The equipment utilized in the initial experiment (investigative SSVEP) was provided by the School of Aerospace, Mechanical and Mechatronic Engineering at The University of Sydney. Equipment utilized in the latter half of the study, the integrated SSVEP and EEG systems, were provided by HeadsafeIP.

<ol>
	<li>McCrory, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Consensus+statement+on+concussion+in+sport-the+5(th)+international+conference+on+concussion+in+sport+held+in+Berlin,+October+2016.">Consensus statement on concussion in sport-the 5(th) international conference on concussion in sport held in Berlin, October 2016.</a> British Journal of Sports Medicine. 51 (11), 838-847 (2017).</li><li>Kilcoyne, K. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reported+concussion+rates+for+three+division+I+football+programs:+an+evaluation+of+the+new+NCAA+concussion+Policy.">Reported concussion rates for three division I football programs: an evaluation of the new NCAA concussion Policy.</a> Sports Health. 6 (5), 402-405 (2014).</li><li>Fuller, C. W., Taylor, A., Raftery, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epidemiology+of+concussion+in+men's+elite+Rugby-7s+(Sevens+World+Series)+and+Rugby-15s+(Rugby+World+Cup,+Junior+World+Championship+and+Rugby+Trophy,+Pacific+Nations+Cup+and+English+Premiership.">Epidemiology of concussion in men's elite Rugby-7s (Sevens World Series) and Rugby-15s (Rugby World Cup, Junior World Championship and Rugby Trophy, Pacific Nations Cup and English Premiership.</a> British Journal of Sports Medicine. 49 (7), 478-483 (2015).</li><li>Gardner, A. J., Iverson, G. L., Williams, W. H., Baker, S., Stanwell, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+systematic+review+and+meta-analysis+of+concussion+in+rugby+union.">A systematic review and meta-analysis of concussion in rugby union.</a> Sports Medicine. 44 (12), 1717-1731 (2014).</li><li>Rice, S. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sport-related+concussion+and+mental+health+outcomes+in+elite+athletes:+a+systematic+review.">Sport-related concussion and mental health outcomes in elite athletes: a systematic review.</a> Sports Medicine. 48 (2), 447-465 (2018).</li><li>Graham, R., Rivara, F. P., Ford, M. A., Spicer, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Institute+of+Medicine+(US)+and+National+Research+Council+(U.S.).+Committee+on+Sports-Related+Concussions+in+Youth+Board+onChildren+Youth+and+Families.">Institute of Medicine (US) and National Research Council (U.S.). Committee on Sports-Related Concussions in Youth Board onChildren Youth and Families.</a> Sports-Related Concussions in Youth: Improving the Science, Changing the Culture. , (2014).</li><li>Partridge, B., Hall, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Repeated+head+injuries+in+Australia's+collision+sports+highlight+ethical+and+evidential+gaps+in+concussion+management+policies.">Repeated head injuries in Australia's collision sports highlight ethical and evidential gaps in concussion management policies.</a> Neuroethics. 8 (1), 39-45 (2015).</li><li>Murray, I. R., Murray, A. D., Robson, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sports+concussion:+time+for+a+culture+change.">Sports concussion: time for a culture change.</a> Clinical Journal of Sport Medicine: Official Journal of the Canadian Academy of Sport Medicine. 25 (2), 75-77 (2015).</li><li>Levin, H. S., Diaz-Arrastia, R. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diagnosis,+prognosis,+and+clinical+management+of+mild+traumatic+brain+injury.">Diagnosis, prognosis, and clinical management of mild traumatic brain injury.</a> The Lancet, Neurology. 14 (5), 506-517 (2015).</li><li>Bey, T., Ostick, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Second+impact+syndrome.">Second impact syndrome.</a> The Journal of Emergency Medicine. 10 (1), 6-10 (2009).</li><li>Meehan, W. P., Mannix, R. C., O'Brien, M. J., Collins, M. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+prevalence+of+undiagnosed+concussions+in+athletes.">The prevalence of undiagnosed concussions in athletes.</a> Clinical Journal of Sport Medicine: Official Journal of the Canadian Academy of Sport Medicine. 23 (5), 339-342 (2013).</li><li>Weinstein, E., Turner, M., Kuzma, B. B., Feuer, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Second+impact+syndrome+in+football:+new+imaging+and+insights+into+a+rare+and+devastating+condition.">Second impact syndrome in football: new imaging and insights into a rare and devastating condition.</a> Journal of Neurosurgery, Pediatrics. 11 (3), 331-334 (2013).</li><li>Stern, R. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+consequences+of+repetitive+brain+trauma:+chronic+traumatic+encephalopathy.">Long-term consequences of repetitive brain trauma: chronic traumatic encephalopathy.</a> PM &amp; R. 3 (10), 460-467 (2011).</li><li>Arciniegas, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+electrophysiologic+assessments+and+mild+traumatic+brain+injury:+state-of-the-science+and+implications+for+clinical+practice.">Clinical electrophysiologic assessments and mild traumatic brain injury: state-of-the-science and implications for clinical practice.</a> International Journal of Psychophysiology. 82 (1), 41-52 (2011).</li><li>Echemendia, R. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Sport+Concussion+Assessment+Tool+5th+Edition+(SCAT5):+Background+and+rationale.">The Sport Concussion Assessment Tool 5th Edition (SCAT5): Background and rationale.</a> British Journal of Sports Medicine. 51 (11), 848-850 (2017).</li><li>Giza, C. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Summary+of+evidence-based+guideline+update:+evaluation+and+management+of+concussion+in+sports:+report+of+the+Guideline+Development+Subcommittee+of+the+American+Academy+of+Neurology.">Summary of evidence-based guideline update: evaluation and management of concussion in sports: report of the Guideline Development Subcommittee of the American Academy of Neurology.</a> Neurology. 80 (24), 2250-2257 (2013).</li><li>Vander Werff, K. R., Rieger, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Auditory+and+cognitive+behavioral+performance+deficits+and+symptom+reporting+in+postconcussion+syndrome+following+mild+traumatic+brain+injury.">Auditory and cognitive behavioral performance deficits and symptom reporting in postconcussion syndrome following mild traumatic brain injury.