Melissa Healy / Los Angeles Times

Albert Einstein had a colossal corpus callosum. And when it comes to this particular piece of neural real estate, it’s pretty clear that size matters.

The corpus callosum carries electrical signals between the brain’s right hemisphere and its left. Stretching nearly the full length of the brain from behind the forehead to the nape of the neck, the corpus callosum is the dense network of neural fibers that make brain regions with very different functions work together.

Chances are, that brawny bundle of white matter cleaving the Swiss physicist’s brain from front to back is part of what made Einstein’s mind so phenomenally creative, according to researchers who have been studying the organ of the man whose name has become synonymous with genius.

When the corpus callosum works well, the human brain is a marvel of social, spatial and verbal reasoning. When it malfunctions — as it appears to do in autism, fetal alcohol syndrome and certain genetic disorders, as well as after traumatic brain injury —the effect on cognition can be disastrous.

Even when he died at the age of 76, Einstein’s corpus callosum was a veritable superhighway of connectivity, researchers reported this week in the journal Brain. Not only was it “thicker in the vast majority of subregions” than the corpus collosi of 15 elderly healthy males; it was also thicker at five key crossings than those of 52 young, healthy males in the prime of their lives.

The study of brains that underlie outsized talent or unusual capabilities is part of a long tradition of neurologists and now of neuroscience, said Dr. John Mazziotta, a brain-mapping expert at the University of California, Los Angeles, who was not involved with the current study.

“You have a unique brain here,” said Mazziotta, who is chairman of neurology at the David Geffen School of Medicine. “Sometimes looking at the extremes of something tells you a lot about how the average works. That’s why these kinds of studies have value.”

Upon Einstein’s death of an aortic aneurysm in 1955, his heirs approved the removal of his brain for scientific study. A trove of histological slides was made, each a minute slice of the universe that lay beneath that shock of white hair.

While some of those slides are housed at Princeton University, where Einstein spent his final years, and at the National Museum of Health and Medicine in Washington D.C., many have been lost or stolen. Without a full picture of Einstein’s brain, the basis of the theoretical physicist’s genius has eluded scientists.

The photographs that form the basis of the new study unexpectedly came to light in 2010. That’s when Florida State University evolutionary anthropologist Dean Falk began making inquiries about some images of Einstein’s brain she had seen in an earlier publication.

The photos, along with some slides and letters, were found among the effects left behind by Dr. Thomas Harvey, the pathologist who had removed Einstein’s brain. Harvey’s heirs went on to donate those to the National Museum of Health & Medicine in Silver Spring, Md.