Delay Dependent Effects on Neural Activity in Event-related fMRI during a Parametric Working Memory Task

Abstract:
Abstract: Many standard working memory tasks are not suited for event related designs because the processes of encoding, storage and retrieval overlap. Therefore we constructed a delayed match-to-sample-task which can be used for event-related fMRI. We used a 2x3 factorial design varying delay and load. Here we report results concerning delay specific neural acitivity of a pilot study. Analysis was performed by means of SPM99b. For the high load condition compared to the lower load conditions we found delay dependent neural activity in the structures relevant for the phonological loop, i.e. left and right supramarginal gyrus, left insula and left inferior frontal cortex. Activity was also observed in the anterior cingulate, right and left superior frontal and the medial superior frontal region. Additionally, activity in the right anterior temporal lobe covaried with the length of the delay period. This area is involved in the object representation of remembered items. We conclude that the described neural structures constitute a neural circuit which is relevant when objects have to be maintained for a longer period of time.