Brain activation in frontotemporal and Alzheimer’s dementia: a functional near-infrared spectroscopy study

Abstract

BackgroundFrontotemporal dementia is an increasingly studied disease, the underlying functional impairments on a neurobiological level of which have not been fully understood. Patients with the behavioral-subtype frontotemporal dementia (bvFTD) are particularly challenging for clinical measurements such as functional imaging due to their behavioral symptoms. Here, an alternative imaging method, functional near-infrared spectroscopy (fNIRS), is introduced to measure task-related cortical brain activation based on blood oxygenation. The current study investigated differences in cortical activation patterns of patients with bvFTD, Alzheimer’s dementia (AD), and healthy elderly subjects measured by fNIRS.MethodEight probable bvFTD patients completed the semantic, phonological, and control conditions of a verbal fluency task. Eight AD patients and eight healthy controls were compared on the same task. Simultaneously, an fNIRS measurement was conducted and analyzed using a correction method based on the expected negative correlation between oxygenated and deoxygenated hemoglobin.ResultsHealthy controls show an increase in cortical activation measured in frontoparietal areas such as the dorsolateral prefrontal cortex. The activation pattern of patients with AD is similar, but weaker. In contrast, bvFTD patients show a more frontopolar pattern, with activation of Broca’s area, instead of the dorsolateral prefrontal cortex and the superior temporal gyrus. The frontoparietal compensation mechanisms, seen in the healthy elderly, were missing in bvFTD patients.ConclusionDifferent frontoparietal cortical activation patterns may indicate a correlate of diverse pathophysiological mechanisms of AD and bvFTD during verbal fluency processing. The AD pattern is weaker and more similar to the healthy pattern, whereas the bvFTD pattern is qualitatively different, namely more frontopolar and without frontoparietal compensation activation. It adheres to a change of cortical activation during the course of the disease.Electronic supplementary materialThe online version of this article (doi:10.1186/s13195-016-0224-8) contains supplementary material, which is available to authorized users.

Neural Correlates of Verb Fluency Performance in Cognitively Healthy Older Adults and Individuals With Dementia: A Pilot fMRI Study

“…As dementia progresses, decreased performance on verbal fluency tasks is observed, and verbal fluency deficits are known pathological markers of cognitive declines due to dementing diseases, even though the deficits are also observed in subclinical populations (Clark et al, 2009;see Belleville et al, 2017;Nikolai et al, 2018). Furthermore, structural and functional neuroimaging studies related to verbal fluency tasks in individuals with MCI or dementia have suggested that cognitively healthy older adults and individuals with dementia exhibit similar brain activation patterns or structural brain changes, differing only in terms of level of activation (i.e., decreased activation in AD; Arai et al, 2006;Metzger et al, 2016) or severity of structural or perfusion changes (Östberg et al, 2007;Metzger et al, 2016;Rodríguez-Aranda et al, 2016). Thus, we utilized a multiple regression approach for the fMRI BOLD responses on the continuum from cognitively healthy older adults to individuals with moderately severe dementia to capture the neural substrates underlying impaired verb fluency performance.…”

“…To date, functional near-infrared spectroscopy (fNIRS) research related to dementia and verbal fluency has indicated that there are decreased hemodynamic responses in the inferior frontotemporal regions in the MCI population (Katzorke et al, 2018) and in the prefrontal and parietal areas in individuals with AD (Arai et al, 2006;Metzger et al, 2016) compared to healthy older adults, revealing the effects of neuropathological changes on brain activation patterns during verbal fluency tasks in these populations. The depth resolution of fNIRS, however, has limited the researchers to investigating relatively lateral brain regions that are more adjacent to the skull (Obrig, 2014); there has been little consideration of deeper brain structures (e.g., subcortical, medial, and insular areas as well as even some cortices), even though fluency tasks have been shown to engage these areas (Beber and Chaves, 2014;Li et al, 2017).…”

Investigation of brain functional connectivity in patients with mild cognitive impairment: A functional near‐infrared spectroscopy (fNIRS) study

“…As a result, fNIRS has been widely used to examine neurodegenerative disorders such as MCI and AD . Previous studies of MCI using fNIRS mostly focused on finding a feature to differentiate a person with MCI from a cognitively unimpaired senior based on the cerebral hemodynamic responses during a cognitive task .…”

Application of functional near-infrared spectroscopy in the healthcare industry: A review

“…241 The activation region in AD patients is di®erent compared to the patients with frontotemporal dementia, as AD patients exhibited activation in the frontoparietal areas. 242 The mean activation pattern of AD patients was lower and slower than those of MCI patients. 224…”

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