Cell Assemblies & Drugs
As you learned in the lectures on cell assemblies, most of our thoughts and perceptions depend on (1) the inborn nerve pathways that mediate early reflexive behavior, and (2) the new pathways, called cell assemblies, that develop when we have learning experiences. Both the inborn and learned neural pathways can be affected by drugs -- recreational, over-the-counter, and prescription. Drugs that affect the brain alter some of the synapses and neurotransmitters that operate at the synapses. Depending on the drug and the synapses it affects, all sorts of different and unusual things can occur, including hallucinations, distorted perception, happy emotions, "bad trips," euphoria, confused thinking, memory loss, addition and hysteria.SD to Memory-CA Triggers Drug Craving
Many of John's students have been interested in learning more about the effects of drugs on the brain. Here are some bits of information that may be of interest. The topics covered in the lengthy document below are summarized in this "Table of Contents" (which is organized chronologically, based on the date when the research was publiced.).
Table of Contents
Ecstasy Impairs Memory
SD to Memory-CA Triggers Drug Craving
Addiction
Marijuana
Crystal Meth
Drug That Elicit Pleasure
Psilocybin, or Hallucinogenic Mushrooms
Biological Psychology
Ecstasy Causes Brain Damage
Brain Shrinkage
Nicotine Accelerates Things
Pregnant Women Using Marijuana
GABA Helps Old Brains Think Like Younger Brains
Marijuana's Effects
Cocaine and Amphetamines Retard Brain DevelopmentEcstasy Impairs Memory
MDMA (or ecstasy) is known to cause memory problems. Volunteers who took the drug for a long period of time underwent memory tests and most aspects of the MDMA users' memories got worse during the year that they were taking the drug and being tested for memory capacity. Marijuana and cocaine are known to hamper thinking, but MDMA hampers memory.
REFERENCE: 10 April 2001, Neurology, by Drs. Zakzanis & Young.This study used rats that had been addicted to cocaine then forced to "go clean." After the rats had "kicked the cocaine habit," stimulation to the memory area of the rat's brain triggered drug cravings and the rats went back to seeking cocaine. Interestingly, stimulation to the area of the brain that produces the "high" feelings associated with cocaine use did not induce drug cravings or attempts to find cocaine.Addiction
REFERENCE: 11 May 2001, Science, vol 292, page 1039.
This and the next paragraph suggest that the cravings of addiction are based memory systems, such as the cell assemblies we develop through learning.Addition is based on the same neurotrophic factors that affect learning and memory. Both alter the formation or loss of dendritic spines and other alterations at synapses. As people get addicted to a drug, they are inducing long lasting neural changes in their brain; and this makes them more prone to relapses even after years of abstinence. The more a person uses addictive drugs, the more their brain develops a "memory" of that drug. Later, relapses can be triggered by any SD's (stimuli that are "keys to memory") that activate the long lasting memories of the drug.Marijuana
REFERENCE: 22 June 2001, Science, vol 292, pp 2266-2267.
The implication is clear. Avoid additive drugs and you can avoid developing long-lasting brain memories of them. The fewer "memories" of that drug you have, the less likely you are to be to relapse and fall back into craving that drug at some later point in life. The more you use a drug, the harder it is to get off the drug and stay off it.Males are 2.5 times more likely to use marijuana. Smoking marijuana causes some of the same problems as smoking tobacco, and smoking marijuana exposes the lungs to 3-4 times more tar than do cigarettes. THC, the active ingredient in marijuana, reduces the bodies defenses needed for fighting infection (such as pneumonia) and cancer. Driving while under the influence of marijuana is dangerous, since the user is intoxicated. A study of airplane pilots found that they had delayed reaction times even 24 hours after smoking pot. Older smokers tun the risk of a five fold increase of having a heart attack. This is especially serious of a person who has a disease (such as diabetes) that puts them at heightened risk of cardiovascular problems.Crystal Meth
REFERENCE: LA Times, July 9, 2001, pp S1 and S4.Crystal methamphetamine causes a powerful high with sexual arousal. It makes many users sexually insatiable. When people get high on crystal, they often feel invincible and they have no fear of sexually transmitted diseases. When people come down from the high, they often become very depressed and paranoid -- and eager to get more crystal in their bodies. Many users are contracting HIV (the virus that causes AIDS) because they do all sorts of sexual activities (including anal sex, the most dangerous form of sex) while high.Drug That Elicit Pleasure
Crystal causes the release of dopamine and other chemicals in the brain; and these chemicals cause the emotional high and sexual arousal. Crystal has a half-life of about 12 hours, so people still have enough to feel a high some 24 hours after taking the drug. But when the drug wears off, the depression feels to bad that it feels like an eternity. So here is a drug that hits the reinforcement and punishment systems in the brain, producing an amazing high followed by a painful low.
