Representational similarity patterns predict subsequent source memory but are disrupted by task switching in temporo-occipital regions
Carolin Sievers1, Fraser W. Smith1, Janak Saada1, Louis Renoult1; 1University of East Anglia, UK
The present experiment used functional magnetic resonance imaging to investigate representational similarity patterns across repeated stimulus encoding in either a same task or a task switching condition. Twenty adult participants performed categorization tasks during the encoding phase, followed by an unexpected recognition-source memory task. During encoding, each stimulus was presented four times and participants either performed the same task repeatedly or a different task at each of the four encoding presentations. We hypothesized subsequent correct source memory judgements to be associated with higher neural pattern similarity between encoding episodes compared to incorrect source memory judgements. Furthermore, we predicted pattern similarity to be lowered when different tasks were performed. In line with these hypotheses, neural similarity was found to be higher for correct compared to incorrect subsequent source memory judgements. Moreover, pattern similarity in frontal regions, including the superior frontal gyrus predicted source memory performance irrespective of encoding task condition, while temporo-occipital regions only predicted source memory outcome when the same task was performed repeatedly. These results suggest that frontal regions represent source information regardless of associated encoding operations, consistent with their implications in task switching. Pattern similarity in posterior regions did not discriminate between subsequent correct and incorrect source judgements when stimuli were incidentally encoded in different tasks highlighting the need for consistent encoding and task-related reactivation in order to predict subsequent source memory.
Topic Area: LONG-TERM MEMORY: Episodic