Microglia
Research has discovered dystrophic (defective development) human microglia. "These cells are characterized by abnormalities in their cytoplasmic structure, such as deramified, atrophic, fragmented or unusually tortuous processes, frequently bearing spheroidal or bulbous swellings." The incidence of dystrophic microglia increases with aging. Microglial degeneration and death have been reported in research on Prion disease, Schizophrenia and Alzheimer's disease, indicating that microglial deterioration might be involved in neurodegenerative diseases. A complication of this theory is the fact that it is difficult to distinguish between "activated" and "dystrophic" microglia in the human brain.
Beth Stevens
Stevens has identified microglia as playing a central role in neuron-glia communication. As the resident phagocytes of the central nervous system (CNS), microglia survey their local environment, clear cellular debris, and make contact with neurons to aid in synaptic pruning during development and learning. She has proposed a "quad-partite" expansion of the tripartite synapse model by including microglia as functional participants in developing and mature synapses.