[Age-related changes in interneuronal synapses in human cerebral cortex]

In 5 persons that did not suffer from any psychical or neurological illnesses, at the age of 75-83 years, ultrastructure of dendrites, axons and axonal terminals was studied in the 40th field of the cerebral cortex, layer after layer. Various forms of changes in the dendrites were revealed demonstrating certain degenerative alterations in them and their loss of synaptic contacts with the axonal terminals. Two types of the axonal changes were followed. One of them, the most spread, has features of functional alterations (a tight arrangement of a great number of coarse neurotubules, while the axoplasm is remained). The state of such fibers is considered by the authors as a reversible one. Changes of the other type of axons (they are deprived of normal organells of axoplasm) are considered by the authors as irreversible. Degeneration of the axonal terminals, noted in all cortical layers, is realized mainly according to the "dark" type and seldom--according to the "light" one. In most cases these contacts are performed by unchanged dendrites. A gradual degeneration and death of neurocytes should be considered as a main course of the disturbances in the interneuronal connections of the cortex.