Stimulation of Cingulo-opercular Alertness Network

Score on a 4-item subscale of the 17-item Dementia Cognitive Fluctuation Scale (DCFS), developed to address limitations in prior scales and has good test-retest and inter-rater reliability; this subscale highly discriminates between dementia with Lewy bodies (DLB) and other dementia groups. The DCFS is a subjective report of cognitive fluctuation, the spontaneous change in cognitive ability which is a core diagnostic feature of DLB. Total subscale scores range from 4 to 20, with higher scores indicating greater cognitive fluctuations. A decrease in score between Baseline and Post-Testing indicates an improvement in cognitive fluctuation.

Time frame: Baseline and Post-Testing (3-4 weeks)

Population: Data is reported for participants who completed both baseline and week 3/4 measures.

The n-back test is a working memory task where a participant identify a stimulus that matches the stimulus experienced n steps back. Participants performed a 2-back test, in which they were asked to remember and press a button when presented with a stimulus that appeared two steps before the current one (e.g. square, circle, square). The number of correct and incorrect identifications are normalized (z-score). Total score is the z-score of correct button presses minus the z-score of incorrect button presses. Possible scores range from -4.85 to 4.85. A higher score (d') reflects better discrimination between target and non-target stimuli, and therefore better working memory performance. A positive change (increase) in 2-back score (d') between Baseline and Post-Testing indicates an improvement in working memory performance.

Time frame: Baseline, 3-4 weeks

Population: 12 participants completed the n-back working memory task at both Baseline and Post-Testing, however one participant used an incorrect button to make responses at Baseline, so these responses were not recorded, leaving 11 participants with recorded data at Baseline and Post-Testing. Of these 11, 5 performed below chance (\<50% hit rate) on the control task at one or both timepoints and were excluded from analysis.

Functional connectivity measures whether activity in different brain regions show similar patterns of change over time. Graph theory metrics of resting-state fMRI can characterize functional connectivity among nodes (regions) of a brain network, and well as between nodes of different brain networks. Network segregation is the difference of within-network and between-network connectivity as a proportion of within-network connectivity, such that higher numbers reflect more segregation. Given that network segregation typically decreases with normal and pathological aging, higher network segregation is generally considered cognitively beneficial. Network segregation was examined for the ventral attention network (the actual focus of stimulation based on observed cholinergic denervation) and the original cingulo-opercular network, which was predicted at the time of grant proposal (but not supported by the observed cholinergic denervation).

Time frame: Baseline and Post-Testing (3-4 weeks)

Population: Ten participants completed resting-State fMRI at Baseline and Post-Testing. Two participants were not eligible for MRI.

Outcome Measure Description: Interference score in time to complete the Color Word Interference Test version of the Stroop task from the Delis-Kaplan Executive Function System. Participants 1) identify a series of colors, 2) read color words (e.g. blue) all written in black ink, and 3) name the ink color of color words printed in incongruous colored inks (e.g. for the word green written in red ink, the correct response is red). Tasks are performed as quickly as possible. Time to complete each task is recorded. Interference score is calculated as the time to complete the color-word (interference) test (CWT), less the average of the time to complete the color task (CT) and word-reading task (WT): CWT - ((CT + WT)/2). The score has a theoretical valid range of 0 - 300; a lower score suggests better cognitive control. A negative change (decrease) in score between Baseline and Post-Testing indicates improvement in cognitive control performance.

Time frame: Baseline, 3-4 weeks

Population: 8 participants completed the Color Word Interference Test at Baseline and Post-Testing. 4 participants did not complete the test. Negative scores are technically possible, but given the known robust and reliable cognitive effort required in color word interference, a negative interference score would call into question the validity of the administration and be excluded. No participants' scores were negative and therefore none were excluded for this reason..