Final answer:
The medial lemniscus system crosses the midline of the medulla through decussation. This occurs after the first neuronal synapse at the nucleus gracilis or nucleus cuneatus and before ascending as the medial lemniscus to the thalamus.
Step-by-step explanation:
The medial lemniscus system is a part of the dorsal column-medial lemniscus pathway, which is one of the major sensory pathways that bring somatosensory information to the brain. This system comprises a series of three neurons. The axons in the dorsal column terminate at either the nucleus gracilis or nucleus cuneatus in the medulla, forming the first synaptic relay.
The second neuron projects from these nuclei and crosses the midline of the medulla in a process known as decussation. The decussated axons then ascend through the brain stem as the medial lemniscus. After decussation, these axons continue to the thalamus, synapsing with the third neuron in the pathway. The third neuron, in turn, sends axons to the postcentral gyrus of the cerebral cortex for the initial processing and conscious perception of somatosensory stimuli.