Brain Activity Correlates With Cognitive Performance Deterioration During Sleep Deprivation

Fluctuation in cortical excitation/inhibition modulates capability of attention across time scales ranging from hours to seconds

Sustained attention, as the basis of general cognitive ability, naturally varies across different time scales, spanning from hours, e.g. from wakefulness to drowsiness state, to seconds, e.g. trial-by-trail fluctuation in a task session. Whether there is a unified mechanism underneath such trans-scale variability remains unclear. Here we show that fluctuation of cortical excitation/inhibition (E/I) is a strong modulator to sustained attention in humans across time scales. First, we observed the ability to attend varied across different brain states (wakefulness, postprandial somnolence, sleep deprived), as well as within any single state with larger swings. Second, regardless of the time scale involved, we found highly attentive state was always linked to more balanced cortical E/I characterized by electroencephalography (EEG) features, while deviations from the balanced state led to temporal decline in attention, suggesting the fluctuation of cortical E/I as a common mechanism underneath trans-scale attentional variability. Furthermore, we found the variations of both sustained attention and cortical E/I indices exhibited fractal structure in the temporal domain, exhibiting features of self-similarity. Taken together, these results demonstrate that sustained attention naturally varies across different time scales in a more complex way than previously appreciated, with the cortical E/I as a shared neurophysiological modulator.

Purkinje cell dysfunction causes disrupted sleep in ataxic mice

Purkinje cell dysfunction disrupts movement and causes disorders such as ataxia. Recent evidence suggests that Purkinje cell dysfunction may also alter sleep regulation. Here, we used an ataxic mouse model generated by silencing Purkinje cell neurotransmission (L7Cre;Vgatfx/fx) to better understand how cerebellar dysfunction impacts sleep physiology. We focused our analysis on sleep architecture and electrocorticography (ECoG) patterns based on their relevance to extracting physiological measurements during sleep. We found that circadian activity was unaltered in the mutant mice, although their sleep parameters and ECoG patterns were modified. The L7Cre;Vgatfx/fx mutant mice had decreased wakefulness and rapid eye movement (REM) sleep, whereas non-REM sleep was increased. The mutants had an extended latency to REM sleep, which is also observed in human patients with ataxia. Spectral analysis of ECoG signals revealed alterations in the power distribution across different frequency bands defining sleep. Therefore, Purkinje cell dysfunction may influence wakefulness and equilibrium of distinct sleep stages in ataxia. Our findings posit a connection between cerebellar dysfunction and disrupted sleep and underscore the importance of examining cerebellar circuit function in sleep disorders.

Brain waves spectral analysis of human responses to odorous and non-odorous substances: a preliminary study

OBJECTIVE

The aim of this study was to identify the potential electrophysiological biomarkers of human responses by comparing the electroencephalogram brain wave changes towards lavender versus normal saline in a healthy human population.

METHOD

This study included a total of 44 participants without subjective olfactory disturbances. Lavender and normal saline were used as the olfactory stimulant and control. Electroencephalogram was recorded and power spectra were analysed by the spectral analysis for each alpha, beta, delta, theta and gamma bandwidth frequency upon exposure to lavender and normal saline independently.

RESULTS

The oscillatory brain activities in response to the olfactory stimulant indicated that the lavender smell decreased the beta activity in the left frontal (F7 electrode) and central region (C3 electrode) with a reduction in the gamma activity in the right parietal region (P4 electrode) (p < 0.05).

CONCLUSION

Olfactory stimulants result in changes of electrical brain activities in different brain regions, as evidenced by the topographical brain map and spectra analysis of each brain wave.

