Behavior-dLDS: A decomposed linear dynamical systems model for neural activity partially constrained by behavior
Organizations: Department of Biomedical Engineering Center for Imaging Science Johns Hopkins University · Department of Biology University of North Carolina · Janelia Research Campus Howard Hughes Medical Institute
Abstract
Brain-wide recordings of large-scale networks of neurons now provide an unprecedented view into how the brain drives behavior. However, brain activity contains both information directly related to behavior as well as the potential for many internal computations. Moreover, observable behavior is executed not only by the brain, but also by the spinal cord and peripheral nervous system. Behavior is a coarse-grained product of neural activity, and we thus take the view that it can be best represented by lower-dimensional latent neural dynamics. Capturing this indirect relationship while disambiguating behavior-generating networks from internal computations running in parallel requires new modeling approaches that can embody the parallel and distributed nature of large-scale neural populations. We thus present behavior-decomposed linear dynamical systems (b-dLDS) to disentangle simultaneously recorded subsystems and identify how the latent neural subsystems relate to behavior. We demonstrate the ability of b-dLDS to decouple behavioral vs. internal computations on controlled, simulated data, showing improvements over a state-of-the-art model that uses behavior to supervise all dynamics based on behavior. We also demonstrate b-dLDS's interpretability benefits on a task-driven RNN dataset featuring a nonlinear relationship between behavior and activations. We then show that b-dLDS can further scale up to tens of thousands of neurons by applying our model to a large-scale recording of a zebrafish hindbrain during the complex positional homeostasis behavior, wherein b-dLDS highlights asymmetry in behavior-related dynamic connectivity networks.
Figures & tables
| Model | Iterations | / norm | ||
|---|---|---|---|---|
| b-dLDS | 500 | 5 | 2.6 | 0.99 |
| 50 | 0.66 | 0.99 | ||
| 100 | 0.39 | 0.99 | ||
| 200 | 0.07 | 0.96 | ||
| b-dLDS-x | 500 | 0.9644 | 3.88 | 0.95 |
| 5 | 4.44 | 0.96 |
| Criteria | “Left” side | “Right” side | % asymmetry |
|---|---|---|---|
| # neuron centroids | 2550 | 2400 | 6% |
| Variance of dF/F over time per trace | mean 0.0099, median 0.0052, std 0.0153 | mean 0.0109, median 0.0057, std 0.0174 | 9% (means) |
| per neuron | mean 0.38, median 0.35, std 0.23 | mean 0.46, median 0.43, std 0.27 | 17% (means) |
| # start/end points for largest connections | 6 of 25 DOs: 18%-118% |
Appendix figures & tables17 assets
Supplementary material from the paper’s appendix.
Appendix
| Model | Seed | Max | Idx | Max | Idx | Max | Idx | Time (s) | RAM (KB) | ||
|---|---|---|---|---|---|---|---|---|---|---|---|
| max | , | max | max | ||||||||
| value | vs. | vs. | |||||||||
| b-dLDS | 1 | 0.91 | 0.96 | 0.68 | 25 | 0.82 | 25 | 0.36 | 3 | 6.11E+04 | -2.17E+08 |
| 2 | 0.9 | 0.95 | 0.29 | 20 | 0.84 | 25 | 0.36 | 43 | 6.09E+04 | -2.18E+08 | |
| 3 | 0.91 | 0.97 | 0.74 | 3 | 0.84 | 3 | 0.33 | 21 | 4.74E+04 | 7.91E+07 |
| Parameter | Meaning | How to set | Settings used for zebrafish models (in order of appearance in Table 3 ) |
|---|---|---|---|
| nF | number of dynamics operators (DOs) | Based on models used in zebrafish figures. Also tried matching nF to N for fairness of and vs. comparisons. | 25 (first 7 model types); 50 (last 3 model types, “nF=50”) |
| N | number of latent dimensions | Based on models used in zebrafish figures. | 50 |
| lambda_val | regularization: sparsity of states ( ) | Based on models used in zebrafish figures. | 0.05 |
| lambda_history | regularization: smoothness of states ( ), but more specifically, reconstruction of states from dynamics operators and dynamics coefficients | Based on models used in zebrafish figures (with exceptions for b-dLDS-x BayesOpt). | 0.23; 0.1154 (b-dLDS-x BayesOpt model types) |
