Showing papers by "Ann M. Peiffer published in 2008"

Relating Imaging Indices of White Matter Integrity and Volume in Healthy Older Adults

Abstract: Age-related alterations in white matter have the potential to profoundly affect cognitive functioning. In fact, magnetic resonance imaging (MRI) studies using fractional anisotropy (FA) to measure white matter integrity reveal a positive correlation between FA and behavioral performance in older adults. Confounding these results are imaging studies demonstrating age-related white matter atrophy in some areas displaying altered FA, suggesting changes in diffusion may be simply an epiphenomenon of tissue loss. In the current study, structural MRI techniques were used to identify the relationship between white matter integrity and decreased volume in healthy aging adults. The data demonstrated that white matter atrophy did in fact account for differences in some areas, but significant FA decreases remained across much of the white matter after adjusting for atrophy. Results suggest a complex relationship between changes in white matter integrity and volume. FA appears to be more sensitive than volume loss to changes in normal appearing tissue, and these FA changes may actually precede white matter atrophy in some brain areas. As such, the ability to detect early white matter alterations may facilitate development of targeted treatments that prevent or slow age-related white matter degradation and associated cognitive sequelae.

Cross-modal deactivations during modality-specific selective attention.

Abstract: Processing stimuli in one sensory modality is known to result in suppression of other sensory-specific cortices. Additionally, behavioral experiments suggest that the primary consequence of paying attention to a specific sensory modality is poorer task performance in the unattended sensory modality. This study was designed to determine how focusing attention on the auditory or visual modality impacts neural activity in cortical regions responsible for processing stimuli in the unattended modality. Functional MRI data were collected in 15 participants who completed a cued detection paradigm. This task allowed us to assess the effects of modality-specific attention both during the presence and the absence of targets in the attended modality. The results of this experiment demonstrate that attention to a single sensory modality can result in decreased activity in cortical regions that process information from an unattended sensory modality (cross-modal deactivations). The effects of attention are likely additive with stimulus-driven effects with the largest deactivations being observed during modality-specific selective attention, in the presence of a stimulus in that modality. Modality-specific selective attention results in behavioral decrements in unattended sensory modalities. The imaging results presented here provide a neural signature (cross-modal deactivation) for modality-specific selective attention.

Fostering a culture of responsible lab conduct.

Abstract: There is much debate and research devoted to determining the best practice for teaching responsible conduct of research (RCR) to trainees as federally required (1, 2). The majority of institutional programs require trainees (i.e., graduate students and postdoctoral fellows) to attend instruction isolated from the laboratory. However, laboratory behavior is our field's “hidden curriculum,” and the principal investigator and senior laboratory staff represent the professional role models that trainees see on a daily basis, whether good or bad (3). At Wake Forest, over the past 3 years, we have implemented a program of 15-minute discussions that takes place after our weekly journal club. This amounts to about 11 to 12 hours of training per year. Each laboratory member takes a turn selecting a topic, many of which are also being discussed among scientists, policy-makers, and taxpayers. All laboratory personnel attend, and discussions include a variety of viewpoints as well as discourse on the policies for best practices within the laboratory. We believe that by moving the ethical discussion into the laboratory environment and empowering individual scientists at all seniority levels to actively participate in expanding their own awareness of RCR issues facing research and science policy, we can change the culture of the laboratory itself for the better.

Resurrecting brinley plots for a novel use: meta-analyses of functional brain imaging data in older adults

Abstract: By plotting response times of young and older adults across a variety of tasks, Brinley spurred investigation and debate into the theory of general cognitive slowing. Though controversial, Brinley plots can assess between-task differences, the impact of increasing task demand, and the relationship between responses in two groups of subjects. Since a relationship exists between response times and the blood-oxygen level dependent (BOLD) signal of functional MRI (fMRI), Brinley's plotting method could be applied as a meta-analysis tool in fMRI studies of aging. Here, fledgling "Peiffer plots" are discussed for their potential impact on understanding general cognitive brain activity in aging. Preliminary results suggest that general cognitive slowing may be localized at the sensorimotor transformation in the precentral gyrus. Although this meta-analysis method is naturally used with imaging studies of aging, theoretically it may be applied to other study pairs (e.g., schizophrenic versus normal) or imaging datasets (e.g., PET).