What are brainwaves?

Driving home from TAM this weekend I saw an anti-abortion billboard that said something like “heartbeat at 3 weeks, brainwaves at 6 weeks.” Without getting into a debate over the morality of abortion, I wonder if anyone knows exactly what brainwaves are and how important they may be to determining when life begins?

As I understand the brain, cells make electical connections with each other and the specific pathways electric pulses follow in the brain produce thoughts and behavior. If this is accruate, where do the waves come from? Should I wear a tin foil hat to keep my brain waves from escaping?

[Goshawk]

http://science.howstuffworks.com/brain1.htm

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Neurons
Your brain is made of approximately 100-billion nerve cells, called neurons. Neurons have the amazing ability to gather and transmit electrochemical signals -- they are something like the gates and wires in a computer. Neurons share the same characteristics and have the same parts as other cells, but the electrochemical aspect lets them transmit signals over long distances (up to several feet or a few meters) and pass messages to each other... [ more ]

http://brain.web-us.com/brainwavesfunction.htm

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It is well known that the brain is an electrochemical organ; researchers have speculated that a fully functioning brain can generate as much as 10 watts of electrical power. Other more conservative investigators calculate that if all 10 billion interconnected nerve cells discharged at one time that a single electrode placed on the human scalp would record something like five millionths to 50 millionths of a volt. If you had enough scalps hooked up you might be able to light a flashlight bulb.

Even though this electrical power is very limited, it does occur in very specific ways that are characteristic of the human brain. Electrical activity emanating from the brain is displayed in the form of brainwaves. There are four categories of these brainwaves, ranging from the most activity to the least activity... [more]

http://enchantedmind.com/html/scienc...tum_brain.html

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When a perception of any kind takes place, an electrical impulse is sent from the senses to appropriate neurons in the brain. This impulse is carried along the axon out to the dendrites. Between each of the billions of dendrite connections within our brains there are little gaps. These gaps, called synapses, are microscopic in size. Communication takes place between these synapses through the use of neurotransmitters.

Quantum physics has determined that wave patterns are the essential building blocks of the brain's electrochemical neurotransmitters. It is at the synapse that quantum wave patterns are transformed into neurotransmitters. Through this neuronal synaptic firing the translated wave frequencies are made coherent. These coherent frequencies are then transferred from dendrite to dendrite to the appropriate areas of the brain.

Tinfoil hats are not necessary since the electricity in your brain follows pathways called "dendrites" Electricity doesn't leak out of your head for the same reason that it doesn't leak out of the electrical outlets in your home--its own rules say that it has to stay on the pathways. In your home, it's the wiring. In your brain, it's the dendrites.

[arcticpenguin]

The connections between brain cells are not purely electrical, they are electro-chemical. between neurons hte primary means of connection is synapses. One neuron releases chemical neurotransmitters into the synapse and they are picked up by receptors on the other side.

Within a neuron, especially down the long extensions they have to connect to numerous other neurons, a signal is sent as an "action potential". An electrical depolarization triggered by ion channels (possibly the result of summing signals from a number of synapses) triggers a "wave" down the axon as the voltage change opens ion channels, which let in ions. At the end of axon is probably a synapse where the neuron passes the signal chemically to another neuron.

Brainwaves are measurable changes in the electromagnetic field in/around the brain, presumably a byproduct of all those ion channel happenings. They do not represent activity of individual neurons, but a composite overall frequency due to activity of all the neurons in the brain. Presence of measurable brain waves would be considered an indicator of neural activiity.

There is nothing you could or should do to prevent your brain waves from 'escaping'. (Yes, I know you were just kidding) and there is no evidence that any but an extremely powerful external electromagnetic field would influence brain activity.

[gmol]

I always thought brainwaves (as measured) were differences in skin conductance around the head, presumably due to the electromagnetic activity (whatever that is) going on inside....can anyone confirm/deny?

So to measure a brainwave, you would need to measure the electromagnetic field around someone’s head? That field would fluctuate as more electricity was present in one place or another in the brain due to the acitivity there?

