Effect of aging on the subjective magnitude of vibration

Two groups of subjects were tested using the method of Absolute Magnitude Estimation (AME) to determine the effect of age on the subjective intensity of vibration delivered to the skin of the hand. The mean age of the younger group was 23.5 years and that of the older group was 68.6 years. Average thresholds in the older group were higher in both the Pacinian (P) and non-Pacinian channel (NP II). The subjective magnitude of vibration was substantially lower at all intensities in the older group. Individual results clearly showed that the P channel saturates near the detection threshold of the NP II channel.     

The Effects of Aging on Information-Processing Channels in the Sense of Touch: I. Absolute Sensitivity

Thresholds for detecting vibrotactile signals of variable frequency applied to the thenar eminence of the hand by small and large contactors were measured in subjects ranging in age from 10 to 89 years. Thresholds were found to increase as a function of age, but the rate of increase was greater after than before the age of 65 years. The rate of loss of vibrotactile sensitivity was substantially greater in the P channel (mediated by Pacinian corpuscles) than in the NP I channel (mediated by rapidly adapting fibers), the NP II channel (mediated by slowly adapting type II fibers), or the NP HI channel (mediated by slowly adapting type I fibers). Women were frequently found to have greater sensitivity than men.     

Independent responses of Pacinian and Non-Pacinian systems with hand-transmitted vibration detected from masked thresholds

This study was designed to identify psychophysical channels responsible for the detection of hand-transmitted vibration. Perception thresholds for vibration (16, 31.5, 63 and 125?Hz sinusoidal for 600?ms) at the distal phalanx of the middle finger and the whole hand were determined with and without simultaneous masking stimuli (1/3 octave bandwidth Gaussian random vibration centered on either 16?Hz or 125?Hz for 3000?ms, varying in magnitude 0 to 30?dB above threshold). At all frequencies from 16 to 125?Hz, absolute thresholds for the hand were significantly lower than those for the finger. Changes in threshold as a function of masker level were used to estimate the thresholds of three psychophysical channels (i.e. P, NP I, and NP II channels). Increased vibrotactile sensitivity of the hand compared to the finger seems to be not entirely due to increased spatial summation via the Pacinian system (P channel); non-Pacinian system (NP I and NP II channels) also contributed to perception. Differing transmission of vibration between the hand and the finger may have also influenced the thresholds.     

Independent responses of Pacinian and Non-Pacinian systems with hand-transmitted vibration detected from masked thresholds

This study was designed to identify psychophysical channels responsible for the detection of hand-transmitted vibration. Perception thresholds for vibration (16, 31.5, 63 and 125 Hz sinusoidal for 600 ms) at the distal phalanx of the middle finger and the whole hand were determined with and without simultaneous masking stimuli (1/3 octave bandwidth Gaussian random vibration centered on either 16 Hz or 125 Hz for 3000 ms, varying in magnitude 0 to 30 dB above threshold). At all frequencies from 16 to 125 Hz, absolute thresholds for the hand were significantly lower than those for the finger. Changes in threshold as a function of masker level were used to estimate the thresholds of three psychophysical channels (i.e. P, NP I, and NP II channels). Increased vibrotactile sensitivity of the hand compared to the finger seems to be not entirely due to increased spatial summation via the Pacinian system (P channel); non-Pacinian system (NP I and NP II channels) also contributed to perception. Differing transmission of vibration between the hand and the finger may have also influenced the thresholds.     

