Do You Know Where You Are? Place Memory

Non-human animal research has demonstrated the importance of a structure known as the hippocampus in processing a map of the animal’s environment stored in memory. Specific brain cells (neurons) in this structure, often referred to as place cells, fire when the animal is in a specific location. However, the contribution of these cells in human spatial memory has been uncertain.

A recent paper looked at the role of human hippocampal neurons in place learning using brain imaging techniques in patients with a rare condition known as Transient Global Amnesia.

Patients with Transient Global Amnesia have nearly total lack of memory of past events except for things of high importance like personal identity and are unable to form new memories. These episodes usually last about 6 to 10 hours and otherwise these patients are alert and seem normal. Relatively small areas of the part of the hippocampus thought to be important for place memory become temporarily disrupted (lesion) and can be detected with brain imaging techniques 1 to 3 days after the onset of a patient’s loss of memory.

These patients were tested in a place memory task while they experienced memory loss. Later the associated brain lesion was imaged. Patients with Transient Global Amnesia episode were significantly impaired in place memory tasks compared with normal subjects.

The paper, titled “Focal Lesions of Human Hippocampal CA1 Neurons in Transient Global Amnesia Impair Place Memory” and published June 11, 2010 in Science, demonstrates that at least some of the large amount of research done on the hippocampus’ role in place memory in non-human animals is applicable to humans.