Notes on Learning and Memory

Brain Regions Involved in Learning and Memory

  • Long-term Memory
    • Types:
    • Declarative (Explicit)
      • Subtypes:
      • Episodic
      • Semantic
    • Nondeclarative (Implicit)
      • Subtypes:
      • Skill learning (Procedural)
      • Priming
      • Classical Conditioning
      • Nonassociative Learning
      • Spatial Memory
  • Associated Brain Regions:
    • Declarative Memory:
    • Hippocampus
    • Medial Temporal Lobe
    • Neocortex
    • Nondeclarative Memory:
    • Striatum
    • Motor Cortex
    • Cerebellum
    • Amygdala
    • Short-term Memory:
    • Prefrontal Cortex

Understanding Memory

  • Learning:
    • Process of acquiring new information or behaviors through practice or experience.
  • Memory:
    • Ability to store, retain, and retrieve encoded information.
    • Complex system that adjusts based on input and experience, not just stimulus-response reflex.

Physical Changes Required for Memory Storage

  • Neuroplasticity:
    • Neurons adapt and remodel in response to experiences.
    • Synaptic changes measured physiologically, can be presynaptic, postsynaptic, or both.
  • Types of Changes:
    • Increased neurotransmitter release.
    • Changes in receptor interactions and inactivation rates.
    • Structural changes at synapses (formation/loss of synapses).

Neuronal Remodeling in Memory

  • Environmental Factors:
    • Enriched environments lead to significant brain enhancements compared to impoverished environments.
    • Results in thicker cortex, enhanced cholinergic activity, and more dendritic branches.
  • Aplysia Model:
    • Used to study simple learning (nonassociative learning).
    • Habituation, dishabituation, and sensitization observed through synaptic changes.
    • Habituation leads to reduced neurotransmitter release, showing learned responses.

Learning in Mammals: Cerebellum's Role

  • Eye-blink Reflex:
    • Associated with classical conditioning; requires cerebellar circuits.
  • Synaptic plasticity:
    • Functional changes (potentiation/depression) occur based on activity and learning.

Memory and Synaptic Plasticity in Hippocampal Circuits

  • Hebb’s Theory:
    • "Fire together, wire together" to strengthen synaptic connections.
    • Long-term potentiation (LTP) observed in response to repeated stimulation enhances memory.
  • Molecular Mechanisms:
    • Receptors:
    • AMPA and NMDA receptors play crucial roles in synaptic response and memory formation.
    • Protein Kinases:
    • Activate processes that lead to long-term memory storage, including CREB activation affecting gene transcription.

Age-Related Changes in Learning and Memory

  • Healthy Aging:
    • Impairments in conscious recollection, working memory, and creation of new memories.
  • Pathological Aging:
    • Alzheimer’s disease leading to severe cognitive decline and loss of cholinergic pathways.
  • Cholinesterase Inhibitors & Nootropics:
    • Enhance cognitive function and memory, especially beneficial as aging progresses.

Artificial Activation of Engram

  • Optogenetics:
    • Mice genetically modified to activate specific neurons in learning contexts.
    • Reactivation of these neurons captures the content of learned fear responses even in neutral contexts, indicating the specificity of memory traces.

Forgetting Mechanisms

  • Types of Forgetting:
    • Erasure/storage failure, retrieval failure, and theoretical disuse.
    • Active processes such as synaptic changes may facilitate forgetting to prioritize survival and adaptability.