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The Neurobiology of Addiction. Kim Edward Light, Ph.D. Professor, College of Pharmacy University of Arkansas for Medical Sciences. Objectives. Review definitions for abuse, dependance, and addiction.

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the neurobiology of addiction

The Neurobiology of Addiction

Kim Edward Light, Ph.D.

Professor, College of Pharmacy

University of Arkansas for Medical Sciences

objectives
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.
definitions
Definitions
  • DSM-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).
alcohol or drug abuse
Alcohol or Drug Abuse

DSM-IV Definitions

  • one (or more) of the following, occurring within a 12-month period
    • recurrent substance use resulting in a failure to fulfill major role obligations at work, school, or home
    • recurrent substance use in situations in which it is physically hazardous
    • recurrent substance-related legal problems
    • continued substance use despite having persistent or recurrent social or interpersonal problems caused or exacerbated by the effects of the substance
alcohol or drug dependence
Alcohol or Drug Dependence

DSM-IV Definitions

  • three (or more) of the following, occurring at any time in the same 12-month period:
  • Tolerance
  • Withdrawal
  • Relapse
  • A great deal of time is spent in activities necessary to obtain, use or recover from the substance
  • Important social, occupational, or recreational activities are given up or reduced because of substance use
  • Continued use despite adverse consequences
addiction
Addiction

The 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.

addiction7
Addiction

Characterized by:

  • Impaired control over drug use,
  • Craving and/or compulsive use,
  • Continued use despite harm,
  • Relapse.
addiction neurobiology
Addiction Neurobiology
  • Animal models
    • Must demonstrate these behaviors
    • Neuronal substrates and basis can be investigated.

Slide image from NIDA

reward pathway
Reward Pathway
  • Intracranial self-stimulation identifies neural pathways
  • Reinforcement or “reward” involves
    • the acquisition of pleasure (positive)
    • the avoidance of pain (negative).
  • Several important brain areas
limbic system

Cingulate gyrus

Hippocampus

Amygdala

Dentate Gyrus

“Reward Pathway”

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 reward
hypothalamic structures

Hypothalamus

Pituitary Gland

Hypothalamic Structures
  • Controls hunger, thirst, reproductive drive, temperature, blood pressure
  • Maintains hormonal balance

Stress Response Center

slide12

Prefrontal & Orbitofrontal Cortex

Prefrontal Orbitofrontal Cortex

Cognition, Judgment, Planning, Inhibitions, Personality,

Right/wrong

Decision making

why rewards
Why Rewards?
  • Natural Rewards or Instinctive Behaviors promote survival
    • Food acquisition
    • Water intake
    • Procreation (sex)
    • Nurturing / protection
  • Activities that “feel good” are noticed and repeated
brain structures of reward

ACG

PFC

NcA

VTA

OFC

Brain Structures of Reward

ACG - Anterior Cingulate Gyrus

PFC - Pre-frontal cortex

OFC - Orbitofrontal cortex

NcA - Nucleus Accumbens

VTA - Ventral Tegmental Area

neurotransmitters and reward

Glu

Op

DA

GABA

GABA

Op

Neurotransmitters and Reward

Nucleus

Accumbens

Frontal Cortex

ACG

(+)

(-)

(+)

Saliency

(-)

(-)

Ventral Tegmental Area

Op – opiate pathway

Glu – glutamate pathway

GABA – GABA pathway

DA – dopamine pathway

(-)

pre frontal cortex functions
Pre-frontal Cortex Functions
  • Limit or reducing consumptive behavior
  • Inhibition of the amygdala (fear) and the stress response
  • Shifting attention
  • Balancing several inputs at once (multi-tasking)
  • Focusing short term memory for processing to long term
orbitofrontal cortex function
Orbitofrontal Cortex Function
  • Processing emotional behavior
  • Interpretation of emotional behavior
  • Information for planning
  • Linking an actions with a negative consequence
anterior cingulate gyrus functions
Anterior Cingulate Gyrus Functions
  • Emotion and awareness
  • Mediates conflict between emotional desires and intellectual values
    • “wanting” - and - “likely harm or wrongness”
  • Intellect control of emotion
motivation
Motivation
  • Important process that drives human behavior
    • Appetitive - desire or “appetite”; commonly associated with “hedonic” or the seeking of pleasure
    • Aversive – avoidance of pain or unpleasant experiences
motivation21
Motivation
  • Pleasure and pain are the principle aspects of motivational processes;
    • Arise in the Limbic areas of the brain
    • Meaning or interpretation provided by the PFC, OFC, ACG.
  • Two states of stress -Hypothalamus
    • Eustress (positive)
    • Distress (negative)
addiction neurobiology22
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/or

    • a diminished ability of the prefrontal cortex and anterior cingulate gyrus to properly formulate responses to emotional information delivered by the limbic and hypothalamic areas.
slide23

Intellect

Intellect

Emotional

Emotional

addiction current hypothesis
Addiction Current hypothesis
  • Pathology of addiction involves

inherent (genetic)

and/or

drug-induced

alterations 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.

review
Review
  • Definition of abuse, dependance, and addiction.
  • Brain pathways that mediate and govern behaviors.
  • Neurobiology of reward and its interpretation
  • Activation 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.