Method of Acute Alertness Level Evaluation after Exposure

to Blue and Red Light (based on EEG): Technical Aspects

Agnieszka Wolska

, Dariusz Sawicki

, Kamila Nowak

, Mariusz Wisełka

and Marcin Kołodziej

Central Institute for Labour Protection, National Research Institute (CIOP-PIB), Warsaw, Poland

Warsaw University of Technology, Institute of Theory of Electrical Engineering,

Measurement and Information Systems, Warsaw, Poland

Keywords: EEG, Acute Alertness, Exposure to Light, Evaluation Method, Technical Aspects.

Abstract: Since maintaining a high level of alertness is a very important factor on many workstations a number of

studies on alertness level evaluation have been carrying out. The effects of light exposure on alertness level

have been the subject of many studies with EEG registration, but technical aspects of planning experiment

are not well described. The aim of the article is to present the evaluation method of acute alertness level

after exposure to blue and red light based on EEG registration with special attention to technical aspects of

used methodology. The preliminary results obtained during the pilot study confirmed that elaborated

method fulfils our expectations and gives opportunity to assess the acute alertness after exposure to light.

1 INTRODUCTION

Light is one of the most important environmental

factors both for humans and all living organisms. It

is simply needed for life. It is able to affect physical,

physiological and psychological behaviors of

humans (Bellia et al., 2011). Light stimulus both

enables the vision and affects biological non-visual

effects. The existence of intrinsically photosensitive

retinal ganglion cell (ipRGc) containing the

melanopsin makes it possible to capture the non-

visual information of light and activate the circadian

system. Daily light/dark patterns reaching the retina

play an important role in regulating the circadian

rhythms (Figueiro, 2013). The non-visual response

to light depends on the light wavelength and

intensity (irradiance level at the eye), time and

duration of exposure. Light may affect human

behaviors in indirect or direct way. The indirect way

is thorough the circadian timing system, and the

response is mainly long-term, mediated by processes

such as: melatonin suppression, core body

temperature regulation, alertness and cognition

(Łaszewska et al., 2017, Chellappa et al., 2011,

Cajochen et al, 2007, 2010). This is why this non-

visual response is often named as circadian effect of

light.

Many studies showed that the effect of blue light

exposure had been stronger than white light. It is

explained by maximum sensitivity of ipRGc on short

wavelength visible radiation between 460 and 480

nm. The direct non-visual effect of light is non-

circadian, i.e. without circadian clock changes.

These effects could be acute and short term, not

exceeding the period of 24 h (Łaszewska et al.,

2017, Cajochen et al., 2007, Chellappa et al., 2011).

Since maintaining a high level of alertness is a very

important factor on many workstations and on night

shift workstations many studies of alertness level

evaluation have been conducted. The effects of light

exposure on alertness were the subject of numerous

electrophysiological studies (Łaszewska et al., 2017,

Figueiro et al., 2010, 2016, Sahin and Figueiro,

2013, Chang et al., 2013, Sahin et al., 2014, Phipps-

Nelson et al., 2009). However, a unified and

standardized method of carrying out the studies does

not exist. The differences in methodology concerns:

duration and daytime of exposure, intensity of light

and procedure of EEG registration (during or after

exposure to light, with or without behavioural

control).

There are also different methods of EEG signal

analysis to assess the alertness level, however the

Theta and Alpha bands are usually under

consideration. Most of studies examined the

influence of blue or white light on alerting response

Wolska, A., Sawicki, D., Nowak, K., Wisełka, M. and Kołodziej, M.

Method of Acute Alertness Level Evaluation after Exposure to Blue and Red Light (based on EEG): Technical Aspects.

DOI: 10.5220/0006922500530060

In Proceedings of the 6th International Congress on Neurotechnology, Electronics and Informatics (NEUROTECHNIX 2018), pages 53-60

ISBN: 978-989-758-326-1

on suppressing the melatonin level, but some recent

research indicated that also red light increases level

of alertness (Figueiro et al., 2009, Figueiro and Rea,

2010, 2017, Plitnick et al., 2010, Sahin and Figueiro,

2013, Okamoto et al., 2014, Łaszewska et al., 2017).

