3 research outputs found
Computational Approach to Dendritic Spine Taxonomy and Shape Transition Analysis
The common approach in morphological analysis of dendritic spines of mammalian neuronal cells is to categorize spines into subpopulations based on whether they are stubby, mushroom, thin, or filopodia shaped. The corresponding cellular models of synaptic plasticity, long-term potentiation, and long-term depression associate the synaptic strength with either spine enlargement or spine shrinkage. Although a variety of automatic spine segmentation and feature extraction methods were developed recently, no approaches allowing for an automatic and unbiased distinction between dendritic spine subpopulations and detailed computational models of spine behavior exist. We propose an automatic and statistically based method for the unsupervised construction of spine shape taxonomy based on arbitrary features. The taxonomy is then utilized in the newly introduced computational model of behavior, which relies on transitions between shapes. Models of different populations are compared using supplied bootstrap-based statistical tests. We compared two populations of spines at two time points. The first population was stimulated with long-term potentiation, and the other in the resting state was used as a control. The comparison of shape transition characteristics allowed us to identify the differences between population behaviors. Although some extreme changes were observed in the stimulated population, statistically significant differences were found only when whole models were compared. The source code of our software is freely available for non-commercial use1
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Nanoscale synaptic plasticity of aspiny interneuron dendrites with respect to characteristic fine structures
Long term plastic changes in synaptic function have been reported in GABAergic
inhibitory interneurons in the mammalian hippocampus but structural changes associated
with plasticity at the predominantly aspiny dendrites is not known. Aspiny dendrites are
known to exhibit two distinct morphological types, smooth and varicose. Because of their
rarity in neuropil we reimaged tissue in which long-term potentiation (LTP) had been
induced by theta-burst stimulation (TBS) in acute hippocampal slices from mature rat
using the tSEM method to obtain sufficiently large fields and measured the response of
aspiny synapses. We report significant changes in synapse size after potentiation
induction in the slice that is influenced by the type of fine structure on which it occurs.
We developed quantitative methods to distinguish smooth from varicose aspiny dendrites
and within varicose dendrites we found that the varicose and inter-varicose regions could
respond differently to TBS. After potentiation induction in the slice synapse ultrastructure
and mitochondria distribution changed in different directions in our two experiments but
the relationship of synapse change and mitochondrial redistribution was consistent. In
both experiments inter-varicose synapses significantly enlarged and were more likely to
occur near mitochondria. In one experiment varicose synapses enlarged and were
associated with more mitochondria. In the other synapses did not change but were less
likely to associate with mitochondria. In smooth type synapses both experiments showed
lower association with mitochondria and synapses either did not change or significantly
decreased. Our findings of divergent ultrastructural changes among different aspiny
dendrite regions may help to reconcile some of the disparate findings showing that
similar stimulation protocols can lead to depressed or potentiated responses from
inhibitory interneurons.Neuroscienc