Long-term depression

Definition

Long-term depression (LTD) is a process that results in a long-lasting decrease in synaptic strength following specific patterns of activity. This mechanism is crucial for various forms of synaptic plasticity, allowing neurons to weaken synaptic connections in response to low-frequency stimulation, which is essential for adjusting neuronal circuits and refining motor learning.

5 Must Know Facts For Your Next Test

1. LTD is often induced by low-frequency stimulation, typically less than 1 Hz, which leads to a decrease in the postsynaptic neuron's response to neurotransmitters.
2. This mechanism helps in motor learning by allowing the cerebellum to fine-tune movements through the weakening of unnecessary or redundant synaptic connections.
3. LTD can involve complex intracellular signaling pathways, often mediated by calcium influx and subsequent activation of protein phosphatases that remove phosphate groups from proteins involved in synaptic transmission.
4. In addition to motor learning, LTD has been implicated in various forms of behavioral adaptation and memory processes, demonstrating its role in shaping how we learn from experience.
5. Disruptions in the mechanisms underlying LTD may be linked to various neurological disorders, highlighting its importance in maintaining normal cognitive functions.

Review Questions

• How does long-term depression contribute to the refinement of motor skills in the cerebellum?
  • Long-term depression plays a vital role in motor skill refinement within the cerebellum by weakening synaptic connections that are not essential for a given motor task. When low-frequency stimulation occurs, LTD reduces the strength of these unnecessary connections, allowing for a more efficient neural circuitry that promotes accurate and coordinated movements. This selective weakening aids the cerebellum in adapting motor outputs based on experience and practice.
• Discuss the relationship between long-term depression and spike-timing-dependent plasticity in shaping synaptic connections.
  • Long-term depression is closely related to spike-timing-dependent plasticity (STDP), where the timing of spikes from pre- and postsynaptic neurons determines whether the synapse is strengthened or weakened. In STDP, if presynaptic spikes occur shortly before postsynaptic spikes, long-term potentiation occurs; however, if the order is reversed, LTD can result. This timing-dependent mechanism allows for fine-tuning of synaptic strengths based on activity patterns, contributing to learning and memory processes.
• Evaluate the implications of impaired long-term depression mechanisms on cognitive function and potential neurological disorders.
  • Impairments in long-term depression can lead to significant disruptions in cognitive functions such as learning and memory. Since LTD helps modulate synaptic strength and refine neuronal circuits, its dysfunction may contribute to neurological disorders like Alzheimer’s disease or autism spectrum disorders. The inability to properly weaken unneeded synapses can result in information overload or maladaptive behaviors, indicating that understanding LTD is crucial for developing therapeutic strategies aimed at restoring normal cognitive functions.

Related terms

Long-term potentiation: A long-lasting increase in synaptic strength resulting from high-frequency stimulation of neurons, which complements LTD by enhancing the connections that are important for memory and learning.

Synaptic plasticity: The ability of synapses to strengthen or weaken over time, in response to increases or decreases in their activity, playing a key role in learning and memory.

Calcium signaling: The process through which calcium ions act as vital second messengers in neurons, influencing various cellular functions including the induction of LTD.