Which structure is most capable of modulating sensory input?

A) Primary afferents
B) Secondary afferents
C) Substantia gelatinosa
D) Spinothalamic tract

The substantia gelatinosa is a structure in the dorsal horn of the spinal cord that plays a crucial role in modulating sensory input. It receives input from both primary and secondary afferents, and can both amplify or reduce the signal that is sent to higher brain centers. The spinothalamic tract carries sensory information from the spinal cord to the thalamus, but does not play as direct a role in modulating sensory input. Primary afferents carry sensory information from the periphery to the spinal cord, but do not have the capacity to modulate this input.