Investigating Fractal Analysis as a Diagnostic Tool That Probes the Connectivity of Hippocampal Neurons
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Date
2022-06-23
Authors
Rowland, Conor
Harland, Julian H.
Smith, Julian H.
Moslehi, Saba
Dalrymple-Alford, John
Taylor, Richard P.
Journal Title
Journal ISSN
Volume Title
Publisher
Frontiers in Physiology
Abstract
Many of nature’s fractal objects benefit from the favorable functionality that results from
their pattern repetition at multiple scales. Our recent research focused on the importance
of fractal scaling in establishing connectivity between neurons. Fractal dimension DA of the
neuron arbors was shown to relate to the optimization of competing functional
constraints—the ability of dendrites to connect to other neurons versus the costs
associated with building the dendrites. Here, we consider whether pathological states
of neurons might affect this fractal optimization and if changes in DA might therefore be
used as a diagnostic tool in parallel with traditional measures like Sholl analyses. We use
confocal microscopy to obtain images of CA1 pyramidal neurons in the coronal plane of
the dorsal rat hippocampus and construct 3-dimensional models of the dendritic arbors
using Neurolucida software. We examine six rodent groups which vary in brain condition
(whether they had lesions in the anterior thalamic nuclei, ATN) and experience (their
housing environment and experience in a spatial task). Previously, we showed ATN lesions
reduced spine density in hippocampal CA1 neurons, whereas enriched housing increased
spine density in both ATN lesion and sham rats. Here, we investigate whether ATN lesions
and experience also effect the complexity and connectivity of CA1 dendritic arbors. We
show that sham rats exposed to enriched housing and spatial memory training exhibited
higher complexity (as measured by DA) and connectivity compared to other groups. When
we categorize the rodent groups into those with or without lesions, we find that both
categories achieve an optimal balance of connectivity with respect to material cost.
However, the DA value used to achieve this optimization does not change between
these two categories, suggesting any morphological differences induced by the lesions are
too small to influence the optimization process. Accordingly, we highlight considerations
associated with applying our technique to publicly accessible repositories of neuron
images with a broader range of pathological conditions.
Description
12 pages
Keywords
Neurons, Connectivity, Fractal analysis, Fractal dimension (D), Modified Sholl Analysis, Neuromorphology, Hippocampal CA1, Anterior thalmic nuclei
Citation
Rowland C, Harland B, Smith JH, Moslehi S, Dalrymple-Alford J and Taylor RP (2022) Investigating Fractal Analysis as a Diagnostic Tool That Probes the Connectivity of Hippocampal Neurons. Front. Physiol. 13:932598. doi: 10.3389/fphys.2022.932598