Poster A65, Saturday, March 24, 1:30–3:30 pm, Exhibit Hall C
Temporal Contiguity Deficits in Medial Temporal Lobe Amnesia
Joseph Di Lascio1, Daniela Palombo1, Per Sederberg2, Marc Howard1, Mieke Verfaellie1; 1Boston University, 2Ohio State University
According to the Temporal Context Model (TCM), episodic memory depends on reinstatement of a prior experienced context, which is thought to rely on the medial temporal lobes (MTL; Howard et al., 2006). This hypothesis has proven difficult to directly test under common behavioral experimental protocols, such as free recall, due to near floor performance by patients with MTL lesions. To circumvent this issue, we tested MTL amnesic patients and matched healthy controls on a modified free recall protocol with serial repetition of presented items. This technique was successful in boosting free recall in amnesia, thereby allowing examination of statistical properties such as probability of first recall and lag conditional response probability (lag CRP), which refers to response probability as a function of temporal lag. Because items studied closely together in a study list share a similar temporal context, they also tend to be recalled in proximity to each other. As expected, amnesic patients had fewer recalls as well as disrupted temporal contiguity effects as measured using the lag CRP. We quantify the differences in recall dynamics between patients and controls using a version of the TCM (Sederberg, et al., 2008) with a parameterization that allows for more direct measurement of temporal contiguity effects. A model in which parameters affecting overall recall, primacy, and the recovery of temporal context are allowed to vary between groups best describes the effects of amnesia. These findings provide novel evidence that the MTL is necessary for recovering a prior episodic context, in accordance with TCM.
Topic Area: LONG-TERM MEMORY: Episodic