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Limbic system? Strychnine? Neck bones?
Colliding action potentials Spinal cord width? Ballismus?
Gray/white matter Purpose of knee jerk reflex Ecstasy/Gender Effects
Drug detection? Disorder web sites? Deaths/Smoking
Methamphetamine/Vision Leg one way/Hand other way? Tract vs. Nerve
Brain cookie cutter? Fish have tongues? Elements in human body?
What is a beta-blocker? New graduate salary? MDMA = Ecstasy?
Drug called Doves? Ears grow? When Stroop?

J.K.: Is the limbic system present in both hemispheres?

Answer: Yes, areas of the limbic system are found in both hemispheres. The limbic system is composed of several structures including the cingulate cortex, the hippocampus, amygdala, mamillary bodies, anterior nucleus of the thalamus and interconnecting pathways. These structures are found in both hemispheres.

W.A.: How does strychnine affect the nervous system?

Answer: Strychnine blocks receptors for the neurotransmitter called glycine. Glycine is an inhibitory neurotransmitter used in many places of the nervous system including the spinal cord, brain stem and cerebellum. Strychnine therefore blocks inhibition and can cause convulsions, muscles cramping and respiratory problems.

B.L.: Do ALL mammals have seven neck bones?

Answer: Mice, cats, dogs, horses, whales, humans and most other mammals have only seven neck bones (cervical vertebrate), but there are exceptions to this rule. The manatee and the two-toed sloth have only SIX cervical vertebrae and the three-toed sloth has NINE cervical vertebrae.

K.A.: What would happen if two action potentials coming from opposite directions collide? Would they sum up to a specific point or would they cancel each other out?

Answer: Colliding action potentials cancel each other out because the refractory period of either spike prevents the continuation of an impulse in either direction.

N.V.: What is the width of the spinal cord?

Answer: It depends on what segment of the spinal cord and which plane you measure:

Midthoracic area (tranverse diameter) = 10 mm
Midthoracic area (sagittal diameter) = 8 mm
Cervical enlargement (transverse diameter) = 13-14 mm
Cervical enlargement (sagittal diameter) = 9 mm
Lumbar enlargement (transverse diameter) = 12 mm
Lumbar enlargement (sagittal diameter) = 8.5 mm

(Reference: Carpenter, M.B. and Sutin, J.S. Human Neuroanatomy, Baltimore: Williams & Wilkins, 1983.)

L.H.: What is the origin of the word "ballismus?"

Answer: Ballismus comes from the Greek word "ballismos" meaning "a jumping about" or "dancing."

P.R.: What is the difference between gray matter and white matter?

Answer: Gray matter consists primarily of neuron cell bodies. For example, in the brain, gray matter forms the outside layers of cortex and nuclei deep within the brain. White matter consists of myelinated axons.

A.C.: What is the purpose of the knee jerk reflex?

Answer: The knee jerk reflex helps with posture. When the knee bends, it stretches the leg muscle (quadriceps femoris). The muscle stretch starts the reflex and the leg straightens.

E.B.: Does the drug Ecstasy (MDMA) affect women and men differently?

Answer: Few studies have examined gender differences of the effects of MDMA. However, Liechti et al. (2001) reported that the perceptual changes, anxiety and adverse effects (e.g., jaw clenching, dry mouth, appetite changes) of MDMA are greater in women than in men. Blood pressure increases caused by MDMA are higher in men than in women.

Reference: Liechti, M.E., Gamma, A. and Vollenweider, F.X. Gender differences in the subjective effects of MDMA. Psychopharmacology (Berl). 154:161-168, 2001.

A.A.: For how long can drugs be detected after you take them?

Answer: It depends on the drug and the test. Urine tests are the most common way drugs are detected. However, samples of a person's blood, saliva, breath, sweat and hair can also be tested to detect drug use. The presence of breakdown products (metabolites) in a sample is an indication of drug use.

According to The Medical Letter, August 19, 2002 (Volume 44), the following drugs can be detected in urine:

According to Keltner, N.L. and Folks, D.G., in Psychotropic Drugs, (St. Louis: Elsevier Mosby, 2005):

The duration of drugs in the blood and urine
Drug Duration in Blood Duration in Urine
Amphetamines 72 hours 2-4 days
Barbiturates 7 days Up to 30 days
Benzodiazepine 7 days Up to 30 days
Cocaine 48-72 hours 1-3 days
Demerol 48 hours 24 hours
Heroin 72 hours 2-3 days
LSD 72 hours 24-72 hours
Marijuana Up to 15 weeks 1-3 days (causal use);
up to 30 days (chronic use)
Methadone 1-7 days 2-4 days
Methamphetamine 7 days 2-4 days
Morphine 72 hours 24-48 hours
Phencyclidine (PCP) 7 days 2-7 days

P.W. I am looking for a list of (brain) neurological disorders to use as a reference for students doing research projects.

