Neuronal processing of noxious thermal stimuli mediated by dendritic Ca²⁺ influx in Drosophila somatosensory neurons

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Summary:

This study describes the response of Class IV sensory neurons in Drosophila larvae to distinct noxious stimuli (heat and light). Using a highly sophisticated experimental setup combining UV-mediated focal heat application, electrophysiology and calcium imaging, the authors show that "burst and pause" activity pattern of Class IV neurons accompanying a calcium transient is induced by heat but not light. In dTrpA1 mutants or L-type voltage-gated calcium channel mutants, the "burst and pause" activity pattern, calcium transients and the behavioral response to noxious heat (rolling) are blocked. Optogenetic induction of an activity pattern mimicking the "burst and pause" activity slightly increased the frequency of rolling. From these results, the authors propose an interesting hypothesis that specific pattern of neural activity mediates transmission of specific modality.

Essential revisions:

The one concern was that the linkage between burst coding and rolling is not as strong as the prose indicates. The authors should reword their conclusions in the Abstract, Results and Discussion in more conservative language and make it clear that rolling can (and does) occur without bursting. Bursting appears to enhance rolling, but it is not necessary. In particular, the phrase "necessary and sufficient" needs to be removed since the data do not support this claim.