| lambda_b | regularization: sparsity of dynamics coefficients ( ) | Based on models used in zebrafish figures. | 0.05 |
| Parameter | Meaning | How to set | Settings used for 4 simulation types |
|---|---|---|---|
| nF | number of dynamics operators (DOs) | First set to 2x the number of PCs required for 95% variance explained. Then decrease until the median number of active dynamics coefficients starts decreasing. (Goal: minimize the number of DOs while maintaining the inherent dimensionality of the data.) Alternative heuristic: use the number of known behavioral states as a benchmark and double it to get the starting point for the number of DOs, and then start decreasing from there. | 15 |
| N | number of latent dimensions | Known based on data, given that . | 8 |
| lambda_val | regularization: sparsity of states | Increase to reduce the number of states active at the same time (moderately sensitive) | 1.0000e-04 |
| lambda_history | regularization: smoothness of states , but more specifically, reconstruction of states from dynamics operators and dynamics coefficients | Increase to encourage states to change smoothly from time point to time point (less sensitive) | 1.0000e-04 |
| lambda_b | regularization: sparsity of dynamics coefficients (c) | Increase to reduce the number of DOs active at the same time (sensitive) | 0.25 |
| Parameter | Meaning | How to set | Settings used (if differ, first b-dLDS setting shown; then b-dLDS-x) |
|---|---|---|---|
| nF | number of dynamics operators (DOs) | Set to 2x the number of PCs required for 95% variance explained. | 16 |
| N | number of latent dimensions | Known based on data, given that . | 128 |
| lambda_val | regularization: sparsity of states ( ) | Optimize with BayesOpt. | 0.9772;0.0293 |
| lambda_history | regularization: smoothness of states ( ), but more specifically, reconstruction of states from dynamics operators and dynamics coefficients | Optimize with BayesOpt. | 0.8702;0.0636 |
| lambda_b | regularization: sparsity of dynamics coefficients ( ) | Optimize with BayesOpt. | 0.25908;0.0315 |
| Parameter | Meaning | How to set | Settings used for zebrafish models (1 vs. 4 behavior inputs) |
|---|---|---|---|
| nF | number of dynamics operators (DOs) | First set to 2x the number of PCs required for 95% variance explained. Then decrease until the median number of active dynamics coefficients starts decreasing. (Goal: minimize the number of DOs while maintaining the inherent dimensionality of the data.) Alternative heuristic: use the number of known behavioral states as a benchmark and double it to get the starting point for the number of DOs, and then start decreasing from there. | 25 |
| N | number of latent dimensions | Set to at least the number of PCs required for 80-90% variance explained. | 50 |
| lambda_val | regularization: sparsity of states | Increase to reduce the number of states active at the same time (moderately sensitive) | 0.05 |
| lambda_history | regularization: smoothness of states ( ), but more specifically, reconstruction of states from dynamics operators and dynamics coefficients | Increase to encourage states to change smoothly from time point to time point (less sensitive) | 0.23 |
| lambda_b | regularization: sparsity of dynamics coefficients | Increase to reduce the number of DOs active at the same time (sensitive) | 0.05 |
| Model | Param. | Val. | Median use | Mean | Mean | Mean | * Setting used | ||
|---|---|---|---|---|---|---|---|---|---|
| Zebrafish | N | 25 | 7 | 6.67 | 0.98 | 0.97 | 0.73 | 0.72 | |
| hindbrain | 25 | 6 | 0.98 | 0.70 | |||||
| 25 | 7 | 0.95 | 0.72 | ||||||
| 35 | 6 | 6.00 | 0.97 | 0.97 | 0.78 | 0.78 | |||
| 35 | 6 | 0.99 | 0.78 | ||||||
| 35 | 6 | 0.97 | 0.79 |
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