Emergent elasticity in the neural code for space
summary
Evidence shows grid code coherence decays within 40 seconds without landmarks, so a solvable attractor-plus-Hebbian model is built: landmark synapses learn by plasticity and behave like particles on springs — an emergent elasticity whose rest lengths match physical landmark separations. The model predicts small history-dependent shifts (~1–2 cm) in grid fields conditioned on last border touch and a bifurcation under virtual-reality gain changes producing either steady phase lags or full remapping; large datasets and VR recordings confirm these signatures.
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chapters (29)
- 0:00Intro
- 2:18The extraction of spatial position from the periphery
- 3:25A fundamental consistency requirement relating path integration to landmark based error correction
- 4:17Talk outline
- 9:24Options have different dependencies on trajectory angle
- 10:54Error is corrected in a direction- dependent manner
- 11:531D Attractor Model
- 14:14Landmark influence
- 15:05Landmark Learning
- 15:55Don't worry (1): there are equations underlying all this Don't worry (2): I won't show them again
- 21:33Simplest Case
- 21:46Before Learning
- 22:57After Learning
- 23:36Interpretation
- 25:37Emergent Mechanical Relaxation of Internal Maps Particles - Landmark Synapses
- 27:33Generalization to two dimensions
- 29:09Distortions
- 33:26Matches Experimental Observations
- 34:17Bending of Firing Fields
- 35:47Topological Defects
- 36:48How to create a topological defect in grid cells
- 38:38Head-fixed virtual reality offers near-perfect cue control
- 39:17Cell types in VR give analogous behavior
- 40:31Gain manipulations reveal influence of visual and locomotor speed cues on grid and border cells
- 41:19Attractor-Landmark Model
- 45:07Gain Increase: Attractor is slower than landmarks
- 45:21Weak Gain Increase
- 45:48Strong Gain Decrease
- 46:05Landmark Friction Why doesn't field number double?
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