This results proved that alerting effect could be

obtained not only by suppressing the melatonin

level.

However, it is proved that blue and red light

could increase the alertness level, both during the

night and day but the duration of elicited alertness

after exposure to particular color of light still

remains not well known.

The aim of the article is to present the method of

acute alertness level evaluation after exposure to

blue and red light based on EEG registration with

special attention to technical aspects of used

methodology. Preliminary results obtained during

the pilot study are also presented.

2 TECHNICAL ASPECTS OF

EXPERIMENT –

EXPECTATIONS

2.1 Light Exposure

Lighting conditions play a very important role,

because the effect of exposure to light as an acute

change in alertness is observed. Since it has been

proven that exposure to red or blue light could

increase the alertness level, the verification of the

elaborated method in a pilot study should show if the

obtained results are in accordance with these

findings. The main assumption of light exposure for

planned pilot experiments was the application of two

monochromatic lights: blue light (max. emission

470 nm) and red light (max. emission 630 nm),

according to previous studies. This condition could

be realized by using electroluminescent diodes

(LEDs): blue LEDs and red LEDs respectively.

The next assumption was to obtain an

appropriate level of illuminance at the participant’s

eyes during the exposure to blue and red light.

According to the previous studies (Okamoto et al.,

2014, Figueiro and Rea, 2010, Sahin and Figueiro,

2013, Łaszewska et al., 2017) the illuminance at the

eyes of 40 lx both for blue and red light should be

enough to induce alerting effect observed in EEG.

This assumption should be fulfilled by specially

designed lamp with blue and red LED modules,

equipped with current control of luminous flux and

diffusor to eliminate possible discomfort glare. The

geometry of lamp position and participant’s eye

could be different. Usually, the lamp is positioned in

front of observer’s eye (Figueiro and Rea, 2010,

Sahin and Figueiro, 2013), or over the head

(suspended on the ceiling, not directly observed)

(Sawicki et al., 2016), or two lamps on the desktop

centered at 45 angle from midline aside of sightline

(Alkozei et al, 2016). The latter of the above

mentioned solutions was chosen for our study.

The next important aspect was to create the

reference lighting conditions – dim light, which are

usually realized as white general illumination of

illuminance at the eye below 5 lx (Sahin et al., 2014,

Plitnick et al., 2010, Cajochen, 2007, Figueiro et al.,

2016). This lighting condition, as a reference

lighting used for 30 minutes washout period before

exposure, was established as the next assumption for

the experiment.

2.2 EEG Registration

The choice of equipment for EEG registration

usually depends both on the aim of the planned

study and on equipment resources or financial

possibilities to buy a new equipment. In most

medical and research applications the equipment

allows for placing gelled (or dry) electrodes on the

scalp according to the International 10-20 system.

However, this kind of professional equipment is

relatively expensive. There are also low-cost

consumer electronic devices with proven correct

registration of EEG signals (like Emotiv Epoc).

They are simple to use, wireless devices, usually

equipped with saline electrodes, however the they

contain fewer electrodes than the standard EEG i.e.

the midline electrodes are missing. Therefore, as we

planned to carry out the analyses for the alertness

assessment, we chose the system with 32-electrodes

placed according to the 10-20 system (see 3.1 for

details) that included i.a. midline electrodes (Fz, Cz,

Pz, Oz).

2.3 User’s Centered Devices

EEG registration is very sensitive to different

physiological artefacts like blinking, yawning,

moving the head or the body. To avoid motion-

related artefacts it is worth using the chin support.

During 30 minutes of exposure to light the

participants must have open eyes. To avoid

unintentional closing of the eyes, it is recommended

to use a preview camera for eyes/face observation of

the participant by the person conducting the

experiment.

NEUROTECHNIX 2018 - 6th International Congress on Neurotechnology, Electronics and Informatics

2.4 Management and Synchronization

Taking into account the need to monitor and manage

the experiment during the whole session the test-

stand should be separated from the monitoring and

control stand.

The assumptions for management application

(software for management of the experiment) were

as follows: at the beginning of the experiment, enter

the participant's personal code only once and call up

the appropriate version of the experiment, perform

the following tests after confirmation by the

operator, counting out the exposure time.

