(DVD) is a persistent increase in synaptic connections caused by recent patterns of activity. These patterns of synaptic activity cause a prolonged increase in signal transmission between two neurons. The opposite of VPD is long-term depression, which causes a prolonged decrease in synaptic strength, one of several phenomena underlying synaptic plasticity, the ability of chemical synapses to change their strength. Since memory is thought to be encoded by a change in the strength of synaptic connections, long-term potentiation (LTP) is widely regarded as one of the main cellular mechanisms underlying learning and memory. Long-term potentiation (LTP) was discovered in the hippocampus of the rabbit Terje Lemo in 1966 and has remained a popular object of research ever since.