Human Factors and Aging: Identifying and Compensating for Age-related Deficits in Sensory and Cognitive Function.

Introduction Human factors is an interdisciplinary field organized around the central endeavor of fitting the designed environment to the individual. The process of achieving optimal person-environment interaction requires knowledge about the broad range of human functional capacity; including --but not limited to --anthropometry, biomechanics, sensory processes and cognitive psychology. It has been said that "theory and practice are the same in theory but different in practice". Nowhere is this predicament more true than in the field of human factors. Although primarily regarded as an applied field of science, those who practice human factors on a daily basis must rely heavily upon theory and principles generated through basic research. This reliance upon sound theoretical constructs is made necessary by the fact that design solutions to person-environment interface problems rarely generalize across situations. Rather, it is the theoretical constructs that explain human behavior and the principles they generate that are transferable across design domains. Thus, human factors as a practice is intimately bound to its theoretical principles. Practice cannot proceed without theory. This chapter attempts to provide the reader with a introduction to the theoretical principles of experimental psychology as they relate to the more specific domain of aging and technology. This survey is limited in its scope in so far as it pertains only to the area of cognitive psychology. As such, it explores the age-related changes in sensory processes, attention and memory that present challenges to an older person's ability to 2 interact with his or her environment. Some opportunities for applying this knowledge toward the optimization of the person-environment interface are presented. Hopefully, the basic research findings and principles reviewed herein --and the accompanying examples and recommendations for improving functional capacity --will inspire the reader to generate innovative approaches toward designing a better fit between the designed environment and persons of all ages. Vision Anatomical Changes The maximum diameter of the pupil declines with advancing adult age (a condition known as senile miosis). Under low light conditions, the resting diameter of the pupil falls from 7 mm at age 20 to approximately 4 mm at 80 years of age Although senile miosis reduces the amount of light reaching the retina, there is reason to suspect that smaller pupil diameters may actually benefit visual performance in older adults in many situations by increasing the contrast of the retinal image (see Sloane, Owlsey & Alvarez, 1988). The crystalline lens of the eye becomes increasingly opaque as individuals grow older. This loss of transparency appears to be particularly pronounced at short wavelengths; that is, for blue light At the level of the retina, there is some evidence of photoreceptor and ganglion cell loss with advancing age (e.g., Oculomotor Function Small but systematic declines in the latency, velocity and accuracy of saccadic eye movements have been observed among older adults (e.g., Studies of pursuit eye movements show that younger observers can accurately track targets with angular velocities up to 30 degrees per second whereas pursuit accuracy among older observers breaks down for targets exceeding 10 degrees per second The regulation of eye movements is strongly influenced by vestibular processes (i.e., input from the organ of "balance" located within the inner ear). Several studies have demonstrated that vestibular contributions to ocular function break down among older adults (e.g., Dark Adaptation The sudden transition from a high level of ambient illumination to a very low one is accompanied by a significant reduction in visual sensitivity. Some portion of this loss in light sensitivity is typically recovered once the visual system has had a chance to adapt to the lower level of illumination. Such dark adaptation processes occur in two phases: a photopic phase (cone vision) lasting 6-8 minutes and a concomitant scotopic phase (rod vision) extending approximately 30 minutes 6 Visual Acuity Visual acuity is a measure of the visual system's ability to resolve fine spatial detail. The ability to resolve well-illuminated, high-contrast spatial features which subtend a visual angle of 1 minute of arc (minarc) represents normal (i.e., 20/20 Snellen) acuity. Since the crystalline lens of the eye must accommodate, or change shape, in order to focus on near targets, separate visual acuities for near (16 inches) versus far (20 feet) targets are often measured. Since small amounts of refractive error in the eye yield reliable decrements in acuity, the acuity test has been widely adopted as the basis for correcting optical aberrations of the eye with eyeglasses or contact lenses Near acuity. The human eye is "designed" to focus upon objects that are 20 feet (or farther) away. In order to clearly focus light coming from objects closer than 20 feet, the crystalline lens within each eye needs to increase its light refracting power by bending itself into a more convex shape. As noted above, the crystalline lens becomes less capable of bending as we grow older (i.e., presbyopia). Consequently, by the mid-forties people begin to have difficulty focusing upon printed text that is closer than 