Timing of potential and metabolic brain energy.
The temporal relationship between cerebral electro-physiological activities, higher brain functions and brain energy metabolism is reviewed. The duration of action potentials and transmission through glutamate and GABA are most often less than 5 ms. Subjects may perform complex psycho-physiological tasks within 50 to 200 ms, and perception of conscious experience requires 0.5 to 2 s. Activation of cerebral oxygen consumption starts after at least 100 ms and increases of local blood flow become maximal after about 1 s. Current imaging technologies are unable to detect rapid physiological brain functions. We introduce the concepts of potential and metabolic brain energy to distinguish trans-membrane gradients of ions or neurotransmitters and the capacity to generate energy from intra- or extra-cerebral substrates, respectively. Higher brain functions, such as memory retrieval, speaking, consciousness and self-consciousness are so fast that their execution depends primarily on fast neurotransmission (in the millisecond range) and action-potentials. In other words: brain functioning requires primarily maximal potential energy. Metabolic brain energy is necessary to restore and maintain the potential energy.
Korf
Jakob
J
Department of Psychiatry and Graduate School of Behavioural and Cognitive Neurosciences, Groningen University, Groningen, The Netherlands. j.korf@psy.umcg.nl
Gramsbergen
Jan Bert
JB
D000200:Action Potentials / Q000502:physiology* / Q000528:radiation effects; D000818:Animals; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D004734:Energy Metabolism / Q000502:physiology*; D018698:Glutamic Acid / Q000378:metabolism; D006439:Hemodynamics / Q000502:physiology / Q000528:radiation effects; D006728:Hormones / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D006728:Hormones; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid