Oeur and Margulies BMC Neurosci (2020) 21:52 https://doi.org/10.1186/s12868-020-00601-4 BMC Neuroscience RESEARCH ARTICLE Open Access Target detection in healthy 4-week old piglets from a passive two-tone auditory oddball paradigm R. Anna Oeur1 and Susan S. Margulies1,2* Abstract Background: Passive auditory oddball tests are efort independent assessments that evaluate auditory processing and are suitable for paediatric patient groups. Our goal was to develop a two-tone auditory oddball test protocol and use this clinical assessment in an immature large animal model. Event-related potentials captured middle latency P1, N1, and P2 responses in 4-week old (N 16, female) piglets using a custom piglet 32- electrode array on 3 non-con- secutive days. The efect of target tone= frequency (250 Hz and 4000 Hz) on middle latency responses were tested in a subset of animals. Results: Results show that infrequent target tone pulses elicit greater N1 amplitudes than frequent standard tone pulses. There was no efect of day. Electrodes covering the front of the head tend to elicit greater waveform responses. P2 amplitudes increased for higher frequency target tones (4000 Hz) than the regular 1000 Hz target tones (p < 0.05). Conclusions: Two-tone auditory oddball tests produced consistent responses day-to-day. This clinical assessment was successful in the immature large animal model. Keywords: Auditory oddball paradigm, EEG, Event-related potential, Porcine Highlights Background Approximately 283,000 children and adolescents • Two-tone auditory oddball tests were successfully (< 18 years old) visit the emergency department for a assessed in an immature large animal model. sports related traumatic brain injury (TBI) [1]. Consider- • Consistent N1, P2 amplitudes were observed across ing the number of people who fail to seek medical care three non-consecutive test days. due to the seemingly ‘mild’ nature of some brain injury • Infrequent target tone pulses elicited greater ampli- symptoms, the incidence of sports related TBI is likely tude responses than frequent standard tone pulses. much higher and has been estimated to be between 1.3 and 3.8 million [2]. Te primary cause of non-fatal TBI for those 0–4 years old are from falls, and those 5–19 years old are from sport and recreation activities [3]. Mild TBI diagnosis relies on self-reported signs and symptoms and voluntary participatory assessments [4] resulting in greater challenges capturing accurate report- *Correspondence: [email protected] ing and evaluation in the young paediatric population. 2 Emory University, Health Sciences Research Building 1760 Haygood Tere is heightened concern for mTBI in this age group Drive, Suite W242, 30322 Atlanta, Georgia due to the potential long-term neurological sequelae Full list of author information is available at the end of the article afecting cognition and behavior hindering learning and © The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creat iveco mmons .org/licen ses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creat iveco mmons .org/publi cdoma in/ zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Oeur and Margulies BMC Neurosci (2020) 21:52 Page 2 of 9 development, thus supporting the need for objective bio- pressing a button at the presentation of a target stimu- markers of mTBI that are not dependent upon patient lus can involve diferent auditory pathways [18]. Despite reporting and efort [5]. more complex tasks revealing subtleties in auditory def- Electroencephalography (EEG) is a promising tool cits after mTBI [19, 20], these participatory assessments in the study of neurological diseases as it measures the may present an added challenge in the paediatric patient. electrical potential of the brain on the millisecond scale In addition to non-uniform test protocols and stimulus and provides a real-time assessment of neural processes. paradigms employed across studies, diverse fndings can Event related potentials (ERPs), measure brain-related also be attributed to participant ages, sample sizes and activity in response to a stimulus and relates cerebral the mechanisms or causes of head trauma [21, 22]. Te function with defcits and injury outcomes [6, 7]. Audi- mechanism of injury plays a primary role in the patterns tory ERPs from infants and children in response to of trauma where biomechanical characteristics such as speech and sound processing have been correlated with the direction of head movement and relative levels of the development of language suggesting that early dif- head rotation