'arm's length' in distance 7 Far acuity. Until around 70 years of age, the vast majority of problems leading to diminished (far) visual acuity are due to refractive errors that can be corrected using eyeglasses or contact lenses Age deficits in visual acuity, in both healthy and pathological eyes, are exacerbated under challenging viewing conditions. Haegerstrom-Pornoy, These visual disabilities in the presence of glare are especially problematic for low contrast stimuli Contrast Sensitivity The capacity to visually detect and identify spatial forms varies as a function of target size, orientation and contrast Studies of age differences in the contrast sensitivity function reveal that older adults demonstrate weakened visual sensitivity for stimulus objects much larger than those they can recognize on a standard acuity test (e.g., The additional information provided by the contrast sensitivity function -relative to simple measures of acuity -has extended and improved the ability to predict and explain age differences in real-world visual performance (e.g., Dewar, Peripheral Vision The spatial resolving powers of the visual system decline markedly as targets move away from central vision into the peripheral visual field. Letter size must be increased by a factor of 0.046 (i.e., 2.7 minarc must be added to the height of a letter) for every degree of eccentricity away from the point of fixation Motion Perception Numerous studies have demonstrated age-related decrements in motion sensitivity and/or the accuracy of speed perception. Yet, the nature and the magnitude of these effects vary tremendously across investigations (see Color Vision Normal observers are capable of distinguishing among more than 100,000 hues in side by side comparisons Dalderup and Fredricks (1969) reported notable age-related deficiencies in color discrimination ability among those over 70 years of age. Gilbert (1957) conducted a large-scale study of color discrimination ability in observers ranging from 10 to 93 years of age. Although all observers demonstrated more discrimination errors among blues and greens (shorter wavelengths) than among yellows and reds on a hue sequential ordering task, this increased tendency to "confuse" related shades within the blue-green range was especially pronounced among older observers. Numerous other studies have reported that age-related declines in color discrimination are more pronounced for hues in the 12 short wavelength region of the spectrum (e.g., Eisner, Fleming, However, more recent investigations suggest this phenomenon may result from a differential loss of sensitivity in short-wavelength photoreceptors and/or their opponent neural projections to the brain As with other visual functions, age-related deficits in color discrimination are exacerbated under low light conditions (e.g., Although the magnitude of the age-related decrements in blue-green color discrimination noted above is small, Cody, Hurd & Bootman (1990) demonstrated that a significant proportion of older adults made errors when trying to distinguish between medicine capsules with similar color-coded markings. Findings like those reported by Knoblauch, et al. (1997) suggest that such errors can probably be minimized when more optimal lighting conditions are employed. Finally, a recent investigation by 13 Compensating for Age-Related Visual Deficits The age differences in the structure and function of the visual system outlined above suggest numerous opportunities for enhancing performance via optimized design. Some guidelines for achieving these ends are listed below. Additional details regarding the optimization of visual environments for older persons can be found in 1. In general, increased levels of ambient and task illumination are required to optimized visual performance for older adults. Increased illumination helps overcome the opacity of the ocular media and is known to mitigate age differences in text legibility, object recognition and color discrimination. 2. Increased levels of luminance contrast are required to meet the visual needs of older persons. 3. Minimize the need to perform "near" work. When close-up work cannot be avoided, older persons should be fitted with eyeglasses optimized for the specific working distance required by the task. 4. Chose text font sizes of at least 12 points in character height to accommodate the needs of those 60-75 years of age. Font heights of 18 points are required to accommodate the needs of the 85th percentile 80 year-old 5. Deploy lighting strategies that minimize the opportunity for disability glare effects. Avoid narrow angles of incidence and/or use indirect lighting schemes where possible. Special text fonts have been developed that mitigate age-related reductions in legibility due to a form of disability glare known as irradiation effects (i.e., the Clearview™ highway sign font; see Garvey, Pietrucha & Meeker, 1998 ). 6. Minimize dependence upon peripheral vision. 7. Adopt marking strategies that enhance motion perception and/or speed estimation capabilities. For example, the use of vehicle daytime running lights may provide disproportionate performance and safety benefits for older drivers ( see Koorstra, Bijleveld & Hagenzieker, 1997). 14 8. Use larger color contrast steps when discrimination between short wavelength (blue, green) colors is required. 