Peter Huttenlocher, a pediatric neurologist who was known as much for his rapport with children in the clinic as for his groundbreaking research on pediatric neurological disorders and neural plasticity, died from pneumonia and complications of Parkinson's disease on Aug. 15, at 82 years old. A professor emeritus and former director of pediatric neurology at the University of Chicago at the time of his death, Dr. Huttenlocher's work was said to have transformed the understanding and perception of the human brain and its capacity for development.
Starting in the late 70s Dr. Huttenlocher authored several landmark studies on synapses — and how they changed in number from childhood into adulthood. Using an electron microscope, he counted synapses in postmortem brains ranging in age from newborns to a 90-year-old — observing an increase in neuronal connections in the young brain, and the subsequent “synaptic pruning” or elimination of weaker connections in the brain as an individual continued to age.
In later work, he described timetables for this process and linked the development of new neuron-to-neuron connections in certain brain regions with children gaining cognitive skills, the University of Chicago noted in a description of his work. In the auditory cortex, Dr. Huttenlocher observed, synaptic density peaked early, at about three months old, then tapered to adult levels by age 12. In the visual cortex, density peaked at eight to 12 months, and then declined to adult levels by about age 12. In the frontal cortex, important for higher-order thinking, synaptic density peaked at around three years of age and slowly declined into the middle teen years.
Nobel Laureate Eric Kandel, MD, professor of brain science and the director of the Kavli Institute for Brain Science at Columbia University in New York, noted that Dr. Huttenlocher's discoveries had a profound impact on early childhood education, prompting the introduction of certain subjects like second languages and musical training.
“It would be hard to think of another discovery that is so central to our understanding of pediatric neurology,” Dr. Kandel said in a statement to the University of Chicago. “There was the suggestion, based on animal studies, that humans might assemble these connections between neurons after birth. But no one was thinking about young children subsequently losing those connections. We now know how absolutely crucial synaptic pruning is to mental development and that defects in this system can lead to severe cognitive deficits.”
Remembering his former colleague, Richard Henry Mattson, MD, professor emeritus and senior research scientist in neurology, and epilepsy fellowship director at Yale University School of Medicine, said: “I came to Yale a little after he had arrived in the 60s, and we worked together very closely with adult residency trainees. [When he left to teach at the University of Chicago,] I saw a lot of his patients, and he was sorely missed. He was a fine man and very respected by staff, patients, and families,” Dr. Mattson told Neurology Today.
“Three words describe Peter: kind, gentle, brilliant,” said Carter Snead, MD, professor of pediatrics and medicine (neurology), head of neurology, and director of the Centre for Brain and Behavior at the Hospital for Sick Children in Ontario, Canada. Dr. Snead was trained by Dr. Huttenlocher at Yale University.
“Peter has been a mentor and role model all of my professional life. To ever disappoint him was unthinkable. He is responsible for whatever success I have achieved in my career,” he added.
Over the course of his career, Dr. Huttenlocher cared for numerous children with neurological disorders, and published more than 80 papers on brain development and pediatric neurologic disorders, including Reyes syndrome, tuberous sclerosis, and seizure disorders. In 2002, he published the book Neural Plasticity: The Effects of Environment on the Development of the Cerebral Cortex (Harvard University Press), which synthesized his work on developmental brain development.
The son of a chemist and an opera singer, Dr. Huttenlocher was born in Oberlahnstein, Germany in 1931. His mother immigrated to the United States after refusing to join the Nazi Party — and in 1949, at age 18, Dr. Huttenlocher and his brother moved to America as well. Dr. Huttenlocher enrolled at the University of Buffalo in New York, where he earned a bachelor's degree in philosophy. In 1957, Dr. Huttenlocher earned his medical degree from Harvard Medical School, and then completed a residency at Boston Children's Hospital and Massachusetts General Hospital (MGH). He completed research fellowships at both the National Institutes of Health and MGH.
From 1964 to 1966, Dr. Huttenlocher worked as an assistant professor in pediatric neurology at Harvard, and then at Yale University Medical School. In 1974, Dr. Huttenlocher became a professor at the University of Chicago, where he would remain for nearly 30 years. (In 2003, he became professor emeritus.)
Dr. Huttenlocher had a deep love for classical music, German Expressionist art, and baking cakes and fruit pastries. He is survived by his wife, three children, and four grandchildren.
•. Huttenlocher PR., et al. Dendritic and synaptic pathology in mental retardation. Pediatr Neurol. 1991; 7:(2):79––85.
•. Huttenlocher PR., et al. Synapse elimination and plasticity in developing human cerebral cortex. Am J Ment Defic. 1984; 88:(5):488–496.
•. Huttenlocher PR., deCourten C, Garey LJ, et al. Synaptogenesis in human visual cortex-evidence for synapse elimination during normal development. Neurosci Lett. 1982; 33:247–252.
•. Huttenlocher PR., et al. Synaptic density in human frontal cortex - developmental changes and effects of aging. Brain Res. 1979; 163:(2):195–205.