a purely neuronal disorder, results from single-cell transcriptomics have suggested that oligodendrocytes may play an important role in the early stages of Parkinson's. Although these findings are of high relevance, particularly to the search for effective disease-modifying therapies, the actual functional role of oligodendrocytes in Parkinson's disease remains highly speculative and requires a concerted scientific effort to be better understood. This Unsolved Mystery discusses the limited understanding of oligodendrocytes in PD, highlighting unresolved questions regarding functional changes in oligodendroglia, the role of myelin in nigral dopaminergic neurons, the impact of the toxic environment, and the aggregation of alpha-synuclein within oligodendrocytes.
Dissociable roles of central striatum and anterior lateral motor area in initiating and sustaining naturalistic behavior.
Understanding how corticostriatal circuits mediate behavioral selection and initiation in a naturalistic setting is critical to understanding behavior choice and execution in unconstrained situations. The central striatum (CS) is well poised to play an important role in these spontaneous processes. Using fiber photometry and optogenetics, we identify a role for CS in grooming initiation. However, CS-evoked movements resemble short grooming fragments, suggesting additional input is required to appropriately sustain behavior once initiated. Consistent with this idea, the anterior lateral motor area (ALM) demonstrates a slow ramp in activity that peaks at grooming termination, supporting a potential role for ALM in encoding grooming bout length. Furthermore, optogenetic stimulation of ALM-CS terminals generates sustained grooming responses. Finally, dual-region photometry indicates that CS activation precedes ALM during grooming. Taken together, these data support a model in which CS is involved in grooming initiation, while ALM may encode grooming bout length.
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Progress in Voltage Imaging
Recent advances in the field of Voltage Imaging, with a special focus on new constructs and novel implementations.
Navigation & Localization
Work related to place tuning, spatial navigation, orientation and direction. Mainly includes articles on connectivity in the hippocampus, retrosplenial cortex, and related areas.
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Social Exclusion Amplifies Behavioral Responses to Physical Pain via Insular Neuromodulation
The Pain Overlap Theory proposes that the experience of social pain overlaps with and amplifies the experience of physical pain by sharing parts of the same underlying process- ing systems. In humans, the insular cortex has been implicated in this overlap of physical and social pain, but a mechanistic link has not been made. To determine whether social pain can subsequently impact responses to nociceptive stimuli via convergent electrical signals (spikes) or convergent chemical signals (neuromodulators), we designed a novel Social Exclusion paradigm termed the Fear of Missing Out (FOMO) Task which facilitates a mechanistic investigation in mice. We found that socially-excluded mice display more severe responses to physical pain, disrupted valence encoding, and impaired neural representations of nociceptive stimuli. We performed a systematic biosensor panel and found that endocannabinoid and oxytocin signaling in the insular cortex have opposing responses during trials where mice were attending or not attending to the Social Exclusion events respectively, demonstrating distinct neuromodulatory substrates that underpin different states of Social Exclusion. We also found that intra-insular blockade of oxytocin signaling increased the response to physical pain following Social Exclusion. Together these findings suggest Social Exclusion effectively alters physical pain perception using neuromodulatory signaling in the insular cortex.
Combining pangenomics and population genetics finds chromosomal re-arrangements, accessory-like chromosome segments, copy number variations and transposon polymorphisms in wheat and rye powdery mildew
Grass powdery mildews (Blumeria spp.) include economically important fungal crop pathogens with complex and highly repetitive genomes. To investigate the diversity and genome evolution in Blumeria graminis, we combined population genetic and pangenomic analyses using a worldwide sample of 399 wheat powdery mildew isolates. Additionally, we produced high-quality genome assemblies for seven isolates from wheat and one from rye powdery mildew. Using these, we compiled the first grass powdery mildew pangenome comprising 11 Blumeria graminis isolates. We found multiple chromosomal rearrangements between the isolates that grow on wheat, rye and/or triticale hosts. Interestingly, chr-11 showed some characteristics of accessory chromosomes such as presence/absence of large chromosomal segments and higher sequence diversity. Additionally, we identified nearly 67,000 cases of copy number variations (CNVs), which were highly enriched within effector gene families. Furthermore, we found evidence for recent and high transposable element (TE) activity, such as high numbers of TE insertion polymorphisms. Analyses of TE families showed enrichment 1 kb to 2 kb up- and downstream of effector genes, and we also found high levels of TE insertion polymorphisms between populations. Our results demonstrate that chromosomal variations, gene family expansions and contractions, and TE activity are important sources of genome diversification and diversity in grass powdery mildews. Our findings indicate that a combination of pangenomic and population genetics analyses is needed to understand drivers of evolution in plant pathogenic fungi in a comprehensive way.