Final answer:
Presynaptic modulation involves a neurotransmitter affecting the membrane potential in another neuron at an axoaxonic synapse.
Step-by-step explanation:
Presynaptic modulation involves a neurotransmitter from the axon terminal of one neuron affecting the membrane potential of an axon terminal from another neuron on which the first has synapsed (axoaxonic synapse).
Chemical synapses are the junctions between neurons where neurotransmitters are released from the axon terminal of the presynaptic neuron and bind to receptors on the dendrites of the postsynaptic neuron.
These neurotransmitters can be either excitatory or inhibitory, meaning they can either increase or decrease the chance of an action potential in the postsynaptic neuron.
Therefore, the statement is true.