Complex sentence: Nonsynaptic plasticity is the mechanism responsible for modifications of these channels in the axon, leading to a change in strength of the neuronal action potential, invariably affecting the strength of synaptic mechanisms, and thus the depth and length of memory encoding.
Split into simpler sentences: Nonsynaptic plasticity is the mechanism responsible for modifications of these channels in the axon, leading to a change in strength of the neuronal action potential. This action potential or excitability change will invariably affect the strength of synaptic mechanisms, and thus the depth and length of memory encoding.