Long-Term Depression (LTD)
Long-term depression (LTD) occurs in the central nervous system (the brain and the spinal cord) and may be responsible for some learning and memory deficits along with some brain illnesses. LTD is a biological process in the brain and is different from the concept of depression in a therapeutic/clinical sense (which is long term pervasive sadness).
It occurs when there is a decrease in the strength of a Synaptic Transmission. A synapse is the whole junction between neurons and are where communication information is transmitted from neuron to neuron. Learning encourages synapses to grow, expand, and link up to one another in a process known as synaptic plasticity. If stimulated synapses can grow in humans until death. But if a synaptic area decreases in strength it may eventually progress into LTD.