For security reasons the stimuli delivery and

experiment management should be carried out on

separate computers.

3 TECHNICAL ASPECTS OF

EXPERIMENT –

IMPLEMENTATION

3.1 Stand for Experimental Tests

The stand for experimental tests for alertness level

assessment after exposure to different color of light

based on EEG registration was developed according

to the above mentioned assumptions. The

experimental stand consisted of two main sections:

 test stand (where the participant performed

behavioral tests, and was exposed to particular

light of controlled parameters);

 control and monitoring stand (where the

person conducting the test could observe the

stimuli presented on participant’s screen, EEG

signal during the recording and the

participant’s face during exposure to light).

The view of the stand for experimental test is

presented in Figure 1.

Raw EEG signal was continuously recorded from

32 Ag/AgCl active electrodes placed on a cap

according to the 10-20 International system using

256-channel g.Hlamp amplifier (Guger

Technologies, Graz, Austria). It was digitized at

sampling rate of 256 Hz. The ground electrode was

placed at Afz and the common reference electrode at

FCz. All impedances were kept below 30kΩ during

the whole recording session.

A Simulink model (running under Matlab 2014a)

was used to control the registration of the signal. It

consisted of the building block provided by the

manufacturer of the system (Guger Technologies,

Graz, Austria).

Presentation ® v.20.0 (Neurobehavioral Systems

Inc.) was installed on a separate computer for stimuli

presentation (see Figure 1). TCP/IP protocol was

used as it is a simple, stable and fast way to allow

communication and data exchange between two

computers (even with two different operational

systems). The Protocol used port 5000 to send and

acquire data (on server and client application

respectively) because it allows the application to

share data via TCP/IP protocol.

The registration of the resting state EEG (rsEEG)

was performed three times during the pilot study

experimental sessions. The delivery of fixation point

was presented on the screen in front of participant.

Another computer was dedicated to operate and

control two lamps (type MOL-02) for exposure to

red and blue light (manufactured by GL Optic

Poland). The lamps consisted of 2 red (630 nm) and

Figure 1: The experimental stand – the distributed and complex measurement and control system.

Method of Acute Alertness Level Evaluation after Exposure to Blue and Red Light (based on EEG): Technical Aspects

2 blue (465 nm) LED modules which were also

equipped with a diffusor (20x30 cm ) to reduce

luminance (to avoid direct glare). According to

Alkozei et al. (Alkozei et al., 2016) both lamps were

positioned at 80 cm distance measured at the

participant’s nasion, with each light cantered at a 45

degree angle from midline (see Figure 1). The

established illuminance level for exposure was 40 lx

both for red and blue light.

The computer software (management

application) was developed to control and

synchronize the experiment process in distributed

computer system. The management application was

written by the Authors in Matlab environment and

installed on the computer for EEG registration,

which played the role of server. The computer with

Presentation software, played the role of the client.

The management application “led” the experimental

session from the first to the last test, including 30

minutes of exposure time countdown. The main

programing difficulty encountered during designing

the management application was the incompatibility

of two software environments (Matlab and

Presentation). To solve this problem a third party

program was developed in C# as the application

connecting both environments. Since the control

panel of g.Tech was created in Simulink (Matlab’s

environment) it was self-explanatory to create the

optimal Matlab script to control the preview of both

the experimental trigger and the EEG signal. Matlab

is also able to work as a data server, and in this case

the data was used to trigger the next step of the

experiment, which allowed the Authors to create

optimal control environment. Main function of the

software consisted of three major parts. In the first

part the user was prompted to fill in the information

about the current experiment subject. The second

part worked as a server code that established the

communication between two computers. Third part

was the control over g.Tech Simulink model such as

starting data acquisition, saving files, controlling

proper naming and stopping Simulink. It is

important to mark that the first part was filled only

once at the beginning of the experiment. The second

and the third part were working in one loop.