</a> Journal of Speech, Language, and Hearing Research: JSLHR. 62 (7), 1-18 (2019).</li><li>Asken, B. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Concussion-like+symptom+reporting+in+non-concussed+collegiate+athletes.">Concussion-like symptom reporting in non-concussed collegiate athletes.</a> Archives of Clinical Neuropsychology. 32 (8), 963-971 (2017).</li><li>Echemendia, R. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=What+tests+and+measures+should+be+added+to+the+SCAT3+and+related+tests+to+improve+their+reliability,+sensitivity+and/or+specificity+in+sideline+concussion+diagnosis?+A+systematic+review.">What tests and measures should be added to the SCAT3 and related tests to improve their reliability, sensitivity and/or specificity in sideline concussion diagnosis? A systematic review.</a> British Journal of Sports Medicine. 51 (11), 895-901 (2017).</li><li>Ragan, B., Herrmann, S., Kang, M., Mack, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Psychometric+evaluation+of+the+standardized+assessment+of+concussion:+evaluation+of+baseline+score+validity+using+item+analysis.">Psychometric evaluation of the standardized assessment of concussion: evaluation of baseline score validity using item analysis.</a> Athletic Training &amp; Sports Health Care. 1, 180-187 (2009).</li><li>Freed, S., Hellerstein, L. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visual+electrodiagnostic+findings+in+mild+traumatic+brain+injury.">Visual electrodiagnostic findings in mild traumatic brain injury.</a> Brain Injury. 11 (1), 25-36 (1997).</li><li>Boutin, D., Lassonde, M., Robert, M., Vanassing, P., Ellemberg, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neurophysiological+assessment+prior+to+and+following+sports-related+concussion+during+childhood:+A+case+study.">Neurophysiological assessment prior to and following sports-related concussion during childhood: A case study.</a> Neurocase. 14 (3), 239-248 (2008).</li><li>Phurailatpam, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evoked+potentials:+Visual+evoked+potentials+(VEPs):+Clinical+uses,+origin,+and+confounding+parameters.">Evoked potentials: Visual evoked potentials (VEPs): Clinical uses, origin, and confounding parameters.</a> Journal of Medical Society. 28 (3), 140-144 (2014).</li><li>Kothari, R., Bokariya, P., Singh, S., Singh, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Comprehensive+review+on+methodologies+employed+for+visual+evoked+potentials.">A Comprehensive review on methodologies employed for visual evoked potentials.</a> Scientifica. 2016, 1-9 (2016).</li><li>Dreyer, A. M., Herrmann, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Frequency-modulated+steady-state+visual+evoked+potentials:+a+new+stimulation+method+for+brain-computer+interfaces.">Frequency-modulated steady-state visual evoked potentials: a new stimulation method for brain-computer interfaces.</a> Journal of Neuroscience Methods. 241, 1-9 (2015).</li><li>Norcia, A. M., Appelbaum, L. G., Ales, J. M., Cottereau, B. R., Rossion, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+steady-state+visual+evoked+potential+in+vision+research:+A+review.">The steady-state visual evoked potential in vision research: A review.</a> Journal of Vision. 15 (6), 4 (2015).</li><li>Herbst, S., Javadi, A. -. H., Busch, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+long+depends+on+how+fast+-+perceived+flicker+frequencies+dilate+subjective+duration.">How long depends on how fast - perceived flicker frequencies dilate subjective duration.</a> Journal of Vision. 12, 141 (2012).</li><li>Handy, T. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Event-related Potentials: A Methods Handbook. , (2005).</li><li>Kappenman, E. S., Luck, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Oxford Handbook of Event-Related Potential Components. , (2012).</li><li>. Rugby AU Codes and Policies, Safety and Welfare. Concussion Management Available from: <a target="_blank" href="https://australia.rugby/about/codes-and-policies/safety-and-welfare/concussion-management">https://australia.rugby/about/codes-and-policies/safety-and-welfare/concussion-management</a> (2021)</li><li>Moyer, J. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Standards+for+data+acquisition+and+software-based+analysis+of+in+vivo+electroencephalography+recordings+from+animals.+A+TASK1-WG5+report+of+the+AES/ILAE+Translational+Task+Force+of+the+ILAE.">Standards for data acquisition and software-based analysis of in vivo electroencephalography recordings from animals. A TASK1-WG5 report of the AES/ILAE Translational Task Force of the ILAE.</a> Epilepsia. 58, 53-67 (2017).</li><li>Liu, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> IEEE International Conference on Virtual Environments Human-Computer Interfaces and Measurement Systems (VECIMS) Proceedings. , 34-37 (2012).</li><li>Fong, D. H. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Steady-state+visual-evoked+potentials+as+a+biomarker+for+concussion:+a+pilot+study.">Steady-state visual-evoked potentials as a biomarker for concussion: a pilot study.</a> Frontiers in Neuroscience. 14, 171 (2020).</li><li>Alsalaheen, B., Stockdale, K., Pechumer, D., Broglio, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Validity+of+the+Immediate+Post+Concussion+Assessment+and+Cognitive+Testing+(ImPACT).">Validity of the Immediate Post Concussion Assessment and Cognitive Testing (ImPACT).</a> Sports Medicine. 46 (10), 1487-1501 (2016).</li><li>Slobounov, S. M., Sebastianelli, W. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Concussions in Athletics: from Brain to Behaviour. , (2014).</li><li>Drislane, F. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Clincal Neurophysiology Primer. , 461-473 (2007).</li><li>Moore, R. D., Broglio, S. P., Hillman, C. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sport-related+concussion+and+sensory+function+in+young+adults.">Sport-related concussion and sensory function in young adults.</a> Journal of Athletic Training. 49 (1), 36-41 (2014).</li><li>Yadav, N. K., Ciuffreda, K. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Objective+assessment+of+visual+attention+in+mild+traumatic+brain+injury+(mTBI)+using+visual-evoked+potentials+(VEP).">Objective assessment of visual attention in mild traumatic brain injury (mTBI) using visual-evoked potentials (VEP).</a> Brain Injury. 29 (3), 352-365 (2015).</li></ol>

