Since we watched the video in class about the curious case of Clive Wearing, the man with no short-term memory, I have had many nightmarish reflections trying to imagine a world in which I am constantly awakening. As said in class, “This blows my dome!” The neural substrates of human episodic memory remain a mystery to neuroscientists though its study has progressed considerably. Episodic memory contains autobiographical information that includes contextual, temporal, spatial, and emotional information. When a person recollects some event in their life, they are accessing long-term episodic memory stores and engaging in what some researchers call “mental time travel.”
Mental time travel has many evolutionary benefits, and its development in the human brain has many implications for survival and success. The ability to compare the same complex spatial arrangement at different times gives a sense of continuity and familiarity. Furthermore, it allows someone to remember danger or safety since emotional information can also be a component, as well as detailed information about the environment which in earlier times could have included information like food stores or water supplies. As a nomadic species, the ability to remember many places in time gave us a survival advantage because we could move comfortably from one area to another depending on environmental conditions. Of course, times have changed, and episodic memory serves some different purposes today but many of its functions are still applicable to modern man.
` Recently, researchers at University of Pennsylvania claimed to have found a neural signature of mental time travel. “How could they possibly do this?” you may be asking yourself. The answer: epileptic patients. Patients with epileptic seizures will sometimes have 50-150 electrodes implanted in areas around their brain in order to determine the focal point of their seizures. Coincidentally, some lucky memory researchers are able to get their hands on these patients for study. They had patients memorize lists of unrelated words while simultaneously recording the electrical activity of the brain. Remarkably, upon recall, the same activation patterns occur. These researchers claim that this is evidence of mental time travel, but this is a very simple and controlled process.
When a person experiences an event, there are many active neural circuits in the brain. Incoming sensory information activates some networks, pre-existing knowledge activates others and so on. During a salient event, simultaneous activation strengthens these networks so that they will tend to fire together. These phenomena can be explained in Hebbeian terms, “Neurons that fire together, wire together.” Though the processes involving LTP are much more complicated than this, the statement generally applies as to how researchers think memory works. However, in some cases, a human no longer has the capacity for this function, like in the case of Clive Wearing.
Clive Wearing suffers from severe retrograde and anterograde amnesia. He cannot remember the past, and he has no ability to form new memories. Essentially, he is living only in the present. For Buddhists, this is quite an accomplishment, but for Clive Wearing, it’s a curse. He associates his condition with that of death. He is constantly awaking from years of sleep, and there is only darkness behind him, and only darkness ahead of him. Though I hesitate to say this, much reflection has brought me to the conclusion that Clive has “no self,” and that the self is intrinsically related to episodic memory.