Kosuke Itoh ^1* Norihide Kikumura ² Tamao Maeda ^3,4 Satoshi Hirata ³ Monamie Ringhofer ²

• ¹ Niigata University, Niigata, Niigata, Japan
• ² Teikyo University of Science, Uenohara, Japan
• ³ Kyoto University, Kyoto, Japan
• ⁴ The Graduate University of Advanced Sciences (SOKENDA), Hayama, Japan

Despite the long history of the horse-human bond, our understanding of the brain and mind of horses remains limited due to the lack of methods to investigate their brain functions. This study introduces a novel methodology for completely non-invasive, multi-channel recording of electroencephalography (EEG) and evoked potentials in awake horses to examine equine auditory cortical processing. The new approach utilizes specially designed brush-shaped active electrodes that facilitate stable signal acquisition through the hair coat by penetrating electrode pins and integrated pre-amplifiers. A 12-channel electrode array provided greater scalp coverage than prior work. As a proof of concept, clear cortical auditory evoked potentials (CAEPs) were recorded in response to sound onsets and offsets. The equine CAEP waveform morphology resembled the human P1-N1-P2-N2 complex, although the latencies were shorter than typical human values. The CAEP amplitudes were maximal at centroparietal electrodes, contrasting with the frontocentral distribution seen in humans, potentially explained by differences in auditory cortex orientation between species. This non-invasive multi-electrode method enables the evaluation of cognitive abilities, normal and abnormal brain functions, and advances scientific understanding of the equine mind. It offers potential widespread applications for recording EEGs and evoked potentials in awake horses and other medium-to-large mammalian species. their associated disorders (Murphy and Arkins, 2007; Brubaker and Udell, 2016), reflecting the inherent challenges of conducting laboratory experiments with these animals.Scalp-recorded cortical evoked potentials (EPs) and event-related potentials elicited by sensory stimuli, such as auditory, visual, and somatosensory stimuli, serve as valuable tools in human medicine and neuroscience for non-invasively probing cerebral functions and associated disorders. However, the utilization of scalp-recorded cortical EPs in equine subjects has been scarce, despite their potential benefits. This underutilization stems primarily from methodological challenges specific to recording cortical EPs in alert horses, rather than a general difficulty in acquiring electrical signals from the living equine brain. Prior studies have successfully recorded continuous electroencephalograms (EEGs) in conscious horses (