Sometimes, however, they claimed they could remember vivid scenes. They often said that memories were like a dream, more generalised experiences that did not have particular time and space points of reference. Perhaps in this highly artificial situation, the electrical stimulation was locally kick-starting the medial temporal lobe, without recruiting other requisite but more remote regions. Penfield's pioneering studies involved 500 patients who were undergoing neurosurgery.

As there are no sensors for pain within the brain itself, it is possible for the brain to be exposed in conscious patients without them feeling any pain. With the patients' consent, Penfield used the operations, which had to be performed in any case, to investigate the storage of memory in the brain. As the surface of the brain was exposed and the patients were fully conscious, he was able to stimulate different parts of the cortex electrically while documenting the reports of the patients as to what they were experiencing.Most of the time, perhaps not surprisingly, the patients did not report any new experience. For other animals, perhaps memory of an event is more generic, less anchored by unique time and place co-ordinates. A cat may not remember a specific spring day when it caught a mouse in the back garden just after drinking a saucer of milk and before climbing a tree, but it may have a more general recall of catching mice.However, in the mid-l900s, Wilder Penfield, a surgeon in Canada, contrived a situation where human memories can seem to be more like this generic type of memory. Damage to the area where facts have been personalised into events by time and space referencing would not actually destroy memory itself but rather would uncouple facts from the contexts in which they occurred. Specific events would be reduced to mere generic facts in that they would have no unique features in time and space.If the prefrontal cortex is needed for this type of time-space allocation of events, it follows that this type of memory for events would be particularly pronounced in humans, with our disproportionately large prefrontal cortex.

Once the pink elephant is displaced from the jungle hideaway in which you saw him one night last summer, he is reduced to the generic thought that elephants can be pink. Hence the medial thalamus can be seen as important in the consolidation of memories.Another type of memory malfunction is source amnesia, a loss of when and where an event occurred. If there is no space or time reference, events cannot be differentiated, and there is no personal involvement of the individual with what has happened. As events are unique and personal, while facts are generic and free of time and space frames of reference, it follows that source amnesia will primarily affect memory for events rather than for facts.

Whereas memory for both facts and events appears to rely on the integrity of the hippocampus and the medial temporal lobe, memory for events seems affected by damage to a third area, the prefrontal cortex.Damage to the medial thalamus, which has connections with the prefrontal cortex, can also result in errors in the time-space allocation of memories. Memories can pop up out of context, irrelevant to the speech and ideas of that moment. The prefrontal cortex presumably has some influence not just in the way events are recalled but also in how they are associated with related events.Facts, as in semantic memory, need differ only from the events of episodic memory in that they are removed from a specific moment and place. Unlike the examples of amnesia we have looked at so far, the problem was temporary. Despite this, there is a permanent inability for memory of events that occurred while the amnesia lasted, presumably while the medial thalamus was malfunctioning.