The density of synapses and neurons in normal, mentally defective ageing human brains.
The densities of synapses and neurons were measured in 7 neurosurgical specimens of cerebral cortex, regarded as normal controls. The average result was 6 times 10-11 synapses/cm3, 15-6 times 10-6 neurons/cm3, and 38,000 synapses per neuron. Specimens of frontal and temporal cortex from 7 ageing brains (68 to 89 years) gave closely similar counts of neurons and synapses. Seven specimens from 3 severely retarded brains gave similar counts of neurons and slightly higher counts of synapses. A deficit of synaptic development is thus not a necessarre discussed.
D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging; D002452:Cell Count; D002540:Cerebral Cortex / Q000166:cytology / Q000473:pathology*; D004314:Down Syndrome / Q000473:pathology; D005260:Female; D005625:Frontal Lobe / Q000473:pathology; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009474:Neurons; D010296:Parietal Lobe / Q000473:pathology; D013569:Synapses; D013702:Temporal Lobe / Q000473:pathology