[arcticpenguin]

I'm not sure about this. A friend measured my brainwaves once, and I recall having electrodes attached to my scalp, so skin conductance might be the deal. If you were just measuring hte electromagnetic field you wouldn't need to make actual contact. But I can't swear to it.

[gmol]

Quote:

Originally posted by gmol
I always thought brainwaves (as measured) were differences in skin conductance around the head, presumably due to the electromagnetic activity (whatever that is) going on inside....can anyone confirm/deny?

As such it would make it very difficult for one to measure the brainwaves of an embryo...

[Dylab]

I hope this doesn't start a debate...

Quote:

Originally posted by bcr19374
Driving home from TAM this weekend I saw an anti-abortion billboard that said something like “heartbeat at 3 weeks, brainwaves at 6 weeks.”

Are you sure that it said 3 weeks and 6 weeks... Could it be months?

Quoting Carl Sagan's article on the issue (he was pro-choice in case there is any bias):

"By the third week, around the time of the first missed menstrual period, the forming embryo is about 2 millimeters long and is developing various body parts. Only at this stage does it begin to be dependent on a rudimentary placenta. It looks a little like a segmented worm. "

"By the sixth week, the embryo is 13 millimeteres (about ˝ inch) long. The eyes are still on the side of the head, as in most animals, and the reptilian face has connected slits where the mouth and nose eventually will be. "

"Thinking occurs, of course, in the brain--principally in the top layers of the convoluted "gray matter" called the cerebral cortex. The roughly 100 billion neurons in the brain constitute the material basis of thought. The neurons are connected to each other, and their linkups play a major role in what we experience as thinking. But large-scale linking up of neurons doesn't begin until the 24th to 27th week of pregnancy--the sixth month.

By placing harmless electrodes on a subject's head, scientists can measure the electrical activity produced by the network of neurons inside the skull. Different kinds of mental activity show different kinds of brain waves. But brain waves with regular patterns typical of adult human brains do not appear in the fetus until about the 30th week of pregnancy--near the beginning of the third trimester. Fetuses younger than this--however alive and active they may be--lack the necessary brain architecture. They cannot yet think. "

The article is here:
http://www.2think.org/science_abortion.shtml


I couldn't find a secondary source for this information so if it somebody can correct this if he is wrong then it would be appreciated.

I’m not absolutely sure but I do believe it said weeks. I saw the billboard twice, once on the way to Ft. Lauderdale and once on the way back and both times it struck me as odd.

[arcticpenguin]

Given that these people have a political agenda, I wouldn't rely on them for scientific facts.

There is a very interesting article in the February issue of Discover magazine on The scientist who hated abortion. An anti-abortion endocrinologist carried out a study to check for correlation between abortions and breast cancer. He didn't even ahve the qualifications for this, so he and his pals had to pull in a biostatistician. They found a very weak correlation. That was enough for him, he went straight away to lobbying congress and putting up posters.

Several subsequent studies have refuted his finding, and one even showed clearly what was wrong with his study (women will lie about whether they have had abortions), but he refuses to back down, and has taken to attacking the other studies.

[Cecil]

Quote:

Originally posted by bcr19374
Should I wear a tin foil hat to keep my brain waves from escaping?

Silly. Tin foil hats are to prevent the aliens from interfering with your brainwaves. Everyone knows you need to wear copper hats to prevent your brainwaves from escaping.

Or you could just wear a bronze hat and kill two birds with one stone.

[Goshawk]

http://www.bio.unc.edu/courses/2001f...-001/nerve.htm

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How do electroencephalograms work?

Electrodes on the skin detect voltage changes produced by depolarizations and repolarizations of nerve cells in the brain.

The "brainwaves detectable at 6 weeks" factoid is very nicely debunked here.

http://eileen.250x.com/Main/Einstein/Brain_Waves.htm

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Have you heard the common claim that "fetal brain waves" have been measured very early in pregnancy? Ever wondered how exactly that was done, and if it's true?

