Memory for spatio-temporal contextual details during the retrieval of naturalistic episodes

Abstract

Episodic memory entails the storage of events together with their spatio-temporal context and retrieval comprises the subjective experience of a link between the person who remembers and the episode itself. We used an encoding procedure with mobile-phones to generate experimentally-controlled episodes in the real world: object-images were sent to the participants' phone, with encoding durations up to 3 weeks. In other groups of participants, the same objects were encoded during the exploration of a virtual town (45 min) or using a standard laboratory paradigm, with pairs of object/place-images presented in a sequence of unrelated trials (15 min). At retrieval, we tested subjective memory for the objects (remember/familiar) and memory for the context (place and time). We found that accurate and confident context-memory increased the likelihood of “remember” responses, in all encoding contexts. We also tested the participants' ability to judge the temporal-order of the encoded episodes. Using a model of temporal similarity, we demonstrate scale-invariant properties of order-retrieval, but also highlight the contribution of non-chronological factors. We conclude that the mechanisms governing episodic memory retrieval can operate across a wide range of spatio-temporal contexts and that the multi-dimensional nature of the episodic traces contributes to the subjective experience of retrieval.

The influence of the precuneus on the hippocampus determines the subjective quality of memory during the retrieval of naturalistic episodes

“…Accordingly, the results of the logistic analysis con rmed the contribution of con dent source-memory to Rem responses during episode retrieval (cf. our previous results using the same encoding, retrieval and analysis procedures in a purely behavioral study 43 ). The signal plots show the parameters estimates at the peak-voxel and for all the episode-retrieval conditions.…”

“…The latter indicates that source memory contributed to the subjective report about the memory quality during the episode retrieval (Figure. 2; see also 43 ). Most important, the results of the analyses of effective connectivity supported our main prediction that subjective quality of retrieval -which is a characterising aspect of episodic memoryentailed a modulation of the connectivity between the precuneus and the hippocampus, as well as the connectivity between HC and the vmPFC (Figure .…”

“…We operationalised the "subjective sense of episodic recollection" considering the trials when the participants correctly recognized an object that they had seen in the environment and subjectively reported that they could remember place/time of the event (i.e., Rem-responses). Moreover, we sought to con rm that Rem-responses were indeed associated with memory for contextual information by including a series of 2-forced-choice discriminations and con dence judgments about the place and the time of encoding (Figure . 1B, see also 43 ). Analyses of effective connectivity using Dynamic Causal Modeling 44 (DCM) tested speci c hypotheses about the modulatory in uence of episodic retrieval (i.e.…”

“…After con rming at the behavioral level that memory for the place/time-context contributed to the subjective quality of retrieval (see Figure . 2 for details; and our previous work 43 for analogous results), we tested for brain areas that activated during the episode-retrieval phase of the trials (see Figure . 1B).…”

“…Following the procedure that we employed in a previous behavioral study using the same paradigm 43 , the analysis of the behavioral data sought to con rm that source memory contributes to the subjective memory status of the encoded objects: namely that correct and con dent place/time discrimination is associated with an increase of the likelihood to recognize old/seen objects as "Remembered", as opposed to just "Familiar".…”