Browsing by Author "Wang, Fang"

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    Neural Correlates of Temporal Context Processing
    Wang, Fang (Virginia Tech, 2016-12-20)
    Temporal context memory is a type of episodic memory that refers to memory for the timing of events. Temporal context includes environmental cues that provide information about the time point at which an event happened. The purpose of the present studies is to investigate the brain mechanisms underlying temporal context processing by using both fMRI and ERP techniques. The fMRI study investigated whether hippocampal representations in CA1 and DG/CA3 subfields were sensitive to the flow of physical time, and if so, whether the number of events that occur during a time period influences the temporal representation of a target event. Results showed that both CA1 and DG/CA3 were sensitive to the flow of physical time, which was indicated by higher representational similarity between two pictures that occurred closer in time than those that occurred more distant in time. However, the variety of preceding events did not influence temporal representation, which was demonstrated by the lack of a significant representational similarity difference between two pictures that were interleaved with variable events as opposed to similar events. The ERP study compared the ERP correlates of temporal to spatial context. Results showed that temporal and spatial contexts had overlapping ERP effects except that the ERP effects of temporal context were more frontally distributed than spatial context. Both the fMRI and ERP studies indicate that temporal context is associated with similar neural correlates to other types of context in episodic memory.
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    Neural correlates of temporal context retrieval
    Wang, Fang (Virginia Tech, 2014-05-07)
    Temporal context memory is memory for the timing of events. People can make temporal judgments based on strategies such as assessing the relative familiarity of events or inferring temporal order from the semantic associations among events. The purpose of present study is to investigate the brain regions that support temporal context retrieval in the absence of such non-temporal strategies (i.e. pure temporal context memory). We used three word familiar phrases (triplets) as stimuli. In study phase, three words were presented quickly one after another in either familiar or scrambled order. Participants were instructed to read aloud each word and try to remember the order of the words. Then they were tested on their memory for the order of the words in each triplet. We propose that memory for the scrambled triplets reflects primarily temporal retrieval for two reasons. First, participants were prevented from using semantic strategies during encoding. Second, the relative familiarity of the words in each triplet was similar and not diagnostic of the order of the words during encoding. Neuroimaging results indicate that temporal context retrieval, memory for the order of words in scrambled triplets, was associated with the hippocampus, parahippocampal cortex, ventromedial prefrontal cortex, retrosplenial cortex, and posterior cingulate, which are consistent with the retrieval of non-temporal context in episodic memory. The results also suggest that temporal context retrieval could rely on familiarity, which was demonstrated by the higher accuracy and greater activation of PRc in familiar phrases and scrambled triplets presented in studied order in the test phase.