Loss of Functional Hemispheric Asymmetry in Alzheimer's Dementia

Bilateral prefrontal cortex oxygenation responses to a verbal fluency task: a multichannel time-resolved near-infrared topography study

“…65 Five verbal tasks showed a significant left-hemispheric lateralization that can best be elicited by linguistic tasks that require active or creative processing of the verbal material such as constructing a sentence with given words or retrieving words. The bilateral increase of blood flow velocity in the middle cerebral arteries on VFT is consistent with the increase of O 2 Hb observed during VFT in this study by NIR TRS and in other studies using a one-/two-channel NIR cw systems 26,30,36,43 and by multichannel NIR cw systems. 38,44 Although the increase of O 2 Hb on VFT is usually accompanied by a smaller decrease in HHb, in our study, this pattern was not observed in three out of the seven subjects.…”

“…26,30,36,43 The prefrontal cortex of both hemispheres was activated by the VFT, i.e., O 2 Hb increased and HHb decreased significantly with respect to the corresponding baselines. Using multichannel fNIRS on both hemispheres, a significant increase in O 2 Hb not accompanied by a decrease in HHb was found; 44 conversely, a significant increase in O 2 Hb accompanied by a decrease in HHb was found in another study.…”

“…[20][21][22][23][24] In particular, the prefrontal cortex ͑the anterior portion of the frontal lobe͒ and the frontal lobe ͑the front part of the brain involved in planning, organizing, problem solving, selective attention, etc.͒, both involved in higher cognitive functions and in the determination of the personality, have been studied using various neuropsychological tests including mental calculation tasks, continuous performance task, Wisconsin Card Sorting task, color-word matching Stroop task, etc. [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] Another cognitive paradigm known to activate the prefrontal cortex is the verbal fluency task ͑VFT͒. The VFT is a neuropsycological task that enables assessment of the subject's ability to retrieve nouns based on a common criterion.…”