Thresholds for the perception of hand-transmitted vibration: dependence on contact area and contact location

The detection of vibration applied to the glabrous skin of the hand varies with contact conditions. Three experiments have been conducted to relate variations in the perception of hand-transmitted vibration to previously reported properties of tactile channels. The effects of a surround around the area of contact, the size of the area of contact, the location of the area of contact, the contact force, and the hand posture on perception of thresholds were determined for 8-500 Hz vibration. Removal of a surround around a contact area on the fingertip elevated thresholds of the NP II channel (FA I fibres) at frequencies less than 31.5 Hz and reduced thresholds of the Pacinian channel (FA II fibres) at frequencies greater than about 63 Hz. When no surround was present, thresholds reduced systematically as the contact area increased from the fingertip to the whole hand at frequencies from 16 to 125 Hz, although the decrease was not inversely proportional to the increase in contact area. The results are partly explained by spatial summation in the Pacinian channel (FA II fibres) and the involvement of the NP II channel (SA II) with some influence of biodynamic responses and contact pressures. There were regional differences in sensitivity over the hand within the NP I channel but not within the Pacinian channel: the NP I thresholds (less than 31.5 Hz) decreased from proximal to distal regions of the hand, whereas the Pacinian thresholds (125 Hz) were independent of contact location over the hand.     

Effects of temperature on the subjective magnitude of vibration

Absolute magnitude estimation (AME) was used to determine the effects of skin temperature on the subjective magnitude of vibration delivered to the thenar eminence of the right hand. Measurements were made at three frequencies chosen to selectively activate cutaneous mechanoreceptor channels, namely NP I and NP III (Meissner and Merkel cell-neurite receptors, respectively) at 15 Hz, Pacinian (250 Hz, 400 Hz) and NP III (Ruffini endings) at 400 Hz. Skin temperatures at 15, 20 and 40 degrees C were tested at 11 suprathreshold displacement levels. It was concluded that the subjective magnitude of vibration is influenced by temperature in the Pacinian channel, but in the NP I and NP III channels the temperature of the skin did not have an effect upon judgements of subjective magnitude. This is consistent with earlier work by Verrillo and Bolanowski (J Acoust Soc Am 80: 528-532, 1986) and Bolanowski et al. (J Acoust Soc Am 84: 1680-1694, 1988); both studies show only modest effects of temperature at threshold at frequencies below approximately 40 Hz.     

A dose-response investigation of the benefits of napping in healthy young,middle-aged and older adults

Older adults experience more fragmented sleep, greater daytime sleepiness and, nap more often than younger adults. Little research has investigated the effects of napping on waking function in older adults. In the present study, waking cognitive performance was examined in 10 young (mean age = 28 years), 10 middle-aged (mean age = 42 years) and 12 older adults (mean age = 61 years) following 60-min, 20-min and no nap conditions. It was expected that the older adults would need a longer nap to accrue benefits. Napping led to improvements for all age groups in subjective sleepiness, fatigue and accuracy on a serial addition/subtraction task. Waking electroencephalogram (EEG) confirmed that the participants were more physiologically alert following naps. There were no age differences in subjective reports or cognitive tasks; however, older adults had higher beta and gamma in the waking EEG, suggesting that they needed increased effort to maintain performance. Overall, older adults had smaller P2 amplitudes, reflecting their difficulty in inhibiting irrelevant stimuli, and delayed latencies and smaller amplitude P300s to novel stimuli, reflecting deficits in their frontal lobe functioning. Although older adults did garner benefits from napping, there was no evidence that they required longer naps to experience improvement.

     

Effects of age,replicative lifespan and growth rate of human nucleus pulposus cells on selecting age range for cell-based biological therapies for degenerative disc diseases

Autologous disc cell implantation, growth factors and gene therapy appear to be promising therapies for disc regeneration. Unfortunately, the replicative lifespan and growth kinetics of human nucleus pulposus (NP) cells related to host age are unclear. We investigated the potential relations among age, replicative lifespan and growth rate of NP cells, and determined the age range that is suitable for cell-based biological therapies for degenerative disc diseases. We used NP tissues classified by decade into five age groups: 30s, 40s, 50s, 60s and 70s. The mean cumulative population doubling level (PDL) and population doubling rate (PDR) of NP cells were assessed by decade. We also investigated correlations between cumulative PDL and age, and between PDR and age. The mean cumulative PDL and PDR decreased significantly in patients in their 60s. The mean cumulative PDL and PDR in the younger groups (30s, 40s and 50s) were significantly higher than those in the older groups (60s and 70s). There also were significant negative correlations between cumulative PDL and age, and between PDR and age. We found that the replicative lifespan and growth rate of human NP cells decreased with age. The replicative potential of NP cells decreased significantly in patients 60 years old and older. Young individuals less than 60 years old may be suitable candidates for NP cell-based biological therapies for treating degenerative disc diseases.     

