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The Effects of Light on Cognition

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by

Elena Kramarz

on 29 May 2014

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Transcript of The Effects of Light on Cognition

Hypothesis
We hypothesized that if participants are exposed to decreasing intensities of light, a decreased score will be seen on the Stroop Test, indicating a depressed cognitive ability.
Background
The importance of light for human cognitive brain function is emphasized by the role of melanopsin.
Melanopsin is a photopigment which may provide a unique form of “photic memory” for human cognition. It is a type of light sensitive cell photoreceptor in the eye.
Melanopsin is a visual pigment that does not contribute to vision, rather it helps set Circadian rhythms.
Ultimately meaning that the integration of light exposure over long periods of time can help optimize cognitive brain function.
The hypothalamus is the mediator and controller of the endocrine, autonomic, and behavioral functions.
Objective
To determine the effect of light intensity on cognition by using the Stroop test.
The Effect of Light on
Cognition through the Stroop Test

A group of nerves called the suprachiasmatic nucleus, or SCN, controls circadian rhythms and is located in an area of the brain called the hypothalamus.
This includes the regulation of body temperature, control of food and water intake, and other daily psychological and physiological functions.
Stroop test consisted of 4 columns of 15 words (60 total) printed in three different ink colors: red, blue,green. The only possible word choices to construct these columns are the words “RED”, “BLUE”, and “GREEN”. The columns were not in a specific pattern.
Procedures
Each participant (20 students total- 10 male and 10 female) completed a Stroop Test in three different levels of decreasing light intensity.
Data & Results
Discussion
Continuation in the future...
Jennifer Aguilar and Elena Kramarz
Circadian rhythms are physical, mental, and behavioral changes that follow a roughly 24 hour cycle, responding primarily to light and darkness in humans.
In this case, easy to think of the melanopsin as a plant that "grows" under light. Cognitive ability, the aspects such as awareness, perception, reasoning, and judgment, "grows under light".
Test was conducted in the Clean Room.
Constant- Flashlight from iPhone under Stroop Test paper

Bright Test- All lights on in room, door open

Dim Test- All lights off, door open, classroom lights outside illuminate, low light

Dark Test- All lights off, door closed, complete darkness
The participant was asked to complete a different Stroop Test after each light change. Accuracy and speed recorded for each session. Sleep and wake time were also logged.
Mean of 48.85 sec.
Using the Standard Deviation we have a "standard" way of knowing what is normal/frequent.
Mean of 55.55
σ of 14
69
41
Standard deviation of (σ) 10
Mean of 52.1
σ of 13
65
39
58
38
SPEED:
ACCURACY:
Mean of 1.05
σ of .77
1.82
.27
Mean of 2.35
3.75
.95
σ of .95
Mean of 2.15
σ of 1.52
3.67
.62
Overall:
Speed was faster in bright light and slowest in dim light.

Accuracy was more precise in bright light and less in dark light.

Hypothesis supported
BUT those who go to sleep "early" 9-10:30PM did better in bright light.
Those who go to sleep "late" >10:30PM-2AM did better in dark light.

Not taken into account by our hypothesis.
Melatonin is a hormone made by the pineal gland, a small gland in the brain. Melatonin helps control your sleep and wake cycles.
The body has its own internal clock that controls your natural cycle of sleeping and waking hours. In part, your body clock controls how much melatonin your body makes. Normally, melatonin levels begin to rise in the mid to late evening, remain high for most of the night, and then drop in the early morning hours.
Light affects how much melatonin your body produces. During the shorter days of the winter months, your body may produce melatonin either earlier or later in the day than usual.

Natural melatonin levels slowly drop with age. Some older adults make very small amounts of it or none at all.
It is important to understand each participant has a different circadian rhythm.
On average, our participants sleep 6.7 hours, instead of the recommended 8.
6 7 6 7 7 8 7 6 7 7 9 9 6 6 7 6 5 4 9 5
hours slept
Mean of 6.7 hr
Theories
A study from Dr. Michael J. Breus shows structural differences in the brains of people with different sleep-wake tendencies. Brain scans of early risers, night owls, and "intermediate" chronotypes who fell in between the two ends of the spectrum were collected.
Unlike the others, night owls show reduced integrity of white matter in several areas of the brain.
White matter is fatty tissue in the brain that facilitates communication among nerve cells. Diminished integrity of the brain's white matter has been linked to depression and to disruptions of normal cognitive function.
The lack of white matter
can be linked to sleep depravity, fatigue, daytime sleeplessness, difficulty focusing, physical pain and discomfort.Without functioning white matter, the brain could be like a group of people in proximity to each other but unable to communicate with each other.
White matter contains millions of axons coated in protective sheath of myelin, an insulator. Axons are the longest projections of brain cells and carry a cell’s signal to other cells.
White matter forms different kinds of fiber connections that can connect the left and right hemispheres, this makes possible the neural networks that support higher mental activities.
Myelin forms a sheath that encircles a cell’s axon in such a way that small regions, known as nodes of Ranvier, are left unwrapped. These unwrapped regions permit an enhanced form of electrical transmission called saltatory conduction. When the cell fires its nerve impulse along its axon, the transmission is much more efficient.
The aging brain is characterized by a selective diminution of white matter. In an autopsy study of normal brains from age 20 to 90, white matter loss, by volume, was 28%.
By identifying at what point in the day the brain is best able to operate, rehabilitation therapy can be targeted to that time, when recovery is maximized.
Circadian rhythms can influence sleep-wake cycles, hormone release, body temperature and other important bodily functions. They have been linked to various sleep disorders, such as insomnia.
Ex.) Jet lag
Regarding why participants who went to bed later did overall "better" in a dark setting: Those whose Circadian rhythms are accustomed to performing more complex brain functions in a darker setting adapt easier when placed in a dark setting.
The hypothalamus, where the superachiasmatic nucleus is located, therefore could perhaps function better in the environment that the experiment placed it under.
This, however, is not necessarily a good thing as abnormal circadian rhythms have also been associated with obesity,insomnia, diabetes, depression, bipolar disorder and seasonal affective disorder.
Works Cited
http://www.nigms.nih.gov/Education/Pages/Factsheet_CircadianRhythms.aspx
http://www.neuroanatomy.wisc.edu/coursebook/neuro2(2).pdf
Further experimentation of the effects of light on the brain could lead to studies of light with different wavelengths and frequencies that could act as a stimulant and replace the long term side effects of caffeine.
Classroom settings could be adjusted to disregard turning off the lights during a lesson.
Based on our results:
http://www.ncbi.nlm.nih.gov/pubmed/22450854
http://www.biomedcentral.com/1471-2202/14/115
http://www.ncbi.nlm.nih.gov/pubmed/23775768
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