Phonemic fluency and brain connectivity in age-related macular degeneration: a pilot study.
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2015-03
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Abstract
Age-related macular degeneration (AMD), the leading cause of blindness in developed nations, has been associated with poor performance on tests of phonemic fluency. This pilot study sought to (1) characterize the relationship between phonemic fluency and resting-state functional brain connectivity in AMD patients and (2) determine whether regional connections associated with phonemic fluency in AMD patients were similarly linked to phonemic fluency in healthy participants. Behavior-based connectivity analysis was applied to resting-state, functional magnetic resonance imaging data from seven patients (mean age=79.9±7.5 years) with bilateral AMD who completed fluency tasks prior to imaging. Phonemic fluency was inversely related to the strength of functional connectivity (FC) among six pairs of brain regions, representing eight nodes: left opercular portion of inferior frontal gyrus (which includes Broca's area), left superior temporal gyrus (which includes part of Wernicke's area), inferior parietal lobe (bilaterally), right superior parietal lobe, right supramarginal gyrus, right supplementary motor area, and right precentral gyrus. The FC of these reference links was not related to phonemic fluency among 32 healthy individuals (16 younger adults, mean age=23.5±4.6 years and 16 older adults, mean age=68.3±3.4 years). Compared with healthy individuals, AMD patients exhibited higher mean connectivity within the reference links and within the default mode network, possibly reflecting compensatory changes to support performance in the setting of reduced vision. These findings are consistent with the hypothesis that phonemic fluency deficits in AMD reflect underlying brain changes that develop in the context of AMD.
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Whitson, Heather E, Ying-Hui Chou, Guy G Potter, Michele T Diaz, Nan-Kuei Chen, Eleonora M Lad, Micah A Johnson, Scott W Cousins, et al. (2015). Phonemic fluency and brain connectivity in age-related macular degeneration: a pilot study. Brain connectivity, 5(2). pp. 126–135. 10.1089/brain.2014.0277 Retrieved from https://hdl.handle.net/10161/27509.
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Heather Elizabeth Whitson
Dr. Whitson is a geriatrician, memory care specialist, and clinical researcher. Her career is focused on improving care options and resilience for people with multiple chronic conditions. In particular, she has interest and expertise related to how aging biology and comorbidities impact brain health and risk for Alzheimer's disease. She is co-director of the Duke/UNC Alzheimer's Disease Research Center (Duke/UNC ADRC), which aims to transform dementia care and research in Eastern North Carolina while developing novel preventions and treatment strategies for Alzheimer's disease by identifying aging-related factors across the lifespan that drive risk, progression, or experience of dementia. The Duke/UNC ADRC conducts the Memory and Aging Study, which is tracking brain and cognitive changes in over 400 individuals at risk for dementia in later life. Dr. Whitson also co-Chairs the Alzheimer's Association's Clinical Practice Guideline panel for the use of blood-based biomarkers in the diagnosis of Alzheimer's disease. As a thought leader in a national collaborative focused on the biomedical aspects of resilience, Dr. Whitson seeks to better understand biological, psychological, and contextual factors that determine how well we "bounce back" after acute health stressors and why our resilience capacity changes with age. Dr. Whitson has contributed to work examining resilience to many types of health stressors, including surgery, dialysis, infection, vascular events, and vision loss - often focused on how these stressors affect the brain. She has led multiple studies to examine how the aging brain responds to the late-life stressor of vision loss, and she has developed a rehabilitation model to improve independence in older adults living with comorbid impairments in vision and cognition.
Guy Glenn Potter
David Joseph Madden
My research focuses primarily on the cognitive neuroscience of aging: the investigation of age-related changes in perception, attention, and memory, using both behavioral measures and neuroimaging techniques, including positron emission tomography (PET), functional magnetic resonance imaging (fMRI), and diffusion tensor imaging (DTI).
The behavioral measures have focused on reaction time, with the goal of distinguishing age-related changes in specific cognitive abilities from more general effects arising from a slowing in elementary perceptual processes. The cognitive abilities of interest include selective attention as measured in visual search tasks, semantic and episodic memory retrieval, and executive control processes.
The behavioral measures are necessary to define the cognitive abilities of interest, and the neuroimaging techniques help define the functional neuroanatomy of those abilities. The PET and fMRI measures provide information regarding neural activity during cognitive performance. DTI is a recently developed technique that images the structural integrity of white matter. The white matter tracts of the brain provide critical pathways linking the gray matter regions, and thus this work will complement the studies using PET and fMRI that focus on gray matter activation.
A current focus of the research program is the functional connectivity among regions, not only during cognitive task performance but also during rest. These latter measures, referred to as intrinsic functional connectivity, are beginning to show promise as an index of overall brain functional efficiency, which can be assessed without the implementation of a specific cognitive task. From DTI, information can be obtained regarding how anatomical connectivity constrains intrinsic functional connectivity. It will be important to determine the relative influence of white matter pathway integrity, intrinsic functional connectivity, and task-related functional connectivity, as mediators of age-related differences in behavioral measures of cognitive performance.
Ultimately, the research program can help link age-related changes in cognitive performance to changes in the structure and function of specific neural systems. The results also have implications for clinical translation, in terms of the identification of neural biomarkers for the diagnosis of neural pathology and targeting rehabilitation procedures.
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