Dr. Diamond studied the brains of nine stimulated rats and found that all of them had thicker cerebral cortices than their stimulus-deprived counterparts.
“This was the first time anyone had ever seen a structural change in an animal’s brain based on different kinds of early life experiences,” she and Janet Hopson wrote in “Magic Trees of the Mind: How to Nurture Your Child’s Intelligence, Creativity, and Healthy Emotions From Birth Through Adolescence” (1998).
The results, which Dr. Diamond, Dr. Rozenzweig and the psychologist David Krech published in 1964, helped change scientific understanding of the brain in fundamental ways.
“Dr. Diamond showed anatomically, for the first time, what we now call plasticity of the brain,” George Brooks, a professor of integrative biology at Berkeley, told the university’s news service last month. “In doing so she shattered the old paradigm of understanding the brain as a static and unchangeable entity that simply degenerated as we age.”
Dr. Diamond went on to show that brains can continue to develop through life; identified structural differences between male and female animal brains; and, by testing elderly players at a women’s bridge club, found that complex card play stimulated the body’s immune system.
In one of her most celebrated studies, Dr. Diamond and her second husband, Dr. Arnold Scheibel, the director of the brain research institute at the University of California, Los Angeles, examined four samples from Einstein’s brain. The brain had been spirited away and preserved for decades by Thomas Harvey, the pathologist who performed Einstein’s autopsy in 1955. Dr. Diamond’s specimens arrived by mail in a jar formerly containing Kraft Miracle Whip and looked like “little sugar cubes,” she told The Washington Post in 1985.
Dr. Diamond looked through a microscope and compared stained slices of the samples with brain tissue from 11 former patients at a Veterans Administration hospital. She found that one area of Einstein’s brain — the lower parietal lobe, associated with higher-level mathematical and language functioning — had a high concentration of glial cells, which cushion and feed neurons.
The findings, although headline-grabbing, were inconclusive.
“Many idiots have big brains loaded with glial cells,” Janice Stevens, staff psychiatrist at the neuropsychiatry branch of the National Institute of Mental Health, told The Post. Later research by other scientists, however, showed that glial cells play a hitherto unsuspected role in brain chemistry, helping to build connections between neurons and promoting more complex brain structure.
Marian Cleeves was born on Nov. 11, 1926, in Glendale, Calif., and grew up in nearby La Crescenta. Her father, Montague, was a doctor who had emigrated from Yorkshire, England. Her mother, the former Rosa Marian Wamphler, was a former Latin teacher who cut short her doctoral studies at Berkeley to raise her six children, of whom Marian was the youngest.
Marian saw her first human brain at 15. She had been accompanying her father on his hospital rounds when, through an open door, she caught sight of four men in lab coats standing around a table.
“I have no idea what they were doing, but the sight of that brain, which formerly had the potential to create ideas, was embedded in my brain forever, as clearly as if it were yesterday,” she wrote in her autobiographical essay. “The thought was mesmerizing that that brain represented the most complex mass of protoplasm on this earth and, perhaps, in our galaxy.”
As a professor of integrative biology at Berkeley, she was famous for carrying a preserved brain to her anatomy lectures in a flowered hat box.
She had enrolled at Berkeley after attending Glendale Community College for two years. At Berkeley, she earned a degree in biology in 1948 and a master’s degree in anatomy a year later. She received a doctorate in anatomy in 1953, writing her dissertation on the hypothalamus.
In 1950 she married Richard M. Diamond, later a renowned nuclear chemist at the Lawrence Berkeley National Laboratory. The marriage ended in divorce. In addition to her son Richard, she is survived by another son, Jeff; two daughters, Ann and Catherine Diamond; and five grandchildren. Dr. Scheibel, her second husband, died in April.
Dr. Diamond accepted a position as lecturer at Berkeley after teaching at Harvard, Cornell and the school of medicine at the University of California, San Francisco. She retired three years ago. A documentary, “My Love Affair With the Brain: The Life and Science of Dr. Marian Diamond,” was broadcast on PBS in 2016.
In 1985, the same year her paper “On the Brain of a Scientist: Albert Einstein” appeared in Experimental Neurology, Dr. Diamond published findings of an experiment with older rats — the equivalent of about 75 years old in human terms — that had been placed in a stimulating environment. After six months, they showed a thickening of the cortex, a sign that the brain cells had become larger and more active.
In other words, the brain could grow and prosper, even in old age — a promising finding, and sweet vindication for a theory that had initially encountered resistance. When she presented the results of her first experiments to the annual meeting of the American Association of Anatomists in 1965, a man at the back of the room stood up and shouted, “Young lady, that brain cannot change.”
She wrote in her autobiographical essay: “It was an uphill battle for women scientists then — even more than now — and people at scientific conferences are often terribly critical. But I felt good about the work, and I simply replied, ‘I’m sorry, sir, but we have the initial experiment and the replication experiment that shows it can.’ ”
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