Amnesia also limits imagination
If patients suffer from amnesia as a result of an injured hippocampus, not only is their memory severely impaired, they are also unable to imagine realistic everyday scenes. Researchers working with Eleanor Maguire from University College London had found that their test subjects failed primarily because they failed to put together individual aspects of the fictional scene into a meaningful whole and to paint them vividly in front of their inner eyes.
The researchers had asked ill subjects to come up with suitable scenarios for everyday topics and to report on them. They then used a point system to measure how sophisticated the imagined world was and how much the individual could empathize with it.
The scientists conclude from their results that an essential task of the hippocampus in a he althy brain is to provide spatial cohesion in which individual images and experiences – whether remembered or imagined – can be embedded. Accordingly, Maguire and her colleagues explain hippocampal amnesia by the loss of precisely these abilities. The patients could no longer reconstruct complete sequences of their past from the individual experiences stored elsewhere in the brain - they lose their episodic memory.
Research in recent years has shown that the hippocampus is responsible for aspects of spatial orientation in addition to a whole range of other functions. For a long time, however, its contribution to memory formation was limited to the transfer of information from short-term to long-term memory. The fact that he is also involved in the retrieval of this permanently stored information calls this position into question, but clarifies the previously open question as to why his failure leads to amnesia.