3.2 Management Application for the

Experiment

This tool has two roles. The first role was to send a

data request to the server. The second role, if the

data was available (server enabled), was to send the

trigger information to the virtual COM port, where

Presentation software awaited information. The

program is written in C# and is NET 4.0-compatible,

supported by Windows XP. Windows XP was used

as the computer operating system with a

motherboard supplied with LPT port, through which

the event data was added to signal in g.Tech

amplifier.

The last part of the management application was

a script written in Presentation. Its main purpose was

to conduct, control as well as store the data about the

current experiment. This script was written as a set

of steps divided into parts.

Each subsequent part of the test was started by a

trigger that appeared on the virtual COM port

created on a computer. After being informed that the

subject agreed to the start of the next task, the test

continued.

4 PILOT STUDY PROTOCOL

The aim of pilot study was to evaluate the developed

methodology both from a technical point of view

and to check whether the results of alertness level

obtained after the exposure to blue and red light

confirm previous studies that this color of light

could elicit the alertness level during the day. It was

also important to investigate the correctness of

control in a complex measuring system (effective

and convenient), and work comfort of the

participant.

The protocol was approved by the Senate

Committee of Research Ethics of Józef Piłsudski

University of Physical Education in Warsaw. All

participant gave their written informed consent prior

to the study.

4.1 Participants

The pilot study was carried out during the winter

season. The participants were 10 young, healthy men

aged between 21-30 years old (mean age:

23,63±2,64 years old). All participants met the

following criteria: did not report of any physical or

mental health problems, did not suffer from color

blindness, did not use glasses to work with a

computer, did not use any medication and did not

have problems with sleep. According to the

chronotype identified using Composite Scale of

Morningness – CSM (Smith et al., 1989, Jankowski,

2015) the participants started the experiment session

respectively at 7:30 am (morning chronotype) or at

11:00 am (evening chronotype), similarly to the

study of Maierova (Maierova et al., 2016). The

participants were asked to maintain a fixed regular

NEUROTECHNIX 2018 - 6th International Congress on Neurotechnology, Electronics and Informatics

plan sleep, lasting at least 7 hours during the week

preceding the start of the experiment. Every

participant took part in two experiments, each with

exposure to different light. The session order was

counterbalanced for each individual, to avoid the

impact of familiarizing with the procedure on

results. One week interval between the experiments

was established.

4.2 Method

The experimental session started with filling in a

questionnaire for subjective assessment of the

participant’s wellbeing and checking his sleep diary

filled in during 7 days before experiment. The

participants were then prepared for EEG registration,

which included the use of a gel under the electrodes

to obtain proper impedance level in each electrode

(<30 kΩ). After that, the participants sat in dim light

condition for 30 minutes (wash out period). They

were then asked to place their chin on the chin

support and look at the screen in front of them at the

distance of 60 cm when the first resting state was

carried out. Plus symbol (“+”) was presented on the

screen for 3 minutes together with EEG registration.

After the first registration the exposure light was

switched on for 30 minutes of exposure. The

participants were asked to keep their eyes open

during that time, but the person conducting the

experiment was observing participants’ eyes on the

screen to see their face/eyes preview and to check if

they were not falling asleep. Just after the exposure

the second resting state together with EEG

registration was carried out for the next 3 minutes.

Then, the participants was asked to perform

psychomotor tasks: N-back (0-back,1-back,-2back)

and Go-No-Go alternately, 3 times each. The order

of the presentation of the task was counterbalanced

across the subjects. The stimuli in the tasks were

presented with the Presentation ® v.20.0 software.

After that the third resting state was carried out. As a

result we obtain three EEG registrations of 3-

minutes each: one before the exposure (but after 30

minutes of dim light), second just after 30 minutes

of the exposure to red or blue light (acute alerting

effect) and third after 48 minutes after the exposure

and computer tests in dim light (sustained acute

alerting effect).

5 DATA ANALYSIS

The collected set of EEG signals was analyzed in

order to recognize the change in alertness level. The

initially prepared signal was divided into a set of 1s

fragments. Each fragment was analyzed by Fast

Fourier Transform giving energy in proper bands.

For one user the mean value for proper band was

calculated from a set of 1s fragments. In a typical

analysis of alertness, low bands (Theta, Alpha) are

registered from O1, O2, and Oz and sometimes from

neighboring electrodes. We wanted to simplify the

analysis in our pilot study and we assumed the use

of signal analysis from only one electrode located in

the center of the skull – Oz.

