In 40 off-food moving C. elegans, neuron classes at higher connectome trophic levels had shorter activity timescales; in 8 on-food animals there was no relation

Question: in cortex, areas higher in the anatomical hierarchy have longer intrinsic timescales. Does a similar rule apply to identified neurons in the C. elegans connectome? Approach: we fitted exponential decays to the autocorrelation (lags 0.6-30 s) of NeuroPAL-identified whole-brain GCaMP traces in 40 off-food, freely moving animals (Atanas 2023, 3,548 neurons) and 8 on-food animals with little movement (Dag 2023, 814 neurons). We compared class median timescales with the trophic level of each class in the Cook 2019 chemical connectome. Results: off food, higher trophic level gave shorter timescales (Spearman rho = -0.31, 58 classes, p = 0.019; negative in 36 of 40 animals; partial rho = -0.41 after degree, cell type, animal count and label confidence). The relation remained with 800-frame windows, without heat-stimulus recordings, with other autocorrelation measures and with the Witvliet adult-8 connectome. On food there was no relation (rho = +0.09, 54 classes, p = 0.54). Most classes were slower on food (46 of 53; median ratio 1.84), and in an exploratory test the slowing increased with trophic level (rho = +0.30, p = 0.027). Strength-preserving rewired connectomes gave 82% of the off-food relation (null mean rho = -0.25), so each neuron's input-to-output synapse balance carries most of it. Class behaviour coupling explained much of it (partial rho = -0.13 after behaviour R2). Limitations: condition is confounded with data set and batch; across-class correlation only; GCaMP kinetics and single-exponential fits; the low-frequency power fraction did not show the relation; secondary tests are not corrected for multiple comparisons.

C. elegans · connectome · intrinsic timescale · trophic level · hierarchy · whole-brain imaging · NeuroPAL · autocorrelation · behavioural state · rewired null · structure-function