"There clearly were more synapses found in subjects with intellectually skilled professions, such as engineering or teaching," said James E. Black, who is part of a team examining post-mortem brain tissue at the University of Illinois Beckman Institute for Advanced Science and Technology. "With our approach, however, we can't determine if extra professional experience actually caused new synapses to form, or if people with more synapses tended to choose challenging professions."

The team's preliminary findings were presented in late October at the 29th annual meeting of the Society for Neuroscience in Miami.

Black and his Russian colleagues used an electron microscope that allowed for a systematic count of brain cells (neurons) and synapses (the connections between neurons) in 16 healthy people. Based on family interviews, the subjects were then divided by their profession and amount of education, with a high-level category corresponding to skilled occupations requiring more than a high school degree. The researchers examined tissue from the uppermost layers of the prefrontal cortex - an area of the brain used in complex reasoning - and counted two different types of synapses. They also examined the same types of synapses in occipital cortex, an area involved in simple visual perception.

Subjects with more professional training had 17 percent more synapses for each neuron than did their less educated counterparts. Synapse formation is thought to be a means of storing the information obtained through experience.

"The animal literature strongly indicates that experience can drive the formation of new synapses," said Black, a physician and professor of clinical psychiatry at the U. of I. at Chicago and a professor of neuroscience and psychology on the Urbana-Champaign campus.

A study by Arnold Scheibel of UCLA found a correlation between education and neuron branching in another brain region, a finding that would support the synapse data. "Because humans learn an enormous amount of information during development, there is good reason to think that they store this information in the form of new synaptic connections between neurons," Black said.

No significant differences were found in the subjects' occipital cortex or in the numbers of the second type of synapse, suggesting that professional training may affect only certain types of synapses.

The study is part of a larger project examining brain changes that may be related to schizophrenia, which affects synapses in the prefrontal cortex. While schizophrenia can greatly interfere with a person's quality of life, Black said, new medications offer a good possibility of recovery.

The research team includes Dr. Natalya Uranova and colleagues in Moscow, and Black, Anna Klintsova and William T. Greenough of the U. of I.

Note: If no author is given, the source is cited instead.

• Neuroscience
• Brain Injury
• Intelligence

• Neural development
• Sensory neuron
• Neurobiology
• Chemical synapse
• Amygdala
• Computational neuroscience