Mutual Information between EDA and EEG in Multiple Cognitive Tasks and Sleep Deprivation Conditions

Sleep deprivation, a widespread phenomenon that affects one-third of normal American adults, induces adverse changes in physical and cognitive performance, which in turn increases the occurrence of accidents. Sleep deprivation is known to increase resting blood pressure and decrease muscle sympathetic nerve activity. Monitoring changes in the interplay between the central and autonomic sympathetic nervous system can be a potential indicator of human's readiness to perform tasks that involve a certain level of cognitive load (e.g., driving). The electroencephalogram (EEG) is the standard to assess the brain's activity. The electrodermal activity (EDA) is a reflection of the general state of arousal regulated by the activation of the sympathetic nervous system through sweat gland stimulation. In this work, we calculated the mutual information between EDA and EEG recordings in order to consider linear and non-linear interactions and provide an insight of the relationship between brain activity and peripheral autonomic sympathetic activity. We analyzed EEG and EDA data from ten participants performing four cognitive tasks every two hours during 24 h (12 trials). We decomposed EEG data into delta, theta, alpha, beta, and gamma spectral components, and EDA into tonic and phasic components. The results demonstrate high values of mutual information between the EDA and delta component of EEG, mainly in working memory tasks. Additionally, we found an increase in the theta component of EEG in the presence of fatigue caused by sleep deprivation, the alpha component in tasks demanding inhibition and attention, and the delta component in working memory tasks. In terms of the location of brain activity, most of the tasks report high mutual information in frontal regions in the initial trials, with a trend to decrease and become uniform for all the nine analyzed EEG channels as a consequence of the sleep deprivation effect. Our results evidence the interplay between central and sympathetic nervous activity and can be used to mitigate the consequences of sleep deprivation.

Purkinje cell dysfunction causes disrupted sleep in ataxic mice

Purkinje cell dysfunction causes movement disorders such as ataxia, however, recent evidence suggests that Purkinje cell dysfunction may also alter sleep regulation. Here, we used an ataxia mouse model generated by silencing Purkinje cell neurotransmission ( L7 Cre ;Vgat fx/fx ) to better understand how cerebellar dysfunction impacts sleep physiology. We focused our analysis on sleep architecture and electrocorticography (ECoG) patterns based on their relevance to extracting physiological measurements during sleep. We found that circadian activity is unaltered in the mutant mice, although their sleep parameters and ECoG patterns are modified. The L7 Cre ;Vgat fx/fx mutant mice have decreased wakefulness and rapid eye movement (REM) sleep, while non-rapid eye movement (NREM) sleep is increased. The mutant mice have an extended latency to REM sleep, which is also observed in human ataxia patients. Spectral analysis of ECoG signals revealed alterations in the power distribution across different frequency bands defining sleep. Therefore, Purkinje cell dysfunction may influence wakefulness and equilibrium of distinct sleep stages in ataxia. Our findings posit a connection between cerebellar dysfunction and disrupted sleep and underscore the importance of examining cerebellar circuit function in sleep disorders.

Summary Statement

Utilizing a precise genetic mouse model of ataxia, we provide insights into the cerebellum's role in sleep regulation, highlighting its potential as a therapeutic target for motor disorders-related sleep disruptions.

Multimodal assessment of effects of urban environments on psychological wellbeing

The built environment is a ubiquitous factor of modern human life, which fundamentally affects human wellbeing. Most existing research on the psychological effects of urban environments is predominantly based on subjective self-report measures, which provide valuable insights into subjective experiences, but are also affected by conscious and subconscious bias. In the current study, we evaluate a multimodal approach to capturing wellbeing by employing objective mobile physiological and neurophysiological measurement technologies alongside self-reports to capture the impact of two different urban environments. Moreover, we endeavoured to comprehensively measure and, when possible, control the physical aspects of the environment. Our study specifically aimed to discover differences between psychological wellbeing indicators in adults across low-density vs. moderate-density urban environments. Data collection took place in two urban outdoor locations in Australia. Statistical comparison of the two locations indicated that low urban density led to comparatively higher levels of psychological wellbeing compared to moderate urban density. Self-reports indicated that the low-density environment led to higher levels of subjective feelings of comfort and safety and reduced levels of negative mood. In line with the subjective reports, in the low-density environment compared to the moderate-density environment, individuals showed higher levels of EEG theta activity, while EEG beta and heart rate measures were lower. The research outcome provides insights into how urban density affects people's wellbeing and showcases the benefits of employing ecologically-valid multimodal psychological-environmental measurement approaches to effectively evaluate the psychological impacts of built environments.

