Abstract

The brain’s computational power is limited by its energy supply. By devising an energy budget for the grey matter, I will explain how key design features of the brain, such as the millisecond timescale of neural processing, the properties of glutamate receptors and the size of synaptic boutons, are determined by the energy supply the brain receives as oxygen and glucose. I will examine why the white matter uses less energy than the grey matter, whether myelination really saves energy, and whether internodal axons need metabolic support from their myelinating glia. I will present a simple account of how information flow through synapses relates to the energy used by the synapses and show that this explains why synapses are unreliable transmitters of information. I will demonstrate that the primary locus of control of the brain’s energy supply is in capillaries rather than arterioles. Finally, I will describe how, in diseases like stroke, cerebral palsy and spinal cord injury, failure of the energy supply leads to glutamate transporter reversal, which damages neurons and oligodendrocytes and causes mental and physical disability.