Neurotransmitters

neurotransmitter

a type of neurochemical that carries information between neurons, acting within the synaptic gap and can be inhibitory or excitatory; they are affected by agonists and antagonists

acetylcholine (ACh)

a neurotransmitter and natural agonist for hippocampal activity; involved in memory, arousal and excitatory neurotransmission

excitatory synapse

increases the likelihood of the postsynaptic neuron firing an action potential

inhibitory synapse

decreases the likelihood of a postsynaptic neuron firing an action potential

agonist

occupy receptor sites and activate them; neurotransmitters are technically agonists

antagonist

occupy receptor sites but do not activate them, instead they block receptor activation by agonists

fMRI

brain imaging technique that shows real-time activity via blood flow

Antonova (2011) - Aim

to investigate if scopolamine (an antagonist to acetylcholine) would affect hippocampal activity in the creation of spatial memories

Antonova - Method

20 healthy males with mean age of 28; true laboratory experiment, repeated measures, volunteered sampling

Antonova - Procedure

• Injected with either scopolamine or a placebo 70-90 minutes before experimental task

• Put into fMRI where they were scanned while playing the “Arena Task”, a complex virtual reality game to test the creation of spatial memories

• Participants learn a location of a pole and then the screen goes blank for 30 seconds. They were told to actively rehearse how to get to he pole

• From a new starting point, participants have to locate the pole

• Brain activity measured for 6 trials

• Asked to return 3-4 weeks later and redid the test but with the opposite treatment

Antonova - Results 

• When participants were injected with Scopolamine, they showed a significant reduction in the activation of the hippocampus compared to when they were given the placebo

Antonova Conclusion:

Antonova concluded that acetylcholine could play a key role in the encoding of spatial memories in humans.

Antonova - Link

• Supports the role of the neurotransmitter acetylcholine (ACh), in spatial memory, particularly through its action in the hippocampus

• Demonstrate the importance of this neurotransmission because interfering with normal acetylcholine signaling was associated with altered hippocampal activity during spatial-memory processing

• As the change in hippocampal activation occurred while participants were completing a spatial-memory task, the findings connect acetylcholine activity with the neural processes involved in spatial memory

• This suggests that acetylcholine contributes to communication within neural networks involved in the encoding and processing of spatial information

Antonva - Link to agonist

• Demonstrate the effect of the agonist acetylcholine on spatial memory, by showing what occurs when its normal action is blocked by scopolamine

• Used scopolamine to block these receptors, preventing acetylcholine from binding to and activating normally

• Normal action of the agonist acetylcholine was blocked, participants showed reduced hippocampal activity during the spatial-memory task

• Demonstrates the normal action of the agonist, binding to and activating its receptors, contributing to hippocampal activity involved in spatial memory

Antonova - Link to Antagonist

• Demonstrates the effect of an antagonist on behaviour by showing how scopolamine, an acetylcholine antagonist, influences spatial memory

• Findings suggest that disrupting acetylcholine activity interferes with the hippocampal processes involved in spatial memory