Long-term depression

Definition

Long-term depression (LTD) is a form of synaptic plasticity characterized by a long-lasting decrease in the strength of synaptic transmission following certain patterns of activity. This process is crucial for the refinement of neural circuits, allowing the brain to adapt to new experiences and learn from them by weakening synapses that are less active or less important, thereby facilitating more efficient signaling among neurons.

5 Must Know Facts For Your Next Test

1. LTD typically occurs when there is low-frequency stimulation of neurons, leading to a decrease in calcium influx, which triggers molecular pathways that result in synaptic weakening.
2. This mechanism is thought to be important for processes like memory erasure and the fine-tuning of neural connections during development.
3. LTD can be induced in various brain regions, including the hippocampus and cerebellum, highlighting its role in different types of learning and motor coordination.
4. Abnormalities in LTD have been linked to several neurological disorders, such as Alzheimer's disease, where the inability to properly regulate synaptic strength can contribute to cognitive decline.
5. LTD is often considered the counterpart to long-term potentiation (LTP), as both processes work together to enhance or diminish the efficacy of synaptic connections based on experience.

Review Questions

• How does long-term depression contribute to learning and memory processes in the brain?
  • Long-term depression contributes to learning and memory by allowing the brain to adapt and reorganize neural circuits based on experiences. By weakening less active synapses, LTD helps refine connections and enhances the efficiency of important pathways. This process ensures that information relevant to learning is more readily accessible, while redundant or less useful connections are downregulated.
• Compare and contrast long-term depression and long-term potentiation in terms of their mechanisms and effects on synaptic strength.
  • Long-term depression (LTD) and long-term potentiation (LTP) are both critical forms of synaptic plasticity but have opposite effects on synaptic strength. While LTD results in a lasting decrease in synaptic efficacy due to low-frequency stimulation and reduced calcium influx, LTP involves an increase in synaptic strength through high-frequency stimulation and increased calcium signaling. Together, they help maintain balance in neuronal communication, enabling learning and adaptation.
• Evaluate the implications of dysfunctional long-term depression in neurological disorders such as Alzheimer's disease.
  • Dysfunctional long-term depression in neurological disorders like Alzheimer's disease can significantly impair cognitive functions. When LTD is not properly regulated, it may lead to excessive synaptic strengthening or a failure to weaken irrelevant connections, disrupting normal neural processing. This dysregulation can contribute to memory loss and other cognitive deficits observed in patients, highlighting the importance of LTD in maintaining healthy brain function.

Related terms

Long-term potentiation: Long-term potentiation (LTP) is another form of synaptic plasticity that involves a long-lasting increase in synaptic strength following high-frequency stimulation of a synapse.

Synaptic plasticity: Synaptic plasticity refers to the ability of synapses to strengthen or weaken over time, which is fundamental for learning and memory.

Calcium signaling: Calcium signaling is a key mechanism in both LTD and LTP, where fluctuations in intracellular calcium levels play a significant role in modulating synaptic strength.