Analysis of β rhythm induction in acute brain slices using field potential imaging with ultra-high-density CMOS-based microelectrode array.

Carbachol-induced beta rhythms in acute brain slices provide a promising ex vivo platform for evaluating compound effects under arousal-like hippocampal activity. Although microelectrode array (MEA) systems offer a non-invasive means of recording network dynamics, conventional MEAs have been limited by low electrode counts and small sensing areas, allowing only fragmented evaluation of neural activity. In this study, we applied field potential imaging (FPI) using an ultra-high-density (UHD) CMOS-MEA comprising 236,880 electrodes to simultaneously and spatially resolve carbachol-induced activity changes in the hippocampus and neocortex. Treatment with 10 {micro}M carbachol reliably induced oscillatory activity in the hippocampus at 1.33 {+/-} 0.33 Hz. Repetitive and temporally precise firing patterns originated in the CA3 region and propagated toward CA1. The average duration of individual oscillatory events was 52.82 {+/-} 6.44 ms, corresponding to a frequency of 18.93 {+/-} 3.03 Hz--within the beta frequency band. Cluster analysis based on waveform morphology revealed spatial groupings that reflected underlying anatomical structures. Beta-band power was significantly enhanced in both hippocampal and cortical regions following carbachol treatment. These findings demonstrate that the FPI platform enables high-resolution mapping of relationships between anatomical structures and brain function in acute slices, and holds promise as a pharmacological evaluation tool for assessing compound effects on hippocampal and cortical networks under wakefulness-like conditions.