Good question, and no, it's not true. Instead, as with many "pro-life" assertions, it's based on very old research that has been taken out of context or misreported. It also depends on an incorrect, misleading definition of "brain waves," which is a nontechnical term anyway. Here's the real story... [more]

http://www.psychology.mcmaster.ca/3g...aldevelop.html

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Behavioural milestones of fetal development

6-8 weeks
heart beat by 4 weeks
reflexive movement
brainstem activity by 10 weeks
movement -- can bend trunk & neck, rotate pelvis, extend upper arms down & back, open jaw
reflexive response to touch (1st reflex)
all reflexes of the newborn except breathing and crying have developed by 4 months

5-7 months
cortical brain waves EEG (all neurons are formed)

http://www.tnr.com/013100/easterbrook013100.html

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... But science also shows that by the third trimester the fetus has become much more human than once thought--exhibiting, in particular, full brain activity.

< snip>

Now research is beginning to show that by the beginning of the third trimester the fetus has sensations and brain activity and exhibits other signs of formed humanity.

Most striking are electroencephalogram (EEG) readings of the brain waves of the third-trimester fetus. Until recently, little was known about fetal brain activity because EEG devices do not work unless electrodes are attached to the scalp, which is never done while the fetus is in the womb. But the past decade has seen a fantastic increase in doctors' ability to save babies born prematurely. That in turn has provided a supply of fetal-aged subjects who are out of the womb and in the neonatal intensive care ward, where their EEG readings can be obtained.
EEGs show that third-trimester babies display complex brain activity similar to that found in full-term newborns.

< snip >

The fetus's heart begins to beat, and by about the twentieth week the fetus can kick. Kicking is probably a spasm, too, at least initially, because the fetal cerebral cortex, the center of voluntary brain function, is not yet "wired," its neurons still nonfunctional. (Readings from 20- to 22-week-old premature babies who died at birth show only very feeble EEG signals.)

From the twenty-second week to the twenty-fourth week, connections start to be established between the cortex and the thalamus, the part of the brain that translates thoughts into nervous-system commands.

This would seem to indicate that the ""Brainwaves are detectable at 6 weeks" factoid is wrong, if it takes installing electrodes on the scalp to detect brainwaves. Obviously, a 6-week-old fetus, which is only a half-inch long, probably can't have electrodes installed in its scalp.

http://www.ship.edu/~cgboeree/genpsyfetaldev.html

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Weeks 13 to 16 -- 6 inches:

These weeks mark the beginning of the second trimester. A lthough the skin of the fetus is almost transparent, fine hair develops on the head called lanugo. The fetus makes active movements, including sucking, which leads to some swallowing of the amniotic fluid. A thin dark substance called meconium is made in the intestinal tract. The heart beats120-150 beats per minute and brain waves detectable.

A four-month-old fetus is about the size of an avocado, plenty big enough to have some electrodes stuck on there.

So, it's just an anti-abortion factoid, and is not supported by medical evidence.

Thanks for the help on this one, guys!

[Soapy Sam]

Actually, brain waves do leak.

Usually via the mouth.

[jasonmccoy]

Quote:

Originally posted by arcticpenguin
The connections between brain cells are not purely electrical, they are electro-chemical. between neurons hte primary means of connection is synapses. One neuron releases chemical neurotransmitters into the synapse and they are picked up by receptors on the other side.

This is not an attempt to argue trivial matters. I simply wanted to bring your attention to something I recently read by a world renown neuroscientist named Joseph LeDouzx. In his book, Synaptic Self , he writes Although terminals most often form connections with dendrites, they can also contact cell bodies or other axons. (2) Dendrites too can also communicate between one another. (3) There are also synapses through which communication between presynaptic and postsynaptic sites is purely electrical, but chemical transmission is the most prevalent. (1)




References



1. Rozental et al. 2000 & Fukuda and Koska 2000

2. Zigmond et al. 1999; Kandel et al. 2000

3. Chen et al. 2000




Have you ever heard of "pure" electrical communication? What about gap junctions? Just curious.

[espritch]

Quote:

Actually, brain waves do leak.

Usually via the mouth.

Alas, no effective means has yet been found for preventing this kind of leakage.