  During mammalian development the cerebral metabolic rate correlates
qualitatively with synaptogenesis, and both often exhibit bimodal temporal
profiles. Despite these non-monotonic dependencies, it is found based on
empirical data for different mammals that regional metabolic rate per synapse
is approximately conserved from birth to adulthood for a given species (with a
slight deviation from this constancy for human visual and temporal cortices
during adolescence). A typical synapse uses about $(7\pm 2)\cdot 10^{3}$
glucose molecules per second in primate cerebral cortex, and about 5 times of
that amount in cat and rat visual cortices. A theoretical model for brain
metabolic expenditure is used to estimate synaptic signaling and neural spiking
activity during development. It is found that synaptic efficacy is generally
inversely correlated with average firing rate, and additionally, synapses
consume a bulk of metabolic energy, roughly $50-90 %$ during most of the
developmental process (except human temporal cortex $ < 50%$). Overall, these
results suggest a tight regulation of brain electrical and chemical activities
during the formation and consolidation of neural connections. This presumably
reflects strong energetic constraints on brain development.
