Memory Recorders are Alphas who are able to retrieve and store specific memories from a person, then play them back to the person or to others.
Memory is the encoding, storage, and retrieval of information. In the human brain, a large portion of these functions lie in the hippocampus. Cortisol is one of the neurochemical agents in the hippocampus, activated by stress. It works in conjunction with adrenaline to produce "flash bulb memories." These memories are much more vivid than regular memories, using all five senses, creating a sort of surround-sound memory.
Memory Record alphas are able, through touch, to record just such a memory from another person. One likely method is that their body is able to exactly sense cortisol levels and neuroelectrical signals associated with a memory, and then feed the information back to another neural system, amplified. This fools the brain into thinking that it is experiencing the memory in the present.
Unfortunately, this ability also short-circuits the alpha's ability to form his/her own memories. Studies have shown that an overload of cortisol can effect short and long-term memory. Being in regular contact with high doses of cortisol fries the alpha's hippocampus, giving them symptoms similar to Alzheimer's.