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Title: The non-signalling energy budget of the brain and brain energy as a constraint for information processing
Author: Engl, E.
ISNI:       0000 0004 8497 707X
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2016
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The brain's energy use on signalling has been well-described, but only about half the brain's energy consumption is directly related to information processing. In this thesis, I first assess experimentally the energetic cost of the main non-signalling processes in the brain. I find that the turnover of the actin and the microtubule cytoskeleton is a major energy drain on juvenile rat brain slices. While lipid synthesis is similarly energetically expensive, the energetic cost of protein synthesis is negligible. In the next part of my thesis, I show in brain slices that both strong and weak synapses in the brain's visual system transmit information in an energy-efficient way. I first investigate information transfer and energy consumption at the strong retinogeniculate relay synapse in the dorsal lateral geniculate nucleus of the thalamus. By varying the effective size of the postsynaptic conductance using dynamic clamp, I show that the physiological magnitude of excitatory postsynaptic currents maximises energetic efficiency, i.e. information transmitted per ATP used, rather than maximising the amount of information transferred. I then demonstrate that the same principle of energetic efficiency shapes information transmission at the next synapse in the visual circuit, the weaker thalamocortical synapse. Thus, postsynaptic terminals, where most energy in the brain is consumed, have their properties tuned for energetic efficiency. Next, I assess serotonergic modulation of energetic efficiency at the retinogeniculate synapse, and find a mild effect of a selective 5-HT1 receptor agonist on synaptic transmission characteristics, while energetic efficiency remains unchanged. Finally, I model the current expected to be associated with the uptake of N-acetyl-L-aspartate, a crucial energy substrate in the white matter, into oligodendrocyte lineage cells. In sum, my results show that the brain's non-signalling tasks are surprisingly energetically expensive, and that energy-efficient information transfer is a fundamental principle of brain function.
Supervisor: Attwell, D. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available