They play an active role in establishing and maintaining the fundamental patterns of neuron circuits. They produce growth and trophic factors, playing a key role in regeneration and plasticity. Some play an active role in the formation of myelin which speeds impulse conduction. Myelinated fibers conduct more rapidly than unmyelinated fibers. Glial cells play a crucial role in immunological responses to various infections and toxic agents.
Glial cells increase in number when nerve cells grow with enrichment.
With these definitions you can now appreciate how important glial cells are to serve the nerve cells. Back to our story. In the early 1960s, the laboratories both of Joseph Altman at Purdue and ours had found that the cerebral cortex from rats living in enriched environments had more glial cells per neuron than the cortex from rats living in impoverished environments. Active cortical neurons needed more support cells. The graduate students had clipped a photo of the box with Einstein's brain from Science magazine and attached it to the laboratory wall.