THE ROLE OF NEUROTRANSMITTERS AND NEUROHORMONES IN LEARNING & MEMORY
Different neurotransmitters tend to have different roles in learning and memory. Researchers have yet to entirely isolate or explain every effect of each one. Generally, they all enable communication of the information being learned and initiate or contribute to important structural changes at the synapse that help ensure the memory is durable and long-lasting when formed
Study design dot point:
•The role of neurotransmitters and neurohormones in the neural basis of memory and learning (including the role of glutamate in synaptic plasticity and the role of adrenaline in the consolidation of emotionally arousing experiences).
Study design dot point:
•The role of neurotransmitters and neurohormones in the neural basis of memory and learning (including the role of glutamate in synaptic plasticity and the role of adrenaline in the consolidation of emotionally arousing experiences).
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THE ROLE OF GLUTAMATE IN SYNAPTIC PLASTICITY
Glutamate is the main excitatory neurotransmitter in the brain for learning.
The role of glutamate in synaptic plasticity can be demonstrated using Skinner’s study of rats in operant conditioning (something we will be studying). As the hungry rat has learnt that it will receive a tasty food pellet each time it presses a lever, it is likely to press the lever repeatedly. In the rat’s brain, the learnt behaviour (pressing the lever) to get the reward (food) causes the release of glutamate from the presynaptic neurons into the synaptic gap between the presynaptic and postsynaptic neurons.
The glutamate acts on two types of glutamate receptors in the rat’s postsynaptic neuron: the AMPA receptor, which activates the postsynaptic neuron, and the NMDA receptor, which produces long-lasting modifications to the synapse. The repeated glutamate release also stimulates the release of dopamine, which in turn prompts growth in the rat’s postsynaptic neuron of an increased number of dendritic spines.
Dendritic spines are outgrowths from the dendrites in the synaptic gap. These make the postsynaptic neuron more sensitive to future ring by neighbouring presynaptic neurons. Altogether, this process has the effect of increasing the efficiency of the neural pathways for the learnt behaviour.
The role of glutamate in synaptic plasticity can be demonstrated using Skinner’s study of rats in operant conditioning (something we will be studying). As the hungry rat has learnt that it will receive a tasty food pellet each time it presses a lever, it is likely to press the lever repeatedly. In the rat’s brain, the learnt behaviour (pressing the lever) to get the reward (food) causes the release of glutamate from the presynaptic neurons into the synaptic gap between the presynaptic and postsynaptic neurons.
The glutamate acts on two types of glutamate receptors in the rat’s postsynaptic neuron: the AMPA receptor, which activates the postsynaptic neuron, and the NMDA receptor, which produces long-lasting modifications to the synapse. The repeated glutamate release also stimulates the release of dopamine, which in turn prompts growth in the rat’s postsynaptic neuron of an increased number of dendritic spines.
Dendritic spines are outgrowths from the dendrites in the synaptic gap. These make the postsynaptic neuron more sensitive to future ring by neighbouring presynaptic neurons. Altogether, this process has the effect of increasing the efficiency of the neural pathways for the learnt behaviour.
THE ROLE OF ADRENALINE IN CONSOLIDATION OF EMOTIONALLY AROUSING EXPERIENCES
Low amounts of adrenaline, secreted within 30 seconds of learning, have a role in the consolidation of memory. Emotions that produce adrenaline therefore have an effect on the strength of a newly forming memory. The memories that are formed under circumstances of emotional arousal are often vital to survival. For example, memory of an aggressive dog helps us to show caution about aggressive dogs in the future. Similarly, animals learn to fear predators when they are emotionally aroused through the release of adrenaline. However, too much adrenaline at the time of memory formation can be counterproductive to the consolidation of the memory.
FLASHBULB MEMORIES
Flashbulb memories are detailed, vivid and long-lasting memories of important or emotional events in our lives. Cahill and his colleagues (1994) investigated the adrenalin hormone that is released in the fight- flight-freeze response and found evidence to support the notion that flashbulb memories are indeed affected by adrenalin. The researchers found that participants who were shown an emotionally arousing image of a boy in an accident had a more enhanced memory of the event than the participants who were shown images that were not emotionally arousing