Retrograde and Anterograde Amnesia

Retrograde and Anterograde Amnesia happened to me at the same time when I (supposedly) fell down from my bicycle last Sunday. The names sound really fearsome but for me the period involved is really small (5-6 seconds of Retrograde and ~30 minutes of Anterograde).

In retrograde amnesia, the subject (that's me) is unable to recall events that occurred before the development of amnesia. The reason in my case was a mild head injury and shock. And I forgot the event of falling down altogether. According to Ribot's Law, there is a time-gradient in retrograde amnesia. Recent memories are more likely to be lost than the more remote memories. So, I lost the last 5-6 seconds before the head injure completely although I was able to remember the events before that gradually within a short time. For the first few hours it seemed that the time (2-3 hours) was a dream. But as people informed me the events that happened in that period, I gradually recollected some of the events (except for the 5 seconds period).

In anterograde amnesia, the subject loses the ability to create memory. There are two types of memory in human brain. One is short-term memory which is used for immediate processing and one is long-term memory which is used as a permanent storage for later retrieval. In anterograde amnesia, the process of writing from short term memory to long term memory is affected. I don't remember what happened during the 30 minute period after the injury. People said, I handed over my bi-cycle to Omair, came back to my room walking, asked my friend for Dettol, called my girlfriend once, took the bicycle keys back from Omair etc. But I don't remember these things at all. In most cases (including mine) subjects loss declarative memory (recollection of facts) and not procedural memory (how to do things).

References

1. http://en.wikipedia.org/wiki/Retrograde_amnesia
2. http://en.wikipedia.org/wiki/Ribot%27s_Law
3. http://en.wikipedia.org/wiki/Anterograde_amnesia