Lecture Notes: Understanding Memory, Learning, and Related Neurological Aspects

1. Definitions

• Learning: Acquiring new information
• Memory: Storing and retrieving information
• Engram: Physical basis of a memory in the brain

2. Case Studies: Amnesia (H.M., K.C., N.A.)

• H.M.

  • Removal of hippocampus and medial temporal lobe structures
  • Unable to form new declarative memories, retained implicit (procedural) memories
  • Demonstrates different memory systems related to brain regions

• K.C.

  • Extensive hippocampal damage
  • Severe episodic amnesia; retained semantic knowledge
  • Highlights the hippocampus's role in episodic memory

• N.A.

  • Damage to diencephalic structures
  • Anterograde amnesia and some retrograde amnesia
  • Emphasizes hippocampus significance for declarative memories

3. Types of Amnesia

• Anterograde Amnesia: Inability to form new memories; often due to medial temporal lobe damage
• Retrograde Amnesia: Inability to remember past events; linked to cortical damage

4. Memory Types

• Declarative Memory: Conscious recall (facts/events)
  • Episodic: Personal experiences
  • Semantic: General knowledge
• Nondeclarative Memory: Unconscious memory (skills, habits)
  • Skill Learning: Repetition-based tasks
  • Priming: Faster responses due to prior exposure

5. Brain Regions in Memory

• Formation: Hippocampus, entorhinal cortex, prefrontal cortex
• Storage: Temporal lobes, frontal lobes (semantic knowledge stored in neocortex)
• Retrieval: Prefrontal cortex, hippocampus

6. Animal Models of Declarative Memory

• Difficulty due to lack of verbal reporting
• Tests: Object recognition (semantic-like), Morris water maze (spatial/episodic memory)

7. Conditioning

• Classical Conditioning: Association between stimuli
  • Unconditioned Stimulus/Response: Natural reaction
  • Conditioned Stimulus/Response: Learned reaction
• Operant Conditioning: Action-consequence association
  • Reinforcement: Increases behavior
  • Punishment: Decreases behavior
  • Positive/Negative: Adding/removing a stimulus

8. Memory Processing

• Encoding: Transforming sensory inputs
• Consolidation: Stabilizing memory traces
• Retrieval: Accessing stored information

9. Memory Stability and Reconsolidation

• Retrieved memories are unstable (labile) and can be modified
• Studies show that disruption during reconsolidation can alter memory strength

10. Neuronal and Synaptic Plasticity

• Neurogenesis: New neurons
• Synaptogenesis: New synapses
• Synaptic Plasticity: Changes in synaptic strength
  • LTP: Long-term potentiation (increased strength)
  • LTD: Long-term depression (decreased strength)

11. Long-term Potentiation (LTP)

• Early Phase LTP
  • Short-term, no protein synthesis
  • Involves CaMKII, PKA, PKC
• Late Phase LTP
  • Long-term, requires protein synthesis
  • Involves CREB, new proteins

12. Drugs and Addiction

• Addiction: Compulsive drug seeking despite negative consequences
• Progression: Occasional use → addiction → abstinence → relapse
• Triggers: Stress, drug exposure, environmental cues

13. Dopaminergic Pathways and Reward

• Mesolimbic Pathway: Central to reward experience
• VTA and Nucleus Accumbens (NAc): Key areas for dopamine release

14. Homeostasis and Behavioral Responses

• Homeostasis: Stable internal environment
• Negative Feedback: Mechanism to reverse changes
• Behavioral vs Physiological Responses: Actions vs internal changes

These notes summarize key concepts and studies related to memory, learning, amnesia, conditioning, addiction, and homeostasis, providing a broad overview of how different brain regions and processes contribute to these phenomena.