Age-related thermoregulatory differences during core cooling in humans

The current study assessed sympathetic neuronal and vasomotor responses, total body oxygen consumption, and sensory thermal perception to identify thermoregulatory differences in younger and older human subjects during core cooling. Cold fluid (40 ml/kg, 4 degrees C) was given intravenously over 30 min to decrease core temperature (Tc) in eight younger (age 18-23) and eight older (age 55-71) individuals. Compared with younger subjects, the older subjects had significantly lower Tc thresholds for vasoconstriction (35.5 +/- 0.3 vs. 36.2 +/- 0.2 degrees C, P = 0.03), heat production (35.2 +/- 0.4 vs. 35.9 +/- 0.1 degrees C, P = 0.04), and plasma norepinephrine (NE) responses (35.0 vs. 36.0 degrees C, P < 0.05). Despite a lower Tc nadir during cooling, the maximum intensities of the vasoconstriction (P = 0.03) and heat production (P = 0.006) responses were less in the older compared with the younger subjects, whereas subjective thermal comfort scores were similar. Plasma NE concentrations increased fourfold in the younger but only twofold in the older subjects at maximal Tc cooling. The vasomotor response for a given change in plasma NE concentration was decreased in the older group (P = 0.01). In summary, aging is associated with 1) a decreased Tc threshold and maximum response intensity for vasoconstriction, total body oxygen consumption, and NE release, 2) decreased vasomotor responsiveness to NE, and 3) decreased subjective sensory thermal perception.     

Evaluation of a fast forward rotating shift schedule in the steel industry with a special focus on ageing and sleep

The aim of this study was to explore the effect of a change in the speed and direction of shift rotation on the sleep and wakefulness of younger and older workers. A continuous three-shift schedule was changed from a slow backward rotating (EEE-MMMNNN-----) to a fast forward rotating system (MMEENN----). Sixteen subjects (mean age 42 years) were studied before and one year after the change in schedule. Two age groups were compared: ten younger men (mean age 35 years) and six older men (mean age 53 years). The effects of the new work schedule were evaluated by a questionnaire (modified SSI), and on-site registrations with an actigraph and sleep log for one shift cycle (10-15 days) before and after the new schedule. After the change in schedule, subjective sleep problems decreased and alertness increased during the morning shifts. The change in schedule influenced sleep differently in the two age-groups. Both the subjective and objective quality of sleep improved among the older workers. The results indicate that a fast forward rotating shift schedule is more suitable for older workers than a slower backward rotating system.     

The frequency selectivity of information-processing channels in the tactile sensory system

The frequency selectivity of the P, NP I, and NP II channels of the four-channel model of mechanoreception for glabrous skin was measured psychophysically by an adaptation tuning curve procedure. The results substantially extend the frequency range over which the frequency selectivity of these channels is known and further confirm the hypothesis that the input stage of each of these channels consists of specific sensory nerve fibers and associated receptors. Specifically, the frequency characteristics of Pacinian nerve fibers, rapidly adapting (RA) nerve fibers, and slowly adapting Type II (SA II) nerve fibers were found to be the peripheral neurophysiological correlates of the P, NP I, and NP II channels, respectively. The finding that the tuning characteristic for a test stimulus of 250 Hz delivered through a small (0.008 cm2) contactor depended dramatically on the duration of the test stimulus whereas the detection threshold did not, provides new evidence in support of the hypothesis that separate NP II and P channels exist.     