There is no remedy (such as methadone maintenance) to help people get off crystal; so it is very addictive. Many a person has not been able to kick this drug, and it can ruin any chance a person might have had to have a normal life.
REFERENCE: LA Times Magazine, October 7, 2001, pages 12-15 and 29-30.An article in the highly respected journal, Science, helps us understand the effect of pleasure-eliciting drugs. Drugs that feel good are primary reinforcers, and they are addictive because they co-opt both memory and motivation systems, not just pleasure systems in the brain. Their use causes short-term surges in dopamine and other neurotransmitters that trigger pleasure and reward. However, the brain quickly adapts to this deluge of pleasure, and the pleasure circuits desensitize-- producing tolerance to the drug. At this point, people need to use more of the drug to get the same "high" that they got at first. This leads to addition, even if the drugs no longer bring much pleasure.
Addiction is based on the learning and memory systems of the brain. Through Pavlovian conditioning, the stimuli that are present just before using pleasure- inducing drugs become CSs for positive drug-related pleasure emotions. In the future, the presence of these CSs can cause drug cravings; and this is a big part of the addition process.
Some of the CSs for drug cravings operate at the unconscious level, contributing to the compulsive aspects of addiction. If a person happens to perceive one of the drug-related CSs, the drug craving can pop up, even if the person has no conscious awareness of the presence of the CS. Even subtle context cues can become CSs for compulsive drug urges. Just being in a room that resembles a room where the person took drugs in the past can be enough of a CS to elicit strong drug urges. Hence, "many recovered drug users say they fight cravings for the rest of their lives."
"Although each drug of abuse has its idiosyncratic effects, all specialize in bombarding the brain's dopamine-mediated reward circuits. Long-term abuse can wear out these pathways, reducing the number of receptors that respond to dopamine." Even people who have been drup free for months do not have a complete recovery of their dopamine pathways. The loss of dopamine receptors interferes with motivation and pleasure. The loss also interferes with learning and movement, creating memory problems and damage to motor coordination.
Also, the loss of dopamine receptors causes the brain to become less sensitive to natural reinforcers, such as the "pleasure of seeing a friend, watching a movie, the curiosity that drives exploration." So people turn ever more to drugs (as the other reinforcers lose their power). This is when people start neglecting their friends, families, jobs and health. The article says: "It isn't that the crack-addicted mother does not love her children. She just loves drugs more."
There is a great picture on page 984 that shows how cocaine causes the extra growth of dendrites and dendritic trees on nerve B. Thus people who use cocaine, develop these extra large number of dendrites that makes the brain extra hungry for cocaine. They are the drug receptors that increase an individual's sensitivity to drugs, while the damage to the dopamine-mediated reward circuits (described in the pior two paragraphs) destroys the brain's ability to experience pleasure from the drugs.
When people "go off" a pleasure-inducing drug, they experience withdrawal symptoms (since their body has become dependent on the drug). The psychological feelings of withdrawal are closely akin to the dark feelings associated with extended mourning for the loss of pleasure and security. These feelings can be intense mood drops that cause a spike in irritability, depression or other negative emotions.
REFERENCE: Science, Vol 294, November 2, 2001, pages 983-984.
