What term describes a long-term decrease in synaptic strength?

The correct term for a long-term decrease in synaptic strength is Long-Term Depression (LTD). This phenomenon is significant in neurobiology, particularly in the context of synaptic plasticity, which is the ability of synapses to strengthen or weaken over time in response to increases or decreases in their activity. LTD typically results from certain patterns of activity at synapses that lead to a persistent reduction in synaptic efficacy.

Long-Term Depression is crucial for various cognitive processes, including learning and memory, as it helps to refine neural circuits and establish more efficient pathways by weakening connections that may not be utilized as often. This process contrasts with Long-Term Potentiation (LTP), which is the strengthening of synaptic connections.

The other options refer to different concepts or shorter duration changes in synaptic strength. Synaptic Erosion isn't a recognized term in the context of synaptic changes, and Short-Term Depression describes a temporary decrease in synaptic strength, which does not persist over the long term like LTD does. Hence, Long-Term Depression is the appropriate term when discussing a sustained reduction in synaptic strength.