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PMID-23273272 A cellular mechanism for cortical associations: and organizing principle for the cerebral cortex
See also: PMID-25174710 Sensory-evoked LTP driven by dendritic plateau potentials in vivo
And: The binding solution?, a blog post covering Bittner 2015 that looks at rapid dendritic plasticity in the hippocampus as a means of binding stimuli to place fields. | ||
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PMID-24204224 The Convallis rule for unsupervised learning in cortical networks 2013 - Pierre Yger 1 , Kenneth D Harris This paper aims to unify and reconcile experimental evidence of in-vivo learning rules with established STDP rules. In particular, the STDP rule fails to accurately predict change in strength in response to spike triplets, e.g. pre-post-pre or post-pre-post. Their model instead involves the competition between two time-constant threshold circuits / coincidence detectors, one which controls LTD and another LTP, and is such an extension of the classical BCM rule. (BCM: inputs below a threshold will weaken a synapse; those above it will strengthen. ) They derive the model from optimization criteria that neurons should try to optimize the skewedness of the distribution of their membrane potential: much time spent either firing spikes or strongly inhibited. This maps to a objective function F that looks like a valley - hence the 'convallis' in the name (latin for valley); the objective is differentiated to yield a weighting function for weight changes; they also add a shrinkage function (line + heaviside function) to gate weight changes 'off' at resting membrane potential. A network of firing neurons successfully groups correlated rate-encoded inputs, better than the STDP rule. it can also cluster auditory inputs of spoken digits converted into cochleogram. But this all seems relatively toy-like: of course algorithms can associate inputs that co-occur. The same result was found for a recurrent balanced E-I network with the same cochleogram, and convalis performed better than STDP.  Meh. Perhaps the biggest thing I got from the paper was how poorly STDP fares with spike triplets: Pre following post does not 'necessarily' cause LTD; it's more complicated than that, and more consistent with the two different-timeconstant coincidence detectors. This is satisfying as it allows for apical dendritic depolarization to serve as a contextual binding signal - without negatively impacting the associated synaptic weights. | ||
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PMID-25258080 A critical time window for dopamine actions on the structural plasticity of dendritic spines
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PMID-28650477 Video rate volumetric Ca2+ imaging across cortex using seeded iterative demixing (SID) microscopy
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