Presentation on theme: "The Neurobiology of Addiction"— Presentation transcript:
1 The Neurobiology of Addiction Kim Edward Light, Ph.D.Professor, College of PharmacyUniversity of Arkansas for Medical Sciences
2 Objectives Review definitions for abuse, dependance, and addiction. Outline the brain areas involved in drug use and drug seeking including the limbic, hypothalamic, prefrontal cortex, orbitofrontal cortex, and anterior cingulate gyrus.Delineate the meaning of reward and how neuronal pathways are involved in signaling reward.Identify the neurotransmitter mediating the reward signal and how various behaviors and substances trigger reward neurotransmission.Outline the current neural interconnections involved in reward neurotransmission.Identify how motivation controls behavior and impacts drug abuse and addiction.
3 DefinitionsDSM-IV, Diagnostic and Statistical Manual of Mental Disorders, ed 4. American Psychiatric Association, Washington, 1994.The American Society of Addiction Medicine (ASAM).The American Academy of Pain Medicine (AAPM).The American Pain Society (APS).
4 Alcohol or Drug AbuseDSM-IV Definitionsone (or more) of the following, occurring within a 12-month periodrecurrent substance use resulting in a failure to fulfill major role obligations at work, school, or homerecurrent substance use in situations in which it is physically hazardousrecurrent substance-related legal problemscontinued substance use despite having persistent or recurrent social or interpersonal problems caused or exacerbated by the effects of the substance
5 Alcohol or Drug Dependence DSM-IV Definitionsthree (or more) of the following, occurring at any time in the same 12-month period:ToleranceWithdrawalRelapseA great deal of time is spent in activities necessary to obtain, use or recover from the substanceImportant social, occupational, or recreational activities are given up or reduced because of substance useContinued use despite adverse consequences
6 AddictionThe American Society of Addiction Medicine (ASAM), the American Academy of Pain Medicine (AAPM), and the American Pain Society (APS)Addiction is a primary, chronic, neurobiological disease, with genetic, psychosocial, and environmental factors influencing its development and manifestations.
7 Addiction Impaired control over drug use, Characterized by:Impaired control over drug use,Craving and/or compulsive use,Continued use despite harm,Relapse.
8 Addiction Neurobiology Animal modelsMust demonstrate these behaviorsNeuronal substrates and basis can be investigated.Slide image from NIDA
9 Reward PathwayIntracranial self-stimulation identifies neural pathwaysReinforcement or “reward” involvesthe acquisition of pleasure (positive)the avoidance of pain (negative).Several important brain areas
10 Limbic System Several structures contained in both hemispheres Linkages to the hypothalamus and other portions of the mid-brain.Concerned with feelings and emotions.Critical to memory processing and rewardCingulate gyrusAmygdalaHippocampusDentate Gyrus“Reward Pathway”
15 Reward Signaling Mediated by Dopamine Neurotransmission ActivityIncrease in DA release NcAFood or sexual activity50 – 100%Alcohol, MJ, Nicotine125 – 225%Morphine, Heroin%Cocaine400%Methamphetamine1000%
17 Pre-frontal Cortex Functions Limit or reducing consumptive behaviorInhibition of the amygdala (fear) and the stress responseShifting attentionBalancing several inputs at once (multi-tasking)Focusing short term memory for processing to long term
18 Orbitofrontal Cortex Function Processing emotional behaviorInterpretation of emotional behaviorInformation for planningLinking an actions with a negative consequence
19 Anterior Cingulate Gyrus Functions Emotion and awarenessMediates conflict between emotional desires and intellectual values“wanting” - and - “likely harm or wrongness”Intellect control of emotion
20 Motivation Important process that drives human behavior Appetitive - desire or “appetite”; commonly associated with “hedonic” or the seeking of pleasureAversive – avoidance of pain or unpleasant experiences
21 MotivationPleasure and pain are the principle aspects of motivational processes;Arise in the Limbic areas of the brainMeaning or interpretation provided by the PFC, OFC, ACG.Two states of stress - HypothalamusEustress (positive)Distress (negative)
22 Addiction Neurobiology On a neurobiological basis then addiction can be viewed as:a disruption or dysfunction of these pathways that may involve inadequate reward signaling from the limbic areas associated with certain behaviors,and/ora diminished ability of the prefrontal cortex and anterior cingulate gyrus to properly formulate responses to emotional information delivered by the limbic and hypothalamic areas.
24 Addiction Current hypothesis Pathology of addiction involvesinherent (genetic)and/ordrug-inducedalterations in the ability of the PFC, OFC, ACG to process and appropriately respond to information identified as important by DA neurotransmission from the reward pathway.
25 Review Definition of abuse, dependance, and addiction. Brain pathways that mediate and govern behaviors.Neurobiology of reward and its interpretationActivation of the reward pathway by drugs of abuse.Alterations in the higher brain areas that receive the reward pathway communication.Role of motivation in behavioral control and the hypothesized pathology of addiction.