Retrograde amnesia

This consists of loss of memory for events that occurred at a time when brain function was unimpaired. It is therefore generally due to failure of retrieval although this is usually very selective – islands of memory in a sea of amnesia often emerge. An analogous phenomenon may be encountered in collective memory. For example particular incidents may be recalled, and reflected in various repositories, although there is loss of memory concerning the processes which connected them together and with the present.