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Automatic Adaptation to Fast Input Changes in a Time-Invariant Neural Circuit

Fig 3

Schematic neural networks implementing predictive coding, through feedforward (a) or feedback (b) inhibition.

Networks’ parameters are: (a) Feedforward: , . (b) Feedback: α, Γ. In both circuits, the unit that outputs p_t is termed the principal cell, and the unit that outputs n_t the interneuron. There are two synapses onto each interneuron: (1) its external input and (2) a representation of its internal dynamics (right of the dashed line). We can describe its internal dynamics in this way because the interneuron is a leaky integrator, i.e. its internal dynamics (Eq (8)) are an infinite sum of past outputs, discounted at each time step by a fixed multiplier. Therefore, they can be represented by a delayed input across a synapse, with a multiplicative discounting factor, as in (a) and (b).

doi: https://doi.org/10.1371/journal.pcbi.1004315.g003