E7 Synaptic plasticity (Hebb, LTP/LTD, STDP)

Title

Synaptic plasticity describes how the effective weight w of a synapse (proportional to g_syn_max at E04) changes as a function of the correlated activity between the presynaptic and postsynaptic neuron. The classical Hebb's rule postulates that the synapse is strengthened when both neurons are active simultaneously; Variants like Oja's rule add a normalization term that prevents unlimited growth. The BCM model introduces a sliding threshold that depends on the average postsynaptic activity, allowing the same correlation to produce potentiation or depression depending on the recent history of the neuron. Relative firing time-dependent plasticity (STDP) captures the causal asymmetry observed experimentally: a presynaptic firing preceding the postsynaptic firing tends to potentiate the synapse, while the reverse order tends to depress it. In biophysical terms, these changes are largely mediated by the intracellular concentration of postsynaptic Ca2+, which acts as a common signal to trigger LTP or LTD cascades depending on their magnitude and temporal dynamics.

ID:4265