Corpus callosum
From Memory Alpha, the free Star Trek reference
The corpus callosum is the connecting structure between the two hemispheres of the mammalian-type humanoid brain.
After being exposed to the effects of the Cytherian probe, Dr. Crusher noted that the corpus callosum in Reginald Barclay's brain was so active that the two sides of his brain were essentially functioning as one. (TNG: "The Nth Degree")
