Neuroscience

eLife assessment

Modi et al. investigate the question of how learned information guides behavior. They combine optogenetic conditioning in Drosophila to spatially restrict the formation of olfactory memory traces in mushroom bodies (MBs), where olfactory memory traces are formed during pavlovian olfactory conditioning and follow up with behavioral studies and physiological analysis to examine how flies use these 'minimal memories' during learned olfactory discrimination. They discover that MBONs' responses predict behavioral outcomes, with odor responses showing physiological differences under conditions where broadly similar odorants must be discriminated. Thus, flies use olfactory memory templates flexibly to suit their behavioral needs. Modi et al. conclude that a hitherto unknown mechanism downstream of mushroom body output neurons creates these context-specific responses at the MBONs. Overall, the experiments provide convincing physiological evidence for a neural mechanism that underlies a contextual basis for the precision of memory recall, which constitutes a fundamentally important advance in our understanding of the neurobiology of memory retrieval, however, the authors need to more deeply consider caveats to their arguments, more deeply discuss differences and similarities with prior publications and bolster their data by including a few controls that are currently missing.

eLife assessment

The authors set out to characterize a function of Drosophila glia that form an expansion of myelin-like membranes that might facilitate rapid nerve conduction. A combination of Drosophila genetics, antibody staining, and electron microscopy is used to characterize this "myelin" and the role of glial wrapping in clustering of sodium/potassium channels at motor exit points. The results are valuable, as they would point to Drosophila as a new, genetically accessible model organism to study myelin evolution. While the results are interesting, the strength of the evidence provided is incomplete due to inadequate quantification of the data provided.

eLife assessment

Studies of prey behavior have the potential to provide insight into the chemical encoding of stress in the brain and the mechanisms by which this generates behavioral plasticity. In this important work, the authors identify a novel predation-evoked behavior in the nematode C. elegans and implicate dopamine in its implementation. While the support for some claims in the current paper is incomplete, this work provides an exciting foundation for future studies of behavioral plasticity in this powerful system.

eLife assessment

This study presents a useful application of a prior model published by the authors to a new dataset. The results from this approach were interesting and solid but the conclusions that one can make from the application of the model to only one paper are limited in scope and would depend on further probing to know if the model itself has face validity as a model of ventral visual stream function.

eLife assessment:

This study offers new fundamental information on a role for the sodium/potassium pump in sleep regulation. Elegant methods were used to provide compelling evidence supporting the claim. The work will be of interest to sleep researchers in zebrafish as well as in other species for future investigation.

eLife assessment

This important work provides evidence that artificial recurrent neural networks can be used to investigate neural mechanisms underlying reversible remapping of spatial representations. Authors perform convincing state of the art analyses showing how population activity preserves the encoding of spatial position despite remappings due to the tracking of an internal variable. This paper will be of interest to neuroscientists studying contextual computations, neural representation of space and links between artificial neural networks and the brain.

eLife assessment

The authors provide a new powerful tool as well as a large database that should be useful to the neuroscience community, but not only. The authors developed and applied a methodology to automatically estimate the volume, cell number, and density of mice brains from multiple regions, by detecting the native fluorescence of the cell nuclei. Using this platform, they analyzed an existing dataset containing multiple mouse brains, available in the Allen Mouse Connectivity project. The data provides a comprehensive neuroanatomical comparison of brain nuclei between males and females, between hemispheres, and between 2 strains of lab mice.

eLife assessment

In its current form, the reviewers felt that the work describing the use of a CycleGAN for alignment of neural activity from a neural interface across sessions was useful, with solid evidence showing that it improved performance over similar-concept previous approaches.

eLife assessment

Small subthreshold dendritic-somatic depolarizations can propagate to presynaptic nerve endings and may modulate transmitter release, but the mechanisms of this modulation remain poorly understood because the technical challenge of recording from small bouton synapse. Here the authors directly record from small cerebellar bouton terminals In paired somatic and presynaptic recordings, they demonstrate that small synaptic potentials can travel within 2 to 3 ms to the bouton and arrive there with an amplitude attenuated by 20 to 70% with respect to the somatically recorded potential. As expected, this amplitude attenuation depends on axon length. In recordings of MLI-Purkinje cell pairs the authors further demonstrate that small somatic subthreshold depolarizations of about 20 mV size can enhance AP-triggered IPSCs recorded in the Purkinje cells and change synaptic plasticity during AP trains. In order to address mechanisms of such presynaptic modulation, the authors measure presynaptic AP waveforms via cell attached recordings and found these very stable. On the other hand, presynaptic ICa(V) directly recorded in voltage-clamped MLI boutons facilitated in response to small pre-depolarizations and such facilitated ICa(V) produced larger IPSCs in paired recordings of MLI boutons and coupled Purkinje cells. The authors propose that an accumulation of partially gated channels during small presynaptic depolarizations is able to produce more rapid gating of VGCCs during the AP waveform on arrival of an invading presynaptic AP.

eLife assessment

The phenomenon of summit disease, where complex animal behaviours are controlled by single-celled parasites, captivates biologists and non-scientists alike. In this valuable study, the authors use a laboratory model (Drosophila melanogaster infected with Entomophthora muscae) for this disease to provide compelling evidence for the neuroanatomical and physiological underpinnings of summit disease. This is an excellent example of how seemingly intractable questions in behavioural ecology can be effectively addressed in laboratory settings using decades of work in creating 'models' for biology.