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Description
Memory for the temporal order of items or events in a sequence declines with normal aging and may be one of the earliest cognitive markers of neurodegenerative disorders such as Parkinson's disease (PD). The frontal lobes are thought to be critical for temporal order memory. Therefore, it is hypothesized that temporal order memory deficits exhibited in PD stem from frontal-striatal dysfunction associated with the disorders. While temporal order memory deficits have been exhibited in PD patients, little is known about the effects of interference on temporal order memory in those with the disease. The present study examined the effects of temporal interference on temporal order memory in individuals diagnosed with PD and demographically similar healthy older adults. On each sample phase, participants were presented with a random sequence of circles appearing one at a time in eight different locations on a computer screen and were instructed to remember the sequence in which the circles appeared. On the choice phase, two circles were presented simultaneously in their respective locations and participants were asked which circle appeared earliest in the prior sequence. The task involved manipulations of the temporal lag (0, 2, 4, and 6), defined as the number of circles occurring in the sample phase sequence between the two choice phase circles. Shorter temporal lags (e.g. 0 and 2 lags) were hypothesized to result in greater interference compared to longer lags (e.g. 4 and 6 lags). The results demonstrated that on high interference trials (0 and 2 lags), no group differences were found. However, older adults significantly outperformed individuals with PD on low interference trials (4 and 6 lags). Although differences were found between the groups, both improved as interference decreased. The findings indicate that temporal order memory is impaired in individuals with PD compared to older adults and that temporal order memory is affected by varying levels of interference in both groups of participants. Since both groups improved with lowered interference, the findings may have important implications for behavioral interventions that minimize temporal interference to improve memory function in older adults and, to a lesser extent, in individuals with PD.
