Lecture 9 - Neural Mechanisms of Learning and Memory Flashcards
What is synaptic plasticity?
Synaptic plasticity is the ability of synapses to strengthen or weaken over time in response to increases or decreases in activity, forming the basis for learning and memory
What is plasticity in a simple neural chain?
When a presynaptic neuron synapses (connects) directly onto a postsynaptic neuron, and repeated activation strengthens the response of the postsynaptic cell
What is plasticity in a superordinate circuit?
When a third neuron modulates the connection between a presynaptic sensory neuron (e.g., sensory) and a postsynaptic neuron (e.g., motor), either enhancing or suppressing the communication
What 3 changes can occur in neurons after learning?
1) Increased neurotransmitter release
2) Increased postsynaptic responsiveness
3) A combination of both (pre and postsynaptic changes)
What is habituation?
Habituation is a form of non-associative learning where repeated exposure to a benign stimulus leads to decreased behavioural response
What example illustrates habituation in Aplysia?
Repeated touching the siphon of Aplysia causes a reduced gill withdrawal response over time
What happens at the neuronal level during short-term habituation in Aplysia?
There’s a decrease in glutamate release from the sensory neuron, leading to reduced motor neuron activation
What structural change occurs in long-term habituation
Fewer synaptic connections between sensory and motor neurons (e.g., reduced from 90 to 30 connections in Aplysia)
What is the term for the synaptic change underlying habituation? What does it mean?
Homosynaptic depression: A pathway-specific reduction in synaptic strength at the trained synapse
How does short-term and long-term habituation differ?
- Short-term habituation: Reduced neurotransmitter release (glutamate)
- Long-term habituation: Structural reduction in synaptic connections
Is the motor neuron damaged in habituation?
No, the motor neuron remains functional but is no longer activated due to decreased input from the sensory neuron
What is sensitisation?
Sensitisation is a form of non-associative learning where an intensified response occurs after a strong or unpleasant stimulus due to heightened arousal
How is sensitisation demonstrated in Aplysia?
A mild tail shock increases the gill response to a subsequent siphon touch
What neurotransmitter is released during sensitisation and what is its effect?
Serotonin is released during sensitisation, increasing calcium in the sensory neuron, leading to more glutamate release and a stronger motor response
What is spike broadening?
Spike broadening is a prolonged action potential in the sensory neuron caused by serotonin, allowing more calcium influx and greater neurotransmitter release
How does sensitisation affect the whole system?
Sensitization creates a system-wide increase in responsiveness (general arousal), not just at the site of stimulation
What happens in long-term sensitisation?
In long-term sensitisation, new synaptic connections are formed between the sensory and motor neurons, increasing the strength of response over time
How is long-term sensitisation different from long-term habituation?
- Sensitisation: Growth of synapses
- Habituation: Loss of synapses
What cellular process supports short-term learning?
Changes in neurotransmitter release support short-term learning (e.g., decreased in habituation, increased in sensitisation)
What supports long-term learning at the cellular level?
Structural changes in synaptic connections: either growth (sensitisation) or reduction (habituation)
What technique is used to measure neurotransmitter release at synapses?
Quantal analysis
What did Eric Kandal discover about learning and memory?
Eric Kandal discovered that learning involved changes in synaptic strength, specifically through synaptic plasticity, as shown in studies with Aplysia
According to Eric Kandel, what causes habituation in Aplysia?
Homosynaptic depression: A decrease in neurotransmitter release at a specific synapse due to repeated stimulation
What is the basic process by which neurons communicate with each other?
- Neurons communicate via synaptic transmission
- This is where a presynaptic neuron releases neurotransmitters (e.g., glutamate) into the synaptic cleft
- The neurotransmitters bind to receptors on the postsynaptic neuron
- This causes it to depolarise and potentially fire an action potential
