The Mechanism Of Temporal Order Memory Retrieval In Macaques

Humans recall the past by replaying fragments of events temporally.Here,we demonstrate a similar effect in macaques.We collected six rhesus monkeys and seven human subjects’ data with temporal-order judgement(TOJ)task.The reaction time data is suggestive of a non-linear,time-compressed forward memory replay mechanism in the macaque.In contrast with humans,such compression of replay is however not sophisticated enough to allow them to skip over irrelevant information by compressing the encoded video globally.The LATER model fitting results also reveal that the monkeys detect event contextual boundaries and such detection facilitates recall by an increased rate of information accumulation.However,the neuronal correlates of memory recall and temporal context in the macaques remains understudied.To elucidate these issues,we recorded multi-unit activities simultaneously with 32 independently movable microelectrodes in the precuneus area on two monkeys,while they performed a temporal order judgement(TOJ)task between two frames extracted from videos they had watched and encoded.Ensemble analysis results reviewed that precuneus activity during learning episodes would be influenced by temporal context.Besides,we also found that the firing activity during encoding is related to their subsequent memory judgement.The decoding analysis results show that the firings for the initial phase of TOJ are more significantly correlated with the encoding phase as compared to the latter phase of TOJ,revealing some fine-tuned temporal dynamics during TOJ which is consistent with our behavioral RT findings.Altogether,these findings help delineate the neuronal signature for temporal-order judgement and temporal-context for dynamic cinematic information in the macaque parietal cortex.All in all,from the results of behavioral and neurophysiology,we found that macaque tend to using a time-compressed,forward replay-like strategy to recall the temporal order information.Besides,the neuronal correlates of memory recall and temporal context was revealed in precuneus of macaques.