Sample response

Neurotransmitters play an important role in human behaviour.  Neurotransmitters are released from the terminal buttons of a neuron and then travel across a synapse where they attach to receptor sites on the postsynaptic membrane. Some neurotransmitters are seen as more excitatory - that is, they make the target neuron more likely to "fire" an action potential. A neurotransmitter can sometimes have either an excitatory or an inhibitory effect, depending on the receptor sites that it binds to.

One example of how a neurotransmitter binds to excitatory receptor sites is the role of acetylcholine in the formation of spatial memories. Antonova demonstrated that blocking ACh receptors affects our ability to create spatial memories.  She carried out a double-blind experiment with twenty men. The participants were randomly allocated to one of two conditions. They were injected with either scopolamine (an ACh antagonist) or a placebo.

The participants were then put into an fMRI where they were scanned while playing a virtual reality game. The goal was for the participants to navigate around a field to find a pole. After they learned where the pole was located, the screen would go blank for 30 seconds.  When the field reappeared, the participant was at a new starting point. The men would have to use their spatial memory to determine how to get to the pole.

The researchers found that when participants were injected with scopolamine, they demonstrated a significant reduction in the activation of the hippocampus compared to when they received a placebo. This indicates that in the placebo condition, AcH was binding to excitatory synapses that led to the creation of spatial memories, whereas in the Scopalomine condition, these receptor sites were blocked so ACh could not bind to the site and cause the action potential to fire.

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