No abstract

We present a novel data smoothing and analysis framework for cortical thickness data defined on the brain cortical manifold. Gaussian kernel smoothing, which weights neighboring observations according to their 3D Euclidean distance, has been widely used in 3D brain images to increase the signal-to-noise ratio. When the observations lie on a convoluted brain surface, however, it is more natural to assign the weights based on the geodesic distance along the surface. We therefore develop a framework for geodesic distance-based kernel smoothing and statistical analysis on the cortical manifolds. As an illustration, we apply our methods in detecting the regions of abnormal cortical thickness in 16 high functioning autistic children via random field based multiple comparison correction that utilizes the new smoothing technique.

We present a unified statistical approach to deformation-based morphometry applied to the cortical surface. The cerebral cortex has the topology of a 2D highly convoluted sheet. As the brain develops over time, the cortical surface area, thickness, curvature and total gray matter volume change. It is highly likely that such age-related surface changes are not uniform. By measuring how such surface metrics change over time, the regions of the most rapid structural changes can be localized. We avoided using surface flattening, which distorts the inherent geometry of the cortex in our analysis and it is only used in visualization. To increase the signal to noise ratio, diffusion smoothing, which generalizes Gaussian kernel smoothing to an arbitrary curved cortical surface, has been developed and applied to surface data. Afterwards, statistical inference on the cortical surface will be performed via random fields theory. As an illustration, we demonstrate how this new surface-based morphometry can be applied in localizing the cortical regions of the gray matter tissue growth and loss in the brain images longitudinally collected in the group of children and adolescents.

A number of reports indicate an extremely low running-related injury frequency in barefoot populations in contrast to reports about shod populations. It is hypothesized that the adaptations which produce shock absorption, an inherent consequence of barefoot activity and a mechanism responsible for the low injury frequency in unshod populations, are related to deflection of the medial longitudinal arch of the foot on loading. It is also hypothesized that the known inability of this arch of the shod foot to deflect without failure (foot rigidity) is responsible for the high injury frequency in shod populations. To evaluate these hypotheses, 17 recreational runners were analyzed to study the adaptive pattern of the medial longitudinal arch of the foot due to increased barefoot weightbearing activity. Changes occurred in the medial longitudinal arch which allowed deflection of this arch on loading which substantiated the hypotheses. Other evidence suggests that sensory feedback largely from the glabrous epithelium of the foot is the element of barefoot activity which induced these adaptations. The sensory insulation inherent in the modem running shoe appears responsible for the high injury frequency associated with running. The injuries are considered "pseudo-neuropathic" in nature.

Ankle sprains are common sports injuries. Inadequate foot position awareness is thought to be the fundamental cause of these injuries. Ankle taping may decrease risk of injury through improving foot position awareness. The benefit of taping is thought to decrease with duration of exercise because of poor tape adherence to human skin. This study was a randomized, crossover, controlled comparison experiment that tested the hypothesis that ankle taping improves foot position awareness before and after exercise. A sample of 24 healthy young blindfolded volunteers, wearing their own athletic shoes, indicated perceived slope direction and estimated slope amplitude when bearing full body weight and standing on a series of blocks. The top slope of the blocks varied between 00 and 250, in 2.50 increments, to orient the plantar surface with respect to the leg toward pronation, supination, plantarflexion, and dorsiflexion, relative to its position on a flat surface. Foot position awareness, which was considered the reciprocal of surface slope estimate error, varied with testing condition, particularly when surface slope was greater than 100, presumably the most important range considering ankle injuries. In this higher range absolute position error was 4.230 taped, and 5.530 untaped (P < 0.001). Following exercise, in the higher range absolute position error was 2.5 % worse when taped and 35.5 % worse when untaped (P < 0.001). These data support the hypothesis that ankle taping improves proprioception before and after exercise. They also indicate that foot position awareness declines with exercise. Compared to barefoot data (position error 1.9 70), foot position error was 107.5 % poorer with athletic footwear when untaped (absolute position error 4. 110), and 58.1% worse when taped (position error 3.130). This suggests that ankle taping partly corrects impaired proprioception caused by modem athletic footwear and exercise. Footwear could be optimized to reduce the incidence of these injuries.

Abstract. Spatial normalization is a key process in cross-sectional studies of brain structure and function using MRI, fMRI, PET and other imaging techniques. A wide range of 3D image deformation algorithms have been developed, all of which involve design choices that are subject to debate. Moreover, most have numerical parameters whose value must be specified by the user. This paper proposes a principled method for evaluating design choices and choosing parameter values. This method can also be used to compare competing spatial normalization algorithms. We demonstrate the method through a performance analysis of a particular nonaffine deformation algorithm, ANIMAL.

We examined the hypothesis that awareness of foot position in terms of the slope of the weight-bearing surface declines with age. We further postulated that the decline would be due to a change in plantar tactile sensibility, and that footwear would further impair position judgments. We compared 15 men aged over 65 years (mean age 73) with 36 men aged under 40 (mean age 30) in terms of estimates of amplitude and direction of surface slopes. We employed a ratio scale of 0-10 representing actual slopes of 0 degrees-25 degrees in increments of 2.5 degrees. In order to examine whether subjects overestimated high angles they were told that the scale ranged from 0 to 15. We found significant differences between the two groups in terms of estimates and the effect of footwear. Psychophysical functions for estimate of slope were 0.95 for the young when barefoot and 0.71 when shod compared with 0.80 and 0.81 respectively for the older men. We conclude that sensitivity to foot position declines with age, mainly owing to loss of plantar tactile sensitivity. Footwear impairs foot position awareness in both young and old. Loss of foot position awareness may contribute to the frequency of falls in later life.

For optimal stability, shoes with thin, hard soles are preferable for older individuals. Health professionals should exercise caution when recommending shoes with thick, yielding midsoles, such as running shoes, to unstable elderly individuals. Older men and women with a history of falls or who are obviously unstable, should avoid barefoot locomotion.