For most people during normal readiness state

(and with open eyes) the amplitudes of Theta waves

(4.5-8 Hz) and Alpha waves (8–12 Hz) are minimal.

Practically these waves do not exist in such

situation. This is confirmed by numerous

publications (Klimesch, 2012, Sahin and Figueiro,

2013, Okamoto et al., 2014, Baek and Min, 2015).

The main problem in analysis of EEG signals for

alertness recognition is individual differences

between the participants. Many researchers try to

remedy this problem by specific analysis. For

example, the Author of the paper (Chang et al.,

2013) analyzed the sum of Theta and Alpha bands in

order to cover a wide range of frequency.

The analysis was based on a new measure of

alertness (TAAT

max

) introduced in 2016 (Sawicki et

al., 2016). Using FFT we have prepared the

following bands: Theta (4-8 Hz), AlphaTheta (5-

9 Hz), AlphaLow (8-10 Hz), AlphaHigh (10-12 Hz)

and applied the formula (1):

TAAT

max

= max(DF

, DF

) (1)

where DF

is the difference of power in Theta

band. This is calculated as energy before – energy

after. DF

, DF

are the differences of

power in the AlphaLow, AlphaHigh and AlphaTheta

band respectively. Since the decrease in signal level

is correlated with an increase in alertness, the higher

the TAAT

max

, the higher the alertness level.

6 RESULTS AND DISCUSSION

As expected, the highest impact on alertness was

observed in the use of blue light and it was clear in

the case of almost all participants. The typical box

plot for analyzed bands for one participant is

presented in Figure 2. We have also calculated

statistical significance between the first and the

second registration (1-2), which is in all considered

bands statistically significant p<0.05.

Method of Acute Alertness Level Evaluation after Exposure to Blue and Red Light (based on EEG): Technical Aspects

The TAAT

max

measure for all participants was

calculated to assess the differences between two

states: after the exposure to light in relation to the

state before the exposure (acute alerting effect), and

after a period of performing computer tests

following the exposure to light in relation to the state

before the exposure (sustained acute alerting effect).

The calculated TAAT

max

measures showing the

impact of blue and red light on alertness level are

presented in Figures 3 and 4, respectively.

There is a visible impact of blue light exposure

on the increase in acute alertness level in the first

period after the exposure (Figure 3). After 45

minutes of performing computer tests following the

exposure the impact on alertness level was weaker.

The acute alertness level seems to decrease with

time. It could be related to mental tiredness of

participants performing the computer psychomotor

tasks.

In the use of red light (Figure 4) the impact was

not so clear in the case of all participants, but the

tendency of increasing the alertness was visible.

These results for exposure to both blue and red light

influencing the alertness level are consistent with

previous results, which introduced TAAT

max

as a

new measure of alertness (Sawicki et al., 2016).

Although the number of the participants was small,

the results obtained so far suggest that the applied

methodology and the experimental setup is

appropriate. More subjects of both chronotype is

needed to draw more reliable conclusions.

First of all the methodology meets our

expectations and provides an opportunity to assess

the acute alertness after the exposure to light. Our

results confirmed previous studies concerning

alerting effect of blue and red light (Figueiro et al.,

2016, Figuerio and Rea, 2010, Chang et al., 2013,

Sahin and Figueiro, 2013, Łaszewska et al., 2017,

Figure 2: An example of box plots for participant R05N. Box plots of energy value in bands: Theta, AlphaTheta, AlphaLow,

AlphaHigh. Energy is presented in three measure points: (1) before the exposure to blue light, (2) just after the exposure to

blue light, (3) after a period of performing computer tests following the exposure to blue light.

NEUROTECHNIX 2018 - 6th International Congress on Neurotechnology, Electronics and Informatics

Sawicki et al., 2016). Interview with the participants

after the experiments confirmed that work stand

provided them with comfort during the experimental

session. In the opinion of participants and Authors

this was a valuable contribution to minimizing the

impact of discomfort-related factors on the obtained

results.

