Edited by: Robert Timothy Richard Huckstepp, University of Warwick, United Kingdom
Reviewed by: Germán Gálvez-García, University of La Frontera, Chile
Richard Bruce Bolster, University of Winnipeg, Canada
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Objective, rapid evaluation of cognitive function is critical for identifying situational impairment due to sleep deprivation. The present study used brain vital sign monitoring to evaluate acute changes in cognitive function for healthy adults. Thirty (30) participants were scanned using portable electroencephalography before and after either a night of regular sleep or a night of total sleep deprivation. Brain vital signs were extracted from three established event-related potential components: (1) the N100 (Auditory sensation); (2) the P300 (Basic attention); and (3) the N400 (Cognitive processing) for all time points. As predicted, the P300 amplitude was significantly reduced in the sleep deprivation group. The findings indicate that it is possible to detect situational cognitive impairment due to sleep deprivation using objective, rapid brain vital sign monitoring.
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Cognitive impairment is often associated with a wide range of conditions, including Alzheimer’s Disease, traumatic brain injury, Parkinson’s Disease, schizophrenia, epilepsy, and stroke (
Previous research has suggested that cognitive function can be objectively evaluated using event-related potentials (ERPs) (
As such, certain ERPs are sensitive to changes in cognitive processing related to sleep deprivation. In particular, numerous studies have shown that changes in the P300, an ERP component related to attention and information processing, is affected by sleep deprivation (
In 2016, we developed a brain vital sign framework that incorporates the N100, P300, and N400 into a rapid, standardized, intuitive, and easy to use approach to evaluate cognitive brain function (
In the present study, brain vital sign evaluations were conducted using the NeuroCatch Platform. NeuroCatch uses an auditory stimulus sequence including auditory oddball stimuli and word pairs to elicit the N100, P300, and N400 responses from a rapid EEG scan. In this study, 30 participants were assessed before and after either a typical night of sleep or a night of total sleep deprivation. The study objective was to evaluate whether situational cognitive impairment, due to sleep deprivation, could be detected through monitoring brain vital signs. The hypothesis predicted specific sleep deprivation impacts on the P300 and the N400.
Participants were healthy adults with self-described regular sleep patterns for at least the previous 2 weeks, no diagnosis of any sleep disorder, and not currently taking sleep medications, supplements, or medications that effect sleep (see
A pilot study was completed with 3 participants to assess required sample size. These data were not included in the study analysis. Sample size was calculated using GPower (version 3.1.9.7) based on estimated moderate effect sizes for the primary repeated measures analysis.
Effect Size: 0.25, Alpha Error Probability: 0.00833 (Bonferonni’s Adjusted for multiple comparisons) Beta Error Probability: 0.8 Groups: 2 Measurements: 2 Correlation among repeated measures: 0.8.
In addition, 0.8 is the estimated minimum test–retest correlation coefficient reported by
The minimum required sample size was determined to be 30 participants, and accounting for a 20% contingency for participant dropout the total minimum intended screening was 36 participants.
In total, 38 participants were screened, of which 37 passed screening. Five participants who passed screening were unable to participate due to schedule conflicts or COVID-19 related issues. The remaining 32 participants were randomly assigned to either the Sleep Deprivation (SDEP) or Control Group (CTRL). Two participants withdrew from the study prior to the Day 2 assessments. All remaining participants completed the study in groups. There was no significant difference in age between the SDEP and CTRL groups [
Participant demographics.
Group | Age | Sex | Handedness | |
SDEP | 15 | 31.07 ± 6.32 | 8 female, 7 male | 14 right, 1 left |
CTRL | 15 | 28.60 ± 5.75 | 10 female, 5 male | 13 right, 1 left, 1 both |
This study was approved by the Advarra Canadian Research Ethics Board and registered on
A controlled caffeine ingestion intervention was completed after the described study (Post 2, ∼10:30–12:00 p.m.), and has been analyzed as a separate study.
Overnight, the SDEP participants stayed in a large conference room, with two research staff present. A variety of activities were available to the participants such as games, movies, puzzles, and coloring books. Participants were provided with food and water throughout the night. From Baseline 2 through to Post 1 assessment, SDEP participants did not consume caffeine.
Outcome measures at each of the timepoints included NeuroCatch scans and additional behavioral cognitive assessments. The present paper will focus on the NeuroCatch scan results specific to brain vital sign monitoring. Behavioral cognitive assessment results are the focus of separate analyses.
