An energy budget for signaling in the grey matter of the brain.
Level 5 - mechanism / opinion, no new human data
Mechanism-based computational modeling and energy budget analysis using published physiological data (Level 5 by CEBM / design analogy).
PubMed 11598490 · doi:10.1097/00004647-200110000-00001
What was done
Anatomical and physiological data were used to analyze energy expenditure across components of excitatory signaling in rodent grey matter, modeling the costs of action potentials, postsynaptic glutamate effects, resting potentials, and glutamate recycling.
What was found
Action potentials and postsynaptic effects of glutamate were predicted to consume 47% and 34% of signaling energy, respectively, while resting potential consumed 13% and glutamate recycling used 3%. An increase in activity of 1 action potential per cortical neuron per second was estimated to raise oxygen consumption by 145 mL/100 g grey matter per hour. The model predicts distributed coding with <=15% of neurons simultaneously active to minimize energy consumption, and indicates that functional magnetic resonance imaging signals are likely dominated by synaptic currents and action potential propagation.
Why it matters
This provides a quantitative framework connecting neural metabolic demands to sparse coding principles and the biophysical interpretation of functional neuroimaging signals.
Limits
The estimates are based on computational synthesis of existing anatomical and physiological data rather than new direct empirical measurements. The model is specific to rodent excitatory grey matter signaling and does not provide empirical sample sizes or direct human data.
Cited by
- supports Up to 50% of the ATP in active neurons is consumed by sodium and calcium pumps to restore resting membrane ion gradients after firing.