Lecture on Neurotransmission and Acetylcholine

Neurotransmitters

• Brain chemicals that communicate information throughout the body.
• Relay signals and continue electrical impulses through neurons in the brain.
• Types of Neurotransmitters:
  • Inhibitory: Calm and restore the balance of chemicals in the brain.
  • Excitatory: Stimulate the brain.

Neurotransmission

• Process:
  • An electrical impulse travels down the neuron's axon.
  • Upon reaching the axonal terminal, a neurotransmitter is released crossing the synaptic gap to the next neuron.
  • Neurotransmitters stored in terminal buttons fit into receptor sites on the post-synaptic cell.
  • Some neurotransmitters are reabsorbed via reuptake or broken down (degradation).
• Molecules Influencing Neurotransmitters:
  • Agonist Molecules: Increase neurotransmitter effect by mimicking neurotransmitters and binding to receptor sites.
  • Antagonist Molecules: Reduce neurotransmitter effect by blocking receptor sites.

Memory and Acetylcholine

• Acetylcholine is found in both the peripheral and central nervous systems and is crucial for attention, learning, and memory.
• Scopolamine blocks acetylcholine receptors.
• Acetylcholine separates encoding and retrieval of memories, aiding in memory consolidation in the hippocampus.

Study 1: Antonova et al. (2011)

• Aim: Investigate the role of acetylcholine in encoding cognitive maps using scopolamine.
• Sample: 20 healthy male adults, mean age 28.
• Procedure:
  • Double-blind, participants injected with scopolamine or placebo.
  • Use of fMRI to observe participants playing a virtual reality maze game.
  • Repeated measures design with participants returning for second test.
  • Brain activity measured over six trials.
• Findings: Scopolamine reduced hippocampus activation, indicating acetylcholine's role in spatial memory encoding.
• Conclusion: Acetylcholine is significant in spatial memory consolidation.
• Evaluation:
  • fMRI shows biological relation of scopolamine to memory formation.
  • Findings indicate acetylcholine's role in memory processes.
  • Limitations due to artificial setting, reductionist approach, and stress experienced by participants.

Study 2: Rogers and Kesner (2003)

• Aim: Determine the role of acetylcholine in spatial memory formation and retrieval.
• Procedure:
  • 30 rats acclimated to a maze, injected with scopolamine or saline.
  • Injections given directly into the hippocampus.
  • Errors assessed during trials to measure encoding and retrieval of memory.
• Findings: Scopolamine group took longer and made more errors, affecting learning but not retrieval of established memories.
• Conclusions: Acetylcholine important for spatial memory consolidation.
• Evaluation:
  • Use of rats limits generalizability to humans.
  • Important implications for Alzheimer's treatment.
  • Study's narrow focus limits understanding of acetylcholine's role in other memory forms.