Neural reinstatement and the amount of information recollected

Abstract

Recent functional neuroimaging studies have attempted to understand the cognitive and neural bases of episodic memory retrieval, as well as the extent to which different retrieval judgments reflect qualitative as opposed to continuous changes in neural signals. The present study addressed this issue by investigating the reinstatement of episodic content according to the amount of information available at retrieval. Subjects encoded a series of words in the context of three distinct tasks, while a manipulation of presentation duration (4 or 8s) was also employed. A later recognition memory test was used to segregate trials according to whether or not they were accompanied by the recollection of details from encoding. Functional MRI data acquired during both the encoding and retrieval phases were used in conjunction with multi-voxel pattern-analysis (MVPA) to provide a measure of the degree to which encoding-related patterns of brain activity were later reactivated (reinstated) at the time of retrieval. Critically, the magnitude of reinstatement differed with respect to the encoding manipulation, such that reinstatement was stronger for items associated with the longer presentation duration. Together with duration-related differences in retrieval activity in left posterior parietal cortex, the results provide neural evidence for the reinstatement of different amounts of episodic information, consistent with the idea that recollection is based on a continuous neural signal.