Nonlinear dynamics of EEG responses to unmanned vehicle visual detection with different levels of task difficulty

The main objective of this study was to examine the presence of chaos in the EEG recordings of brain activity under simulated unmanned ground vehicle visual detection scenarios with different levels of task difficulty. One hundred and fifty people participated in the experiment and completed four visual detection task scenarios: (1) change detection, (2) a threat detection task, (3) a dual-task with different change detection task rates, and (4) a dual-task with different threat detection task rates. We used the largest Lyapunov exponent and correlation dimension of the EEG data and performed 0-1 tests on the EEG data. The results revealed a change in the level of nonlinearity in the EEG data corresponding to different levels of cognitive task difficulty. The differences in EEG nonlinearity measures among the studied levels of task difficulty, as well as between a single task scenario and a dual-task scenario, have also been assessed. The results increase our understanding of the nature of unmanned systems' operational requirements.

The Interlinking of Alpha Waves and Visuospatial Cognition in Motor-Based Domains

The manner in which we perceive and respond in accordance to the world is encompassed by our ability to process multimodal input stimuli. In other words, in order to perform any task, especially at a high degree of proficiency, high dependence is placed upon our ability to interact with, interpret, and visualize input stimuli from our environment, known as visuospatial cognition (Chueh et al., 2017). This article will explore and encapsulate the importance of visuospatial cognition, in terms of the link it has with the performance of tasks in various fields, such as artistry, musical performance, and athleticism. Alpha wave investigation will be discussed as a means of both identifying and characterizing the degree of performance within these domains. Findings from this investigation may be used as a modality to optimize performance in the explored domains (e.g., with Neurofeedback techniques). The limitations of using Electroencephalography (EEG) to support the enhancement of this task performance and the recommendations to elicit further research, will also be explored.

A Systematic Review on the Adult Alpha Brainwave Activity After Essential Oil Inhalation

Aroma extracts from plant species have been utilized since ancient times for a variety of discomforting circumstances. Aromatherapy is a recognized complementary therapeutic treatment performed in various ways such as massage or dermal application, with its main uses involving relaxation, pain relief, and stress management. Several studies have outlined that inhalation of fragrance may influence the brain function since their components can cross the blood-brain barrier and interact with central nervous system receptors. The aim of this review was to systematically present findings regarding alpha brain wave activity reported exclusively by electroencephalography. The study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The PubMed and Scopus databases were screened for relevant papers, based on specific eligibility criteria. The final step of the process resulted in 13 studies published between 1998 and 2021, using different essential oils. Most of the studies revealed the increase of alpha brainwave activity post-essential oil inhalation. Given the proven positive outcomes of increased alpha wave activity on several domains such as cognitive performance and better mental state, further research on the impact of essential oil inhalation is warranted.

Sleep Deprivation-Induced Changes in Baseline Brain Activity and Vigilant Attention Performance

Sleep deprivation (SD) negatively affects several aspects of cognitive performance, and one of the most widely-used tools to evaluate these effects is the Psychomotor Vigilance Test (PVT). The present study investigated the possibility of predicting changes induced by SD in vigilant attention performance by evaluating the baseline electroencephalographic (EEG) activity immediately preceding the PVT stimuli onset. All participants (n = 10) underwent EEG recordings during 10 min of PVT before and after a night of SD. For each participant, the root mean square (RMS) of the baseline EEG signal was evaluated for each 1 s time window, and the respective average value was computed. After SD, participants showed slower (and less accurate) performance in the PVT task. Moreover, a close relationship between the changes in the baseline activity with those in cognitive performance was identified at several electrodes (Fp2, F7, F8, P3, T6, O1, Oz, O2), with the highest predictive power at the occipital derivations. These results indicate that vigilant attention impairments induced by SD can be predicted by the pre-stimulus baseline activity changes.

