Influence of baseline hematocrit and hemodilution on BOLD fMRI activation

Levin, Jonathan M.; Frederick, Blaise; Ross, Marjorie H.; Fox, Jonathan F.; Rosenberg, Heidi L. Von; Kaufman, Marc J.; Lange, Nicholas; Mendelson, Jack H.; Cohen, Bruce M.; Renshaw, Perry F.

doi:10.1016/s0730-725x(01)00460-x

Cited by 79 publications

(60 citation statements)

References 28 publications

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“…No participant had a positive breath alcohol concentration or toxicology screen, other than two positive for THC, described previously. A subset of participants (n = 9 for each group) provided blood samples to permit evaluation of blood density (see Table 1), as hematocrit was related to BOLD response in one study (Levin et al, 2001). Participants were administered neuropsychological tests and interviews, trained on the fMRI tasks, then given affective and sleepiness self-report measures.…”

Section: Methodsmentioning

confidence: 99%

Blood Oxygen Level Dependent Response and Spatial Working Memory in Adolescents With Alcohol Use Disorders

Tapert

Schweinsburg

Barlett

et al. 2004

Alcoholism Clin & Exp Res

199

193

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Background: Previous studies have suggested neural disruption and reorganization in young and older adults with alcohol use disorders (AUD). However, it remains unclear at what age and when in the progression of AUD changes in brain functioning might occur. Methods: Alcohol use disordered (n=15) and nonabusing (n=19) males and females ages 15-17 were recruited from local high schools. Functional magnetic resonance imaging (fMRI) data were collected after a minimum of 5 days' abstinence as participants performed spatial working memory and simple motor tasks. Results: Adolescents with AUD showed greater brain response to the spatial working memory task in bilateral parietal cortices, and diminished response in other regions including the left precentral gyrus and bilateral cerebellar areas (clusters ≥ 943 μl, p < .05), although groups did not differ on behavioral measures of task performance. No brain response differences were observed during a simple finger tapping task. The degree of abnormality was greater for teens who reported experiencing more withdrawal or hangover symptoms, and who consumed more alcohol. Conclusions: Adolescents with AUD show abnormalities in brain response to a spatial working memory task, despite adequate performance, suggesting that subtle neuronal reorganization may occur early in the course of AUD.

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Section: Methodsmentioning

confidence: 99%

Blood Oxygen Level Dependent Response and Spatial Working Memory in Adolescents With Alcohol Use Disorders

Tapert

Schweinsburg

Barlett

et al. 2004

Alcoholism Clin & Exp Res

199

193

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“…All three groups also had similar hematocrit, which is important, as BOLD signals may vary with percent hematocrit (Levin et al 2001). The two HIV subgroups were well matched by CD4 counts.…”

Section: Participants' Clinical Datamentioning

confidence: 99%

Antiretroviral Treatment is Associated with Increased Attentional Load-Dependent Brain Activation in HIV Patients

