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Susan M Resnick

Publications and source records attributed to Susan M Resnick.

28 records · Page 2Linked to original sources
PubMed2004

Age differences in orbitofrontal activation: an fMRI investigation of delayed match and nonmatch to sample.

Several investigations have suggested that the orbitofrontal cortex (OFC) may be particularly vulnerable to the effects of age-related changes. We recently reported behavioral data indicating greater age differences in orbitofrontal tasks when directly compared to tasks tapping dorsolateral prefrontal functions. The present study was designed to investigate the neural underpinnings of age differences in OFC functioning. Event-related functional magnetic resonance imaging (fMRI) was performed during delayed match and nonmatch to sample tasks, previously shown to differentially activate medial and lateral OFC in young adults. Sixteen healthy younger [age = 26.7(5.6)] and 16 healthy older individuals [age = 69.1 + 5.6] with similar levels of education and general cognitive functioning participated in the experiment. Participants chose the stimulus from a pair of stimuli matching a previously viewed target (match to sample) or chose the nontarget item (nonmatch to sample) depending upon a trial-specific instruction word. Consistent with previous studies, SPM99 analyses of the younger age group revealed activation for medial OFC regions during the match task compared to the nonmatch task and lateral OFC activation during the nonmatch task compared to the match task. In contrast, older adults showed prefrontal activation only during the match relative to the nonmatch task and posterior temporal and limbic involvement during the nonmatch relative to the match task. Between-group analyses confirmed within-group results suggesting differential age-related recruitment of prefrontal regions when performing match and nonmatch tasks. Results suggest that OFC recruitment during these cognitive tasks changes with age and should be evaluated within the context of other prefrontal subregions to further define differential age effects on frontal functions.

Adult↗
PubMed2004

Cortical surface segmentation and mapping.

Segmentation and mapping of the human cerebral cortex from magnetic resonance (MR) images plays an important role in neuroscience and medicine. This paper describes a comprehensive approach for cortical reconstruction, flattening, and sulcal segmentation. Robustness to imaging artifacts and anatomical consistency are key achievements in an overall approach that is nearly fully automatic and computationally fast. Results demonstrating the application of this approach to a study of cortical thickness changes in aging are presented.

Aging↗
PubMed2004

The Women's Health Initiative Study of Cognitive Aging (WHISCA): a randomized clinical trial of the effects of hormone therapy on age-associated cognitive decline.

The Women's Health Initiative Study of Cognitive Aging (WHISCA) was a two armed, randomized, placebo controlled, clinical trial designed to assess the efficacy of postmenopausal hormone therapy on age related changes in specific cognitive functions. WHISCA was an ancillary study to the Women's Health Initiative (WHI) and the WHI Memory Study (WHIMS) and enrolled 2302 women aged 66 to 84 years (mean 73.9; standard deviation 3.8) who did not meet criteria for dementia. Women were randomly assigned by the WHI to hormone treatment (unopposed conjugated estrogens (CEE) 0.625 mg/day if they were without a uterus; CEE combined with medroxyprogesterone acetate (MPA) 2.5 mg/day otherwise) or placebo for an average of three years before the first WHISCA assessment. WHISCA investigated the effects of hormone therapy on rates of change over time in memory, other aspects of cognition (language, attention, spatial ability), motor function, and mood. In this paper, we present the study rationale and design, including specific cognitive measures, and the challenges of incorporating WHISCA into an ongoing randomized trial. WHISCA provided a unique opportunity to investigate the potential of hormone therapy to modify age related changes in specific cognitive functions. WHISCA also demonstrated the feasibility of adding a detailed cognitive assessment into an ongoing clinical trial to address an important issue in women's health, despite the challenges of maintaining the integrity of the parent studies, ensuring high retention, and achieving high quality assurance across sites.

Age Factors↗
PubMed2003

Longitudinal magnetic resonance imaging studies of older adults: a shrinking brain.

Age-related loss of brain tissue has been inferred from cross-sectional neuroimaging studies, but direct measurements of gray and white matter changes from longitudinal studies are lacking. We quantified longitudinal magnetic resonance imaging (MRI) scans of 92 nondemented older adults (age 59-85 years at baseline) in the Baltimore Longitudinal Study of Aging to determine the rates and regional distribution of gray and white matter tissue loss in older adults. Using images from baseline, 2 year, and 4 year follow-up, we found significant age changes in gray (p < 0.001) and white (p < 0.001) volumes even in a subgroup of 24 very healthy elderly. Annual rates of tissue loss were 5.4 +/- 0.3, 2.4 +/- 0.4, and 3.1 +/- 0.4 cm3 per year for total brain, gray, and white volumes, respectively, and ventricles increased by 1.4 +/- 0.1 cm3 per year (3.7, 1.3, 2.4, and 1.2 cm3, respectively, in very healthy). Frontal and parietal, compared with temporal and occipital, lobar regions showed greater decline. Gray matter loss was most pronounced for orbital and inferior frontal, cingulate, insular, inferior parietal, and to a lesser extent mesial temporal regions, whereas white matter changes were widespread. In this first study of gray and white matter volume changes, we demonstrate significant longitudinal tissue loss for both gray and white matter even in very healthy older adults. These data provide essential information on the rate and regional pattern of age-associated changes against which pathology can be evaluated and suggest slower rates of brain atrophy in individuals who remain medically and cognitively healthy.

Age Factors↗
PubMed2003

Longitudinal changes in verbal memory in older adults: distinguishing the effects of age from repeat testing.

