Brain magnetic resonance imaging (MRI) has been used in epidemiologic studies to characterize subclinical brain disease, including white matter hyperintensity and ventricular enlargement. These markers relate cross-sectionally to physical performance, including gait and balance. Previous MRI reading techniques have defined these markers of brain disease with semiquantitative scoring derived from visual inspection. Recent reading techniques allow volumetric quantification of specific brain structures. Focal atrophy of cortical and subcortical areas might explain the association of these subclinical brain disease markers with mobility impairment in old age. Dr. Rosano has applied a novel volumetric method - the Automated Labeling Pathway (ALP) method - in a small set of brain MRIs from a large cohort study, the Cardiovascular Health Study (CHS), demonstrating its feasibility and suitability for large population studies. She now proposes to extend this pilot to measure brain volumes in at least 300 of these previously collected images. She will determine if focal atrophy in regions related to motor control can discriminate individuals with mobility limitation and can explain the previous associations with white matter hyperintensities and ventricular enlargement.
Specific aims include:

1. To determine if focal gray matter atrophy (basal ganglia, brain stem, frontal lobes, cerebellum) and periventricular white matter atrophy is greater in older adults with mobility limitation compared to functionally intact older adults.
2. To determine if focal gray matter atrophy and periventricular white matter atrophy are related to semiquantitative measures of white matter hyperintensity and ventricular enlargement from previous CHS readings.
3. To determine if focal gray matter atrophy and white matter atrophy explain the previous findings of associations of ventricular enlargement and white matter hyperintensities with slower gait speed and poorer balance.

When an older person faces a changing sensory environment, aging related reductions in sensory function, slowing of central integration processes, and sub-optimal motor output may result in a potentially destabilizing postural response. Expectation may also modify postural responses to a changing environment. Moving visual environments such as busy stores or walkways are examples of changing sensory environments that are common challenges for older adults. The primary objective of this pilot research is to develop novel experimental protocols to examine how older adults respond to sudden changes in the moving visual environment using a virtual reality setting.
The proposed protocols will evaluate postural adaptations due to modification of moving visual inputs. Healthy younger (21-40 years) and older (65+ years) community-dwelling adults will first experience steady-state sinusoidal optic flow stimulation. After subjects have achieved a steady-state postural response, perturbations in amplitude or velocity of the visual stimulus will be made. Changes in the postural response during the perturbation will be assessed by measuring the center of pressure and head sway. The influence of expectation will be examined by comparing responses to perturbations that have a different amplitude or velocity of visual stimulus from the previous trial.
The specific aims of the study are to:

1. Examine the effect of sudden changes in moving visual input on postural responses by measuring within-trial changes in postural sway.


2. Examine the effect of expectation by measuring between-trial postural sway changes to moving visual perturbations.


3. Determine the feasibility of using the protocols in healthy older adults, so that populations of older adults with clinical impairments can be tested.

The purpose of this Developmental Study is to evaluate a novel series of noninvasive tests of vestibulo-ocular function, the Dynamic Visual Acuity test and the Gaze Stabilization Test, using the inVision System. These tests have potential for use in older adults in non-laboratory settings but have not previously been evaluated in older adults. For this pilot study, 20 young and 20 older adults who have undergone previous full assessments of vestibular function will undergo clinical assessment of balance, function and fear of falling and will then carry out the two tasks. The inVision system, made up of computer generated projections of optotype “E”s onto a screen and a head sensor. It assesses visual acuity while actively moving the head and determines the maximum range of head movement about a specified axis at which a patient is able to maintain visual acuity.

White matter hyperintensities (WMH) are well known markers of subclinical cerebrovascular brain disease and are associated with measures of upper and lower extremity performance, including gait and balance. WMH may reflect disruption of the myelin ensheathing cortico-cortical or fronto-subcortical neuronal networks subsequent to ischemia or it may follow neuronal degeneration of the regions of origin. To verify the mechanism linking WMH and mobility impairment, it is first necessary to measure the spatial localization and volume of white matter hyperintensities in association with focal gray matter volumes. Dr Aizenstein has developed one such technique, the Automated Labeling Pathway (ALP), to measure focal gray matter volume in an automated fashion.