Read the equation
The sign convention subtracts presynaptic spike time from postsynaptic spike time. Positive values mean the postsynaptic spike follows the presynaptic one and enter the source’s potentiation branch; nonpositive values enter its depression branch. The returned weight change also depends on the current weight’s distance from its allowed limits.
Terms & definitions
| Term | Meaning in this source |
|---|---|
| delta_t | Post-minus-pre timing in milliseconds |
How it works
Read the definition from its right-hand expression to the quantity on the left. Its surrounding source records the intended input, state, or parameter context. Where the source leaves an operation unspecified, this page preserves that gap.
Assumptions & limits
Source recovery establishes that the expression appears in this record. Its mathematical validity, implementation behavior, and interpretation must be assessed separately. See the linked source and research notes for the checks available for this version.
Original context
Read the surrounding source passage
float A_minus = 0.00525f;// LTD amplitude (slightly larger for stability)
float tau_plus = 20.0f; // ms - LTP time constant
float tau_minus = 20.0f; // ms - LTD time constant
float w_max = 1.0f; // Maximum weight
float w_min = 0.0f; // Minimum weight
// Calculate weight change given spike time difference
// delta_t = t_post - t_pre
float delta_w(float delta_t, float w) const {
if (delta_t > 0) {
// Post after pre → LTP
return A_plus * (w_max - w) * std::exp(-delta_t / tau_plus);
} else {
// Pre after post → LTD
return -A_minus * (w - w_min) * std::exp(delta_t / tau_minus);
}
}
};Exact original notation
delta_t = t_post - t_pre