What is the phenomenon called when stimulation of one sensory system leads to a reaction in another sensory system?

The phenomenon where stimulation of one sensory system leads to a reaction in another sensory system is known as synesthesia. This condition allows for a blending of the senses, where individuals may experience things like seeing colors when they hear music or tasting flavors when they see specific shapes. Synesthesia highlights the brain's interconnectedness and the way sensory information can cross pathways, leading to unique sensory experiences that differ from typical sensory processing.

In contrast, homunculus refers to a representation of the human body's sensory and motor functions mapped onto the brain. Opposite sensation is not a recognized term in this context, and stimulus overlap does not accurately describe the cross-sensory integration seen in synesthesia. Therefore, synesthesia stands out as the correct term for the phenomenon of inter-sensory reactions.