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ADDICTION Derek Early Bio 003 Feb. 5, 2002 What Is Addiction? • An addiction is similar to a compulsion A compulsion is “a repetitive, stereotyped, and unwanted action, that can be resisted only with difficulty” • Loss of voluntary control often leading to selfdefeating behavior Can take many forms What Is Addiction? • Addiction is characterized as dependence syndrome by psychologists • Dependence Syndrome involves “a cluster of physiological, behavioral, and cognitive phenomena in which the use of a substance or a class of substances takes on a much higher priority for a given individual than other behaviors that once had a higher value” What Is Addiction? • Often there is a repeating pattern of elements including: High or pleasure desensitization dependence and withdrawal • High occurrence of relapse in all cases Types of Addiction • Substance • Behavioral • Is there a biological link between these two types of addictions??? Types of Addiction • Substances Depressants (Alcohol) Stimulants (Cocaine, Caffeine, Nicotine) Opioids (Morphine, Heroin) Hallucinogens (LSD) PCP (Ecstasy) Others (Marijuana) Types of Addiction • Behavioral Gambling Food (often dopamine deficient) Sex (loss of control) Shopping Internet What is The Basis of Addiction? • The Brain Addiction is connected to the brain by it’s effects on hormones, memory, and physically desensitization • Psychologists have found substantial evidence against the existence of an “addictive personality” What Is The Basis of Addiction? • Short-term surges in dopamine caused by substances or behaviors activate the brain’s pleasure/reward system. Over time the brain adapts to the surges and is desensitized to the substance or behavior causing the individual to engage in a greater amount of the activity in order to obtain the same pleasure as before. The desensitization can cause the brain to become dependent, which results in withdrawal when the compulsion is not performed. Neurons • 4 main parts: – The Cell Body (houses the nucleus and organelles) – Dendrites (usually short and numerous, receive signals) – Axons (often only one on a neuron and can be very long, sends signals to other neurons or effectors) – Synapse (the junction point between two neurons or a neuron and an effector cell, can be electrical or chemical) Chemical Synapses A stimulus creates an action potential in a neuron and sends it down the axon. Neurons store neurotransmitters, like dopamine, in vesicles located near the end of each axon at the synapse. When the action potential arrives at the synapse it causes the vesicles to fuse with the plasma membrane of the neuron. The vesicles then release the neurotransmitters which diffuse across the membrane into the synaptic cleft. They cross the synaptic cleft and bind to receptors on the next cell’s membrane. They pass through ion channels and create a new action potential. Enzymes break down the left over neurotransmitter (MAO). Changes in Neurons • Long-Term Depression – Decreased responsiveness to action potential by receptor neuron • Long-Term Potentiation – Increased responsiveness to action potential by receptor neuron • LTP is essential in learning and memory making and plays a large role in addiction Dopamine • Neurotransmitter located in the hippocampus, a part of the brain involved in learning reasoning, personality, and part of the limbic system • Plays a role in the brain’s “reward” system (Those who have a below normal level are prone to engaging activities to raise the level) • Also is involved in attention, mood, motivation, learning, and movement Dopamine • Neurons can be sensitized or desensitized to dopamine depending on the nature of the stimulus • Desensitization is a reaction on the part of the nervous system to try and maintain homeostasis despite the increased presence of dopamine Memory Addictive cravings may be brought on by some of the same neurobiological processes involved in memory and learning and cravings are brought on by memories and situations associated with the compulsion This is how triggers are formed Consequences • Addiction causes people to compulsively feed their cravings even if, due to desensitization, they no longer provide pleasure and in the face of a desire to quit Consequences • In the long term pathways and receptors in the brain can wear out meaning that it is harder for the brain’s pleasure/reward system to function • The brain becomes less sensitive to even natural reinforcers the addiction becoming the highest priority in people’s lives Consequences • Neuron’s dendrites build more branching projections and have more synapses that connect to neurons with which the cell communicates regularly connections between the cells are made stronger Conclusions • It is not yet universally accepted that substances and behaviors can produce the same biological effects for those affected by addiction • Evidence supports neuroadaptation that occurs in both cases • Symptoms involving loss of control and relapse are similar as well Bibliography “Watching Cravings in the Brain” Scientific American. September 25, 1997 “Pathway to Addiction” Scientific American. May 13, 1998 Seligman, Martin E. Abnormal Psychology. W.W. Norton and Co., New York, NY: 2001 Holden, Constance. “Behavioral Addictions: Do They Exist” www.sciencemag.org Helmuth, Laura. “Beyond the Pleasure Principle” www.sciencemag.org