The flow of axonal information among hippocampal subregions: 2. Patterned stimulation sharpens routing of information transmission

The subregions of the hippocampal formation are essential for episodic learning and memory formation, yet the spike dynamics of each region contributing to this function are poorly understood, in part because of a lack of access to the inter-regional communicating axons. Here we reconstructed hippocampal networks confined to four subcompartments in 2D cultures on a multi-electrode array that monitors individual communicating axons. In our novel device, somal and axonal activity were measured simultaneously with the ability to ascertain the direction and speed of information transmission. Each subregion and inter-regional axons had unique power-law spiking dynamics, indicating differences in computational functions. After stimulation, spiking and burst rates decreased in all subregions, spikes per burst generally decreased, intraburst spike rates increased, and burst duration decreased, which were specific for each subregion. These changes in spiking dynamics post-stimulation were found ..., Four Chamber In Vitro Hippocampal Neuronal Network Culture
Details were provided previously in Vakilna (Vakilna et al., 2021). Briefly, MEA120 glass multielectrode arrays (MEA) with 120 30 μm diameter electrodes spaced 0.2 mm apart were used as substrates for the culture of neuronal networks (Multichannel Systems, Reutlingen, Germany; ALA Scientific, Farmingdale, NY, USA). The MEA was divided by a custom polydimethylsiloxane (PDMS) device into four subregions each of 9.7 mm2 by 1 mm high wells and 51 microfluidic tunnels 3 μm high x 10 μm wide x 400 μm long spaced 50 μm apart (Figure 2). Five of the 51 interregional tunnels were monitored with pairs of electrodes to determine the direction of action potentials in single axons. This dedicated 19 electrodes into each subregional well. After oxygen plasma treatment of the substrate, the wells were coated with poly-D-lysine for cell adhesion. Hippocampal subregions were micro-dissected from postnatal day 4 Sprague-Dawley rat pups under anes..., , # The Flow of Axonal Information Among Hippocampal Subregions: 2. Subregionally-Specific Network Responses to Patterned Stimulation Sharpens Routing of Information Transmission

Contained are spike data from MultiChannel Systems MEA 120 electrodes in cultured mammalian hippocampi. Directionally specific axonal transmission was measured by the delay between two electrodes spanning a microfluidic tunnel. Tunnels are narrow enough whereas the majority of tunnels contain only one axon. Two stimulation patterns were developed to induce long-term potentiation. High-frequency stimulation (HFS) trains were delivered at high and low theta intervals. The first set of HFS patterns has five cycles delivered at high theta intervals (HFS 5). The second set of HFS patterns has forty cycles delivered at low theta intervals (HFS 40). There are nine unstimulated recordings and six stimulated recordings per stimulation pattern in the same arrays. Axonal tunnels are as follows:

* A6-A7
* B6-B7
* C...