TY - JOUR T1 - Synaptic clustering or scattering? Insight from a model of synaptic plasticity in dendrites JF - bioRxiv DO - 10.1101/029330 SP - 029330 AU - Romain D. Cazé AU - Claudia Clopath AU - Simon R. Schultz Y1 - 2015/01/01 UR - http://biorxiv.org/content/early/2015/10/16/029330.abstract N2 - A large body of theoretical work has shown how dendrites can increase the computational capacity of the neuron. This work predicted that synapses active together should be close together in space, a phenomenon called synaptic clustering. Experimental evidence has shown that, in the absence of sensory stimulation, synapses nearby on the same dendrite tend to be active together more than expected by chance. Synaptic clustering, however, does not seem to be ubiquitous: other groups have reported that nearby synapses can respond to different features of a stimulus during sensory evoked activity. In other words, synapses that are active together during sensory evoked activity can be far apart in space, a phenomenon we term synaptic scattering. To unify these apparently inconsistent experimental results, we use a computational framework to study the formation of a synaptic architecture – a set of synaptic weights – displaying both synaptic clustering and scattering. We present three conditions under which a neuron can learn such synaptic architecture: (i) presynaptic inputs are organized into correlated groups of neurons; (ii) the postsynaptic neuron is compartmentalized in subunits representing dendrites; and (iii) the synaptic plasticity rule is local within a subunit. Importantly, we show that given the same synaptic architecture, synaptic clustering is expressed during spontaneous activity, i.e. in the absence of sensory evoked activity, whereas synaptic scattering is present under evoked activity. Interestingly, reduced dendritic morphology in our model leads to a pathological hyper-excitability, as observed for instance in Alzheimer’s Disease. This work therefore unifies a seemingly contradictory set of experimental observations: we demonstrate that the same synaptic architecture can lead to synaptic clustering and scattering depending on the input structure.Author Summary Neurons connect together through synapses which are distributed on dendrites. The spatial distribution of active synapses on the tree-shaped dendrites is under debate. Do active synapses cluster or scatter on dendrites? Experimentalists observe both types of spatial distributions depending on the presence/absence of a sensory stimulus. Our modelling study explains how the two distributions can co-exist within a single learned synaptic architecture, and we observe in our model clusters/scatters in the absence/presence of a sensory stimulus. We further show that the same learning mechanism can lead to a maladaptive outcome. When the number of dendrites decreases, as observed in Alzheimer’s Disease, neurons become hyper-excitable. This result sheds a new light on the link between dendrites and neuropathologies. ER -