WAVEFORM OF ELEMENTARY SYNAPTIC CURRENTS EMERGE INTO MESOSCOPIC FIELD POTENTIAL PROPERTIES: A NUMERICAL EXPLORATION

Field potentials (FPs) are used as temporal indicators in both physiological and neuropathological research. Finding the pathways and populations of origin is complicated by the myriads of microscopic contributing sources. An intermediate level of spatial aggregation has been explored in recent years that facilitates the scaling up, namely the FP generators, many of which are pathway-specific that provide clean dynamics. We use numerical methods to explore how realistic or imaginary elementary synaptic current waveforms sum to give rise to mesoscopic FPs and if they emerge somehow in FP features. Fragments of FP generators taken in the hippocampus of rodents were reconstructed by using a single realistic elementary waveform, and the estimated train of afferent spikes, i.e., the population afferent dynamics, was then used to test how different elementary waveforms affect reconstructed mesoscopic potentials. Both realistic and mathematical (sine, square or triangle-like) waveforms were tested. The resultant FPs were compared to originals using cross-correlation and other estimates (amplitude, spectral and non-linear properties). Besides a notable impact on FP amplitude, we found sensitive changes in FP features dependent on elementary waveforms, such as power spectra and dimension correlation. We also explored the microscopic dynamics underlying some common patterns, such as sharp waves or gamma oscillations. These results indicate that elementary synaptic waveforms are important to define some mesoscopic properties used to measure/characterize FPs, and they may explain why pathway-specific FP generators can be easily discriminated by using multidimensional spaces built up with FP features (Muñoz-Arnaiz et al., Cerebral Cortex 2025 DOI: 10.1093/cercor/bhaf135).
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