9. Explore the use of computer-based image processing techniques for optimizing the legibility of spatial form (e.g., the recursive-blur optimization technique -see Schieber, 1998). Hearing Anatomical Changes Age-related changes in the outer ear which might potentially impair hearing function include excess accumulations of ear wax which could block the auditory canal (Corso, 1963) as well as a tendency for the auditory canal to narrow or collapse (Schow, Christensen, Hutchinson & Nerbonne, 1978). In the middle ear, the joints connecting the ossicular bones (malleus, incus and stapes) tend to become arthritic and less elastic with advancing age 15 Absolute Sensitivity Adult aging is associated with a significant increase in the stimulus intensity required to detect a sound. This age-related loss of sensitivity (known as presbycusis) is especially pronounced for high-frequency sounds Frequency and Intensity Discrimination The ability to discriminate small changes in the frequency or intensity of sounds is an important subcomponent of complex auditory processing tasks such as speech recognition and sound localization (Corso, 1981). Numerous studies have reported agerelated decrements in these abilities (e.g., Cranford & Stream, 1991; Sound Localization Localization of a sound source is heavily dependent upon the auditory system's ability to process and interpret small differences in intensity and/or time-of-arrival between the two ears Speech Recognition Many studies have reported age-related decrements in speech perception. Particularly dramatic effects have been reported in the classic study by Jerger (1973) who found that speech recognition for monosyllabic words decreased from just below 100% at 20 years 17 of age to less than 60% correct for those 80-89 years of age. Age-related decrements in speech intelligibility are exacerbated under challenging listening conditions such as background noise Age-related decrements in the ability to understand speech can be mitigated somewhat when stimulus intensity levels are increased substantially -suggesting that much of the age-related decrement is mediated by peripheral rather than central mechanisms (GordonSalant, 1987). However, age-related decrements in the perception of "speeded speech", which are remarkably robust, appear to be mediated by central mechanisms as they are not mitigated by increased stimulus intensity level (e.g., What remains to be established is the "attentional costs" of such compensatory processes. Compensating for Age-Related Hearing Deficits The age differences in the structure and function of the auditory system outlined above suggest several opportunities for enhancing performance via optimized design. Some guidelines for achieving these ends are listed below. Additional information regarding the optimization of auditory environments for older persons can be found in 1. Increase stimulus intensity. Age-related declines in auditory perception, including speech recognition, are often mitigated by increasing stimulus volume. 2. Control background noise. Age differences in auditory perception are exacerbated in the presence of background noise. Background noise can be reduced at the source (e.g., replacing noisy heating/air-conditioning equipment with more quiet models) and through the careful selection of architectural elements that reduce reverberation or absorb stray acoustic energy, etc. 3. Avoid the need to detect and/or recognize high-frequency acoustic information. 4. Long-term exposure to high levels of noise (i.e., 88 dB or greater) should be avoided across the life span in order to minimize the cumulative effects of presbycusis. 5. Avoid the need to spatially localize low-frequency sound sources. When this cannot be avoided, provide redundant localization cues such as warning signs or flashing lights. 6. Speech recognition can be significantly enhanced through the use of semantically well-structured prose that is rich in context and redundant. 19 7. Speech recognition among older adults is improved when presented at a reasonable and consistent pace. 8. Technological advances in hearing aid development need to be complemented by proper training of users and compensatory adjustments based upon user feedback. Without such a systems approach, 25-50% of persons fitted with hearing aids refuse to wear them due to various complaints related to comfort and/or function (see Fozard & Gordon-Salant, in press). 9. Embedded computer systems with real-time signal processing capabilities should be combined with the increasingly ubiquitous internet infrastructure (in public and commercial buildings) to provide anytime/anywhere assistive listening support to older adults and other hearing impaired individuals. Attention Attention is a nebulous yet central construct for modern cognitive science. It at once encompasses both the capacity and component operations of human information processing. That is, attention is comprised of both "resources" and "processes". An essential characteristic of attention is that it is highly limited. As such, its functional capacity (i.e., efficiency) can benefit greatly from the application of top-down management or "executive control". These interacting aspects of attention can be organized into four functional categories: (1) attention span, (2) selective attention, Attention Span (or Useful Field of View) Binocular light sensitivity extends across the full (150-180 degree) field of peripheral vision. However, the ability to accurately identify and discriminate visual stimul