The authors declare potential conflicts of interest and state them below:
Adrian Cohen is a director of HeadsafeIP Pty Ltd and is noted on Patent applications related to technology in this area.
Dylan Mahony is an employee of HeadsafeIP. HeadsafeIP undertakes research, development, and commercialization of concussion-related technologies. HeadsafeIP Pty. Ltd may benefit financially if products related to this research are successfully marketed.
Daryl Fong is an employee of Cryptych Pty Ltd. Cryptych Pty Ltd provides consulting services to HeadsafeIP on the compliant manufacturing of its device with respect to regulatory requirements.
David Putrino, Joseph Herrera, and Rebecca Baron are employees of the Icahn School of Medicine at Mount Sinai and participate in sponsored research investigating the use-cases of the improved SSVEP device.

This is the first study to develop a protocol that identifies differences in SSVEP responses in healthy male amateur ruby union players at the three stages of a concussion; pre-injury (baseline), concussed, and recovered (Figure 1). The method included the recruitment and screening of 65 participants who were routinely assessed with an investigational SSVEP setup over the course of a competitive season. As the SSVEP setup was relatively simple and portable, all assessments were conducted in a non-clinical environment, demonstrating the potential use as a point-of-care concussion assessment. The study successfully demonstrated that an individual's ability to generate SSVEPs is attenuated following a diagnosed concussion. The depressive impact of a concussion was seen to diminish following a defined recovery period, as seen when SSVEP values returned to a pre-concussed level for each individual. Statistical analysis between the participant groups showed a significance in the SSVEP attenuation effects. The high test-retest reliability in non-concussed participants highlighted the stability of the electrophysiological biomarker in simple and more refined portable SSVEP systems (Table 2). Additionally, the absolute agreement between an SSVEP system and a traditional EEG amplifier, validates the technology for use as a medical aid capable of obtaining research quality EEG signals (Figure 10).
Since this study was dependent on participants volunteering for post-injury as well as repeated assessments during the rugby season, some logistical modifications had to be made to the method. The estimated time periods between baseline and retests had to be flexible to accommodate the participant's schedules. Despite these measures, some players were still lost to follow up for a variety of miscellaneous reasons, including non-related injuries or lack of interest. This resulted in the use of a more comprehensive statistical calculation, ICC, for the device's reliability across weeks. No adverse events to the SSVEP setup were observed. Some logistic issues were encountered that required minor modifications of the protocol: long or thick hair in particular proved troublesome in acquiring good contact between the headset and the participant's scalp. As poor contact would decrease the quality of the EEG readings (Figure 4), participants with long or thick hair were required to brush and hold their hair up and out to the side of their head while the sensors were placed. An additional exclusion criterion was generated due to this issue, where individuals with complex hairstyles (e.g., dreadlocks) were excluded from this study.
As previously outlined in this paper, current concussion assessment tools are highly subjective and are at the risk of manipulation by an athlete that can ultimately hinder a clinician's ability to make a crucially important diagnosis34. Some athlete tracking studies have attempted to investigate a more objective biomarker for concussion through the use of radiological modalities such as magnetic resonance imaging (MRI) and computed tomography (CT). However, these methods only provide information about macroscopic structural injuries such as hemorrhages which vary from the definition of concussion as a functional brain injury6,35. The results of this study are supported by previous studies that demonstrated VEP to be a functional biomarker36, which is attenuated or delayed in the presence of concussion21,37,38. While there are similarities in these previous VEP study methods with respect to our physical setup and hypothesis, our study expands on the literature via the use of SSVEP over VEP. Furthermore, the protocol varies by investigating real-time assessments of players at the three stages of a concussion compared to traditional control vs concussed case studies. Additionally, the method extends its investigative power by comparing innovative and traditional EEG systems to distinguish potential dissimilarities that may limit their accuracy in obtaining objective electrophysiological measurements. Thus, the protocol used in this study provides a unique and valuable addition to existing literature on objective concussion biomarkers.
Despite the overall success of this protocol, there are several limitations to note. For example, a small degree of intra-participant variability in background EEG noise for assessment conducted in immediate succession was noted. Two protocol-design limitations may prove at fault for this first variability: the first being the 14-channel EEG system's lack of high-fidelity impedance feedback and loose constraints for the effects of fatigue and environmental influence on the subject's attentiveness. While this intra-participant variability was not seen with the other EEG systems used in this protocol, it is worth exploring these effects in more detail to confirm their cause is a result of the headset's design and not an unidentified natural occurrence. Second, most participants had larger SSVEP signals after the second assessment versus the first (Table 1). This may be the result of participants becoming more familiar with the assessment process and consequent behavioral adaptations to the equipment setup, including reduced blinking and restlessness during repeat stimulus presentation. Further studies are needed to determine whether there is indeed a familiarization effect to the SSVEP protocol and, if so, what potential modifications need to be made to reduce its occurrence in future studies. Lastly, it is important to note that due to the extensive dependence on volunteers from a relatively small population of individuals (those at high risk of concussion occurrence with the willingness to be repeatably examined), this study was limited to a small sample size of 65 participants, 12 of whom suffered a concussion. Studies with a larger cohort size will be needed in order to evaluate the robustness of this protocol's assessment of concussion, particularly its sensitivity and specificity. It would also be interesting to see this protocol replicated in a range of age groups whose brain development states vary, from those still developing (adolescents) to those with potential cognitive decline (elderly) and delineate whether or not responsivity significantly differs. With respect to the improved SSVEP system, its comparative study highlighted the in-built limitations of the device in comparison to traditional EEG systems. Traditional EEG systems generally adopt the full 10-20 system of montages, which comprise 21 electrode sites (Figure 7B). The SSVEP system on the other hand only uses three electrode channels (O1, O2, and Oz) corresponding to the visual cortex (Figure 7A). This reduction in capability means the system has a narrower scope of EEG applications and limits the potential analysis that can be conducted on the electrophysiological data obtained within this protocol.
As previously mentioned, further research is required to overcome the limitations of this protocol and test its strength on a larger cohort to assess whether its outcomes are able to be generalized. More importantly, additional studies are required to better understand the mechanisms underlying our finding in SSVEP attenuation. For instance, the changes in SSVEP response found in our concussed participants are most likely representations of disturbances in neuronal function, but it is not yet established whether these are primary (e.g., damaged white matter) or secondary (e.g., neuroinflammatory) phenomena. One potential future application of this method is the investigation into the recovery period associated with neuronal depression and concussion individualized to the subject. A deeper insight into this recovery period may see amendments made to sports return to play (RTP) rules and regulations that better protect an injured athlete. This method also introduces the practicality of a portable SSVEP system applied in non-clinical settings, such as a concussion assessment delivered expediently on the sideline of a sporting field. This has the potential to provide significant benefit to not only medical professionals, but coaches, athletes, and their respective families to address the negative physiological effects of concussion and Second Impact Syndrome10,11. The generation of improved SSVEP systems, such as the portable SSVEP system utilized in this study, may see more advanced equipment and technological applications arise in the field of neurophysiology and SRC that will prove beneficial for the success of future studies.
In summary, this protocol proved successful in its aim of identifying SSVEP as an objective biomarker for concussion in contact sport athletes. The study as a whole provides evidence that SSVEP are significantly attenuated in the presence of a concussion and are capable of being reliably produced at a research quality level through a simplified portable EEG system. We, therefore, propose that SSVEP may be used as a supplemental aid for the assessment of concussive injuries, in particular, the sideline assessment of SRC. Further studies with more refined protocols, advanced techniques, and improved equipment may build upon this study and provide critical information to combat the detrimental effects of concussions on athletes' lives.

