Book T of C
Chap T of C
This is the 2007 version. Click here for the 2017 chapter 06 table of contents.
Retrograde amnesia is the loss of memories that formed before a trauma such as brain injury. A person found wandering around in the street, not knowing who he or she is, suffers from retrograde amnesia. By contrast, anterograde amnesia, H.M.'s type, prevents new memories from being formed after a trauma such as brain injury.
How is anterograde amnesia distinct from retrograde amnesia?
Think of the injury as a point in time. Loss of memories before this point is retrograde amnesia. Retro- means backward. Loss of memory for the time after an injury is called anterograde amnesia. Antero- means forward. H.M. had mostly anterograde amnesia, but he also had a bit of retrograde amnesia. The two years before his operation were blurry to him. Clive Waring had both retrograde and anterograde amnesia, because he could not remember events before or after his encephalitis.
What is evidence that retrograde amnesia involves retrieval failure, not storage failure?
Retrograde amnesia after a trauma such as a car accident is often a form of retrieval failure. We know this because memories lost in retrograde amnesia (e.g. memories for the time right before the crash) often come back. By contrast, lost memories in anterograde amnesia never come back, probably because they were never properly formed in the first place.
The following essay from a student illustrates both retrograde and anterograde amnesias triggered by a powerful hit on the football field.
My senior year in high school was looked upon at Portal High as the year for a great football season. We had a tough schedule, including the defending state champions in Class A: Johnson County High. Herschel Walker, who had just graduated, helped them to the championship. But this was another year, and we were expecting great things from our team.
The night we met Johnson County, our team was really ready emotionally. We shut out a team in our first game and that added enthusiasm for this one. When we kicked off to Johnson County to start the game, I missed a great opportunity to hit the return man because I shied away. But we held them and scored ourselves.
On the ensuing kickoff they ran to my side again. I made up my mind I was going to put a hit on the return man this time. The kickoff seemed like an instant replay of the first, except this time I hit the runner going full speed. It was Herschel's little brother Lorenzo, who weighed 185 pounds. At full speed, the impact of the hit was tremendous. I lay on the ground a couple of seconds and finally struggled up with the help of my teammates.
At that moment, I did not know what was going on. When our team got in the huddle I asked how we scored the touchdown. They asked if I was all right, and (they told me later) our quarterback held up two fingers and asked how many I saw. I do not remember any of that. Only after the half was over did I begin to remember how we had scored and the tackle I made on the kickoff. After that is a complete blank. While I was watching the second half, I tried to recall parts of the first half, but it was lost. To this day most of the first half after my hit is lost to my memory. [Author's files]
How did the football player's experience illustrate characteristics of the two varieties of amnesia?
The retrograde amnesia-for the memory of how the team scored-was temporary. The memory came back. The anterograde amnesia (remembering what happened for the rest of the half after the hit) did not come back. This is typical of what happens with retrograde and anterograde amnesia.
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