Biology subjects

Barbour, B.

Publications and source records attributed to Barbour, B..

3 recordsLinked to original sources

bioRxiv2025

Multivesicular release at a small central excitatory synaptic contact

We set out to study the properties of excitatory synaptic transmission at a central connection likely to consist of a single small synaptic contact. In the cerebellar cortex, molecular layer interneurones extend sparse thin dendrites in a parasagittal plane. The nonbranching parallel fibres traverse at right angles to the dendritic plane, forming en passant excitatory synapses. This arrangement makes it very likely that any synaptic connection between a parallel fibre and an interneurone will involve only a single contact. We obtained 20 paired recordings of synaptically connected granule cells and interneurones in cerebellar slices of immature rat, recorded at room temperature. Three of these pairs were successfully labelled using biocytin and a single point of contact between them was indentified. In 19/20 recordings, multiple release events corresponding to asynchronously released vesicles were frequently resolved following a single action potential. The frequency of these events could not be accounted for by spontaneous EPSCs, whose frequency was very low. We conclude that at this excitatory synaptic contact an action potential can release more than one vesicle.

neuroscience↗

bioRxiv2022

Automatic post-processing and merging of multiple spike-sorting analyses with Lussac

The rise in site counts of multi-electrodes used in extracellular recordings in the brain has driven the development of increasingly automated spike-sorting packages. However, post-processing is still largely manual and it remains difficult to determine the optimal package and parameters for a given recording. It has recently been shown that different packages produce quite disparate outputs, suggesting that a combination of analyses might be beneficial. Here, we describe the formalization of existing and new metrics of unit quality and comparison, then build upon these to automate the creation of a consensus output from multiple analyses. We validated our package against synthetic and real ground truths. Compared to individual analyses, our package increased the yield and quality of correct units (doubling the yield of Purkinje cells in our recordings) and, crucially, eliminated numerous incorrect units that were impossible to identify in a single analysis. These improvements also increase analytical objectivity and reduce manual effort.

neuroscience↗

bioRxiv2020

Large, stable spikes exhibit differential broadening in excitatory and inhibitory neocortical boutons

Presynaptic action potential spikes control neurotransmitter release and thus interneuronal communication. However, the properties and the dynamics of presynaptic spikes in the neocortex remain enigmatic because boutons in the neocortex are small and direct patch-clamp recordings have not been performed. Here we report direct recordings from boutons of neocortical pyramidal neurons and interneurons. Our data reveal rapid and large presynaptic action potentials in layer 5 neurons and fast-spiking interneurons reliably propagating into axon collaterals. For in-depth analyses we validate boutons of mature cultured neurons as models for excitatory neocortical boutons, demonstrating that the presynaptic spike amplitude was unaffected by potassium channels, homeostatic long-term plasticity, and high-frequency firing. In contrast to the stable amplitude, presynaptic spikes profoundly broadened for example during high-frequency firing in layer 5 pyramidal neurons but not in fast-spiking interneurons. Thus, our data demonstrate large presynaptic spikes and fundamental differences between excitatory and inhibitory boutons in the neocortex.

neuroscience↗