Mesoscopic description of hippocampal replay and metastability in spiking neural networks with short-term plasticity
Fig 6
Spontaneous replay switches between multiple environments.
In the (A) mesoscopic and (B) microscopic ring-attractor network storing multiple environments, metastable replay dynamics spontaneously emerge due to finite-size fluctuations when decreasing the population size from N = 500 (orange/red in panels i) to N = 50 (blue/black) per unit. Nonlocal replay events (NLEs) occur randomly in exclusively one of three environments, while activity in the respective other two is suppressed. The resulting activation sequences of replayed environments—in (A) the activation sequence reads 313123122312321—are analyzed with respect to (C) the transition probabilities between subsequently active environments and (D) sequential activation patterns. In the meso- and microscopic models, transitions from environment k to j are equally likely for all pairs (k, j) ∈ {1, 2, 3}2. But the deterministic (macro and RT) models show a clear preference for transitions 1 → 3 → 2 → 1, which is also apparent in the high probability of the corresponding subsequences of three distinct, subsequently active environments. (E) Larger heterogeneity with respect to NLE duration and interburst intervals (IBI), as assessed by the respective means μ and coefficients of variation CV, further distinguishes the more variable metastable regime of the micro-/mesoscopic vis-à-vis macroscopic/deterministic models. Model parameters can be found in Table 1.