Effect of current and midlife obesity status on mortality risk in the elderly

The primary purpose of this study was to determine whether current and midlife obesity status provide independent information on mortality risk in elderly persons. Analyses were based on 3,238 participants from the original Framingham Heart Study (FHS) cohort who lived to at least 70 years of age and who had BMI measures from when they were in their 50s. Within this group of 70-year olds, obesity based on current BMI was associated with a 21% increased risk of mortality (P = 0.019) whereas obesity in 70-year olds based on BMI measures obtained at around 50 years of age was associated with a 55% increased risk of mortality (P < 0.0001). Compared to 70-year olds who were nonobese at both 50 and 70 years of age, mortality risk was increased by 47% (P < 0.001) in those who were obese at both 50 and 70 years of age, increased by 56% (P < 0.001) in those who were obese at 50 years of age and nonobese at 70 years of age, and not significantly different (P > 0.9) in those who were nonobese at 50 years of age and obese at 70 years of age. In summary, in this cohort of elderly adults, midlife and current BMI had independent effects on mortality risk. Specifically, although mortality risk was increased in obese older adults who were already obese at midlife, this was not the case for newly obese older adults. Conversely, nonobese older adults who were obese at midlife had an increased mortality risk. These observations imply that it is imperative to consider an elderly adult's BMI in context of their BMI at midlife.     

Pre-meal water consumption reduces meal energy intake in older but not younger subjects

Objective: To determine whether the consumption of water 30 minutes before an ad libitum meal reduces meal energy intake in young and older adults. Research Methods and Procedures: Healthy, non‐obese young (n = 29; age, 21 to 35 years) and older (n = 21; age, 60 to 80 years) individuals were provided with an ad libitum lunch meal on two occasions. Thirty minutes before the lunch meals, subjects were given either a water preload (WP: 375 mL, women; 500 mL, men) or no preload (NP). Energy intake at the two lunch meals was measured. Visual analog scales were used to assess changes in hunger, fullness, and thirst during the meal studies. Results: There was no significant difference in meal energy intake between conditions in the young subjects (892 + 51 vs. 913 ± 54 kcal for NP and WP, respectively; p = 0.65). However, meal energy intake after the WP was significantly reduced relative to the NP condition in the older subjects (682 + 53 vs. 624 ± 56 kcal for NP and WP, respectively; p = 0.02). This effect was caused primarily by the reduction in meal energy intake after water consumption in older men. Hunger ratings were lower and fullness ratings were higher in older compared with younger adults (p < 0.01). Fullness ratings were higher in the WP condition compared with the NP condition for all subjects (p = 0.01). No age differences in thirst were detected during the test meals. Discussion: Under acute test meal conditions, pre‐meal water consumption reduces meal energy intake in older but not younger adults. Because older adults are at increased risk for overweight and obesity, intervention studies are needed to determine whether pre‐meal water consumption is an effective long‐term weight management strategy for the aging population.     

Adolescents' Psychosocial Maturity,Problem Behavior,and Subjective Age: In Search of the Adultoid

The objectives of this study were to seek empirical confirmation for the existence of a group of adolescents whose maturity status could be labeled as adultoid, and to identify psychosocial correlates of adolescents' maturity status. Cluster analysis of questionnaire data from 209 predominantly White adolescents (10-18 years old) in working- and middle-class 2-parent families identified 3 maturity status groups: adultoids (low psychosocial maturity, high problem behavior, older subjective age); matures (high psychosocial maturity, low problem behavior, slightly older subjective age); and immatures (low psychosocial maturity, low problem behavior, young subjective age). Regressions revealed that several adolescent- and mother-reported variables were linked to maturity status. Relative to their mature and immature counterparts, adultoid adolescents exhibited more advanced physical maturity, earlier expectations for attaining privileges, higher social involvement, and in boys, higher mother-adolescent conflict. Adultoid adolescents do exist, and they differ from mature and immature adolescents in important ways. These results have implications for understanding the diversity in adolescents' levels of maturity.     

