Define Semantic memory
Let’s look more closely at the case of H. M., or as we now know him, Henry Gustav Molaison (see ). In 1953, the hippocampus, the amygdala, and some neighboring structures in the cortex on each side of Henry’s brain were removed because of severe epilepsy. As you’ve already learned, when he woke up after the operation, Henry exhibited severe anterograde amnesia: he could remember recent events for only about 15-30 seconds, which resulted in problems such as the following:
- He was unable to learn his way around the hospital after the operation.
- Soon after reading something, he could remember neither what he had read nor that he had read it.
- After moving to a new house, it took him eight years to learn how to get from one room to another.
- He never learned to find his way back to the house from a distance of more than two blocks.
- When he was moved into a nursing home in 1980, he never learned where he lived or who cared for him.
Henry’s memory problems involved mainly the ability to form new explicit memories, especially those involving life events. On the other hand, he seemed to have little or no trouble forming new implicit memories, especially those involving new behaviors and skills. For example, Henry learned to read words written backwards, to solve particular puzzles, and to walk to the room in which he was tested each year at MIT. Nevertheless, he never remembered that he knew how to perform these tasks because he had not formed explicit memories of them. For example, when walking to the testing room, he would state that he did not know where he was going or why he was walking in that direction (Hilts, 1995).