Addiction Day: Neurobio of addiction
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Addiction is a
chronic progressive behavioral disorder with central feature being COMPULSIVE DRUG USE despite ADVERSE consequences
Addiction pathophys involves
brain reward system and ALTERATIONS that reward enhancing drugs effect on this system
Ventral Tegmental Area is akin to; what is it the source for?
a BARN; location of DA CELL BODIES that will project to NA (reward center) and PFC (executive control)
Nucleus accumebens is; what is its function?
"reward center" of the brain; integrates VTA (DA) and PFC (glutamate) inputs to determine motivational output: 1. incentive (appetitive) 2. reward (consummatory)
PFC will
exert EXECUTIVE control over midbrain structures: judgment, cost-benefit analysis
In PFC, what does DLPFC do?
STATISTICAL ANALYSIS, prioritizing, top down control center (if inactive, can’t assess risks of behavior like drunk driving!!)
In PFC, what does VMPFC do?
assigns EMOTIONAL VALIENCE (drinking feels good, less stress, more social if you don’t have this area)
In PFC, what does OFC do?
impulse prevention (I can beat up that football player, grope that model, drive my care under influence if area lacking)
In PFC, what does ACC do?
VIGILANCE (without this, could scann environment for next beer, vodka, bar)
In PFC, decision making is; limbic drive is
glutamate-driven; dopamine driven (D3 receptors) for static levels of DA neuronal activity to allow homeostatic wakefulness, alertness; and D2 receptors pulsatile for motivation, drive, reward expectations
Drugs acting on brain reward pathways; chronic use leads to
act in brain limbic reward pathways to either 1. enhance DA release 2. enhance DA effects in NA or related structures 3. produce similar effects to DA; reward circuitry changes that promote more future drug use (increased limbic function, decreased PFC function)
Stages of limbic drive:
• VTA (barn) supplies DA to NA • NA receives input and can choose which “horse” to use • Amygdala assigns pleasure, threat, or emotional value to linkage between 1 and 2 (should you do this thing?)
For cortical control of rewards system, steps:
• OFC should suppress doing dangerous or addictive things • VMPFC should attach POSITIVE FEELINGS to NOT doing dangerous things • DLPFC should CALCULATE the true risk/benefit ratio of doing ADDICTIVE things (think of these guys as wranglers in cortex trying to control horses and manage barn)
What can happen with increasing addiction (aka losing the wranglers)?
• Frontal lobe structures less active (less glutamate) and maybe atrophy • Maladaptive addictive (more DA) behaviors increase