infuence the nature and distribution of ferentiation of speech sounds have favorable associations neural tissue traumas and subsequent injury outcomes with learning and reading capability [8–10]. In addition, [23, 24]. Varying levels of these injury factors likely con- auditory ERPs have been used as indices marking severe tribute to the specifc brain structures and functions that language impairment in children ages 9–15 years old result in diverse signs and symptoms associated with in comparison to age matched controls [11]. Auditory mTBI, possibly leading to sub-types of concussion [25]. oddball paradigms and ERPs are common tests used to Preclinical animal models allow control of a number of elicit auditory processing at the cortical level [12, 13], factors, including biomechanical loading characteristics and have been used as a marker of altered cognition in that permit systematic evaluation of structural, func- various diseased populations including concussion [14], tional, and behavioural outcomes. Pigs are a common schizophrenia [15] and autism [16]. Tese tests are efort large animal model used to study neurological disorders independent tests that present infrequent ‘target’ tone and TBI [26, 27]. Te 4-week old piglet brain is an estab- pulses amongst a series of more frequent ‘standard’ tone lished model of paediatric TBI and has been previously pulses. Typically, the target tone elicits greater electri- used to study difuse axonal injury and intracranial haem- cal potentials refected as larger magnitude responses in orrhage [28, 29]. Te anatomy of the pig brain contains comparison to the standard tones. Common response similar distributions of white and grey matter, in addition characteristic of the auditory oddball paradigm refected to well-formed sulci and gyri that are key to modelling in the EEG waveform are a series of positive peaks (P) and the human brain [30, 31]. Te maturation trajectory of negative troughs (N) subsequently labelled in ascending piglet brains are also similar to the young human brain temporal order (P1, N1, P2) or based on time course (P50 with the 3–4 week old and 3 month old piglet paralleling at 50 ms). Auditory stimulation causes an early positive the child and adolescent brain [32–34]. peak, P1 or P50 around 50 ms and is associated with an Te objective of this study is to establish the auditory orientation to a new sound, not yet infuenced by atten- oddball response, a common study paradigm used in tion. What follows is a negative peak around 100 ms humans, in the 4-week old piglet model to benchmark (N1), thought to be associated with early attention and auditory processing in a healthy cohort. It is hypoth- related to detecting sensory changes. A second positive esized that P1, N1, P2 features will be observable in the peak at 200 ms (P2) is also considered to be involved in waveform responses, and that the infrequent randomized early attention [12, 13]. target tones produce a greater response than the frequent Findings in the literature for concussed patient groups standard tones. A second objective was to examine the have reported attenuated amplitudes and longer latency efect of target tone frequency. In a separate set of tests, responses in comparison to a healthy cohort [17]. Te the frequency of the target tone was four times lower on-going hypothesis is that the altered brain is unable (250 Hz) or higher (4000 Hz) than the regular target tone to mobilize attentional resources to elicit similar magni- (1000 Hz). Te standard tone in all cases was 800 Hz. It tude responses (reduced amplitudes) and longer latencies is hypothesized that the greater the 4000 Hz target tone indicate slower processing speeds [12]. Research fndings would produce a greater P1, N1, and P2 amplitudes than have not been congruent across studies where some have the 250 and 1000 Hz target tones. demonstrated no diferences in ERPs between injured and healthy cohorts, which may be a result of subtleties Methods in the auditory oddball paradigm employed [14]. Pas- All procedures were approved by the Institutional Ani- sively listening to tones versus more complex oddball mal Care and Use Committee (IACUC) at Emory Univer- tasks requiring active participation through counting or sity School of Medicine. Experiments were carried out in Oeur and Margulies BMC Neurosci (2020) 21:52 Page 3 of 9 an AAALAC International (Association for Assessment E’ Prime 2.0 (Psychology Software Tools, Inc, Pittsburgh, and Accreditation of Laboratory Animal Care) accred- PA) stimulus presentation software.