Figure 3: Impact of blue light exposure on the alertness

level. Box plots of TAAT

max

for two states: (2-1) after the

exposure, (3-1) after performing computer tests. The

higher the TAAT

max

, the higher the level of alertness

(Sawicki et al., 2016)

Figure 4: Impact of red light exposure on the alertness

level. Box plots of TAAT

max

for two states: (2-1) after the

exposure, (3-1) after performing computer tests. The

higher the TAAT

max

, the higher the level of alertness

(Sawicki et al., 2016).

The second important result of the pilot study

was the confirmation that Author’s management

application (software for experiment management)

meets the requirements in various real working

conditions. It was particularly important to confirm

the correctness of data transmission between two

different operating systems and the synchronization

of the entire registration process. At the same time

the experiments showed that the applied solutions

allowed for simple and effective control of the

experiment. In addition, some programming errors

were detected and corrected during the pilot study.

7 CONCLUSIONS

Various research studies on the influence of lighting

parameters on human wellbeing psychophysiology

of vision and visual ergonomics have been the

subject of research carried out by the Authors of this

article for many years. The long-standing experience

in conducting the experiments with participants has

showed that developing a proper work stand and

procedure constitutes a big, self-contained and

difficult problem. Studies on the influence of light

on alertness level usually described in detail the

conditions and procedure of exposure, while the

technical aspects of experimental stand and

management were omitted. Reading the articles, we

believe that the described experimental conditions

and procedures may be easy to reproduce, but

sometimes surprisingly difficult or impossible to

perform.

Construction of a complex experimental stand

with EEG registration can be a difficult task,

especially when IT problems play an important role.

There may be a complex measurement system

controlled by heterogeneous software. With this in

mind, the Authors of this article wanted to share

their knowledge and experience in planning this type

of study, and believe that the technical aspects that

were described could be useful for those scientists,

who would like to analyze influence of light on

alertness level based on EEG recording in the future.

ACKNOWLEDGEMENTS

This paper has been based on the results of a

research task carried out within the scope of the

fourth stage of the National Programme

"Improvement of safety and working conditions"

partly supported in 2017–2019 --- within the scope

of research and development --- by the Ministry of

Science and Higher Education / National Centre for

Research and Development. The Central Institute for

Labour Protection -- National Research Institute

(CIOP-PIB) is the Programme's main co-ordinator.

Method of Acute Alertness Level Evaluation after Exposure to Blue and Red Light (based on EEG): Technical Aspects

REFERENCES

Alkozei A., Smith R., Pisner D.A, Vanuk J.R, Berryhill

S.M, Fridman A., Shane B.R., Knight S.A., Killgore

W.D.S., 2016. Exposure to blue light increases

subsequent functional activation of the prefrontal

cortex during performance of a working memory task.

Sleep, 39 (9), 1671-1680. https://doi.org/10.5665/

sleep.6090

Baek, H. Min, B.K., 2015. Blue light aids in coping with

the post-lunch dip: an EEG study. Ergonomics, 58 (5),

803-810.

Bellia L., Bisegna F., Spada G., 2011. Lighting in indoor

environments: Visual and non-visual effects of light

sources with different spectral power distributions.

Build Environ 46, 1984-1992. https://doi.org/10.1016/

j.buildenv.2011.04.007

Cajochen C., 2007. Alerting effects of light. Sleep Med

Rev., 11, 453-464.

Cajochen C., Chellappa S., Schmidt C., 2010. What keeps

us awake? The role of clocks and hourglasses, light,

and melatonin. Int Rev Neurobiol, 93, 57-90.

Chang A.M., Scheer F.A.J, Czeisler C.A., Aeschbach D.,

2013. Direct effects of light o alertness, vigilance, and

the waking electroencephalogram in humans depend

on prior light history. Sleep, 36 (8), 1239-1246.

Chellappa S.L., Steiner R., Blattner P., Oelhafen P., Gotz

T., Cajochen C., 2011. Non-visual effects of light on

melatonin, alertness and cognitive performance: can

blue enriched light keep us alert? PLoS One, 6,

e16429.