Changes in Brain Waves During Silent Repetition of OM: A Crossover Study from India

Previously, the electroencephalogram (EEG) recorded while listening to repetition of a Sanskrit monosyllable (i.e., OM) was not significantly different from the EEG recorded during control periods. In the present study, fifteen adult volunteers from northern India (all male, average age 25.0 ± 4.9 years) were assessed using monopolar scalp EEG recordings before, during and after (i) silent repetition of a monosyllable (OM), (ii) silent repetition of 'one' and (iii) quiet rest. In (i), (ii) and (iii) breathing was not consciously modified. The participants had an average of five years' experience of focused meditation (dharana), involving awareness directed to the breath. Participants had no prior experience of silent repetition of either 'OM' or 'one'. They were Indian Hindus for whom OM has special spiritual significance, whereas 'one' does not. The sessions were on separate days in random order. The absolute and relative energy of theta waves in the EEG recorded at Pz-A2 increased significantly during repetition of OM compared to the preceding state. There were no changes during silent repetition of 'one' or during quiet rest. Increased energy in the theta band while awake reflects a state of relaxation devoid of effort. Hence, during silent repetition of OM alone there were changes suggestive of effortless relaxation.

Neural dynamics during emotional video engagement relate to anxiety

Inter-subject correlations (ISCs) of physiological data can reveal common stimulus-driven processing across subjects. ISC has been applied to passive video viewing in small samples to measure common engagement and emotional processing. Here, in a large sample study of healthy adults (N = 163) who watched an emotional film (The Lion Cage by Charlie Chaplin), we recorded electroencephalography (EEG) across participants and measured ISC in theta, alpha and beta frequency bands. Peak ISC on the emotionally engaging video was observed three-quarters into the film clip, during a time period which potentially elicited a positive emotion of relief. Peak ISC in all frequency bands was focused over centro-parietal electrodes localizing to superior parietal cortex. ISC in both alpha and beta frequencies had a significant inverse relationship with anxiety symptoms. Our study suggests that ISC measured during continuous non-event-locked passive viewing may serve as a useful marker for anxious mood.

Changes in Human Electroencephalographic Activity in Response to Agastache rugosa Essential Oil Exposure

Agastache rugosa (Korean mint) is an important medicinal and aromatic plant and its aerial parts have a pleasant fragrance. A. rugosa leaves are used as an ingredient in salads and soups for enhancing the aroma and taste of foods in Korea. However, there is no report on the influence of the aroma of A. rugosa on human psychophysiological activity. Therefore, the present study aimed to investigate the effect of exposure to the essential oil of Korean A. rugosa on human electroencephalographic (EEG) activity. The essential oil of A. rugosa was isolated using steam distillation extraction and its composition was determined by gas chromatography and mass spectrometry (GC–MS) analysis. In the EEG study, 38 healthy volunteers (19 men and 19 women) participated. The EEG readings were analyzed for 25 EEG indices from 29 electrodes placed on the scalp according to the international 10–20 system. The major component in the essential oil of A. rugosa was estragole (89.49%) followed by D-limonene (3.40%), menthone (1.80%), and pulegone (1.86%). In the EEG study, significant decreases in absolute theta (AT) and relative theta (RT) power spectra were observed during the exposure to A. rugosa essential oil when compared to that of no odor exposure. Whereas relative alpha (RA), relative slow alpha (RSA), spectral edge frequency 50% (SEF50), and spectral edge frequency 50% of alpha (ASEF) power spectra values significantly increased. These results reveal that the EEG power spectra changes incurred during the exposure to the essential oil of A. rugosa may be associated with the enhancement of freshness and concentration states of the human brain.