NeuroCatch (HealthTech Connex Inc, BC, Canada) is a rapid, portable, and standardized evaluation of brain vital signs as markers of cognitive brain function. A pre-scan, digital survey consists of questions regarding the participants’ self-described mood, total sleep (hours), caffeine intake, alcohol consumption, nicotine usage, psychoactive usage, and medication usage over the last 24 h. Following the survey, a low-density EEG sensor cap (ANT Neuro Waveguard) with standard Ag/AgCl electrodes was fitted to the participants, and skin-electrode impedances were prepared to below 25 KOhms. Data were recorded from 3 midline electrodes (Fz, Cz, and Pz), with a ground electrode located at Afz, a reference electrode placed on the left earlobe, and a single electrooculogram (EOG) recorded from FPz. The scan takes approximately 6 min and involves repeated auditory stimulation (ear insert headphones) of standard (80 dB) and random rare deviant (105 dB) tone trains ahead of basic spoken word pair primes that either match or mismatch (e.g., pizza/cheese, pizza/window, respectively). The N100 and P300 ERP peaks were identified on the auditory oddball stimuli response (i.e., the rare deviant tones) and the N400 ERP peaks were identified on the semantic mismatch word response. An additional scan was also acquired if the first scan was identified with poor signal quality. During the scans, participants were asked to sit still and fixate on a cross positioned eye-level ∼2 m away. Scans were conducted in quiet, closed rooms to reduce visual and auditory distractions.
Recorded EEG traces were processed in Python. EEG were filtered using a 0.1–20 Hz bandpass and 60 Hz notch filter. Ocular artifacts were corrected using an adaptive filter (
Statistical analysis was conducted in SPSS (IBM SPSS Statistics 29.0.1.0). A mass-univariate repeated measures analysis of variance (
The mass univariate two-way repeated measures ANOVA indicated a significant interaction between group and changes in the P300 amplitude over time [
An overall significant effect of time on N400 amplitude was observed [
Group average waveforms for the P300 (tone stimuli). T1—Day 1 Morning (Baseline 1). T2—Day 1 Evening (Baseline 2). T3—Day 2 Morning (Post 1). Sleep—sleep deprivation group
Group average waveforms for the N400 (word pair stimuli). T1—Day 1 Morning (Baseline 1). T2—Day 1 Evening (Baseline 2). T3—Day 2 Morning (Post 1). Sleep –sleep deprivation group
With the objective to evaluate situational cognitive impairment due to sleep deprivation, the findings supported the hypothesis that brain vital signs would show sleep deprivation effects (
While no significant interaction between time and group was observed for the N400 amplitude, examination of the waveforms suggests the sleep deprivation group overall exhibited a greater reduction in N400 amplitude from T2 (day 1 evening) to T3 (day 2 morning) compared with the control group (
Regarding the N100 component, there was no significant change observed between groups. This pattern of results is consistent with prior literature (
While the present study largely replicates prior findings, it is an important first demonstration of cognitive changes related to sleep deprivation using a readily deployable and accessible clinical tool for evaluation at the point-of-care. By highlighting the practical advantages of brain vital sign monitoring of situational cognitive impairment, it is possible to begin addressing critical situations in which sleep deprivation is a factor (e.g., pilots). Portable and accessible brain vital sign evaluation enables deployment to environments outside of the traditional EEG laboratory. Furthermore, the low-cost of EEG relative to other brain imaging technologies makes this approach increasingly suitable for point-of-care evaluation and distributed clinical trials where ongoing monitoring of cognitive function is required.
Some caveats should be considered: Firstly, the sample size (
The cognitive effects of sleep deprivation are observed in brain vitals signs. Significant differences were observed in a group of sleep deprived participants relative to controls who experienced a typical sleeping routine. Brain vital signs can be a useful tool in researching changes in cognition in control-intervention study designs, as well as potentially in the early and sensitive detection of cognitive impairment. Ongoing work is evaluating the effect of interventions designed to enhance cognitive performance.
The datasets presented in this article are not readily available because the datasets generated and/or analyzed during the current study are not currently publicly available due to intellectual property considerations. Requests to access the datasets should be directed to RD’A,
The studies involving humans were approved by the Advarra Canadian Research Ethics Board. The studies were conducted in accordance with the local legislation and institutional requirements. The participants provided their written informed consent to participate in this study.
KJ: Formal analysis, Methodology, Writing – original draft, Writing – review and editing, Project administration, Conceptualization. TF: Writing – original draft, Writing – review and editing, Formal analysis, Visualization. SF: Conceptualization, Methodology, Writing – original draft, Writing – review and editing. GP: Conceptualization, Methodology, Writing – review and editing. SB: Conceptualization, Methodology, Writing – review and editing. BL: Conceptualization, Methodology, Writing – review and editing. JV: Methodology, Supervision, Writing – review and editing. RD’A: Conceptualization, Methodology, Supervision, Writing – original draft, Writing – review and editing.
The author(s) declare financial support was received for the research, authorship, and/or publication of this article. Funding provided by the Centre for Aging+Brain Health Innovation (CABHI).
We would like to thank the Surrey Neuroplasticity Clinic for their support with data collection for this investigation.
KJ, GP, SB, BL, JV, and RD’A are associated with HealthTech Connex and have a financial interest in the NeuroCatch Platform. JV was employed by Healthcode Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.
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