Figueiro M.G., 2013. Non-Visual Lighting Effects and

Their Impact on Health and Well-Being. In

Encyclopedia of Color Science and Technology.

Springer Science+Business Media New York doi:

10.1007/978-3-642-27851-8_118-4, 1-11.

Figueiro M.G., Bierman A., Plitnick B., Rea M.S., 2009.

Preliminary evidence that both blue and red light can

induce alertness at night. BMC Neurosci, 10. 10:105.

https://doi.org/10.1186/1471-2202-10-105

Figueiro M.G., Rea M.S., 2010. The effects of red and

blue light on circadian variations in cortisol, alpha

amylase and melatonin. Int J Endocrinol., Volume

2010, Article ID 829351, 9 pages, https://doi.org/

10.1155/2010/829351

Figueiro M.G., Rea M.S., 2017. Quantifying circadian

light and its impact. Architectural lighting

http://www.archlighting.com/technology/quantifying-

circadian-light-and-its-impact_o (retrieved 018/04/02).

Figueiro M.G., Sahin, L., Wood, B., Plitnick, B., 2016.

Light at night and measures of alertness and

performance: implications for shift workers. Biol Res

Nurs.. 18 (1), 90-100. https://doi.org/10.1177/

1099800415572873

Jankowski K.S., 2015. Composite Scale of Morningness:

psychometric properties, validity with Munich

ChronoType Questionnare and age/sex differences in

Poland. Eur Psychiatry, 30, 166-171.

Klimesch W., 2012. Alpha-band oscillations, attention,

and controlled access to stored information. Trends

Cogn Sci. 16 (12), 606-617.

Łaszewska K., Goroncy A., Weber P., Pracki T., Tafil-

Klawe M., Pracka D., Złomańczuk P., 2017. Daytime

acute non-visual alerting response in brain activity

occurs as a result of short- and long wavelengths of

light. Journal of psychophysiology. https://doi.org/

10.1027/0269-8803/a000199

Maierova L., Borisuit A., Scartezzini J.L., Jaeggi S.M.,

Schmidt C., Münch M., 2016. Diurnal variations of

hormonal secretion, alertness and cognition in extreme

chronotypes under different lighting conditions.

Nature. Scientific Reports, 1-10. https://doi.org/

10.1038/srep33591

Okamoto Y., Rea M.S., Figueiro M.G., 2014. Temporal

dynamics of EEG activity during short and long

wavelength light exposures in the early morning. BMC

Res Notes, 7: 113, 1-6.

Phipps-Nelson J., Redman J.R., Schlangen L.J.,

Rajaratnam S.M., 2009. Blue light exposure reduces

objective measures of sleepiness during prolonged

night time performance. Chronobiol Int. 26 (5), 891-

912. doi: 10.1080/07420520903044364.

Plitnick B., Figueiro M.G., Wood B., Rea M.S., 2010. The

effects of red and blue light on alertness and mood at

night. Lighting Res. Technol, 42 (4), 449-458.

https://doi.org/10.1177/1477153509360887

Sahin L. and Figueiro M.G., 2013. Alerting effects of

short-wavelength (blue) and long – wavelengths (red)

lights in the afternoon. Physiol Behav. 116-117 (5), 1-

7. https://doi.org/10.1016/j.physbeh.2013.03.014

Sahin L., Wood B.M., Plitick B., Figueiro M.G., 2014.

Daytime light exposure: effects on biomarkers,

measure of alertness and performance. Behav Brain

Res. 274, 176-185. https://doi.org/10.1016/j.bbr. 2014.

08.017

Sawicki, D., Wolska, A., Rosłon, P., Ordysiński, S. 2016.

New EEG Measure of the Alertness Analyzed by

Emotiv EPOC in a Real Working Environment. In

Proc. of the 4th International Congress on

Neurotechnology, Electronics and Informatics,

NEUROTECHNIX 2016, Porto, Portugal, 7-8 Nov.

2016, 35-42. doi: 10.5220/0006041200350042

Smith C.S., Reilly C., Midkiff K., 1989. Evaluation of

three circadian rhythm questionnaires with suggestion

for an improved measure of morningness. J Appl

Psychol., 75, 728-738.

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