People now-a-days are greatly aware of the morbidity caused by brain injuries in sport1. A sports related concussion (SRC) is a form of mild traumatic brain injury (mTBI) that is frequently reported in contact sports such as football, rugby, and boxing2,3,4. The biomechanical transduction of impulsive force to the brain following an impact on the field results in a disruption of neuronal function, leading to both immediate and transient symptoms that affect an athlete&#39;s physical, cognitive, and emotional state1,5. In most cases, these symptoms subdue within a short period of time, granted the athlete is appropriately treated and not exposed to further impacts6.
As SRC is detrimental to the neurological health of players, sports&#39; governing bodies face the challenge of employing accurate and timely concussion diagnosis to allow for a safe return-to-play protocol5,7,8,9. However, concussion detection can be precluded by athletes who minimize or deny symptoms to avoid a concussion diagnosis, thus accelerating their return to play. These actions can potentially increase their risk of Second Impact Syndrome, a condition in which rapid cerebral edema forms following a second head injury during the concussion recovery phase10. Additionally, due to the lack of education around concussion diagnosis and the variable nature of its physiological definition, it is not uncommon for SRC to go unreported or misdiagnosed11. Unfortunately, long periods of repeated and inappropriately managed concussions may lead to a range of chronic neurological impairments, such as chronic traumatic encephalopathy (CTE), which is strongly associated with SRC12,13,14.
In an effort to combat the challenges associated with SRC, sports organizations utilize a variety of concussion assessment tools. The most commonly used and accessible tool, sports concussion assessment tool (SCAT), is a standardized paper test that incorporates physical and cognitive assessments in combination with scaled symptom reporting15,16. However, previous studies have demonstrated that symptom reporting is subjective and unreliable by identifying gender differences within mTBI groups and outliers in the control group17,18. More advanced tools that are utilized at a professional level, such as the Immediate Post-Concussion Assessment Tool (ImPACT), which operates as a Computerized Neurocognitive Test (CNT), also fall victim to manipulation as they require active participation and effort from the athlete. Despite built-in checks for manipulation in CNTs, research has shown that they are prone to ceiling effects and suffer poor reliability19,20. The limitations of these existing assessment tools in combination with a more public understanding of the significant health effects of SRC have resulted in a critical need for an objective biomarker that can accurately and timely diagnose a concussion.
One field that has shown promise in identifying an objective biomarker for concussion is electrophysiology. There is emerging evidence that event-related potentials, in particular visual evoked potentials (VEP) are impaired following a concussion21,22. One subset of VEP; steady-state visual-evoked potentials (SSVEP) are an objective, quantifiable fluctuation of electrical activity that occurs in the brain in response to a specific set of visual stimuli, as measured by electroencephalogram (EEG) technology23,24. SSVEP offer an improved resistance to noise artifacts and variable contact impedance to conventional VEP measurements. Also, due to the controlled frequency of the visual stimulus, there is a reduction in synchronicity between EEG recordings and stimulus, resulting in a more simplified electrical model25,26. This approach has been validated with frequencies between the 12-15 Hz range producing an optimal response of salience for flicker type stimuli27. Overall, these advantages mean SSVEP offer a more robust electrophysiological measurement that can be used in a non-clinical setting such as sports fields and physician offices. This sideline application possibility in combination with the technology&#39;s positive results in previous literature makes it a promising candidate for the identification of an objective biomarker for SRC.
The goal of this study was to investigate potential differences in SSVEP that were recorded from athletes who were assessed by an experienced sports doctor as healthy, concussed, or recovered from a recent concussion. The methodology of the study entailed 65 male amateur rugby union players being routinely assessed with a portable SSVEP system over an 18-week competitive season. Players are to be assessed for a baseline prior to the commencement of full-contact training and re-assessed within 72 h following competitive games. Players who were injured during the season were evaluated for concussions by the team&#39;s physician and re-assessed with the SSVEP system for post-injury and recovery readings. Additionally, this study extends its protocol to validate portable SSVEP system&#39;s ability to obtain research-quality EEG readings that can potentially aid in the sideline assessment of SRC.

