title: Depression-biased reverse plasticity rule is required for stable learning at top-down connections.
abstract: Top-down synapses are ubiquitous throughout neocortex and play a central role in cognition, yet little is known about their development and specificity. During sensory experience, lower neocortical areas are activated before higher ones, causing top-down synapses to experience a preponderance of post-synaptic activity preceding pre-synaptic activity. This timing pattern is the opposite of that experienced by bottom-up synapses, which suggests that different versions of spike-timing dependent synaptic plasticity (STDP) rules may be required at top-down synapses. We consider a two-layer neural network model and investigate which STDP rules can lead to a distribution of top-down synaptic weights that is stable, diverse and avoids strong loops. We introduce a temporally reversed rule (rSTDP) where top-down synapses are potentiated if post-synaptic activity precedes pre-synaptic activity. Combining analytical work and integrate-and-fire simulations, we show that only depression-biased rSTDP (and not classical STDP) produces stable and diverse top-down weights. The conclusions did not change upon addition of homeostatic mechanisms, multiplicative STDP rules or weak external input to the top neurons. Our prediction for rSTDP at top-down synapses, which are distally located, is supported by recent neurophysiological evidence showing the existence of temporally reversed STDP in synapses that are distal to the post-synaptic cell body.
authors.affiliation: Department of Neurology and Ophthalmology, Children's Hospital Boston, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Kendra S
authors.initials: KS
authors.lastname: Burbank
authors.forename: Gabriel
authors.initials: G
authors.lastname: Kreiman
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D003198:Computer Simulation; D006801:Humans; D036881:Long-Term Synaptic Depression / Q000502:physiology*; D008959:Models, Neurological; D019579:Neocortex / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology