27 - Mesolimbic Reward System

Question 1

Proactive (Executive) Inibition

Answer 1

• dlPFC -> dorsal striatum -> activates indirect basal ganglia pathways to prevent movement
• Proactive inhibition is prospective and serves goal attainment (e.g., weight loss)
• dlPFC is major source of inputs to MSNs in indirect pathways to arrest movement

Question 2

Reactive Inhibition

Answer 2

• vmPFC -> projects directly to subthalamic nucleus (STN) via hyperdirect pathway
• Reactive inhibition is stimulus-driven, built up through learning/experience; is more automated, habitual (e.g., applying the brake at a red traffic light, preventing you from driving into traffic)

Question 3

Addictive Substances act on…

Answer 3

• VTA and ventral striatum
• Enhance DA release or block DA reuptake

Question 4

Drug Addiction Stages

Answer 4

• Binge/intoxication
  
  • DA for wanting
  • Opioids for liking
• Withdrawal/negative affect
  
  • D2 loss reduces sensitivity to reward = substance use escalation
  • Meanwhile, CeA/BNST (extended amygdala) drive negative emotional states associated with withdrawal, and desire to mitigate these feelings motivates for continued substance use
• Preoccupation/anticipation
  
  • Glutamate activity in PFC increases, altering how dopamine influences the cortex and reinforcing for habit-like substance seeking
  • Glutamate alters DA influence in cortex

Question 5

Habenula

Answer 5

• End of stria medullaris thalami
• INPUT:
  
  • Ventral pallidum
  • Lateral hypothalamus
• OUTPUT:
  
  • Via fasciculus retroflexus
  • SNc
  • VTA
• FUNCTION: Inhibits DA neurons, so you don’t pair behavior with reinforcement
  
  • Responds to negative stim and DISAPPOINTMENT
• May play a role in depression