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			<td>A1822</td>
			<td>iOS Device</td>
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			<td>iPhone 6s</td>
			<td>Apple</td>
			<td>A1633</td>
			<td>iOS Device</td>
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			<td>iTunes</td>
			<td>Apple</td>
			<td>V12.5.5.5</td>
			<td>Mobile Device Management Utility</td>
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			<td>MATLAB</td>
			<td>MathWorks</td>
			<td>&#160;R2015b</td>
			<td>Numerical Computing Software</td>
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			<td>Nurochek iOS App</td>
			<td>HeadsafeIP</td>
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			<td>SSVEP iOS App Software</td>
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			<td>Polyurethane Sensor Cylinders</td>
			<td>Headsafe</td>
			<td>HSIP01-213</td>
			<td>EEG soft electrode contacts</td>
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			<td>Profusion EEG 5</td>
			<td>Compumedics</td>
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			<td>IBM</td>
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			<td>Statistical Analytics Software</td>
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			<td>Weaver</td>
			<td>92100031</td>
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			<td>Sony</td>
			<td>SVP1132A1CL</td>
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			<td>Xperia Z1</td>
			<td>Sony</td>
			<td>C6906</td>
			<td>LCD Smartphone</td>
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objectively assessing sports concussion utilizing visual evoked potentials

A portable system capable of measuring steady-state visual-evoked potentials (SSVEP) was developed to provide an objective, quantifiable method of electroencephalogram (EEG) testing following a traumatic event. In this study, the portable system was used on 65 healthy rugby players throughout a season to determine whether SSVEP are a reliable electrophysiological biomarker for concussion. Preceding the competition season, all players underwent a baseline SSVEP assessment. During the season, players were re-tested within 72 h of a match for either test-retest reliability or post-injury assessment. In the case of a medically diagnosed concussion, players were reassessed again once deemed recovered by a physician. The SSVEP system consisted of a smartphone housed in a VR-frame delivering a 15 Hz flicker stimulus, while a wireless EEG headset recorded occipital activity. Players were instructed to stare at the screen's fixation point while remaining seated and quiet. Electrodes were arranged according to the 10-20 EEG-positioning nomenclature, with O1-O2 being the recording channels while P1-P2 the references and bias, respectively. All EEG data was processed using a Butterworth bandpass filter, Fourier transformation, and normalization to convert data for frequency analysis. Players SSVEP responses were quantified into a signal-to-noise ratio (SNR), with 15 Hz being the desired signal, and summarized into respective study groups for comparison. Concussed players were seen to have a significantly lower SNR compared to their baseline; however, post-recovery, their SNR was not significantly different from the baseline. Test-retest indicated high device reliability for the portable system. An improved portable SSVEP system was also validated against an established EEG amplifier to ensure the investigative design is capable of obtaining research quality EEG measurements. This is the first study to identify differences in SSVEP responses in amateur athletes following a concussion and indicates the potential for SSVEP as an aid in concussion assessment and management.

Watch this Scientific Journal Video about Objectively Assessing Sports Concussion Utilizing Visual Evoked Potentials at JoVE.com

Objectively Assessing Sports Concussion Utilizing Visual Evoked Potentials

A portable system capable of measuring steady-state visual-evoked potentials was developed and trialed on 65 amateur rugby players over 18 weeks to investigate SSVEP as a potential electrophysiological biomarker for concussion. Players' baselines were measured pre-season, with retesting for reliability, concussion, and recovery assessment being conducted within controlled time-periods, respectively.

A portable system capable of measuring steady-state visual-evoked potentials (SSVEP) was developed to provide an objective, quantifiable method of ...