Total Sleep Deprivation Triggers Greater Activation in the Parietal Brain in the Visual Working Memory Updating Processes: An Event-Related Potentials Study

Working memory functions are known to be altered after total sleep deprivation (TSD). However, few studies have explored the deficits of working memory updating (WMU) after TSD, or the underlying electrophysiological mechanisms of these alterations. In the current exploratory study, we enrolled 14 young male volunteers who performed two kinds of WMU tasks—spatial and object two-back tasks—with simultaneous electroencephalography recordings under two sleep conditions: a normal sleep baseline condition and after 36 h of TSD. Repeated-measures analysis of variance showed that compared with those at baseline, the rates of correct responses in the WMU tasks decreased significantly after TSD. Analysis of event-related potentials revealed that the average amplitude of P3 components decreased significantly in the frontal and central brain regions and increased significantly in the parietal brain regions. Our findings suggest that TSD damages WMU behavior, impairs cognitive functions in the frontal and central brain regions, and triggers greater activation in the parietal brain regions. This is the first study to report the existence of event-related compensatory neural activity. This event-related compensatory effect may provide a new perspective for understanding the mechanisms underlying the influences triggered by sleep loss.

“Sound” Decisions: The Combined Role of Ambient Noise and Cognitive Regulation on the Neurophysiology of Food Cravings

Our ability to evaluate long-term goals over immediate rewards is manifested in the brain’s decision circuit. Simplistically, it can be divided into a fast, impulsive, reward “system 1” and a slow, deliberate, control “system 2.” In a noisy eating environment, our cognitive resources may get depleted, potentially leading to cognitive overload, emotional arousal, and consequently more rash decisions, such as unhealthy food choices. Here, we investigated the combined impact of cognitive regulation and ambient noise on food cravings through neurophysiological activity. Thirty-seven participants were recruited for an adapted version of the Regulation of Craving (ROC) task. All participants underwent two sessions of the ROC task; once with soft ambient restaurant noise (∼50 dB) and once with loud ambient restaurant noise (∼70 dB), while data from electroencephalography (EEG), electrodermal activity (EDA), and self-reported craving were collected for all palatable food images presented in the task. The results indicated that thinking about future (“later”) consequences vs. immediate (“now”) sensations associated with the food decreased cravings, which were mediated by frontal EEG alpha power. Likewise, “later” trials also increased frontal alpha asymmetry (FAA) —an index for emotional motivation. Furthermore, loud (vs. soft) noise increased alpha, beta, and theta activity, but for theta activity, this was solely occurring during “later” trials. Similarly, EDA signal peak probability was also higher during loud noise. Collectively, our findings suggest that the presence of loud ambient noise in conjunction with prospective thinking can lead to the highest emotional arousal and cognitive load as measured by EDA and EEG, respectively, both of which are important in regulating cravings and decisions. Thus, exploring the combined effects of interoceptive regulation and exteroceptive cues on food-related decision-making could be methodologically advantageous in consumer neuroscience and entail theoretical, commercial, and managerial implications.

Physical activity attenuates negative effects of short-term exposure to ambient air pollution on cognitive function

BACKGROUND

As physical activity benefits brain health whereas air pollution damages it, the cognitive response to these exposures may interact.

PURPOSE

This study aimed to assess the short-term joint effect of physical activity and air pollution on cognitive function in a panel of healthy young adults.

METHODS

We followed ninety healthy subjects aged around 22 years from September 2020 to June 2021 and measured their personal exposure to fine particulate matter (PM_2.5) (μg/m³) and daily accelerometer-based moderate-to-vigorous physical activity (MVPA) (min/day) in 4 one-week-long sessions over the study period. At the end of each measurement session, we assessed executive function using Stroop color-word test and collected resting-state electroencephalogram (EEG) signals.

RESULTS

We found short-term PM_2.5 exposure damaged executive function (β_PM25 = 0.0064, p = 0.039) but physical activity could counterbalance it (β_MVPA = -0.0047, p = 0.048), whereby beta-3 wave played as a potential mediating role. MVPA-induced improvement on executive function was larger in polluted air (β_MVPA = -0.010, p = 0.035) than that in clean air (β_MVPA = -0.003, p = 0.45). To offset the negative effect of air pollution on cognitive function, individuals should do extra 13.6 min MVPA every day for every 10 μg/m³ increase in daily PM_2.5.

