Biomedical subjects

Nicole K Speer

Publications and source records attributed to Nicole K Speer.

4 recordsLinked to original sources

PubMed2006

Event understanding and memory in healthy aging and dementia of the Alzheimer type.

Segmenting ongoing activity into events is important for later memory of those activities. In the experiments reported in this article, older adults' segmentation of activity into events was less consistent with group norms than younger adults' segmentation, particularly for older adults diagnosed with mild dementia of the Alzheimer type. Among older adults, poor agreement with others' event segmentation was associated with deficits in recognition memory for pictures taken from the activity and memory for the temporal order of events. Impaired semantic knowledge about events also was associated with memory deficits. The data suggest that semantic knowledge about events guides encoding, facilitating later memory. To the extent that such knowledge or the ability to use it is impaired in aging and dementia, memory suffers.

Activities of Daily Living↗

PubMed2003

Reliability of functional localization using fMRI.

Neuroimaging researchers increasingly take advantage of the known functional properties of brain regions to localize them and probe changes in their activity under different conditions. The utility of this approach depends in part on the reliability of the methods used to define these regions of interest. Two operations may affect the reliability of functionally identified regions: spatially normalizing data to a stereotactic atlas and statistically combining data across participants to form a composite region (as opposed to identifying individual regions for each participant). The effect of these two operations on reliability was evaluated for two functionally identifiable regions: the MT complex and the frontal eye fields. Spatial normalization had almost no effect on within-subject reliability, while grouping across participants negatively affected retest measures of the activation and location of regions defined on separate occasions. We conclude that, for typical sample sizes and numbers of observations per subject, functional localization is most reliable when performed for each individual using data in atlas space.

Adult↗

PubMed2003

Strategy-dependent changes in memory: effects on behavior and brain activity.

In the present study, an implicit strategy manipulation was used to explore the contribution of memory strategy to brain activation and behavioral performance. Participants were biased to use either a short-term (maintenance-focused) or long-term (retrieval-focused) memory strategy within a single memory task through manipulation of task context. In comparing directly matched trials across the different task contexts, we observed clear changes in both behavioral performance and brain activity across a network of regions located primarily within lateral and medial frontal cortex. These effects of the memory strategy manipulation suggest that when a retrieval-focused strategy is induced, mnemonic processes are preferentially engaged during the encoding period. In contrast, when a maintenance-focused strategy is induced, mnemonic processes are preferentially engaged during the delay and response periods. Taken together, the results imply that covert cognitive strategies play an important role in modulating brain activation and behavior during memory tasks.

Adolescent↗

PubMed2003

Activation of human motion processing areas during event perception.

Observers are able to segment continuous everyday activity into meaningful parts. This ability may be related to processing low-level visual cues, such as changes in motion. To address this issue, the present study combined measurement of evoked responses to event boundaries with functional identification of the extrastriate motion complex (MT+) and the frontal eye field (FEF), two regions related to motion perception and eye movements. The results provided strong evidence that MT+ is activated by event boundaries: Individuals' MT+ regions showed strong responses to event boundaries, and MT+ was collocated with a lateral posterior region that responded at event boundaries. The evidence regarding the FEF was less conclusive: The FEF showed reliable but relatively reduced responses to event boundaries, but the FEF was medial and superior to a frontal area that responded at event boundaries. These results suggest that motion cues, and possibly eye movements, may play key roles in event structure perception.

Adult↗