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3.1K Views.  University of Sydney. A portable system capable of measuring steady-state visual-evoked potentials was developed and trialed on 65 amateur rugby players over 18 weeks to investigate SSVEP as a potential electrophysiological biomarker for concussion. Players' baselines were measured pre-season, with retesting for reliability, concussion, and recovery assessment being conducted within controlled time-periods, respectively.

Video: Objectively Assessing Sports Concussion Utilizing Visual Evoked Potentials

Calcium Imaging of Odor-evoked Responses in the Drosophila Antennal Lobe

The antennal lobe is the primary olfactory center in the insect brain and represents the anatomical and functional equivalent of the vertebrate olfactory bulb1-5. Olfactory information in the external world is transmitted to the antennal lobe by olfactory sensory neurons (OSNs), which segregate to distinct regions of neuropil called glomeruli according to the specific olfactory receptor they express. Here, OSN axons synapse with both local interneurons (LNs), whose processes can innervate many different glomeruli, and projection neurons (PNs), which convey olfactory information to higher olfactory brain regions.
Optical imaging of the activity of OSNs, LNs and PNs in the antennal lobe - traditionally using synthetic calcium indicators (e.g. calcium green, FURA-2) or voltage-sensitive dyes (e.g. RH414) - has long been an important technique to understand how olfactory stimuli are represented as spatial and temporal patterns of glomerular activity in many species of insects6-10. Development of genetically-encoded neural activity reporters, such as the fluorescent calcium indicators G-CaMP11,12 and Cameleon13, the bioluminescent calcium indicator GFP-aequorin14,15, or a reporter of synaptic transmission, synapto-pHluorin16 has made the olfactory system of the fruitfly, Drosophila melanogaster, particularly accessible to neurophysiological imaging, complementing its comprehensively-described molecular, electrophysiological and neuroanatomical properties2,4,17. These reporters can be selectively expressed via binary transcriptional control systems (e.g. GAL4/UAS18, LexA/LexAop19,20, Q system21) in defined populations of neurons within the olfactory circuitry to dissect with high spatial and temporal resolution how odor-evoked neural activity is represented, modulated and transformed22-24.
Here we describe the preparation and analysis methods to measure odor-evoked responses in the Drosophila antennal lobe using G-CaMP25-27. The animal preparation is minimally invasive and can be adapted to imaging using wide-field fluorescence, confocal and two-photon microscopes.

Calcium Imaging of Odor-evoked Responses in the Drosophila Antennal Lobe

We describe an established technique to measure and analyze odor-evoked calcium responses in the antennal lobe of living Drosophila melanogaster.

The antennal lobe is the primary olfactory center in the insect brain and represents the anatomical and functional equivalent of the vertebrate olfactory ...

Transretinal ERG Recordings from Mouse Retina: Rod and Cone Photoresponses

There are two distinct classes of image-forming photoreceptors in the vertebrate retina: rods and cones. Rods are able to detect single photons of light whereas cones operate continuously under rapidly changing bright light conditions. Absorption of light by rod- and cone-specific visual pigments in the outer segments of photoreceptors triggers a phototransduction cascade that eventually leads to closure of cyclic nucleotide-gated channels on the plasma membrane and cell hyperpolarization. This light-induced change in membrane current and potential can be registered as a photoresponse, by either classical suction electrode recording technique1,2 or by transretinal electroretinogram recordings (ERG) from isolated retinas with pharmacologically blocked postsynaptic response components3-5. The latter method allows drug-accessible long-lasting recordings from mouse photoreceptors and is particularly useful for obtaining stable photoresponses from the scarce and fragile mouse cones. In the case of cones, such experiments can be performed both in dark-adapted conditions and following intense illumination that bleaches essentially all visual pigment, to monitor the process of cone photosensitivity recovery during dark adaptation6,7. In this video, we will show how to perform rod- and M/L-cone-driven transretinal recordings from dark-adapted mouse retina. Rod recordings will be carried out using retina of wild type (C57Bl/6) mice. For simplicity, cone recordings will be obtained from genetically modified rod transducin &alpha;-subunit knockout (T&alpha;-/-) mice which lack rod signaling8.

We describe a relatively simple method of transretinal electroretinogram (ERG) recordings for obtaining rod and cone photoresponses from intact mouse retina. This approach takes advantage of the block of synaptic transmission from photoreceptors to isolate their light responses and record them using field electrodes placed across the isolated flat-mounted retina.

There are two distinct classes of image-forming photoreceptors in the vertebrate retina: rods and cones. Rods are able to detect single photons of light ...

Extracting Visual Evoked Potentials from EEG Data Recorded During fMRI-guided Transcranial Magnetic Stimulation

Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological effects. Specifically, by creating a transient interference with the normal activity of a target region and measuring changes in an electrophysiological signal, we can establish a causal link between the stimulated brain area or network and the electrophysiological signal that we record. If target brain areas are functionally defined with prior fMRI scan, TMS could be used to link the fMRI activations with evoked potentials recorded. However, conducting such experiments presents significant technical challenges given the high amplitude artifacts introduced into the EEG signal by the magnetic pulse, and the difficulty to successfully target areas that were functionally defined by fMRI. Here we describe a methodology for combining these three common tools: TMS, EEG, and fMRI. We explain how to guide the stimulator&#39;s coil to the desired target area using anatomical or functional MRI data, how to record EEG during concurrent TMS, how to design an ERP study suitable for EEG-TMS combination and how to extract reliable ERP from the recorded data. We will provide representative results from a previously published study, in which fMRI-guided TMS was used concurrently with EEG to show that the face-selective N1 and the body-selective N1 component of the ERP are associated with distinct neural networks in extrastriate cortex. This method allows us to combine the high spatial resolution of fMRI with the high temporal resolution of TMS and EEG and therefore obtain a comprehensive understanding of the neural basis of various cognitive processes.