CONCLUSION

This study implies that physical activity could be used as a preventive approach to compensate the cognitive damages of air pollution.

A cup of black coffee with GI, please! Evidence of geographical indication influence on a coffee tasting experiment

Geographical Indication (GI) certifications enable producers to set production standards and create competitive advantage based on product's origin. In a coffee tasting experiment, brain responses to origin information of 40 participants, grouped equally by gender and involvement level, were collected by electroencephalography to verify: the impact of the GI cue in four brain waves (alpha, beta, delta and theta) and two brain lobes (frontal and temporal); preference; gender and involvement moderations. Results show that women presented power differences in both hemispheres, more channels/waves, which indicates greater sensitivity to the origin cue. Men presented power differences in fewer channels/waves. It is observed that involvement has a tenuous moderation effect when compared to gender. As for preference, the analysis of delta and theta waves indicated that men preferred coffee with GI; while women preferred coffee without GI, even though most of them indicated the opposite when verbally asked at the end of the tasting section.

Performance prediction in a visuo-motor task: the contribution of EEG analysis

Brain state in the time preceding the task affects motor performance at single trial level. Aim of the study was to investigate, through a single trial analysis of the Power Spectral Density (PSD) of the cortical sources of EEG rhythms, whether there are EEG markers, which can predict trial-by-trial the subject's performance as measured by the reaction time (RT). 20 healthy adult volunteers performed a specific visuomotor task while continuously recorded with a 64 electrodes EEG. For each single trial, the PSD of the cortical sources of EEG rhythms was obtained from EEG data to cortical current density time series in 12 regions of interest at Brodmann areas level. Results showed a statistically significant increase of posterior and limbic alpha 1 and of frontal beta 2 power, and a reduction of frontal and limbic delta and of temporal alpha 1 power, during triggering stimulus presentation for better performance, namely faster responses. At single trial level, correlation analyses between RTs and significant PSD, revealed positive correlations in frontal delta, temporal alpha 1, and limbic delta bands, and negative ones in frontal beta 2, parietal alpha 1, and occipital alpha 1 bands. Furthermore, the subject's faster responses have been found as correlated with the similarity between the PSD values in parietal and occipital alpha 1. Predicting individual's performance at single trial level, might be extremely useful in the clinical context, since it could allow to launch rehabilitative therapies in the most efficient brain state, avoiding useless interventions.

Decreased Functional Connectivity Between the Right Precuneus and Middle Frontal Gyrus Is Related to Attentional Decline Following Acute Sleep Deprivation

Objectives

Acute sleep deprivation (SD) seriously affects cognitive functions, such as attention, memory, and response inhibition. Previous neuroimaging studies have demonstrated a close relationship between the functional activities of the precuneus (PC) and the function of alert attention. However, the specific effect of the PC on attention decline after acute SD has not been elucidated. In this study, we used resting-state functional magnetic resonance imaging (fMRI) to study the relationship between the changes of the PC functional connectivity and alertness decline after total SD.

Methods

Thirty healthy, right-handed adult men participated in the experiment. Alert attention and functional connectivity were assessed by the Psychomotor Vigilance Test and a resting-state fMRI scan before and after total SD. The region of interest to region of interest (“ROI-to-ROI”) correlation was employed to analyze the relationship between the PC and other brain regions after acute SD.

Results

Participants showed decreased alert attention after total SD. In addition, SD induced decreased functional connectivity between the right PC and the right middle frontal gyrus (MFG). Moreover, there was a significant correlation between the decreased PC functional connectivity and alertness decline after total SD.

Conclusion

Our findings suggest that the interruption of the connection between the right PC and the right MFG is related to the observed decline in alert attention after acute SD. These results provide evidence further elucidating the cognitive impairment model of SD.

