| dc.description.abstract | This thesis examines how the context in which an item is studied affects the phenomenological experience of the rememberer. Previous research has extensively studied how the match between study and test context affect subsequent memory performance; however, little work has attempted to examine how visual context information provided at study affects later recollection when that context information is not re-presented at retrieval. In particular, the quality of the memory retrieved may be enhanced when highly meaningful visual context information is provided at study. In each of seven experiments in the current thesis, participants studied words presented with context information high or low in meaningful content, and on a later recognition memory test made a Remember, Know, or New response to the words presented alone. Experiment 1 showed that participants had better overall memory, specifically recollection, for words studied with pictures of intact as opposed to scrambled faces. In Experiment 2, these results were replicated and recollection was shown to be higher for words studied with versus without pictures of faces. Experiment 3 showed that participants had higher memory performance, and recollection in particular, for words studied with upright compared to inverted faces. In Experiment 4, participants showed equivalent memory for words studied with novel or familiar faces. These results suggest that recollection benefits when visual context information high in meaningful content accompanies study words, and that this benefit is not related to the novelty of the context.
To further test the claim that participants engage in elaborative processes at study to bind item and context information, improving subsequent recollection, the subsequent set of experiments examined how normal, healthy aging affects participants’ ability to use context information provided at study to benefit subsequent recollection. Older adults have been shown to experience deficits both in memory for context and in recollection, suggesting that they might fail to use context effectively to increase recollection, in contrast to younger adults. Experiment 5 found that younger, but not older, adults showed higher recollection for words studied with faces as compared to rectangles. To determine the type of cognitive processing required to obtain recollection benefits, and to examine whether instruction could alleviate age-related deficits, in Experiment 6, the type of processing engaged during the encoding of context-word pairs was manipulated. Younger and older adults studied words presented with a picture of a face under a surface feature or binding feature instruction condition. Both age groups showed higher recollection in the binding than surface instruction condition. Results suggest that older adults do not spontaneously engage in the processes required to boost recollection when visual context information is provided at study, although instructional manipulation during encoding lessens this deficit. This is in line with the Associative Deficit Hypothesis (Naveh-Benjamin, 2000), suggesting that older adults’ recollection deficit involves a specific difficulty in binding item and context information.
The final experiment used functional Magnetic Resonance Imaging (fMRI) to examine the neural correlates of recollection, specifically testing the hypothesis that sensory-specific reactivation of context information occurs during item recollection. In Experiment 7, brain activation for Remember responses given to words studied with and without meaningful context information was compared. Behaviourally, 8 of the 14 participants showed a higher proportion of Remember responses to words studied with faces than scrambled faces, and 6 did not. Whole brain analysis showed that, for only those participants who showed higher memory performance for words studied with faces, activation in the fusiform gyrus and hippocampus was higher, and a region-of-interest analysis showed increased activation in the functionally-defined FFA (identified in a localizer task), for Remember responses given to words studied with faces compared to scrambled faces. A regression analysis additionally showed that activation in the fusiform gyrus increased as the relative recollection benefit for words studied with meaningful (face) compared to non-meaningful (scrambled face) context information increased across participants. Results suggest that encoding context can influence the pattern of recollection responses on a recognition task and that sensory-specific reactivation is related to behavioural performance. The findings of these experiments suggest that participants can use context information high in meaningful content at study to improve subsequent recollection and I suggest that this involves the use of elaborative processes at encoding that integrates item and meaningful contexts. Such recollection benefits can also be observed in older adults when they are provided experimental instructions to bind item and context at encoding. In addition, the brain regions used to process context information are reactivated at retrieval and, importantly, that this neural pattern determines whether a boost in recollection, from the encoding manipulation, is observed. Participants can thus use context information provided at study to boost subsequent recollection, and I suggest that this involves cognitive processes that bind item and context information at encoding and the reactivation of sensory-specific brain regions at retrieval. | en |
