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Reduced Prefrontal Oxygenation in Alzheimer Disease During Verbal Fluency Tasks

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Objective

Near-infrared spectroscopy (NIRS) is an optical method to measure changes in the concentration of oxygenated hemoglobin (O2Hb) and deoxygenated hemoglobin (HHb) in the vascular system of the brain tissue. Because NIRS is easy to assess and does not have any side effects, it seems perfectly suitable for functional measurements in psychiatric patients or fragile subjects. As previous research suggested changes in functional brain activation in prefrontal brain areas of patients with dementia, the aim of this study was to replicate these findings by means of multichannel NIRS.

Methods

In the present study, the authors investigated 16 patients with Alzheimer disease and 16 healthy subjects (similar in age and sex) during performance of a verbal fluency task.

Results

The results clearly showed an activation pattern during active phase as compared to baseline phase in the form of decreases in HHb and increases in O2Hb, with a reduced increase of O2Hb for patients.

Conclusion

These results indicate a diminished activation of the dorsolateral prefrontal cortex in patients with Alzheimer disease. Future research has to show whether this decreased activation pattern might be a suitable predictor for the effectiveness of treatment in dementias.

Section snippets

Subjects

The NIRS-measurement on patients and healthy participants was in accordance with the Declaration of Helsinki, Finland, and approved by the Ethical Committee of the University of Wuerzburg. Sixteen patients with dementia (5 male and 11 female) and a healthy control group (6 male and 10 female) were investigated after giving written informed consent. The mean age was 69.5 ± 8.4 years for the patients and 67.9 ± 5.4 years for the comparison group (t(30) <1, p = 0.53).

The patients were inpatients

Behavioral Data

Dementia patients had a significantly worse behavioral performance for the letter (10.0 ± 5.6; t(30) = 4.9, p <0.001) as well as the category version (16.1 ± 5.5; t(30) = 9.6, p <0.001) of the VFT compared to the control group (letter version: 19.8 ± 5.8; category version: 33.6 ± 4.8).

Letter Version of the VFT

In the letter version of the VFT, we found significant main effects related to the factors channels (F(3.00, 90.05) = 6.68, p <0.001) and time (F(1, 3 0) = 11.1, p <0.01) for HHb. Additionally, the interaction

DISCUSSION

In the category and letter versions of the VFT, both the dementia and control groups displayed an increase of O2Hb and a decrease of HHb, which is considered to be the typical NIRS pattern during activation. In both conditions, the increase in O2Hb was more pronounced for the healthy comparison group than for dementia patients, whereas no general differences concerning diagnosis were found for HHb.

As previously described,23 the HHb reduction occurred mainly over superior sensor positions in the

References (28)

Cited by (68)

  • Functional near-infrared spectroscopy reveals decreased resting oxygenation levels and task-related oxygenation changes in mild cognitive impairment and dementia: A systematic review

    2020, Journal of Psychiatric Research
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    This baseline shift will look like a positive hemodynamic response and will often result in Type I errors. Given that many fNIRS studies have shown that NC controls produced more words than MCI/AD patients over the course of a trial (e.g., Herrmann et al., 2008; Yeung et al., 2016a), NC controls might have more motion artifacts, and thus potentially more Type I errors. We found that three studies have corrected motion artifacts by applying correlation-based motion correction (Metzger et al., 2016), principal component analysis (Arai et al., 2006), or spline interpolation (Nguyen et al., 2019), while others either have not or have corrected motion artifacts only using very basic moving-average methods.

  • Decreased hemodynamic response in inferior frontotemporal regions in elderly with mild cognitive impairment

    2018, Psychiatry Research - Neuroimaging
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    Our finding of the decreased hemodynamic response during a category but not letter VFT is partly in line with the literature. A decreased hemodynamic response during a VFT especially in prefrontal regions has been repeatedly found when comparing participants with AD with healthy controls, not only during the category VFT but also during the letter VFT (Arai et al., 2006; Herrmann et al., 2008; Metzger et al., 2016; Richter et al., 2007). Arai et al. (2006) discovered that participants with MCI had a decreased hemodynamic response only in parietal regions during a letter VFT compared to healthy controls.

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This work was supported by a grant from the Alzhe-imer Forschung Initiative (to A.J.F.).

The authors thank Hitachi Medical Corporation for the ETG-100 equipment and technical support and Mrs. Groebner for dedicated assistance in data recording.

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