Fig. 3: Network model indicates PO drift is a trade-off between Hebbian plasticity and synaptic volatility.

a Model schematic: two-layer network with \(n\) orientation-tuned presynaptic neurons (pre) connected topographically with weights \((w)\) to \(n\) orientation-selective postsynaptic neurons (post). \(n\) = 500. b Synaptic plasticity rule: weights \((w)\) are updated in proportion to the sum of stimulus-driven changes (\(H\); scaled by k) and synaptic volatility (\(\xi\)), both scaled by a propensity factor proportional to initial weight (\(\rho (w)\)). c POs of postsynaptic neurons in the model 20 days apart, under baseline stimulus conditions. d Median drift magnitude (|∆PO|) increases over time, and is comparable under baseline (black) and orientation-deprived (green) conditions. e Same as d but for mean drift rate (|PO_day–PO_day–1|). f Median convergence (∆|rPO|) over time for baseline (black) and orientation-deprived (green) conditions. g Initial distance from experienced orientation (|rPO|) shows little correlation with drift magnitude after 28-day deprivation. Two-sided Spearman’s correlation r = 0.118 (p = 0.008, n = 500). h Spearman’s correlation between drift magnitude and initial distance from experienced orientation (as shown in g) in networks with different ratios of Hebbian plasticity to synaptic volatility (\(H/\xi\); see b). Synaptic volatility is constant, while the Hebbian component is scaled by k. Correlation increases with longer deprivation time. Large Hebbian plasticity component also leads to increased correlation. Dashed lines indicate \(H/\xi\) ratio in the other panels and 28-day deprivation length. i Shuffling drift direction but not magnitude abolishes the median convergence effect of the model during orientation deprivation. Green: model data and shuffles (n = 500). Gray: experimental data from Fig. 2g, i, median convergence and shuffles. Error bars are bootstrapped 95% CIs; n = 414 neurons from seven mice. j Effect of omitting either the Hebbian or the synaptic volatility contribution from the plasticity rule on PO convergence, during 28 days of orientation-deprived conditions. k Effect of omitting either the Hebbian or the synaptic volatility contribution from the plasticity rule on PO drift magnitude, during 28 days of baseline stimulation conditions. l The model displays limited recovery after input statistics return to baseline conditions. During recovery, median convergence is negative and slowly increases in magnitude over time (blue), but is incomplete even after 1000 days (~3 years). Mean (solid line/data point) and standard deviation (shaded region/error bars) over 50 model iterations. Source data are provided as a Source Data file.