At the time of his death of an aortic aneurysm at age 76, Albert Einstein's brain was no bigger, and weighed no more, than the brain of an average older male.
But beneath that unique organ's external folds and fissures, our universe was re-conceived. So not surprisingly, when photographs of Einstein's post-mortem brain unexpectedly came to light recently, scientists were keen to find evidence of the genius that lay within.
The result is a remarkably detailed look at the surface of Einstein's brain, published recently in the journal Brain. Among the unusual features of Einstein's cerebral cortex, portrayed in a series of 14 high-quality photographs, are evidence of his early training as a violinist, his highly evolved skill in imagining events and simulating their consequences, and his remarkable powers of nonverbal visuospatial processing.
These tantalizing pieces of evidence are not obvious: In most cases, they must be deduced by the existence of extra folds, larger-than-usual bulges or other anatomical quirks seen on the surface of the cerebral cortex.
The "tension-based theory" of how the brain's convolutions and sulci are formed suggests that the surface of the brain - its growth limited by the skull - folds in on itself to make room as clusters of neurons connect, reconnect and reorganize themselves with mental exercise. The resulting growth in neurons and connective tissue should show up as asymmetry in the shapes and sizes of the brain's hemispheres, and in the distinctive sub-areas of the brain that process perception, movement and high-level thought.
Upon Einstein's death, his heirs approved the removal of his brain, and a trove of histological slides were made, documenting minute slices of the theoretical-physicist's brain. And if only they could all be found, more evidence of Einstein's genius might be gleaned.
One hundred sixty of the slides, made from 240 "blocks" of Einstein's brain, are at Princeton's University Medical Center, and an additional 560 slides are housed at the National Museum of Health and Medicine, until recently on the grounds of Walter Reed Army Medical Center in Washington. But the whereabouts of many slides are unknown. (Slices of Einstein's preserved brain tissue are known to be in Ontario, California, Alabama, Argentina, Japan, Hawaii and Philadelphia.)
Among the asymmetries observed by the authors of the Brain article are Einstein's parietal lobes, where much of the circuitry for visuospatial and mathematical thinking is housed. On the surface of Einstein's primary motor cortex, an enlarged "knob" is evident in the area where the brain "represents" the left hand: The authors of the study surmised that this is probably the result of Einstein's early and extensive training on the violin.
The surfaces of Einstein's visual cortex were found to be particularly dense with folds - evidence, perhaps, of the physicist's unique talent for closing his eyes and visualizing objects, the authors wrote.
Not so surprising was the finding that Einstein's prefrontal cortices - the seat of higher reasoning and judgment - were "relatively expanded." His brawn there "may have provided underpinnings for some of his extraordinary cognitive abilities, including his productive use of thought experiments," the authors wrote.