Effectiveness of Direct Laser Interference Patterning and Peptide Immobilization on Endothelial Cell Migration for Cardio-Vascular Applications: An In Vitro Study

Endothelial coverage of an exposed cardiovascular stent surface leads to the occurrence of restenosis and late-stent thrombosis several months after implantation. To overcome this difficulty, modification of stent surfaces with topographical or biochemical features may be performed to increase endothelial cells’ (ECs) adhesion and/or migration. This work combines both strategies on cobalt-chromium (CoCr) alloy and studies the potential synergistic effect of linear patterned surfaces that are obtained by direct laser interference patterning (DLIP), coupled with the use of Arg-Gly-Asp (RGD) and Tyr-Ile-Gly-Ser-Arg (YIGSR) peptides. An extensive characterization of the modified surfaces was performed by using AFM, XPS, surface charge, electrochemical analysis and fluorescent methods. The biological response was studied in terms of EC adhesion, migration and proliferation assays. CoCr surfaces were successfully patterned with a periodicity of 10 µm and two different depths, D (≈79 and 762 nm). RGD and YIGSR were immobilized on the surfaces by CPTES silanization. Early EC adhesion was increased on the peptide-functionalized surfaces, especially for YIGSR compared to RGD. High-depth patterns generated 80% of ECs’ alignment within the topographical lines and enhanced EC migration. It is noteworthy that the combined use of the two strategies synergistically accelerated the ECs’ migration and proliferation, proving the potential of this strategy to enhance stent endothelialization

Effectiveness of Direct Laser Interference Patterning and Peptide Immobilization on Endothelial Cell Migration for Cardio-Vascular Applications: An In Vitro Study

Endothelial coverage of an exposed cardiovascular stent surface leads to the occurrence of restenosis and late-stent thrombosis several months after implantation. To overcome this difficulty, modification of stent surfaces with topographical or biochemical features may be performed to increase endothelial cells’ (ECs) adhesion and/or migration. This work combines both strategies on cobalt-chromium (CoCr) alloy and studies the potential synergistic effect of linear patterned surfaces that are obtained by direct laser interference patterning (DLIP), coupled with the use of Arg-Gly-Asp (RGD) and Tyr-Ile-Gly-Ser-Arg (YIGSR) peptides. An extensive characterization of the modified surfaces was performed by using AFM, XPS, surface charge, electrochemical analysis and fluorescent methods. The biological response was studied in terms of EC adhesion, migration and proliferation assays. CoCr surfaces were successfully patterned with a periodicity of 10 µm and two different depths, D (≈79 and 762 nm). RGD and YIGSR were immobilized on the surfaces by CPTES silanization. Early EC adhesion was increased on the peptide-functionalized surfaces, especially for YIGSR compared to RGD. High-depth patterns generated 80% of ECs’ alignment within the topographical lines and enhanced EC migration. It is noteworthy that the combined use of the two strategies synergistically accelerated the ECs’ migration and proliferation, proving the potential of this strategy to enhance stent endothelialization

Accurate method for the Brownian dynamics simulation of spherical particles with hard-body interactions

In Brownian Dynamics simulations, the diffusive motion of the particles is simulated by adding random displacements, proportional to the square root of the chosen time step. When computing average quantities, these Brownian contributions usually average out, and the overall simulation error becomes proportional to the time step. A special situation arises if the particles undergo hard-body interactions that instantaneously change their properties, as in absorption or association processes, chemical reactions, etc. The common "naive simulation method" accounts for these interactions by checking for hard-body overlaps after every time step. Due to the simplification of the diffusive motion, a substantial part of the actual hard-body interactions is not detected by this method, resulting in an overall simulation error proportional to the square root of the time step. In this paper we take the hard-body interactions during the time step interval into account, using the relative positions of the particles at the beginning and at the end of the time step, as provided by the naive method, and the analytical solution for the diffusion of a point particle around an absorbing sphere. Ottinger used a similar approach for the one-dimensional case [Stochastic Processes in Polymeric Fluids (Springer, Berlin, 1996), p. 270]. We applied the "corrected simulation method" to the case of a simple, second-order chemical reaction. The results agree with recent theoretical predictions [K. Hyojoon and Joe S. Kook, Phys. Rev. E 61, 3426 (2000)]. The obtained simulation error is proportional to the time step, instead of its square root. The new method needs substantially less simulation time to obtain the same accuracy. Finally, we briefly discuss a straightforward way to extend the method for simulations of systems with additional (deterministic) forces. (C) 2002 American Institute of Physics