The frequency selectivity of information-processing channels in the tactile sensory system

The frequency selectivity of the P, NP I, and NP II channels of the four-channel model of mechanoreception for glabrous skin was measured psychophysically by an adaptation tuning curve procedure. The results substantially extend the frequency range over which the frequency selectivity of these channels is known and further confirm the hypothesis that the input stage of each of these channels consists of specific sensory nerve fibers and associated receptors. Specifically, the frequency characteristics of Pacinian nerve fibers, rapidly adapting (RA) nerve fibers, and slowly adapting Type II (SA II) nerve fibers were found to be the peripheral neurophysiological correlates of the P, NP I, and NP II channels, respectively. The finding that the tuning characteristic for a test stimulus of 250 Hz delivered through a small (0.008 cm²) contactor depended dramatically on the duration of the test stimulus whereas the detection threshold did not, provides new evidence in support of the hypothesis that separate NP II and P channels exist.     

Temporal gap detection in tactile channels

The ability of observers to detect temporal gaps in bursts of sinusoids or bursts of band-limited noise was measured to assess the temporal acuity of Pacinian (P) and non-Pacinian (NP) tactile information processing channels. The P channel was isolated by delivering high frequency sinusoids or high frequency noise through a large 1.5-cm2 contactor to the thenar eminence. The NP channels were isolated from the P channel by delivering these stimuli as well as stimuli with lower frequencies through a small 0.01-cm2 contactor to the same site. Gap detection thresholds were higher for gaps in noise than for gaps in sinusoids but did not differ among conditions designed to isolate P and NP channels. The finding that temporal acuity does not differ among channels supports the hypothesis that, after termination of a stimulus, the P and NP channels exhibit the same amount of neural persistence. Also consistent with this hypothesis are the earlier findings that the enhancement of the sensation magnitude of a stimulus by a prior stimulus (Verrillo and Gescheider, Percept Psychophys 18: 128-136, 1975) and the duration of sensation after the termination of a stimulus (Gescheider et al., J Acoust Soc Am 91: 1690-1696, 1992) are independent of stimulus frequency. One important implication of this hypothesis, if true, is that the presence of temporal summation in the P channel and its absence in the NP channels, results, not from the lack of neural persistence in the NP channels, but instead, in marked contrast to the P channel, from the lack of a mechanism for integrating persistent neural activity over time.     

Suboptimal health and memory performance of elderly

The influence of health-related incidents on memory test performance and subjective memory ratings was assessed in a) a group of healthy older adults recruited via the register of population (group 1: N = 117, mean age 62 years, range 46-89) and b) a group of healthy older subjects having memory complaints and applying for memory training (group 2: N = 111, mean age 63 years, range 45-85). The study tries to cross-validate a previous study, where the presence and frequency of health-related incidents were related to cognitive performance. The presence of 9 categories of health-related incidents (consultation of a neurologist, systemic diseases, repeated mild concussions, repeated anaesthesia, use of psychotropic medication, alcohol use, other neurotoxic factors, such as exposure to organic solvents, psychiatric disorders, birth complications or developmental problems) was assessed in a semi-structured interview. Memory performance was assessed with a battery covering different aspects of memory. Memory self-ratings were assessed with questionnaires asking for frequencies of memory failures and a general judgement of memory capacity. Health-related incidents occurred in about half of both subject groups and were not related to age or other demographic characteristics. In both subject groups, the presence, nor the number of health-related incidents was related to memory performance or memory complaints and there was no interaction with age. The results are not in agreement with the notion that health-related indices explain age differences in cognitive performance.     

