Short duration synchronization of human theta rhythm during recognition memory.

Structures within the medial temporal lobe, particularly the hippocampus, have long been implicated in human episodic memory. The same structures are known to generate EEG in the theta frequency range in animals. The aim of this experiment was to investigate the time course of changes in the human theta rhythm during a word recognition memory task. In the period 125-250 ms after the visual presentation of a word, theta power increased by an average of 13% compared with the prestimulus baseline period and this increase was more than twice as great for repeated words (18%) as for new ones (8%). These results show that there are short duration changes in the human theta rhythm associated with recognition memory.