Date Approved


Embargo Period


Document Type


Degree Name

PhD Doctor of Philosophy




College of Science & Mathematics


Libon, David J.

Committee Member 1

Nagele, Robert

Committee Member 2

Baliga, Ganesh


Memory; Mild cognitive impairment


Cognition and Perception | Psychology


Background: Fuster (2008) observed that temporal organization modulate executive control mechanisms by generating (1) attention towards test parameters (working memory), (2) the capacity to execute a task (preparatory set), and (3) the ability to inhibit external/internal stimuli (inhibitory control). We investigated Fuster's model (2008) using response latency on visual and verbal working memory tasks in patients with suspected mild cognitive impairment (MCI). Methods: An iPad-version of the Backward Digit Span Test (BDT) and Symbolic Working Memory Test (SWM) were used. Outcome variables were latency for each correct serial position and volumetric subcortical regions using NeuroQuant® software. Results: Mixed-model analyses found within-group differences on both BDT and SWM. Moreover, group by latency interaction for each position as a function of total time was observed on the BDT. Correlations between total time for correct trials and neuropsychological measures of processing speed and visuospatial operations were significant for the BDT. Finally, MRI was not associated with any serial order position. Conclusions: Consistent with Fuster's model, BDT latencies illustrate a tripartite neurocognitive construct. The allocation of latency for correct trials differed between the MCI and non-MCI groups to suggest distinct underlying neurocognitive constructs. Together, latency on verbal WM tasks like the BDT may be a cognitive marker for emergent illness.