The effect of age and gender on the volume and size distribution of neocortical neurons

Since the turn of the last century, the average life expectancy has risen considerably. Lengthening of life span has little merit if the quality of life is not preserved and in the elderly the decline in memory and cognitive abilities is of great concern. We applied a stereological technique, the planar rotator method, in an optical vertical design to get an estimation of the three-dimensional volume of the neocortical nuclei and perikaryon volume in neurons from brain neocortex and the four cortical lobes in 39 normal human subjects ranging from 18 to 93 years old. Although there was a trend with p values of 0.07, the mean global neocortical perikaryon volume was not significantly larger in men compared with women and the mean neuronal nuclear volume was not significantly different in the two sexes. Nonetheless, we found gender differences in both frontal and temporal cortices in the perikaryon volume, but not in the nucleus volume. Earlier findings of a higher neocortical neuron number in men compared with women was repeated in this study and, not unexpectedly, the sum of all neuronal perikaryon volume in neocortex was significantly higher in men than women, primarily as a result of a higher neocortical neuron number.