How does neuronal count change from birth to adulthood?

How does neuronal count change from birth to adulthood?

• A. Increases to 200B.
• B. Remains constant at 150B.
• C. Declines from about 200B at birth to about 100B in adulthood.
• D. Doubles by adulthood.

Answer: (C)

Neuronal numbers are shaped by overproduction followed by selective elimination during development. The brain initially creates a vast supply of neurons, but many undergo programmed cell death and pruning as circuits are refined, so the total number is reduced. This leads to a typical estimate of about 200 billion neurons at birth and roughly 100 billion in adulthood. After early development, the neuron count stabilizes; adult neurogenesis occurs only in limited regions (like parts of the hippocampus) and does not offset the early loss, so the net number does not increase to birth levels. That’s why the statement describing a decline from ~200B to ~100B best fits the data.

Neuronal numbers are shaped by overproduction followed by selective elimination during development. The brain initially creates a vast supply of neurons, but many undergo programmed cell death and pruning as circuits are refined, so the total number is reduced. This leads to a typical estimate of about 200 billion neurons at birth and roughly 100 billion in adulthood. After early development, the neuron count stabilizes; adult neurogenesis occurs only in limited regions (like parts of the hippocampus) and does not offset the early loss, so the net number does not increase to birth levels. That’s why the statement describing a decline from ~200B to ~100B best fits the data.