The core learning method in biological neurons is believed to be something like STDP (Spike-Timing-Dependent Plasticity). Basically, the arrival time of a spike

The core learning method in biological neurons is believed to be something like STDP (Spike-Timing-Dependent Plasticity). Basically, the arrival time of a spike at the post-synaptic end of a neuron is compared to the arrival time of a spike at the pre-synaptic end. The sign and scale of the difference of arrival times will cause a change in the respective synaptic strengths. It has similarities to backprop, and depends on backpropagated signals but backprop is simpler, faster and can exploit knowledge about the loss function (as far as we know STDP cannot). The downside (?) to backprop is that it cannot exploit temporal information like STDP but several recurrent models have found ways around that.