Long-term depression

Definition

Long-term depression (LTD) is a lasting decrease in the strength of synaptic transmission, occurring when synapses are repeatedly stimulated at a low frequency. This process is crucial for synaptic plasticity, allowing for the weakening of certain synaptic connections while strengthening others, which plays a vital role in learning, memory, and neural circuit refinement.

5 Must Know Facts For Your Next Test

1. LTD is often induced by low-frequency stimulation of presynaptic neurons, leading to a prolonged decrease in the postsynaptic neuron's response to neurotransmitters.
2. The mechanisms underlying LTD typically involve a reduction in the number of AMPA receptors at the postsynaptic membrane, decreasing synaptic strength.
3. LTD is thought to be essential for various forms of learning and memory, helping to refine and adjust neural circuits based on experience.
4. Studies have shown that LTD can occur in various brain regions, including the cerebellum and hippocampus, which are critical for motor control and memory formation, respectively.
5. Impairments in LTD have been linked to various neurological disorders, suggesting its importance in maintaining normal cognitive function.

Review Questions

• How does long-term depression contribute to the overall process of synaptic plasticity?
  • Long-term depression is a fundamental aspect of synaptic plasticity, which encompasses both strengthening and weakening of synapses. While long-term potentiation (LTP) enhances synaptic connections through increased receptor activity, LTD serves to decrease synaptic strength and eliminate less important connections. This balance allows for more efficient neural circuits, ultimately facilitating learning and memory by ensuring that only relevant information is retained while irrelevant connections are pruned.
• Discuss the role of calcium signaling in the induction of long-term depression at synapses.
  • Calcium signaling plays a crucial role in the induction of long-term depression. When low-frequency stimulation occurs, calcium ions enter the postsynaptic neuron in smaller amounts compared to high-frequency stimulation that induces LTP. This moderate increase activates specific signaling pathways that lead to the internalization of AMPA receptors from the synaptic membrane. As a result, the decreased presence of these receptors leads to reduced synaptic strength, characteristic of LTD.
• Evaluate the implications of impaired long-term depression on cognitive functions and its potential link to neurological disorders.
  • Impaired long-term depression can have significant implications for cognitive functions such as learning and memory. Since LTD helps fine-tune neural circuits by removing less relevant connections, disruptions in this process may lead to information overload or difficulty in adapting to new experiences. This lack of adaptability has been associated with various neurological disorders like Alzheimer's disease and autism spectrum disorders, where abnormal synaptic plasticity contributes to cognitive deficits and behavioral issues. Understanding these connections opens avenues for therapeutic interventions targeting LTD mechanisms.

Related terms

Long-term potentiation: Long-term potentiation (LTP) is the long-lasting increase in synaptic strength that occurs following high-frequency stimulation of a synapse, complementing the effects of LTD.

Synaptic plasticity: Synaptic plasticity refers to the ability of synapses to strengthen or weaken over time, in response to increases or decreases in their activity, forming the basis for learning and memory.

Calcium signaling: Calcium signaling involves the influx of calcium ions into neurons, which plays a key role in activating intracellular pathways that contribute to processes like LTD and LTP.