Chang

Yakupov

Nakama

et al. 2007

J Neuroimmune Pharmacol

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Objective-The purpose of this paper was to determine whether antiretroviral medications, especially the nucleoside analogue reverse transcriptase inhibitors, lead to altered brain activation due to their potential neurotoxic effects in patients with human immunodeficiency virus (HIV) infection.Methods-Forty-two right-handed men were enrolled in three groups: seronegative controls (SN, n=18), HIV subjects treated with antiretroviral medications (HIV+ ARV, n=12), or not treated with antiretroviral medications (HIV+NARV, n=12). Each subject performed a set of visual attention tasks with increasing difficulty or load (tracking two, three or four balls) during functional magnetic resonance imaging.Results-HIV subjects, both groups combined, showed greater load-dependent increases in brain activation in the right frontal regions compared to . HIV+ARV additionally showed greater load-dependent increases in activation compared to SN in bilateral superior frontal regions (p-corrected=0.032) and a lower percent accuracy on the performance of the most difficult task (tracking four balls). Region of interest analyses further demonstrated that SN showed load-dependent decreases (with repeated trials despite increasing difficulty), while HIV subjects showed load-dependent increases in activation with the more difficult tasks, especially those on ARVs.Interpretation-These findings suggest that chronic ARV treatments may lead to greater requirement of the attentional network reserve and hence less efficient usage of the network and less practice effects in these HIV patients. As the brain has a limited reserve capacity, exhausting the reserve capacity in HIV+ARV would lead to declined performance with more difficult tasks that require more attention. Prior functional magnetic resonance imaging (fMRI) studies demonstrated increased usage of reserve brain regions during working memory and attention tasks in HIV patients with mild dementia as well as in those who were neuroasymptomatic (Ernst et al. 2002). With effective antiretroviral treatments (ARVs), HIV-infected individuals are living longer, and the full clinical manifestation of HIV-dementia is less common (Dore et al. 2003;Ghafouri et al. 2006). However, the prevalence of a milder form of cognitive impairment appears to be rising among HIV-infected individuals, possibly due to the longer duration of illness and the additional effect of aging in these patients. Although treatment with ARVs typically leads to improved cognitive performance in HIV patients with dementia or cognitive deficits (Larussa et al. 2006;Sacktor et al. 2006;Sacktor et al. 2000), some studies suggest that some ARV treatments may not benefit the cognitive performance of those with lower nadir CD4 counts (Cysique et al. 2006). In addition, patients treated with nucleoside analogue reverse transcriptase inhibitors (NRTIs) develop a varying degree of myopathy or neuropathy after long-term therapy (Dalakas 2001); however, the effects of these drugs on brain function are not well understood. As NRT...

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“…These include individual differences in the size and location of veins (Bandettini and Wong 1997;Cohen, et al 2004), extracranial arterial disease (Hamzei, et al 2003;Rother, et al 2002), small vessel cerebral disease (Pineiro, et al 2002), pulse or respiration differences (Dagli, et al 1999;, hematocrit concentrations (Levin, et al 2001), baseline CBF (Cohen, et al 2002). Several studies have also revealed that medications and food intake can affect the BOLD signal.…”

Section: Introductionmentioning

confidence: 99%

Reducing vascular variability of fMRI data across aging populations using a breathholding task

Handwerker¹,

Gazzaley²,

Inglis³

et al. 2006

Human Brain Mapping

128

175

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The magnitude and shape of Blood Oxygen Level Dependent (BOLD) responses in functional Magnetic Resonance Imaging (fMRI) studies vary across brain regions, subjects, and populations. This variability may be secondary to neural activity or vasculature differences, thus complicating interpretations of BOLD signal changes in fMRI experiments. We compare the BOLD responses to neural activity and a vascular challenge and test a method to dissociate these influences in 26 younger subjects (ages 18-36) and 24 older subjects (ages 51-78). Each subject performed a visuomotor saccade task (a vascular response to neural activity) and a breath holding task (vascular dilation induced by hypercapnia) during separate runs in the same scanning session. For the saccade task, signal magnitude showed a significant decrease with aging in FEF, SEF, and V1, and a delayed time-to-peak with aging in V1. The signal magnitudes from the saccade and hypercapnia tasks showed significant linear regressions within subjects and across individuals and populations. These two tasks had weaker, but sometimes significant, linear regressions for time-to-peak and coherence phase measures. The significant magnitude decrease with aging in V1 remained after dividing the saccade task magnitude by the hypercapnia task magnitude implying that the signal decrease is neural in origin. These findings may lead to a method to identify vascular reactivity induced differences in the BOLD response across populations and the development of methods to account for the influence of these vasculature differences in a simple, noninvasive manner.Handwerker, Daniel A 3

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Influence of baseline hematocrit and hemodilution on BOLD fMRI activation

Cited by 79 publications

References 28 publications

Blood Oxygen Level Dependent Response and Spatial Working Memory in Adolescents With Alcohol Use Disorders

Blood Oxygen Level Dependent Response and Spatial Working Memory in Adolescents With Alcohol Use Disorders

Antiretroviral Treatment is Associated with Increased Attentional Load-Dependent Brain Activation in HIV Patients

Reducing vascular variability of fMRI data across aging populations using a breathholding task

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