This dissertation explored the cognitive processes and neural substrates underlying the simulation and construction of novel mental representations, by manipulating factors influencing construction ability. Across four experiments, subjects constructed novel events by relating multiple cue words to a single context word in order to make a coherent representation. Experiments 1 and 2 tested whether memory deficits related to age and amnesia due to medial temporal lobe lesions affect event construction performance. Both older adults and patients with amnesia showed deficits in event construction, with poorer performance at increasing mnemonic loads. Moreover, older adults’ construction ability was associated with memory performance, suggesting that associative encoding processes are crucial for simulation tasks.
Experiments 3a and 3b examined whether semantic congruency between items and context influences event construction and subsequent memory. In Experiment 3a, younger adults constructed imagined events with from cue words that were typically or atypically related to the context word. Atypical events were less coherent, and were rated as poorer in quality and more difficult to construct. Experiment 3b also showed an advantage for typical trials on a cued recall test, suggesting the congruency of an imagined event with prior knowledge has a strong influence on its subsequent retrieval.
Experiment 4 used fMRI to determine the neural correlates of imagining. Constructing imagined events activated the hippocampus, medial prefrontal regions, and default mode network regions in comparison to a baseline condition. Moreover, clusters of activation in the anterior hippocampus were positively correlated with construction task performance across all task conditions, whereas activity in the medial frontal poles varied with individual differences in the typicality of imagined events. Posterior hippocampus was associated with the novelty of imagined events, but did not correlate strongly with the anterior hippocampus or task performance.
Taken together, these studies suggest that these regions are crucial when constructing a novel imagined event, regardless of the nature of the stimuli. In particular, the hippocampus may be necessary to bind items during the construction process, especially as representations become increasingly complex.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/65736 |
| Date | 22 August 2014 |
| Creators | Romero, Kristoffer Yves |
| Contributors | Moscovitch, Morris |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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