Dissociation of Subjective and Objective Alertness During Prolonged Wakefulness

BACKGROUND

Although the deterioration of subjective and objective alertness during prolonged wakefulness has been investigated rigorously, whether perceived sleepiness and fatigue are consistent with actual decrements in behavioral performance in the time course is still disputed. The present study examined the dissociation between decrements of subjective alertness and performance deficits during prolonged wakefulness of one night and explored the relationship between body temperature and the impairments of subjective and objective alertness.

PARTICIPANTS AND METHODS

Thirty-eight participants (27 females; age: 21.76 ± 2.37 years old) underwent prolonged wakefulness for one night at habitual bedtime (0:00-6:00 am). Participants completed a 10-min PVT to assess objective alertness, fatigue, and sleepiness ratings to assess subjective alertness every 2 hours, and body temperature was measured every hour during scheduled wakefulness.

RESULTS

Subjective alertness reflected a linear decline with time, but the magnitudes of objective performance deterioration increased significantly between 4:00 and 6:00 am. The increasing magnitudes of performance deficits were associated with the change of body temperature between 4:00 and 6:00 am.

CONCLUSION

These results indicate that the perceived degree of decline in alertness is temporally dissociated with the actual decline in objective vigilance with increased duration of wakefulness. The dissociation of magnitudes of subjective and objective alertness decrements mainly occurs between 4:00 and 6:00 am, and the changes of performance deficits have a relationship with body temperature.

Effects of a 20-min Nap after Sleep Deprivation on Brain Activity and Soccer Performance

We examined effects of a 20-min nap following 3 h of sleep deprivation on brain wave activity, auditory reaction time, the running-based anaerobic sprint test, leg muscle strength and the rating of perceived exertion in male college soccer players. Eleven players underwent three sleep conditions; normal sleep, sleep deprivation and 20-min nap after sleep deprivation. The sleep deprivation demonstrated an increase in the mean power of delta waves over the frontal area and a decrease in the mean power of alpha waves over the parietal area compared to the normal sleep. The nap and the sleep deprivation showed an increase in auditory reaction time compared with those in the normal sleep. The sleep deprivation demonstrated a decrease in the running-based anaerobic sprint test compared to the normal sleep, whereas the nap has partially reversed only minimal power and average power of the running-based anaerobic sprint test. The nap showed a recovery effect on leg muscle strength, but not on the rating of perceived exertion compared with the sleep deprivation. Thus, a 20-min nap after sleep deprivation did not completely return brain activity back to active state and did not entirely reverse the negative impact of sleep deprivation on soccer performance in soccer players.

Neuro-Cognitive Profile of Morning and Evening Chronotypes at Different Times of Day

BACKGROUND

Chronotype is the circadian time preference for sleep-wake timings. However, its impact on cognitive performance is least explored.

OBJECTIVE

The present study investigated the effect of chronotype (morning "M" vs. evening "E") on cognitive measures as a function of time of the day. In addition, the correlation between electroencephalogram (EEG) waves and subjective/objective cognitive measures were investigated.

METHOD

Cognitive status of 28 adult male subjects (15 "M" and 13 "E") was assessed objectively through event-related potential (ERP) by administering visual odd ball paradigm test and subjectively through Montreal Cognitive Assessment questionnaire. In addition, 20 to 30 min of resting EEG was recorded. Recordings were done from 8 to 10 am and from 4 to 6 pm on a single day. Power spectral analysis of EEG for alpha and beta waves at PZ and FZ cortical sites was done after subjecting selected epochs to fast Fourier transformation. Also, latency and amplitude of P300 potential from event-related potential record were measured. Appropriate statistical tests were applied for analysis.

RESULTS

Higher alpha and beta power was observed in "E" at PZ in the evening. "M" showed increased P300 latency and amplitude during evening session for frequent and rare stimuli and vice versa in "E."' Significant negative correlation was seen between latency of rare stimuli and alpha and beta power at FZ site during evening in "E" chronotype only.

CONCLUSION

Result indicates better attention and alertness during evening hours in evening chronotypes and vice versa in morning chronotypes. The findings could be implemented to schedule the mental performance/cognitive load according to individual chronotype.