Biology subjects

Danskin, B.

Publications and source records attributed to Danskin, B..

3 recordsLinked to original sources

bioRxiv2026

Axons organize into micro-tracts around the cortical vasculature

Neural activity is metabolically costly and supported by local increases in cerebral blood flow. The process by which neural activity drives blood flow increase, neurovascular coupling (NVC), remains poorly understood. One persistent knowledge gap is how subcellular compartments are arranged at the vascular wall, where local signaling occurs. This requires a survey of the neurovascular interface at the nanometer scale. To this end, we analyzed a ~1 mm3 volume of mouse visual cortex imaged with serial electron microscopy. We manually labeled different vascular zones, and classified the EM segments surrounding hundreds of vessel segments across these zones. We found that capillaries and venous vessels are surrounded by more axonal volume than arteriolar vessels. Perivascular axons tended to bundle into micro-tracts, where axons ran in parallel and coursed near the vessel wall in a variety of geometric orientations. Micro-tracts cover ~60% of the surface of capillaries, but only 24-40% of every other vascular zone's surface. Finally, we show that the extensive axon arbors of basket cell inhibitor neurons are within micro-tracts. Their axons come in closest proximity to vessels, and on average, approach 2 to 3 fold more vessel segments than other neuronal subtypes. Altogether, perivascular axonal micro-tracts may be an important physical substrate for NVC signaling at capillaries.

neuroscience↗

bioRxiv2026

Direct Reconstruction of DC Cortical Conductivity from Large-Scale Electron Microscopy Data

Electrical conductivity of cortical gray matter governs the magnitude and spatial distribution of electric fields generated by brain stimulation and intrinsic neuronal activity measured with M/EEG and intracortical recordings. However, reported macroscopic conductivity values vary by more than threefold, limiting the fidelity of bioelectromagnetic models and leaving unresolved whether this variability reflects measurement uncertainty or genuine structural heterogeneity of cortical tissue. Here, we present a multiscale computational framework that, for the first time, attempts to derive mesoscale conductivity maps of mouse visual cortex at 50-{micro}m resolution directly from large-volume, segmented nanometer-scale electron microscopy data. The Minnie 65 subvolume of the MICrONS dataset is accurately subdivided into 1,224 50-{micro}m cubic blocks. Each block contains, on average, 40-50 million membrane facets of a highly convoluted and dense cellular structure. Three orthogonal electrode pairs are applied to each isolated block to estimate the three principal components of the conductivity tensor. Quasistatic electric modeling is enabled by an iterative boundary-element fast multipole method (BEM-FMM) under the approximation of non-conducting membranes (DC conductivity). Spatially averaged conductivity values predicted by our framework agree well with prior low-resolution measurements in rats, validating the approach. At the same time, the resulting mesoscale maps reveal pronounced conductivity granularity at 50-100 {micro}m scales as well as significant variations in both radial and tangential directions. These results indicate that mesoscale conductivity heterogeneity could be an intrinsic structural property of the cortex. Limitations and extensions of this study are discussed in detail.

neuroscience↗

bioRxiv2026

Are Synaptic Clefts Directionally Oriented?

Synapses are fundamental building blocks of cortical circuits, yet their geometry is typically regarded as a local property, independent of mesoscale architecture. The prevailing assumption is that synaptic clefts are isotropically oriented in space. Here, we test this assumption by analyzing approximately 117 million synaptic clefts from two independent 1 mm3 electron microscopy datasets: the human H01 middle temporal gyrus and the mouse MICrONS primary visual cortex, using three independent cleft-extraction methods. Across both volumes, we observe that synaptic cleft orientations are not randomly distributed, but instead show statistically significant and spatially coherent directional biases across cortical layers. This mesoscale anisotropy is conserved across species, yet is stronger and more consistent in human association cortex than in mouse sensory cortex, a difference that may reflect the expanded dendritic arbors and greater integrative demands of human pyramidal neurons. We propose that cleft orientation bias is a geometric consequence of the axonal and dendritic architecture that shapes synapse formation, representing a new candidate organizational feature of cortical microarchitecture with potential implications for circuit computation and neuromodulation. These findings motivate targeted physiological studies to determine whether synaptic orientation contributes causally to cortical function.

neuroscience↗