This paper describes a method for collecting and analyzing electroencephalography (EEG) data during concurrent transcranial magnetic stimulation (TMS) guided by activations revealed with functional magnetic resonance imaging (fMRI). A method for TMS artifact removal and extraction of event related potentials is described as well as considerations in paradigm design and experimental setup.

Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological ...

Simultaneous ex vivo Functional Testing of Two Retinas by in vivo Electroretinogram System

An In vivo electroretinogram (ERG) signal is composed of several overlapping components originating from different retinal cell types, as well as noise from extra-retinal sources. Ex vivo ERG provides an efficient method to dissect the function of retinal cells directly from an intact isolated retina of animals or donor eyes. In addition, ex vivo ERG can be used to test the efficacy and safety of potential therapeutic agents on retina tissue from animals or humans. We show here how commercially available in vivo ERG systems can be used to conduct ex vivo ERG recordings from isolated mouse retinas. We combine the light stimulation, electronic and heating units of a standard in vivo system with custom-designed specimen holder, gravity-controlled perfusion system and electromagnetic noise shielding to record low-noise ex vivo ERG signals simultaneously from two retinas with the acquisition software included in commercial in vivo systems. Further, we demonstrate how to use this method in combination with pharmacological treatments that remove specific ERG components in order to dissect the function of certain retinal cell types.

Simultaneous ex vivo Functional Testing of Two Retinas by in vivo Electroretinogram System

Ex vivo ERG can be used to record electrical activity of retinal cells directly from isolated intact retinas of animals or humans. We demonstrate here how common in vivo ERG systems can be adapted for ex vivo ERG recordings in order to dissect the electrical activity of retinal cells.

An In vivo electroretinogram (ERG) signal is composed of several overlapping components originating from different retinal cell types, as well as noise ...

Visual Evoked Potential Recording in a Rat Model of Experimental Optic Nerve Demyelination

The visual evoked potential (VEP) recording is widely used in clinical practice to assess the severity of optic neuritis in its acute phase, and to monitor the disease course in the follow-up period. Changes in the VEP parameters closely correlate with pathological damage in the optic nerve. This protocol provides a detailed description about the rodent model of optic nerve microinjection, in which a partial demyelination lesion is produced in the optic nerve. VEP recording techniques are also discussed. Using skull implanted electrodes, we are able to acquire reproducible intra-session and between-session VEP traces. VEPs can be recorded on individual animals over a period of time to assess the functional changes in the optic nerve longitudinally. The optic nerve demyelination model, in conjunction with the VEP recording protocol, provides a tool to investigate the disease processes associated with demyelination and remyelination, and can potentially be employed to evaluate the effects of new remyelinating drugs or neuroprotective therapies.

Focal demyelination is induced in the optic nerve using lysolecithin microinjection. Visual evoked potentials are recorded via skull electrodes implanted over the visual cortex to examine the signal conduction along the visual pathway in vivo. This protocol details the surgical procedures underlying electrode implantation and optic nerve microinjection.

The visual evoked potential (VEP) recording is widely used in clinical practice to assess the severity of optic neuritis in its acute phase, and to ...

Somatosensory Event-related Potentials from Orofacial Skin Stretch Stimulation

Cortical processing associated with orofacial somatosensory function in speech has received limited experimental attention due to the difficulty of providing precise and controlled stimulation. This article introduces a technique for recording somatosensory event-related potentials (ERP) that uses a novel mechanical stimulation method involving skin deformation using a robotic device. Controlled deformation of the facial skin is used to modulate kinesthetic inputs through excitation of cutaneous mechanoreceptors. By combining somatosensory stimulation with electroencephalographic recording, somatosensory evoked responses can be successfully measured at the level of the cortex. Somatosensory stimulation can be combined with the stimulation of other sensory modalities to assess multisensory interactions. For speech, orofacial stimulation is combined with speech sound stimulation to assess the contribution of multi-sensory processing including the effects of timing differences. The ability to precisely control orofacial somatosensory stimulation during speech perception and speech production with ERP recording is an important tool that provides new insight into the neural organization and neural representations for speech.

This paper introduces a method for obtaining somatosensory event-related potentials following orofacial skin stretch stimulation. The current method can be used to evaluate the contribution of somatosensory afferents to both speech production and speech perception.

Cortical processing associated with orofacial somatosensory function in speech has received limited experimental attention due to the difficulty of ...

Simultaneous Recording of Electroretinography and Visual Evoked Potentials in Anesthetized Rats

The electroretinogram (ERG) and visual evoked potential (VEP) are commonly used to assess the integrity of the visual pathway. The ERG measures the electrical responses of the retina to light stimulation, while the VEP measures the corresponding functional integrity of the visual pathways from the retina to the primary visual cortex following the same light event. The ERG waveform can be broken down into components that reflect responses from different retinal neuronal and glial cell classes. The early components of the VEP waveform represent the integrity of the optic nerve and higher cortical centers. These recordings can be conducted in isolation or together, depending on the application. The methodology described in this paper allows simultaneous assessment of retinal and cortical visual evoked electrophysiology from both eyes and both hemispheres. This is a useful way to more comprehensively assess retinal function and the upstream effects that changes in retinal function can have on visual evoked cortical function.

This protocol describes simultaneous measurement of electroretinogram and visual evoked potentials in anesthetized rats.

