Abstract
Previous research has shown that various types of relational processing, e.g. “binding”, are critically involved in visual short-term memory (STM). Luck & Vogel (1997) showed that when features are bound into objects, more features can be remembered. Jiang, Olson, and Chun (2000) showed that when items are bound into a spatial configuration, more items can be remembered. What brain areas are necessary for binding in visual STM? One possibility is that the medial temporal lobe is involved. The relational processing theory proposes that the medial temporal lobes are critically involved in binding together different elements of a memory trace in long-term memory (Eichenbaum, 1999; Winocur & Kinsbourne, 1978). Whether or not this region is involved in mnemonic binding over short delay intervals is not known. Although prior studies showed that amnesic patients have intact visual STM for simple stimuli they did not examine amnesic performance on STM tasks that required binding.
Here we test medial temporal lobe amnesics and age-matched controls on a STM task for singular or bound information. Subjects were required to remember either three sequentially presented objects, locations, or object-location conjunctions. After a delay of either 1 s or 8 s, recognition performance was assessed. Memory capacity and A prime were computed. Preliminary results show that amnesic patients have intact object STM and location STM but impaired memory for object-location conjunctions. These findings suggest that (1) the medial temporal lobes are not exclusively involved in long-term memory because memory was impaired at short delay intervals; and (2) that different types of visual STM rely on different processing areas, depending on task demands.