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. / Ph. D. / Episodic memory is memory for where and when an event happened. The ability to memorize the timing of events relies on one type of episodic memory: temporal context memory. Temporal context includes environmental cues that provide information about the time point at which an event happened. The purpose of the present studies was to investigate the brain mechanisms underlying temporal context processing by using both functional magnetic resonance imaging (fMRI) and event and event-related potential (ERP) techniques. The fMRI study focused on hippocampus, one of the key brain regions process non-temporal contexts (i.e. spatial context, which refers to where an event happened), and investigated which subfields (CA1 and DG/CA3) in the hippocampus were sensitive to the flow of physical time. And the second purpose of the fMRI study was to examine whether the variety of events that occur during a time period influences the temporal representation. Results showed that both CA1 and DG/CA3 were sensitive to the flow of physical time. However, the variety of events did not influence temporal representation. Since CA1 and DG/CA3 are also critical for non-temporal context processing, these results indicate that temporal context has same neural mechanisms as non-temporal contexts. The ERP study investigated the brain activity as a whole and directly compared the ERP correlates of temporal to non-temporal context. Results showed that temporal and nontemporal contexts had overlapping ERP correlates except that the ERP effects of temporal context were more frontally brain region distributed than spatial context. Therefore, both the fMRI and ERP studies indicate that temporal context is associated with similar neural correlates to other types of context in episodic memory.

Many methodologies have been used to generate false memories, with the misinformation (MI) paradigm and the Deese-Roediger-McDermott (DRM) paradigm being the most commonly studied. The MI paradigm generates false memories based on retroactive interference across episodes, while the DRM paradigm generates false memories based on semantic similarities across stimuli. Since current research is ambiguous about whether the processes for different types of false memories are similar, the purpose of this project was to compare the neural mechanisms between MI and DRM false memories. We used a novel paradigm to limit methodological differences, while maintaining the defining characteristics of each paradigm. We made ERP predictions for false memories in both paradigms based on four current cognitive theories of false memories: fuzzy-trace theory, spreading activation/monitoring theory, global matching models, and source of activation confusion (SAC) model. We found no LPC, FN400, or N2 neural differences between the two types of false memories. This result is discussed in the context of the theories and the implications about our understanding of false memories. Our results support that there may not be mechanistic differences in false memory recollection when paradigms to produce the false memories are similar. / Ph. D. / Many methodologies have been used to generate false memories (or retrieval of an incorrect detail of an experienced event), with the misinformation (MI) paradigm and the Deese-Roediger-McDermott (DRM) paradigm being the most commonly studied. The MI paradigm generates false memories based on incorrectly described details provided by the experimenter across episodes, while the DRM paradigm generates false memories based on semantic similarities across lists of words. Since current research is ambiguous about whether the processes for different types of false memories are similar, the purpose of this project was to compare the MI and DRM false memories. We used a novel paradigm to limit differences driven by different methods, while maintaining the defining characteristics of each paradigm. The four current memory theories informed our event-related potential (time-locked electroencephalogram) predictions. The four theories are fuzzy-trace theory, spreading activation/monitoring theory, global matching models, and source of activation confusion (SAC) model. We found no late positive component (an ERP component indicating recollective processes), FN400 (an ERP component indicating familiarity processes), or N2 (an ERP component indicating conflict) differences between the two types of false memories. This result is discussed in the context of these theories and the implications about our understanding of false memories. Our results support that there may not be differences in false memory recollection when paradigms to produce the false memories are similar.