Answer: You can find a good list at the National Institute of Neurological Disorders and Stroke. There is a link at the top of that page "Request mailed brochures" where you can have free publications about various neurological disorders mailed to you.

Another good resource is Brain Connections, a PDF booklet with email addresses, phone numbers and web sites of various support organizations.

A.K.: How many people die each year from smoking?

Answer: According to the Centers for Disease Control and Prevention:


D.K.: Can using methamphetamine cause vision problems?

Answer: Yes, there are case reports of visual disturbances after methamphetamine use. See:

C.L.: While sitting in a chair, move your right leg in a clockwise motion. At the same time, try to draw a "6" in the air with your right hand. This is difficult to do! Why?

Answer from Dr. Pat F. (Neuroscientist Network member): The motor coordination between upper and lower limbs is interconnected, both unilaterally and bilaterally. These interconnections are a holdover from our quadrupedal gait patterns. They are an evolutionary holdover, but are functional early in life. Recall that all humans, despite being considered bipedal (walking upright on our lower limbs), we are quadrupedal in our early stages of life (crawling as a child). These interconnections serve to provide a coordinated sequencing of movements of the upper and lower limbs. Evidence of these circuits and their retained functionality even in the adult is noted with the arm swing during walking. While some of the movement is passive, there is indeed increased muscle activity and even spinal motor neuron activity corresponding to these movements. This is evidence that they are not simply passive, but actually driven by nervous system activity. If you analyze the arm swing during bipedal gait, you will notice that it corresponds to the same sequence observed with a quadruped gait. These circuits are relatively easily overpowered by conscious voluntary control from higher centers.

So... Short answer, the control of upper and lower limb movements is influenced by 'old' reflex circuitry within the spinal cord and this circuit tries to maintain a symmetry of movement.

Alex A.: What is the difference between a tract and a nerve?

Answer: A tract is a collection of nerve fibers (axons) in the central nervous system. A nerve is a collection of nerve fibers (axons) in the peripheral nervous system.

M.N.: Where can I buy a cookie cutter in the shape of a brain?

Answer: Someone sent me the cookie cutter that I have, but I do not know where he bought it. I found some available on the Internet.

S.M. Do fish have tongues?

Answer: Yes, most fish have tongues. For more information about this topic, see the answer to this question provided by the Australian Museum Fish Site.

S.C.: What are the 10 most common elements in the human body?

Answer: According to The Handy Science Answer Book (1994) compiled by the Science and Technology Department of the Carnegie Library of Philadelphia, the human body is composed of:

Oxygen - 65%
Carbon - 18.5%
Hydrogen - 9.5%
Nitrogen - 3.3%
Calcium - 1.5%
Phosphorus - 1.0%

Potassium, sulfur, sodium, chlorine and magnesium each occur at 0.35% or less. There are other elements found in trace amounts.

Y.D.: What is a beta-blocker?

Answer: A beta-blocker is a drug that binds to beta receptors thus stopping the action of the neurotransmitter called norepinephrine. These drugs work by blocking the action of the sympathetic nervous system on the heart. They can prevent increased heart rate and pumping strength and are used to treat high blood pressure and irregular heartbeats.

T.M.: What is the average salary for a new Neuroscience graduate?

Answer: Many new Ph.D. scientists take post-doctoral fellowships funded through a National Institutes of Health (NIH) grant. The current stipends set by NIH for these fellowships depend on how much experience you have:

Postdoctoral Years         Yearly 
of Experience              Salary
0                         $ 37,740
1                         $ 39,756
2                         $ 42,624
3                         $ 44,304
4                         $ 45,960
5                         $ 47,940
6                         $ 49,836
7 or more                 $ 52,068

A.N.: Is MDMA the same thing as Ecstasy?

Answer: Yes, MDMA and Ecstasy are the same thing. MDMA is the abbreviation for the chemical name of Ecstasy: 3,4 methylenedioxymethamphetamine.

Nancy M. What drug is called "Doves?"

Answer: Doves, White Doves and Love Doves are other names for the drug Ecstasy.

Amy S.: Do ears continue to grow as we get older?

Answer: As people age, their ears get larger. Ear circumference increases an average of 0.51 millimeters per year. (Source: "Ear size as a predictor of chronological age," by R. Tan, V. Osman, and G. Tan. Archives of Gerontology and Geriatrics, Vol. 25., page 187, 1997.)

H.R..: When did J. Ridley Stroop invent the Stroop Test?

Answer: J. Ridley Stroop published his paper about the famous colored word task in 1935. You can read his original paper on the Internet.

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