Abstract
The hippocampus and dorsal striatum are both associated with temporal processing, but they are thought to play distinct roles. The hippocampus has been reported to contribute to storing temporal structure of events in memory, whereas the striatum contributes to temporal motor preparation and reward anticipation. Here, we asked whether the striatum cooperates with the hippocampus in processing the temporal context of memorized visual associations. In our task, participants were trained to implicitly form temporal expectations for one of two possible time intervals associated to specific cue‐target associations, and subsequently were scanned using ultra‐high‐field 7T functional magnetic resonance imaging. During scanning, learned temporal expectations could be violated when the pairs were presented at either the associated or not‐associated time intervals. When temporal expectations were met during testing trials, activity in left and right hippocampal subfields and right putamen decreased, compared to when temporal expectations were not met. Further, psycho‐physiological interactions showed that functional connectivity between left hippocampal subfields and caudate decreased when temporal expectations were not met. Our results indicate that the hippocampus and striatum cooperate to process implicit temporal expectation from mnemonic associations. Our findings provide further support for a hippocampal‐striatal network in temporal associative processing.
Highlights
Extensive research on episodic memory has supported the suggestion that the ability to correctly order events into a coherent and continuous sequence (Tulving, 1984; Kurby and Zacks, 2008) is crucial for various cognitive abilities and functioning of our daily life (e.g., (Vargha-Khadem et al, 1997; Bartsch et al, 2011; Baker et al, 2014))
ROI analyses: hippocampus and striatum For the functional magnetic resonance imaging (fMRI) analysis, we discarded the data of one participant with corrupted image files, leaving N=15 for further analysis
psychophysiological interactions (PPI) of the left CA1 × task onto the striatum In this analysis, we investigated whether functional connectivity between the hippocampal subfield CA1 and striatal nuclei changed with different task conditions
Summary
Extensive research on episodic memory has supported the suggestion that the ability to correctly order events into a coherent and continuous sequence (Tulving, 1984; Kurby and Zacks, 2008) is crucial for various cognitive abilities and functioning of our daily life (e.g., (Vargha-Khadem et al, 1997; Bartsch et al, 2011; Baker et al, 2014)). There is rapidly growing consensus from both animal neurophysiological and human neuroimaging research that the medial temporal lobe, including the hippocampus, is involved in representing temporal information in memory (Eichenbaum, 2013, 2014; Ranganath and Hsieh, 2016). Processing of temporal information has long been associated with activity in the dorsal striatum and other parts of the motor circuit (Matell et al, 2003; Meck et al, 2008; Mello et al, 2015). The dorsal striatum and hippocampus can show increased functional connectivity during memory encoding or retrieval in spatial associative contexts. Investigation of hippocampal-striatal interaction during temporal associative contexts has not yet been described. This was the aim of the current study
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