The electroretinogram (ERG) and visual evoked potential (VEP) are commonly used to assess the integrity of the visual pathway. The ERG measures the ...

Visual Evoked Potential Recordings in Mice Using a Dry Non-invasive Multi-channel Scalp EEG Sensor

For scalp EEG research environments with laboratory mice, we designed a dry-type 16 channel EEG sensor which is non-invasive, deformable, and re-usable because of the plunger-spring-barrel structural facet and mechanical strengths resulting from metal materials. The whole process for acquiring the VEP responses in vivo from a mouse consists of four steps: (1) sensor assembly, (2) animal preparation, (3) VEP measurement, and (4) signal processing. This paper presents representative measurements of VEP responses from multiple mice with a submicro-voltage signal resolution and sub-hundred millisecond temporal resolution. Although the proposed method is safer and more convenient compared to other previously reported animal EEG acquiring methods, there are remaining issues including how to enhance the signal-to-noise ratio and how to apply this technique with freely moving animals. The proposed method utilizes easily available resources and shows a repetitive VEP response with a satisfactory signal quality. Therefore, this method could be utilized for longitudinal experimental studies and reliable translational research exploiting non-invasive paradigms.

We designed a dry-type 16 channel EEG sensor which is non-invasive, deformable, and re-usable. This paper describes the whole process from manufacturing the proposed EEG electrode to signal processing of visual evoked potential (VEP) signals measured on a mouse scalp using a dry non-invasive multi-channel EEG sensor.

For scalp EEG research environments with laboratory mice, we designed a dry-type 16 channel EEG sensor which is non-invasive, deformable, and re-usable ...

Stimulus-specific Cortical Visual Evoked Potential Morphological Patterns

This paper presents a methodology for the recording and analysis of cortical visual evoked potentials (CVEPs) in response to various visual stimuli using 128-channel high-density electroencephalography (EEG). The specific aim of the described stimuli and analyses is to examine whether it is feasible to replicate previously reported CVEP morphological patterns elicited by an apparent motion stimulus, designed to simultaneously stimulate both ventral and dorsal central visual networks, using object and motion stimuli designed to separately stimulate ventral and dorsal visual cortical networks.&#160; Four visual paradigms are presented: 1. Randomized visual objects with consistent temporal presentation. 2. Randomized visual objects with inconsistent temporal presentation (or jitter).&#160; 3. Visual motion via a radial field of coherent central dot motion without jitter.&#160; 4. Visual motion via a radial field of coherent central dot motion with jitter.&#160; These four paradigms are presented in a pseudo-randomized order for each participant.&#160; Jitter is introduced in order to view how possible anticipatory-related effects may affect the morphology of the object-onset and motion-onset CVEP response.&#160; EEG data analyses are described in detail, including steps of data exportation from and importation to signal processing platforms, bad channel identification&#160;and removal, artifact rejection, averaging, and categorization of average CVEP morphological pattern type based upon latency ranges of component peaks. Representative data show that the methodological approach is indeed sensitive in eliciting differential object-onset and motion-onset CVEP morphological patterns and may, therefore, be useful in addressing the larger research aim. Given the high temporal resolution of EEG and the possible application of high-density EEG in source localization analyses, this protocol is ideal for the investigation of distinct CVEP morphological patterns and the underlying neural mechanisms which generate these differential responses.&#160; &#160; &#160;&#160;

In this paper, we present a protocol to investigate differential cortical visual evoked potential morphological patterns through stimulation of ventral and dorsal networks using high-density EEG. Visual object and motion stimulus paradigms, with and without temporal jitter, are described. Visual evoked potential morphological analyses are also outlined.&#160;&#160;

This paper presents a methodology for the recording and analysis of cortical visual evoked potentials (CVEPs) in response to various visual stimuli using ...

A Method for Tracking the Time Evolution of Steady-State Evoked Potentials

Neural entrainment refers to the synchronization of neural activity to the periodicity of sensory stimuli. This synchronization defines the generation of steady-state evoked responses (i.e., oscillations in the electroencephalogram phase-locked to the driving stimuli). The classic interpretation of the amplitude of the steady-state evoked responses assumes a stereotypical time-invariant neural response plus random background fluctuations, such that averaging over repeated presentations of the stimulus recovers the stereotypical response. This approach ignores the dynamics of the steady-state, as in the case of the adaptation elicited by prolonged exposures to the stimulus. To analyze the dynamics of steady-state responses, it can be assumed that the time evolution of the response amplitude is the same in different stimulation runs separated by sufficiently long breaks. Based on this assumption, a method to characterize the time evolution of steady-state responses is presented. A sufficiently large number of recordings are acquired in response to the same experimental condition. Experimental runs (recordings) are column-wise averaged (i.e., runs are averaged but epoch within recordings are not averaged with the preceding segments). The column-wise averaging allows analysis of steady-state responses in recordings with remarkably high signal-to-noise ratios. Therefore, the averaged signal provides an accurate representation of the time evolution of the steady-state response, which can be analyzed in both the time and frequency domains. In this study, a detailed description of the method is provided, using steady-state visually evoked potentials as an example of a response. Advantages and caveats are evaluated based on a comparison with single-trial methods designed to analyze neural entrainment.

A protocol to assess the time evolution of the neural entrainment to external repetitive stimuli is presented. Steady-state recordings of the same experimental condition are acquired and averaged in the time-domain. The steady-state dynamics are analyzed by plotting the response amplitude as a function of time.

Neural entrainment refers to the synchronization of neural activity to the periodicity of sensory stimuli. This synchronization defines the generation of ...