OBJECTIVE: To characterize the relationship between age-related memory change and repeat testing using serial administrations of the California Verbal Learning Test (CVLT) in 385 nondemented Baltimore Longitudinal Study of Aging participants aged 55 and older with two or more memory assessments. METHODS: The authors investigated longitudinal change and the effects of age, sex, education, and repeat testing on new learning and recall by analyzing measures of learning and interference, short- and long-delay free and cued recall, and recognition hits in separate mixed-effects regressions. RESULTS: The authors found cross-sectional effects of age (p < or = 0.001) and sex (p < or = 0.05) on learning and interference, regardless of baseline performance. Younger adults outperformed older adults, and women outperformed men. Longitudinal age changes were documented across total learning and long-delay free and cued recall regardless of baseline scores (p < or = 0.05). In addition, controlling for baseline scores enhanced the sensitivity for detection of longitudinal age changes on Trial 5, short-delay cued recall and recognition hits (p < or = 0.05). The influence of repeated administrations changed with advancing baseline age for total learning and short- and long-delay recall such that younger baseline age was associated with improvement over time whereas older baseline age was associated with decline over time. CONCLUSION: Longitudinal declines in CVLT performance exist in normal aging and are influenced by baseline age. Furthermore, failure to account for the influence of repeat testing with aging may decrease sensitivity to detect pathologic decline.

Age Factors↗
PubMed2002

Measuring size and shape of the hippocampus in MR images using a deformable shape model.

A method for segmentation and quantification of the shape and size of the hippocampus is proposed, based on an automated image analysis algorithm. The algorithm uses a deformable shape model to locate the hippocampus in magnetic resonance images and to determine a geometric representation of its boundary. The deformable model combines three types of information. First, it employs information about the geometric properties of the hippocampal boundary, from a local and relatively finer scale to a more global and relatively coarser scale. Second, the model includes a statistical characterization of normal shape variation across individuals, serving as prior knowledge to the algorithm. Third, the algorithm utilizes a number of manually defined boundary points, which can help guide the model deformation to the appropriate boundaries, wherever these boundaries are weak or not clearly defined in MR images. Excellent agreement is demonstrated between the algorithm and manual segmentations by well-trained raters, with a correlation coefficient equal to 0.97 and algorithm/rater differences statistically equivalent to interrater differences for manual definitions.

Algorithms↗
PubMed2002

Effects of age on virtual environment place navigation and allocentric cognitive mapping.

This study assessed age differences in navigational behavior in a virtual Morris water maze (vMWM) and examined the ability of older adults to develop cognitive maps after vMWM experience. Compared with younger participants, older volunteers traversed a longer linear distance to locate the hidden platform. On the probe trial, younger volunteers spent a greater proportion of their total distance traveled in proximity to the platform and had more platform intersections. Analysis of map reproductions demonstrated that older participants used proximal objects to locate the goal but did not use room-geometry cues to aid navigation. These findings demonstrate age-related deficits on a laboratory measure of place learning and suggest that deficiencies in allocentric mapping may contribute to these deficits.

Adult↗
PubMed2002

Degenerative age changes in white matter connectivity visualized in vivo using magnetic resonance imaging.

Age effects on the signal characteristics of white matter (WM) were examined via magnetic resonance imaging (MRI). Global and local patterns of WM degeneration were demonstrated using a new image analysis methodology. Significant cross-sectional and longitudinal age effects were found in the WM, primarily in the left hemisphere. Importantly, signal changes, which likely reflect WM demyelination, and changes in water, protein and mineral content of tissue, were unrelated to volumetric changes. Thus, measures of tissue characteristics provide unique and complementary information to widely used measures of brain atrophy. Moreover, signal measurements displayed stronger associations with age and can potentially be more sensitive than volumetric measures as indicators of preclinical disease, because they reflect changes in the underlying tissue composition. To our knowledge, our study is the first documentation of longitudinal age- and region-dependent changes in magnetic resonance signal characteristics of WM fibers, reflecting underlying degenerative effects of aging.

Aged↗
PubMed2002

Longitudinal assessment of serum free testosterone concentration predicts memory performance and cognitive status in elderly men.

Circulating testosterone (T) levels have behavioral and neurological effects in both human and nonhuman species. Both T concentrations and neuropsychological function decrease substantially with age in men. The purpose of this prospective, longitudinal study was to investigate the relationships between age-associated decreases in endogenous serum T and free T concentrations and declines in neuropsychological performance. Participants were volunteers from the Baltimore Longitudinal Study of Aging, aged 50-91 yr at baseline T assessment. Four hundred seven men were followed for an average of 10 yr, with assessments of multiple cognitive domains and contemporaneous determination of serum total T, SHBG, and a free T index (FTI). We administered neuropsychological tests of verbal and visual memory, mental status, visuomotor scanning and attention, verbal knowledge/language, visuospatial ability, and depressive symptomatology. Higher FTI was associated with better scores on visual and verbal memory, visuospatial functioning, and visuomotor scanning and a reduced rate of longitudinal decline in visual memory. Men classified as hypogonadal had significantly lower scores on measures of memory and visuospatial performance and a faster rate of decline in visual memory. No relations between total T or the FTI and measures of verbal knowledge, mental status, or depressive symptoms were observed. These results suggest a possible beneficial relationship between circulating free T concentrations and specific domains of cognitive performance in older men.

Aged↗