The independent influence of concussive and sub-concussive impacts on soccer players' neurophysiological and neuropsychological function R. Davis Moore, PhD a, ⁎, Julien Lepine, MS b , Dave Ellemberg, PhD b a University of South Carolina, Arnold School of Public Health, 921 Assembly Street, Columbia, SC 29201, USA b Université de Montréal, Départment de Kinésiologie, 100 boul. Édouard-Montpetit, Montréal, Québec H3T 1J4, Canada abstract article info Article history: Received 16 July 2016 Received in revised form 27 October 2016 Accepted 11 November 2016 Available online 17 November 2016 Accumulating research demonstrates that repetitive sub-concussive impacts can alter the structure, function and connectivity of the brain. However, the functional significance of these alterations as well as the independent contribution of concussive and sub-concussive impacts to neurophysiological and neuropsychological health are unclear. Accordingly, we compared the neurophysiological and neuropsychological function of contact ath- letes with (concussion group) and without (sub-concussion group) a history of concussion, to non-contact ath- letes. We evaluated event-related brain potentials (ERPs) elicited during an oddball task and performance on a targeted battery of neuropsychological tasks. Athletes in the sub-concussion and concussion groups exhibited similar amplitude reductions in the ERP indices of attentional resource allocation (P3b) and attentional orienting (P3a) relative to non-contact athletes. However, only athletes in the concussion group exhibited reduced ampli- tude in the ERP index of perceptual attention (N1). Athletes in the sub-concussion and concussion groups also exhibited deficits in memory recall relative to non-contact athletes, but athletes in the concussion group also ex- hibited significantly more recall errors than athletes in the sub-concussion group. Additionally, only athletes in the concussion group exhibited response delays during the oddball task. The current findings suggest that sub- concussive impacts are associated with alterations in the neurophysiological and neuropsychological indices of essential cognitive functions, albeit to a lesser degree than the combination of sub-concussive and concussive impacts. © 2016 Elsevier B.V. All rights reserved. Keywords: Sub-concussion Concussion Neurophysiology ERPs Neuropsychology 1. Introduction Although concussions are recognized as the cause of a spectrum of neurological alterations (Marchi et al., 2013), the vast majority of im- pacts incurred during sport fall into the category of sub-concussive (Greenwald et al., 2008; Crisco et al., 2012). A sub-concussive impact is a force imparted to the brain which does not result in the acute mor- bidity and symptoms associated with concussion (Broglio et al., 2012). The force of these impacts varies greatly, ranging from 6 - to 100+ gs (Zhang et al., 2004; McAllister et al., 2012; Broglio et al., 2009; Breedlove et al., 2012). On average, however, a sub-concussive blow from heading in soccer or tackling in football imparts 20–40 linear gs or 1350–2350 rotational rads to the head (McAllister et al., 2012; Svaldi et al., 2015; Breedlove et al., 2012). Athletes routinely incur more than a dozen sub-concussive impacts in a single game (Crisco et al., 2010; McAllister et al., 2012), but unlike concussive injuries, athletes are not removed from play or evaluated following repetitive sub- concussive impacts. As athletes may incur hundreds of sub-concussive impacts during a season, these impacts may represent a serious neuro- logical health issue (McKee et al., 2009; Marchi et al., 2013). Increasing research examines the influence of repetitive sub-concus- sive impacts on the neurophysiological and neuropsychological health of athletes. Studies relying solely on neuropsychological testing report mixed results, with some indicating that sub-concussive blows lead to alterations in attention and executive functions (Straume-Næsheim et al., 2009; Breedlove et al., 2014), while others report little-to-no effect (Guskiewicz et al., 2002; Kaminski et al., 2007; Putukian et al., 2000). In contrast, research utilizing neuroimaging appears consistent in sug- gesting that accumulative sub-concussive impacts lead to alterations in neural structure and function (Abbas et al., 2015; Poole et al., 2014; Marchi et al., 2013; Chun et al., 2015; McAllister et al., 2014; Johnson et al., 2014). For example, Poole et al. (2014) observed that following their football season, high school athletes who incurred sub-concussive impacts exhibited multiple neuro-metabolic alterations in the dorsolat- eral prefrontal (DLPFC) cortex and the primary motor area (M1), brain regions essential to higher cognition and the voluntary control of behav- ior (Aron et al., 2004; Diamond, 2013). Further, the number of sub-con- cussive impacts incurred during the season was correlated with the degree of neuro-metabolic alterations. Thus, repetitive sub-concussive International Journal of Psychophysiology 112 (2017) 22–30 ⁎ Corresponding author. E-mail addresses: moorerd3@mailbox.sc.edu (R.D. Moore), julien.lepine@umontreal.ca (J. Lepine), dave.ellemberg@umontreal.ca (D. Ellemberg). http://dx.doi.org/10.1016/j.ijpsycho.2016.11.011 0167-8760/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect International Journal of Psychophysiology journal homepage: www.elsevier.com/locate/ijpsycho