Biomedical subjects

S Schuh-Hofer

Publications and source records attributed to S Schuh-Hofer.

3 recordsLinked to original sources

PubMed1997

Decrease in parietal cerebral hemoglobin oxygenation during performance of a verbal fluency task in patients with Alzheimer's disease monitored by means of near-infrared spectroscopy (NIRS)--correlation with simultaneous rCBF-PET measurements.

We used near-infrared spectroscopy (NIRS) to study non-invasively changes in cerebral hemoglobin oxygenation in the frontal and parietal cortex during performance of a verbal fluency task in patients with Alzheimer's disease (AD). Whereas healthy elderly subjects (n = 19, age 67 +/- 10 years) showed increases in concentrations of oxygenated hemoglobin [HbO2] (mean (arbitrary units) +/- S.E.M., 1.44 +/- 0.59) and total hemoglobin [HbT] (0.92 +/- 0.81) over the left superior parietal cortex, patients with AD (n = 19, age 71 +/- 10 years) showed significant decreases in [HbO2] (-3.26 +/- 1.30, P < 0.01) as well as [HbT] (-4.45 +/- 1.57, P < 0.01). [HbR] decreased slightly in both groups (-0.62 +/- 0.29 and - 1.18 +/- 0.40, respectively). Using two pairs of NIRS optodes placed on the left superior partietal cortex and on the left prefrontal cortex simultaneous increases in [HbO2] as well as [HbT] in both cortical regions in the healthy elderly subjects (n = 8, age 60 +/- 15) were demonstrated during performance of the task. AD patients (n = 10, age 65 +/- 13 years) showed decreases in [HbO2] and [HbT] in the parietal cortex and, at the same time, increases in [HbO2] and [HbT] in the frontal cortex. Simultaneous NIRS-[HbT] and PET-rCBF measurements showed a significant correlation both when calculated in a 'banana' shaped volume approximated by using cortical thresholds as well as when calculated in a semisphere volume of brain tissue beneath the optodes placed on the head surface (patients with AD, n = 10). The correlation was dependent on the assumed penetration depth of the near-infrared light and was best for all three NIRS variables ([HbO2], [HbR] and [HbT]) when calculated using a semisphere radius of 0.45 cm to 1.35 cm. In conclusion, in Alzheimer's disease a marked reduction of regional cerebral blood flow and cerebral hemoglobin oxygenation may occur during activation of brain function, probably mainly in degenerating brain areas, such as the parietal cortex.

Aged↗

PubMed1996

Near infrared spectroscopy in the diagnosis of Alzheimer's disease.

Near infrared spectroscopy (NIRS) is a new technique that permits noninvasive monitoring of cerebral blood and tissue oxygenation. Recently, we and others have shown that NIRS measurements are sensitive enough to follow changes in cerebral hemoglobin oxygenation due to activation of brain function. Based on these findings we have assessed the influence of aging as well as the influence of neurodegeneration on cerebral hemoglobin oxygenation during mental work. The typical NIRS pattern in young healthy subjects while performing calculation tasks measured in the frontal cortex were increases in oxygenated hemoglobin [HbO2] and total hemoglobin [HbT] while reduced hemoglobin [HbR] decreased. Elderly healthy subjects showed a significant lower mean increase in [HbO2] and [HbT] levels. Regression analysis revealed an age-dependent decline in activation-induced local increase of [HbO2] as well as [HbT]. Furthermore, we monitored changes in cerebral hemoglobin oxygenation in the frontal cortex while patients with probable Alzheimer's disease (AD) performed cognitive tasks. Whereas elderly healthy subjects (as well as patients with major depression, age-associated memory impairments or vascular dementia) again showed clear increases in the local concentrations of [HbO2] and [HbT] during brain activation, AD patients showed significant decreases compared to the baseline levels in both variables that were most pronounced in the parietal cortex. To clarify whether the different patterns in cerebral hemoglobin oxygenation during cognitive activation were due to an altered functional brain organization in AD or to alterations in the cerebrovascular response to neuronal activation, we are currently performing simultaneous NIRS and (015-H20-)PET measurements during performance of a cognitive task (Stroop test). Our finding of a regional reduced oxygen supply during activation of brain function may be of relevance to the development and the time course of neurodegeneration.

Aging↗

PubMed1995

Age dependency of changes in cerebral hemoglobin oxygenation during brain activation: a near-infrared spectroscopy study.

We used near-infrared spectroscopy (NIRS) to study noninvasively the influence of aging on changes in the local concentration of oxygenated hemoglobin ([HbO2]), reduced hemoglobin ([HbR]), and total hemoglobin ([HbT] = [HbR] + [HbO2]) during activation of brain function. Young subjects (n = 12; age, 28 +/- 4 years) performing calculation tasks showed an increase in [HbO2] [mean (arbitrary units) +/- SD, 2.36 +/- 1.07] and [HbT] (2.24 +/- 1.13) in the frontal cortex, while [HbR] (-0.11 +/- 0.48) decreased. Elderly subjects (n = 17; age, 52 +/- 10 years) showed a significantly lower mean increase (p < 0.05) in [HbO2] and [HbT] levels (1.21 +/- 1.38 and 0.72 +/- 1.41, respectively). Regression analysis supports the hypothesis of an age-dependent decline in the activation-induced local increase in [HbO2] (y = -0.241x + 20.062; r = -0.431, p < 0.05) as well as [HbT] (y = -0.346x + 22.496; r = -0.568, p < 0.05). We conclude that NIRS is a promising approach for studying changes in Hb oxygenation during brain activation in physiological aging.

Adult↗