Synaptic plasticity is the ability of synapses, the junctions between neurons that allow them to communicate, to strengthen or weaken over time in response to increases or decreases in their activity. It is the ability of the brain to change and adapt to new information. Synaptic plasticity is one of the important neurochemical foundations of learning and memory, as memories are represented by interconnected neural circuits in the brain. Synaptic plasticity controls how effectively two neurons communicate with each other, and the strength of communication between two synapses can change in both the short term and long term. There are several underlying mechanisms that cooperate to achieve synaptic plasticity, including changes in the quantity of neurotransmitters released into a synapse and changes in how effectively cells respond to those neurotransmitters. Synaptic plasticity is critical for understanding the neural basis of many aspects of normal and pathological brain function, and impairments in synaptic plasticity mechanisms contribute to several prominent neuropsychiatric disorders.