Biomedical subjects

B M Bly

Publications and source records attributed to B M Bly.

9 recordsLinked to original sources

PubMed2005

Objective evidence of cognitive complaints in Chronic Fatigue Syndrome: a BOLD fMRI study of verbal working memory.

Individuals with Chronic Fatigue Syndrome (CFS) often have difficulties with complex auditory information processing. In a series of two Blood Oxygen Level Dependent (BOLD) functional Magnetic Resonance Imaging (fMRI) studies, we compared BOLD signal changes between Controls and individuals with CFS who had documented difficulties in complex auditory information processing (Study 1) and those who did not (Study 2) in response to performance on a simple auditory monitoring and a complex auditory information processing task (mPASAT). We hypothesized that under conditions of cognitive challenge: (1) individuals with CFS who have auditory information processing difficulties will utilize frontal and parietal brain regions to a greater extent than Controls and (2) these differences will be maintained even when objective difficulties in this domain are controlled for. Using blocked design fMRI paradigms in both studies, we first presented the auditory monitoring task followed by the mPASAT. Within and between regions of interest (ROI), group analyses were performed for both studies with statistical parametric mapping (SPM99). Findings showed that individuals with CFS are able to process challenging auditory information as accurately as Controls but utilize more extensive regions of the network associated with the verbal WM system. Individuals with CFS appear to have to exert greater effort to process auditory information as effectively as demographically similar healthy adults. Our findings provide objective evidence for the subjective experience of cognitive difficulties in individuals with CFS.

Acoustic Stimulation↗

PubMed2003

An investigation of working memory rehearsal in multiple sclerosis using fMRI.

The present study examined patterns of cerebral activation during a working memory (WM) rehearsal task in individuals diagnosed with multiple sclerosis (MS) and in healthy adults. BOLD functional magnetic resonance imaging (fMRI) was performed using a 1.5 T GE scanner to assess activation during a WM task adapted from the Sternberg paradigm (Sternberg, 1969). Participants included 8 individuals diagnosed with MS, and 5 healthy controls (HCs) matched for age and education. Task difficulty was manipulated by increasing the length of time that strings of letters were to be rehearsed. Findings revealed increased right prefrontal cortex activation and increased right temporal lobe activation in individuals diagnosed with MS compared to HCs. The potential explanations for increased right hemisphere activation in persons with MS are discussed.

Adolescent↗

PubMed2001

The distribution of BOLD susceptibility effects in the brain is non-Gaussian.

A key assumption underlying fMRI analysis in the general linear model is that the underlying distribution of BOLD Susceptibility is gaussian. Analysis of several common data sets and experimental paradigms shows that the underlying distribution for the BOLD signal is non-Gaussian. Further identification shows that the distribution is probably Gamma and implications for hemodynamic modeling are discussed as well as recommendations concerning inferential testing in heavy-tailed environments.

Brain↗

PubMed2001

Functional magnetic resonance imaging of working memory impairment after traumatic brain injury.

OBJECTIVES: To examine patterns of brain activation while performing a working memory task in persons with moderate to severe traumatic brain injury (TBI) and healthy controls. It is well established that working memory is an area of cognition that is especially vulnerable to disruption after TBI. Although much has been learned about the system of cerebral representation of working memory in healthy people, little is known about how this system is disrupted by TBI. METHODS: Functional magnetic resonance imaging (fMRI) was used to assess brain activation during a working memory task (a modified version of the paced auditory serial addition test) in nine patients with TBI and seven healthy controls. RESULTS: Patients with TBI were able to perform the task, but made significantly more errors than healthy controls. Cerebral activation in both groups was found in similar regions of the frontal, parietal, and temporal lobes, and resembled patterns of activation found in previous neuroimaging studies of working memory in healthy persons. However, compared with the healthy controls, the TBI group displayed a pattern of cerebral activation that was more regionally dispersed and more lateralised to the right hemisphere. Differences in lateralisation were particularly evident in the frontal lobes. CONCLUSIONS: Impairment of working memory in TBI seems to be associated with alterations in functional cerebral activity.

Adult↗

PubMed1999

Squinting with the mind's eye: effects of stimulus resolution on imaginal and perceptual comparisons.

