Drug and Reward

Emphasize understanding the connections among:
- Emotions
- Motor responses
- Autonomic function initiating physical responses
Awareness of general pathways and brain structures involved in the reward system
Detailed knowledge of dopamine's role in reward mechanisms and how addictive drugs affect dopamine signaling and the plasticity of the limbic loop.

Figure 29.2: Illustrates the descending systems controlling somatic and visceral motor effectors in emotional expression.
- The ventral-medial forebrain and hypothalamus can produce motor and emotional responses without requiring motor cortex or consciousness to be involved.

Box 29A: Discusses the contributions of pyramidal and extrapyramidal pathways to facial expressions:
- Distinction between anatomical pathways for voluntary smiles (pyramidal) and emotion-related smiles (extrapyramidal).
- Evidence gathered from patients with brain lesions.
- Challenge: Spotting the difference between a genuine smile elicited by humor and a fake smile by observing the eyes.
- Inquiry into the reasons that can be discerned through eye movement and expression.

Interactive Element: Invitation to partake in a quiz from the New York Times on reading emotions through people's eyes.

Various types of emotions and their expressions discussed:
- Stereotyped responses across cultures
- The integration of sensorimotor behavior and emotions
- Utilization of emotions in social interactions and goal-directed behaviors, highlighting the brain's reward system.
Maladaptations of brain systems underlying emotion are explored, leading to:
- Mood disorders
- Drug addiction
- Cognitive disorders

Examination of early theories of emotion, particularly the James-Lange Theory:
- Example: Saying "cheese" can align mouth orientation like a smile; this bodily posture can evoke happiness.
- Proposition of the theory: The physical behavior precedes and induces the emotional experience (feeling).

Research insights on rapidly projecting faces:
- Subjects may not memorize an angry face shown briefly before an emotionless face.
- Pairing of the angry face with an unpleasant stimulus results in an unconscious emotional response, shown by increased skin conductance.

Comment on instances when people experience unexplained fear or anxiety, leading to attributions of these feelings:
- Associational Learning/Fear Conditioning: Occurs without conscious awareness of sensory stimuli, especially when focused on different tasks or with brief cues.
- These processes may operate independently from declarative memory, which is incurred by the hippocampus, through direct pathways from sensory systems to the amygdala.

Overview of reward areas such as the Nucleus Accumbens (NAC) and associated structures:
- Evidence illustrates the intricate relationships within brain reward pathways.
- Illustrative summary of key components crucial in behavior and psychological well-being.

Description of the origins of neuromodulatory systems:
- Small groups of neurons present in the brain stem core regions (examples: dopamine-containing neurons of the substantia nigra and ventral tegmental area).
- These systems modulate the responses of diffuse neurons across the cortex and other regions.
Impact of psychoactive substances on various systems:
- Serotonergic system with example drug LSD
- Dopaminergic system and its connection with drugs like cocaine and amphetamines.
- Noradrenergic system influenced by methamphetamine.

Mechanisms of Stimulants:
- They block catecholamine reuptake:
- Cocaine specifically targets dopamine (DA) reuptake.
- Amphetamine blocks norepinephrine (NE) and DA reuptake while stimulating DA release.
Visual representation is provided in a figure showcasing the action on catecholamine axon terminals.

Figure 16.17 illustrates changes in activity of dopamine neurons in VTA during stimulus-reward learning:
- Dopamine release is correlated with motivation after a cue, but not at the reward's occurrence.
- Animals with dopamine depletion can still 'like' the reward but lack motivation to seek it.
- Involvement in reward prediction: Increased DA levels indicate rewards that exceed expectations, enhancing motivation for repeating behaviors.

Popular cultural references underscore the understanding that pleasurable activities increase dopamine release. However:
- Experiment breakdown shows that dopamine signaling does not equal pleasure.
- Post-training, dopamine release occurs in response to cues rather than at reward times, reinforcing the role in reward prediction and behavior motivation.

In a situation where an individual looks forward to using a vape but finds it broken:
- Answer: Dopamine levels will decrease compared to baseline due to the expectation of vaping not being satisfied, indicating the brain's reaction to reward anticipation.

Graphical Data: Correlational studies on how natural rewards elevate dopamine levels significantly during sexual and feeding behaviors,
- Quantitative values show variations in dopamine concentrations based on activities.

Findings from Di Chiara and Imperato demonstrate that:
- Addictive drugs like amphetamines and cocaine markedly increase dopamine levels over time, indicating substantial neurophysiological impacts;
- Graphical Representation quantifying the percentage of basal release of DA over time, evidences drastic changes with substance use.

Description of the limbic loop involved in the brain's reward system, specifying:
- Nucleus accumbens serves an integral role instead of the caudate/putamen.
- Modulation of dopaminergic input is from the ventral tegmentum (VTA) rather than substantia nigra.
- Pathways are significantly affected by addictive substances, creating a shift in DA release patterns towards drugs while decreasing responses to natural stimuli.
Example of reward systems includes implanting electrodes that enable self-stimulation, correlating dopamine release with reward cues rather than with the reward itself.