Synaptic plasticity

Summary

This video delves into synaptic plasticity, the brain's ability to strengthen or weaken connections between neurons based on experiences. Highlighting Donald Hebb's postulate, it explains that synchronized neuronal firing enhances connections, while asynchronous firing diminishes them. The processes of long-term potentiation (LTP) and long-term depression (LTD) are examined, emphasizing the crucial role of glutamate receptors and calcium influx in these mechanisms. With a focus on timing, the video illustrates how specific firing patterns influence learning and memory, ultimately shaping thoughts and behaviors.

Takeaways

• 🧠 Synaptic plasticity refers to the brain's ability to change and adapt through physical alterations in neuron connections.
• 📖 Donald Hebb's postulate states that 'cells that fire together, wire together,' meaning simultaneous neuron firing strengthens their connections.
• 🔗 The strength of a synaptic connection is influenced by action potentials that reach the neuron end, leading to neurotransmitter release.
• ⬆️ Long-Term Potentiation (LTP) is the process of strengthening synapses due to the coincident firing of pre- and post-synaptic neurons.
• ⬇️ Long-Term Depression (LTD) refers to the weakening of synapses resulting from non-coincident firing.
• ⏳ The critical window for changes in synaptic strength is around 20 milliseconds, affecting LTP and LTD outcomes.
• ⚡ Spike Timing Dependent Plasticity describes how the timing of neuron firing influences synaptic changes.
• 🌟 AMPA and NMDA receptors play crucial roles in synaptic strength; AMPA allows ion flow for depolarization, while NMDA enables calcium influx for LTP.
• 🔑 A large calcium influx activates calcium-dependent kinases, increasing AMPA receptor availability and promoting LTP.
• ❌ A small calcium influx activates protein phosphatases, decreasing AMPA receptors and leading to LTD.
• 🔄 Changes in synaptic connections through LTP and LTD are fundamental to the brain's capacity for learning and behavioral adaptation.

Q & A

What is synaptic plasticity?

Synaptic plasticity is the process by which the connections between neurons in the brain change and adapt based on experiences, affecting behavior and thought.

Who first proposed the concept of synaptic plasticity?

The concept was first notably proposed by Canadian psychologist Donald Hebb in his book 'The Organization of Behavior.'

What is Hebb's postulate?

Hebb's postulate states that neurons that fire together strengthen their connections, while those that fire apart weaken their connections. This is often summarized as 'cells that fire together wire together.'

What are the two main types of synaptic changes described?

The two main types of synaptic changes are long-term potentiation (LTP), which strengthens synapses, and long-term depression (LTD), which weakens them.

What role do neurotransmitters play in synaptic plasticity?

Neurotransmitters are released at synapses and bind to receptors on the postsynaptic neuron, influencing the strength of the synaptic connection based on the timing of neuronal firing.

What is the significance of the 20-millisecond timing window in synaptic plasticity?

The 20-millisecond timing window is critical for determining whether LTP or LTD occurs, depending on whether the presynaptic neuron fires before or after the postsynaptic neuron.

How do AMPA and NMDA receptors contribute to synaptic plasticity?

AMPA receptors mediate the initial depolarization of the postsynaptic neuron, while NMDA receptors allow calcium ions to flow into the neuron, which is essential for triggering LTP or LTD.

What happens during long-term potentiation (LTP)?

During LTP, a large calcium influx into the postsynaptic neuron leads to the activation of kinases that increase the number of AMPA receptors, enhancing the synaptic response.

What is the outcome of long-term depression (LTD)?

In LTD, a small calcium influx does not activate kinases sufficiently; instead, it activates phosphatases that increase the endocytosis of AMPA receptors, decreasing synaptic strength.

Can synaptic changes occur at individual dendrites?

Yes, synaptic changes are localized to individual dendrites, allowing for specific modulation of synaptic strength and individualized learning processes.