Abstract
An important question in neuroscience research is how best to characterize the role of the medial temporal lobes (MTLs) in memory. Numerous theories have been offered to explain peculiarities in memory performance among patients with lesions to portions of the MTL. Some have suggested, for example, that the hippocampus is critical for episodic but not semantic memory, or that it is critical for long-term but not short-term forms of memory. We have recently found evidence contrary to the latter, long-standing finding: MTL amnesics have impaired visual working memory for locations, faces, and colors in MTL amnesics (Olson et al., VSS 2005).
One explanation for that finding is that the function of some portion of the MTL, perhaps the hippocampus, is to rapidly encode high-fidelity representations. Such representations would be necessary for accurate visual working memory because details are frequently critical to the meaning of visual information. Conversely, it is generally possible to recover the salient information (conceptual meaning) encoded in verbal stimuli without recalling the precise wording that was used; verbal working memory tasks can therefore rely on more gist-like representations. We predicted that patients with MTL damage should exhibit (a) memory resolution problems; and (b) visual working memory, but not verbal working memory deficits. Results of experiments that manipulate similarity of stimulus and probe, time between stimulus and probe, and stimulus type will be discussed.