Neuroplasticity (variously referred to as brain plasticity or cortical plasticity) refers to the changes that occur in the organization of the brain as a result of experience. A surprising consequence of brain plasticity is that the location of a given function can move to another location in the brain as a consequence of training or brain damage. One of my colleagues has shown the types of rearrangement that can be achieved relatively rapidly in the brain due to trauma, including amputation. One of the people who has studied the "phantom limb" phenomenon in humans (as a result of amputations) is V.S. Ramachandran at UCSD and the Salk Institute.
When a cellular neurobiologist refers to plasticity, however, he or she is often referring the changes at a single synapse. For instance, some signaling molecules cause the number of vesicles of transmitter that are released in response to a single action potential to increase or decrease. When all that extra neurotransmitter reach the postsynaptic neuron, they activate a greater number of ligand-gated ion channels and, therefore, there is a bigger response.
So, plasticity on the micro and macro levels both play a part in learning, memory, and adaptation within the nervous system.
A Faraday cage is an enclosure formed by conducting material, or, usually, by a mesh of such material. Such an enclosure nullifies external electrical fields. They are named after a physicist, Michael Faraday, who first describe them.
When an external electrical impulse impacts the Faraday cage, the charges within the cage material redistribute and cancel out the effects of the field inside. They also shield the interior of from electromagnetic radiation -- if the holes are small enough.
Faraday cages are used in the laboratory to shield equipment from stray electrical impulses. This is especially important in doing electrophysiological experiments (a technique in neuroscience), where the voltages and currents measured are very small, and the electromagnetic field from even computers contributes significant electrical noise.
More common examples are places like elevators and stairwells, where cellular phones tend to lose signal, because of the phone being surrounded by a metal cage, formed by either the elevator itself or the metal beams in the walls. Another commonly used Faraday cage is a microwave oven -- the shielding of the oven prevents the microwaves from escaping into the surrounding area.
