The medial temporal lobe and visual working memory: comparisons across tasks, delays, and visual similarity.

Whether the hippocampus and medial temporal lobe (MTL) play any important role in visual working memory is a relatively new and controversial research question. The primary goal of this study was to assess working memory for faces over very short delays in patients with MTL damage. Patients and matched controls were required to remember one face that was parametrically morphed to be more or less similar to a probe face, over either a 1- or an 8-sec delay. Memory was assessed using both forced choice and old-new recognition tasks. The results show that MTL damage impairs both speed and accuracy of visual working memory across tasks. We speculate that the hippocampus is generally necessary for memory encoding.