Subjects either viewed or visualized arrays that were divided into four quadrants, with each quadrant containing a set of stripes. In two experiments, one array contained only relatively narrow (high-resolution) stripes, and one contained only relatively thick (low-resolution) stripes. The subjects compared sets of stripes in different quadrants according to their length, spacing, orientation, or width. When the subjects visualized the arrays, they required much more time to compare high-resolution patterns than low-resolution patterns; when the subjects saw the arrays, they evaluated both types of arrays equally easily. In addition, the results from the third experiment provide strong evidence that people use imagery in this task; in one condition, the subjects evaluated oblique sets of stripes, and in another condition, they evaluated vertical and horizontal stripes. In both imagery and perception, the subjects made more errors when evaluating oblique stimuli; in imagery, they also required more time to evaluate oblique stimuli. The results suggest that additional effort is required in imagery to represent visual patterns with high resolution. This finding demonstrates that, although imagery and perception may activate common brain regions, it is more difficult to represent high-resolution information in imagery than in perception.

Adult↗

PubMed1997

Prefrontal cortex fMRI signal changes are correlated with working memory load.

We investigated whether a nonspatial working memory (WM) task would activate dorsolateral prefrontal cortex (DLPFC) and whether activation would be correlated with WM load. Using functional magnetic resonance imaging we measured regional brain signal changes in 12 normal subjects performing a continuous performance, choice reaction time task that requires WM. A high WM load condition was compared with a non-WM choice reaction time control condition (WM effect) and a low WM load condition (load effect). Significant changes in signal intensity occurred in the DLPFC, frontal motor regions and the intraparietal sulcus (IPS) in both comparisons. These findings support the role of DLPFC and IPS in WM and suggest that signal changes in DLPFC correlate with WM load.

Adult↗

PubMed1997

STAR-HASTE: perfusion imaging without magnetic susceptibility artifact.

A novel magnetic resonance imaging technique (STAR-HASTE) based on pulsed arterial spin labeling using a single shot acquisition method is described for perfusion imaging. The method is similar to EPISTAR in using STAR (Signal Targeting with Alternating Radiofrequency) technique for pulsed radiofrequency labeling of inflowing blood, but uses a half-Fourier single shot turbo spin-echo (HASTE) sequence for data acquisition instead of echo-planar imaging (EPI). Our preliminary studies show that STAR-HASTE permits perfusion imaging to be performed without many of the artifacts encountered with other imaging methods based on EPI acquisition. The novel method not only provides similar perfusion information to that obtained by EPISTAR, as demonstrated in the functional brain imaging study, but also eliminates magnetic susceptibility artifacts and image distortion commonly observed in EPI images. Furthermore, this technique can be readily implemented in MR systems without EPI capability.

Artifacts↗

PubMed1997

Functional anatomy of object recognition in humans: evidence from positron emission tomography and functional magnetic resonance imaging.

The ability to recognize elements of the environment as familiar objects, events, or classes underlies virtually all human cognition. Positron emission tomography and functional magnetic resonance imaging studies of the recognition of visually presented objects suggest that several brain areas crucially support this function. However, a review of these findings reveals great variability in the cortical localization of object recognition in humans. Although there is converging evidence for the importance of the temporal and occipitotemporal cortex in object recognition, a consistent picture of the functional organization within these areas and their relation to function in other cortical regions has not yet emerged from brain imaging studies.

Arousal↗

PubMed1996

Comparison of the BOLD- and EPISTAR-technique for functional brain imaging by using signal detection theory.

Two magnetic resonance imaging techniques, BOLD (blood oxygenation level dependent) and EPISTAR (echo-planar imaging and signal targeting with alternating radio-frequency), were compared for functional brain imaging. Ten volunteers were imaged performing a sequential finger to thumb opposition task alternating with no movement conditions. Techniques were compared using variance maps and signal detection theory (ROC analysis). True positive activation in regions of interest with expected task-dependent signal changes were computed versus false activation rates in regions in which no activation was expected. D-prime coefficients were calculated for each comparison and statistically compared using a paired t test. Activation in the perirolandic region was seen in all volunteers with both techniques. There was no significant difference for the d-prime between BOLD and EPISTAR. These results indicate that based on a different physiologic principle, EPISTAR is an alternative to BOLD to perform fMRI with similar results.

Adult↗