Definition:
Long-Term Depression (LTD) is a form of synaptic plasticity in the brain that leads to a long-lasting decrease in the strength of the synaptic connection between two neurons. It is considered to be the opposite of Long-Term Potentiation (LTP), which results in an increase in synaptic strength.
Key Characteristics:
- LTD is an essential process for regulating synaptic strength and maintaining proper brain function.
- It is primarily observed in excitatory synapses within the central nervous system.
- LTD is induced by prolonged, low-frequency stimulation or coincident pre- and postsynaptic activity.
- The decreased synaptic strength in LTD can last for hours, days, or even longer.
- It is involved in various physiological processes, such as learning, memory formation, and homeostatic plasticity.
Mechanisms of LTD:
LTD is commonly attributed to the internalization of neurotransmitter receptors, specifically α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, which reduces synaptic responsiveness.
This process involves the activation of intracellular signaling cascades and the modification of synaptic proteins, leading to changes in synaptic efficacy and neurotransmission.
Functional Importance:
LTD plays a crucial role in shaping neuronal circuits and synaptic connections, allowing for the refinement of information processing, synaptic scaling, and the regulation of overall synaptic strength.
It is involved in several cognitive processes, including synaptic pruning, spatial learning, motor skill development, and certain behavioral adaptations.
Furthermore, dysregulation of LTD has been implicated in neurodevelopmental and neurodegenerative disorders, highlighting its relevance in maintaining healthy brain functioning.