The effects of age upon the main nucleus of the inferior olive in the human

The neuronal population of the main inferior olivary nucleus was determined by complete cell counts of this structure in 18 human subjects of various ages. The age groups represent a progression from an immature infant of 23 weeks gestation to an 89 year old. The cell population was found to be lowest in the most immature infant (233,360), increasing in number up to the time of birth, the neo‐natal values being 327,330 for the three day old and 380,460 for the three month old. While minor cell fluctuations were noted in the specimens selected from the first to ninth decades, all values were relatively close to a post‐natal mean value of 363,784. A low value of 317,600 was found in an 82 year old and a high value of 405,580 in a 73 year old. Within comparable age groups the cell populations showed a similar pattern of distribution throughout the length of the nucleus.