PSY210 CH13PT5: Hebbian Plasticity

Summary

This video explores Hebbian plasticity, a neural process that supports learning by changing neuron connectivity. Using eye-blink classical conditioning as an example, it explains how repeated pairing of a sound (tone) with an air puff to the eye leads to a learned blink response. Initially, the tone alone is not enough to trigger the blink, but over time, the connection between auditory and motor neurons strengthens. The video sets the stage for discussing long-term potentiation (LTP), a mechanism that explains how synaptic changes solidify learning.

Takeaways

• 🔍 Hebbian plasticity is the process by which neuron connectivity changes to reflect learning, pioneered by Donald Hebb.
• 🧠 Hebb's rule is summarized as 'cells that fire together, wire together,' explaining the cellular basis of learning.
• 👁️ The example used in the video is eye-blink classical conditioning, where a 1000 Hz tone predicts an air puff to the eye.
• 🎯 Before learning, the auditory neuron (carrying sound information) has a weak synapse with the motor neuron controlling the blink.
• 👋 The somatosensory neuron, which detects the air puff near the eye, has a strong synapse with the blink motor neuron.
• 🔄 With repeated trials, the tone becomes predictive of the air puff, causing the auditory neuron to strengthen its connection with the motor neuron, triggering a blink reflexively.
• ⚡ The process of learning is mediated through synaptic changes, primarily long-term potentiation (LTP), which strengthens connections.
• 💡 Long-term potentiation is the mechanism by which neurons sustain changes, allowing learned behaviors to persist over time.
• 🔗 Initially, the auditory signal alone isn't strong enough to cause a blink, but with conditioning, the auditory neuron can trigger the blink without the air puff.
• 🔬 In the next part, the focus will be on understanding the precise changes at the synapse that allow long-term potentiation and learning.

Q & A

What is Hebbian plasticity?

Hebbian plasticity is the process by which neuronal connectivity changes in response to learning, based on the principle that 'cells that fire together, wire together.' It was pioneered by Donald Hebb and explains how synaptic connections strengthen when neurons activate together.

What is the basic principle behind Hebb's rule?

Hebb's rule suggests that the cellular basis of learning occurs when two neurons activate simultaneously, strengthening their connection. This helps to establish associations between stimuli and responses.

How is classical conditioning demonstrated in the example of eye-blink conditioning?

In eye-blink conditioning, an auditory neuron (which detects a tone) has a weak synapse with the motor neuron responsible for blinking, while the somatosensory neuron (which detects a puff of air to the eye) has a strong synapse with the motor neuron. Through repeated trials, the brain learns to associate the tone with the puff of air, eventually causing the tone alone to trigger the blink response.

Why is the connection between the auditory neuron and the motor neuron weak before conditioning?

Before conditioning, the auditory neuron, which responds to the tone, has a weak synapse with the motor neuron because hearing a sound typically does not require a blink response. This connection becomes stronger after conditioning as the brain learns to associate the tone with an air puff.

What role does the somatosensory neuron play in eye-blink conditioning?

The somatosensory neuron detects the puff of air near the eye and has a strong synapse with the motor neuron, which triggers the blink response. This ensures that the blink reflex occurs when something touches the eye, protecting it.

What is long-term potentiation (LTP), and why is it important for learning?

Long-term potentiation (LTP) is a process where synaptic connections are strengthened over time due to repeated activation. It plays a crucial role in learning by ensuring that connections between neurons become more effective, allowing learned behaviors, like the conditioned eye-blink response, to persist.

How do repeated trials contribute to the learning process in classical conditioning?

Repeated trials in classical conditioning reinforce the simultaneous activation of the auditory neuron (tone) and the somatosensory neuron (air puff), which strengthens the synapse between the auditory neuron and the motor neuron. Over time, this leads to the auditory stimulus alone being able to trigger the blink response.

What happens at the synaptic level during the learning of the tone-puff association?

At the synaptic level, the simultaneous firing of the auditory neuron (tone) and somatosensory neuron (air puff) strengthens the connection between the auditory neuron and the motor neuron responsible for blinking. This synaptic strengthening allows the auditory neuron to eventually trigger a blink without the puff.

What is the significance of the phrase 'cells that fire together, wire together' in the context of this example?

The phrase 'cells that fire together, wire together' explains how the repeated simultaneous activation of neurons (auditory and somatosensory neurons) leads to the strengthening of their connections, allowing for learned associations like the tone predicting the puff of air.

What will be discussed in the next part of the video regarding synaptic changes?

The next part of the video will focus on long-term potentiation (LTP), specifically examining the detailed synaptic mechanisms that allow for the strengthening of the connection between neurons and how these changes enable learning to be maintained over time.