Neural correlates of temporal context retrieval for abstract scrambled phrases: Reducing narrative and familiarity-based strategies

Temporal context, memory for the timing of events, can be assessed using non-temporal strategies such as relative familiarity or inference from a semantic narrative. Neuroimaging studies, which have previously encouraged such strategies, find similar patterns of brain regions involved in both temporal and non-temporal context memory. The present study aims to investigate whether previous findings are driven by the use of non-temporal strategies or whether the same pattern of brain regions is identified when relative familiarity and semantic narrative strategies are discouraged. We used abstract phrases (e.g. alone me leave) created by scrambling familiar three-word phrases. The words in the phrases were less concrete than the object image stimuli used in previous studies of temporal context memory (Jenkins and Ranganath, 2010) and were presented quickly while participants read each word aloud. This differed from previous studies in which participants were encouraged to use narrative strategies during encoding (Tubridy and Davachi, 2011) and was designed to discourage use of narrative strategies. The relative familiarity of the words within each phrase was similar and likely not diagnostic of word order during encoding, in order to minimize the use of relative familiarity strategies. Neuroimaging results indicate that temporal context retrieval was associated with the hippocampus, parahippocampal cortex, ventromedial prefrontal cortex, and retrosplenial cortex, which are regions consistent with the retrieval of non-temporal context in episodic memory, suggesting that previous findings were not driven entirely by non-temporal strategies but rather that temporal memory relies on similar brain regions to non-temporal memory.