Vibrotactile thresholds of the Non-Pacinian I channel: I. Methodological issues

Thresholds of the Non-Pacinian I (NP I) channel were measured using a two-interval forced-choice paradigm, a technique independent of the subject's criterion. The studies were performed using the terminal phalanx of the human middle finger with a 40-Hz vibratory stimulus. Unlike most of the previous experiments performed in our laboratory, a contactor surround was not used. This was done to enable comparison with population models of mechanoreceptive fibers in the literature. Since the Pacinian (P) channel and NP I channel have similar vibrotactile thresholds at 40?Hz, a forward-masking procedure was used to elevate the thresholds of the P channel with respect to the NP I channel. While it has been established that the Pacinian fibers are entrained at high stimulus levels, the P channel can be perceptually masked using a 250-Hz stimulus presented prior to the 40-Hz test stimulus. The masking functions were found to be approximately linear on log-log axes and the threshold shifts were found to increase as the masking-stimulus levels increased. The results are discussed in relation to previous studies that were performed at various stimulation sites by using a contactor surround or not. A companion paper presents the variation of NP I-channel thresholds, measured using the methods described herein, and addresses the effects of stimulation along the proximo-distal axis of the phalanx. The companion paper also discusses the predictions of a computational model, recently proposed, in light of the empirical results presented.     

Vibrotactile thresholds of the Non-Pacinian I channel: I. Methodological issues

Thresholds of the Non-Pacinian I (NP I) channel were measured using a two-interval forced-choice paradigm, a technique independent of the subject's criterion. The studies were performed using the terminal phalanx of the human middle finger with a 40-Hz vibratory stimulus. Unlike most of the previous experiments performed in our laboratory, a contactor surround was not used. This was done to enable comparison with population models of mechanoreceptive fibers in the literature. Since the Pacinian (P) channel and NP I channel have similar vibrotactile thresholds at 40?Hz, a forward-masking procedure was used to elevate the thresholds of the P channel with respect to the NP I channel. While it has been established that the Pacinian fibers are entrained at high stimulus levels, the P channel can be perceptually masked using a 250-Hz stimulus presented prior to the 40-Hz test stimulus. The masking functions were found to be approximately linear on log-log axes and the threshold shifts were found to increase as the masking-stimulus levels increased. The results are discussed in relation to previous studies that were performed at various stimulation sites by using a contactor surround or not. A companion paper presents the variation of NP I-channel thresholds, measured using the methods described herein, and addresses the effects of stimulation along the proximo-distal axis of the phalanx. The companion paper also discusses the predictions of a computational model, recently proposed, in light of the empirical results presented.     

Serum osteoprotegerin and RANKL are not specifically altered in women with postmenopausal osteoporosis treated with teriparatide or risedronate: a randomized, controlled trial.

Risedronate and teriparatide have opposite actions on the osteoblast-osteoclast dipole and are expected to influence the RANK/RANKL/osteoprotegerin (OPG) system. We aimed to evaluate changes in serum OPG and RANKL after risedronate or teriparatide administration in postmenopausal osteoporotic women. Seventy-four postmenopausal Caucasian women (age 64.1+/-1.0 years) were studied. Women with osteopenia served as controls (group 1, n=30). Women with osteoporosis were randomly assigned to either risedronate 35 mg once weekly (group 2, n=21) or teriparatide 20 microg once daily (group 3, n=23) for six months. Blood samples for serum RANKL, OPG, N-terminal propeptide of type 1 collagen (P1NP), and C-terminal telopeptide of type 1 collagen (CTx) were obtained before treatment and three and six months after treatment. P1NP and CTx levels remained unchanged in group 1, decreased in group 2 (p<0.001), and increased in group 3 women (p<0.001) throughout the treatment. OPG levels remained unchanged while RANKL decreased gradually in all groups (p<0.001). There was no correlation between OPG or RANKL and P1NP or CTx. Our data suggest that neither antiresorptive nor osteoanabolic therapy causes specific alterations of serum OPG/RANKL levels; therefore, these cytokines cannot substitute for the established markers of bone turnover in the monitoring of response to osteoporosis treatment.