Enhancement of biomimetic enzymatic mineralization of gellan gum polysaccharide hydrogels by plant-derived gallotannins

Mineralization of hydrogel biomaterials with calcium phosphate (CaP) is considered advantageous for bone regeneration. Mineralization can be both induced by the enzyme alkaline phosphatase (ALP) and promoted by calcium-binding biomolecules, such as plant-derived polyphenols. In this study, ALP-loaded gellan gum (GG) hydrogels were enriched with gallotannins, a subclass of polyphenols. Five preparations were compared, namely three tannic acids of differing molecular weight (MW), pentagalloyl glucose (PGG), and a gallotannin-rich extract from mango kernel (Mangifera indica L.). Certain gallotannin preparations promoted mineralization to a greater degree than others. The various gallotannin preparations bound differently to ALP and influenced the size of aggregates of ALP, which may be related to ability to promote mineralization. Human osteoblast-like Saos-2 cells grew in eluate from mineralized hydrogels. Gallotannin incorporation impeded cell growth on hydrogels and did not impart antibacterial activity. In conclusion, gallotannin incorporation aided mineralization but reduced cytocompatibility

Cerebral activations related to ballistic, stepwise interrupted and gradually modulated movements in parkinson patients

Patients with Parkinson's disease (PD) experience impaired initiation and inhibition of movements such as difficulty to start/stop walking. At single-joint level this is accompanied by reduced inhibition of antagonist muscle activity. While normal basal ganglia (BG) contributions to motor control include selecting appropriate muscles by inhibiting others, it is unclear how PD-related changes in BG function cause impaired movement initiation and inhibition at single-joint level. To further elucidate these changes we studied 4 right-hand movement tasks with fMRI, by dissociating activations related to abrupt movement initiation, inhibition and gradual movement modulation. Initiation and inhibition were inferred from ballistic and stepwise interrupted movement, respectively, while smooth wrist circumduction enabled the assessment of gradually modulated movement. Task-related activations were compared between PD patients (N = 12) and healthy subjects (N = 18). In healthy subjects, movement initiation was characterized by antero-ventral striatum, substantia nigra (SN) and premotor activations while inhibition was dominated by subthalamic nucleus (STN) and pallidal activations, in line with the known role of these areas in simple movement. Gradual movement mainly involved antero-dorsal putamen and pallidum. Compared to healthy subjects, patients showed reduced striatal/SN and increased pallidal activation for initiation, whereas for inhibition STN activation was reduced and striatal-thalamo-cortical activation increased. For gradual movement patients showed reduced pallidal and increased thalamo-cortical activation. We conclude that PD-related changes during movement initiation fit the (rather static) model of alterations in direct and indirect BG pathways. Reduced STN activation and regional cortical increased activation in PD during inhibition and gradual movement modulation are better explained by a dynamic model that also takes into account enhanced responsiveness to external stimuli in this disease and the effects of hyper-fluctuating cortical inputs to the striatum and STN in particular

Non-Invasive In Vivo Imaging of Calcium Signaling in Mice

Rapid and transient elevations of Ca2+ within cellular microdomains play a critical role in the regulation of many signal transduction pathways. Described here is a genetic approach for non-invasive detection of localized Ca2+ concentration ([Ca2+]) rises in live animals using bioluminescence imaging (BLI). Transgenic mice conditionally expressing the Ca2+-sensitive bioluminescent reporter GFP-aequorin targeted to the mitochondrial matrix were studied in several experimental paradigms. Rapid [Ca2+] rises inside the mitochondrial matrix could be readily detected during single-twitch muscle contractions. Whole body patterns of [Ca2+] were monitored in freely moving mice and during epileptic seizures. Furthermore, variations in mitochondrial [Ca2+] correlated to behavioral components of the sleep/wake cycle were observed during prolonged whole body recordings of newborn mice. This non-invasive imaging technique opens new avenues for the analysis of Ca2+ signaling whenever whole body information in freely moving animals is desired, in particular during behavioral and developmental studies