Psilocybin, or Hallucinogenic MushroomsAn article written by Ladan Moeenziai explains the behavior of a student on psilocybin, a hallucinogenic mushroom. At about 8:35 pm, during dead week, December, 2001, a 19-year-old UCSB student, Christopher Miller reportedly began running naked from IV to campus. When reaching Mesa Road, Miller ran into the side of 3 moving cars, bouncing off each one and continuing to run. Miller was struck by a 4th car when he jumped out in front of it. He sustained only minor injuries and remained conscious. He was using psilocybin, a hallucinogenic mushroom. He was taken to Cottage Hospital. The driver of one of the cars said, "The whole time I was thinking, did I hit someone or did someone hit me?"Biological Psychology
REFERENCE: Daily Nexus, vol 82, no 49, Dead Week, Fall 2001, p 1.The Department of Psychology offers a couple of courses on biological psychology that go into wonderful detail on the brain and include lots of nice scientific data on the effects of drugs on the brain. The book listed below is used in one of the classes, and it contains a whole chapter (ch #4) on drugs, neurotransmitters and behavior. The topic of prenatal exposure to drugs is covered in a separate chapter, pages 204-205.Ecstasy Causes Brain Damage
REFERENCE: Mark Rosenzweig, Marc Breedlove, and Arnold Leiman (2002). Biological Psychology (3rd edition). Sunderland, MA: Sinauer Associates, Publishers.Long known to disrupt neurons that communicate via the neurotransmitter serotonin, Ecstasy now appears to have even more potential for roughing up the dopamine system. Ecstasy heightens sensations, gives a euphoric rush, and creates feelings of warmth and empathy, apparently by causing neurons to spurt huge quantities of serotonin. Afterward, the CNS is drained of serotonin, making one depressed and unable to concentrate. The amount of ecstasy used in one all-night "rave" may be enough to induce permanent brain damaged and make a person more vulnerable to Parkinson's disease, which is caused by a loss of dopamine-producing neurons. The axons of affected nerves become damaged, reducing their ability to communicate to other nerves.Brain Shrinkage
REFERENCE: George A. Ricaurte and colleagues (2002). "Drug Find Could Give Ravers the Jitters." Science, 27 September, pp 2185-2187 and 2260-2263.As people age (after age 30), their brains shrink and lose weight if they do not do regular cardiovascular exercise. The loss of brain size and weight is matched by declines in cognitive performance. People who swim, walk, job or cycle at least 20 minutes a day, several days a week, show less decline in brain mass than do people who do less cardiovascular exercise. So it is wise to adopt good habits of cardiovascular exercise as soon in life as possible and maintain those habits through all your remaining years.
REFERENCE: Science, 7 March, 2003, page 1511.Nicotine Accelerates Things
In the brain, nicotine sparks activity in the neurons, especially the acetylcholine synapses. The excited neural activity makes smokers feel good, even euphoric; and it is also what makes them crave more. Now we are learning that nicotine also speeds up activity in tumor cells, which can make cancer cells grow faster. (Scientists usually blame all sorts of the other chemicals found in cigarettes -- and not nicotine -- as the causes of cancer; but nicotine can make cancer cells divide faster.) Nicotine also accelerates the again of skin cells, since it has the capacity to accelerate cell activity and cell division. That is why smokers' faces age faster than do nonsmokers.
REFERENCE: Science News, 22 March 2003, pages 184-186.
Pregnant Women Using MarijuanaVarious studies have suggested that children born to women who had used marijuana while pregnant suffered from memory problems and hyperactivity. A recent study on rats provides laboratory evidence that is in line with the prior studies. Female rats were exposed to a marijuana-related drug during pregnancy. Their offspring produced less glutamate (an essential neurotransmitter) in the hippocampus, which is a memory-processing center in the brain. The researcher says, "Our findings suggest that both pregnant and lactating women should avoid using marijuana."
REFERENCE: Science News, 5 April 2003, pages 220-221.
GABA Helps Old Brains Think Like Younger BrainsAs the brain ages, people often experience increased amounts of "cross-talk" between CAs all over their increasingly well-conected brains (as CAs keep hooking up with each other). This "cross-talk" can interfer with logical and clear thinking. Research on primates suggests that adding regular doses of GABA (Gamma-aminobutyric acid) to the brain may help reduce the random "noise" in the brain, due to too much "cross-talk," and this helps old individuals think more clearly. GABA is the brain's major inhibitory neurotransmitter, and it usually declines with age, allowing for the indiscriminant firing of irrelevant neurons. GABA renews powers of discrimination and sensory-information processing that younger individuals have--but which are often lost with advanced age. "Anything that can show a reversal in the effects of aging is really exciting and potentially beneficial" says Julie Mendelson, a neuroscientist at the University of Tolonto. GABA helps the brain extract information from a noisy environment.Marijuana's Effects
REFERENCE: Science, May 2, 2003, page 721-2; and Newsweek, May 12, 2003, page 10.A recent study compared 704 long-term marijuana users with 484 nonusers and found that there was only difference in a series of different measures that were taken. The long-term marijuana users showed no decrement in language skill, reaction time, motor skills, perceptual capacity or reasoning abilities. There was only one difference: The marijuana users had a small decrement in their ability to learn new information.
REFERENCE: Journal of the International Neuropsychological Society, July, 2003.Cocaine and Amphetamines Retard Brain DevelopmentSpeed-type drugs stunt the growth of brain cells. During normal learning, dendrites grow more branches and spines (the tiny receptor sites on the dendrites); but cocaine and amphetamines greatly inhibit the formation of new dendrite branches and spines. Bryan Kolb, the head scientist on the project said, "It may be that the drug exposure has altered [the subjects'] ability to learn from their experience" -- which would make them a lot like human addicts. This is the first study to show that drugs can block the effects of learning experience at the anatomical level in the brain.
REFERENCE: Proceedings of the National Academy of Sciences, end of August, 2003.
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