Activation Model

Specification for threshold-based signal processing

Version: 0.1.0-draft

Overview

The activation model defines how nodes decide whether to process incoming signals. It replaces traditional rate limiting with a biologically-inspired threshold system.

Activation State

Each node MUST maintain an activation state:

ActivationState {
    potential: float32,          // Accumulated signal weight
    threshold: float32,         // Firing threshold
    refractory_until: uint64,   // Nanosecond timestamp
    refractory_period: uint64,  // Refractory duration in nanoseconds
}

Activation Sequence

1. Signal arrives at node via synapse
2. Signal contribution is calculated: contribution = signal.weight * synapse.weight
3. Contribution is added to node’s potential: potential += contribution
4. If potential >= threshold AND node is not in refractory period: a. Node fires (processes the signal) b. Potential resets to 0.0 c. Node enters refractory period
5. If potential < threshold OR node is in refractory: a. Signal is queued for accumulation b. No processing occurs

Dynamic Threshold

The threshold SHOULD adjust dynamically based on node load:

effective_threshold = base_threshold * (1.0 + load_factor)

Where load_factor = current_queue_depth / max_queue_depth.

This ensures that overloaded nodes become more selective, providing natural backpressure.

Refractory Period

After firing, a node MUST enter a refractory period during which it cannot fire again. The RECOMMENDED default is 10 milliseconds. During the refractory period:

• Incoming signals still accumulate potential
• No processing occurs
• No signals are dropped (they queue)

Activation Functions

Implementations MUST support the step activation function. Implementations SHOULD support sigmoid and leaky functions.

Function	Behavior
Step	Binary: fires when potential >= threshold
Sigmoid	Probabilistic: firing probability increases smoothly
Leaky	Always passes a small fraction (leak rate = 0.01)

Configuration

[activation]
base_threshold = 0.5          # REQUIRED
activation_function = "step"   # REQUIRED
refractory_period_ms = 10     # REQUIRED
max_potential = 10.0           # RECOMMENDED
dynamic_threshold = true       # RECOMMENDED