Is the brain optimally organized copy

Is the brain optimally organized copy - Which is optimal...

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Which is optimal for opening cans?
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Which is optimal for putting in screws?
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If you were going camping which would you rather take with you?
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Is the nervous system optimized for……. Speed Energy usage Component failure (i.e. redundancy) Computing power Miniaturization Or for some combination of the above???
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What would prevent the nervous system from being optimized? Developmental (or historical) constraints (it has a preset developmental program that cannot be altered). Pleiotropy (elements must be used for multiple purposes and cannot be altered).
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The brain’s energy budget Sengupta et al., 2010
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The brain is costly!! Our brain uses 20% of our resting oxygen consumption (although it comprises only 2% of our body weight). Most of this (94%) is to power the Na + -K + pump to keep our neuronal batteries charged.
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Distribution of mitochondria matches predicted energy usage
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How do we study if something is optimized? Because we cannot often alter the actual properties of systems, we usually test for optimization by modeling. In a model we look to see if we can identify the “ best ” value of some parameter to maximize or minimize a function.
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How to design a drone?
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How to design a drone?
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Modeling Sometimes when we are unable to do experiments, we can gain insights by making a model. Specify the critical variables (start simple ). Begin with as few unconstrained variables as possible (the more constrained a model is, the more robust and believable the result). State hypotheses and vary model parameters to test hypotheses.
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How to save energy in generating an AP Reduce overlap between Na+ and K+ influx. Reduce AP duration. Reduce AP height. Minimize distance between RP and threshold.
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How to save energy in generating an AP Reduce overlap between Na+ and K+ influx. Reduce AP duration.—if too brief cannot charge the membrane. Reduce AP height.—if too short, won’t generate enough Na current to depolarize far ahead. Minimize distance between RP and threshold. —if too close, risk of spontaneous AP.
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Different model neurons: each has K leak , Na, and K currents. Squid axon Crab motorneuron Mouse fast-spiking neuron Bee Kenyon cell Rat hippocampal interneuron Rat granule cell Mouse thalamo-cortical relay neuron Resting potential
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Is there extra Na+ influx due to overlap of Na+ and K+ currents? Squid axon Crab axon Mouse fast Spiking neuron Rat Hippoc. neuron Bee neuron granule neuron Thalamocortical relay neuron
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If the currents are randomly altered can the neuron be optimized on energy expenditure? Some neurons are already optimal. Others neurons are not at all optimal.
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Many neurons are energy efficient. Niven & Laughlin (2008) Energy limitation as a selective pressure on the evolution of sensory
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Is the brain optimally organized copy - Which is optimal...

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