Electroencephalography (EEG) and measures of nociception in cattle

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Drnec, Kim Ann
Stricklin, William R
Simon, Jonathan Z
The first known bovine laser evoked potential (LEP), an EEG response to noxious laser heat stimuli, was measured in 2-3 year old Holstein cows (n=5). The amplitude of the bovine LEP correlated significantly (P<. 05) with behavior scores, the surrogate for self-reporting in human studies. Importantly, and comparable to human studies, the LEP occurs at a latency within which it is considered that cortical potentials reflect increasingly complex cognitive processes, rather than those that are reflexive and non-conscious. Differences between the bovine and human LEP were also determined, that cannot be fully explained at this time. The lack of standardization for large animal EEG-investigations is problematic regarding data sharing across labs. A proposed standard method, for collecting and processing EEG in cattle was developed and is presented. Compared to human studies, signal processing of bovine data required significantly more stringent rejection criteria for data analysis. For example, while wavelet denoising is often used in human EEG; it was found essential for extracting a bovine LEP. In addition, explicitly addressing whether of not cortical potentials were being recorded was necessary to provide foundational background knowledge of bovine EEG. To this end, EEG was recorded under conditions designed to simulate the suppression and excitation of the primary visual cortex, as is measured in humans using eyes-open and eyes-closed. The simulation contrasted a dark and light environment. I propose this protocol to be used in the future large animal studies to verify that cortical potentials are being measured before EEG data recording. My results demonstrate that bovine EEG is a useful bovine cognitive science method, but more sophisticated signal processing techniques are needed to ameliorate issues of artifact. Lowered signal to noise ratios is considerably problematic for evoked response studies in large animals. Importantly, this research determined that a bovine LEP is measurable, and by analogy to human perceptual studies, I contend this demonstrates the cow experiences both the sensation and perception of noxious stimulus as painful.