Episodic memory is often impaired by the effect of aging. There are two main forms of age-related decline in episodic memory: increased forgetting of experienced events and remembering of events that have not been experienced. Neural correlates of the former types of memory disturbance have been investigated carefully in several previous fMRI studies, but evidence with regard to the latter remains scarce. This review article summarizes previous fMRI findings associated with false memory retrieval and effect of aging on it, and proposes frameworks for understanding the underlying mechanisms. Previous fMRI studies of false memories in young adults have shown significant activation related to false remembering in the lateral prefrontal cortex (PFC), medial PFC including the anterior cingulate cortex (ACC), and superior/inferior parietal cortices. The findings suggest that incompatible interaction between these regions could contribute to the retrieval of false memories related to failure of the process of monitoring retrieved memories. An age-related decrease in activation associated with false remembering has been identified in the lateral PFC, ACC and visual cortices such as the precuneus or occipital lobe. Decreasing activation in these regions in older adults indicates that the age-related increase of false remembering could be caused by decreased interaction between the monitoring and remembering systems in older adults compared to young adults. Future fMRI research into false memories should include further investigation of how the processing of false memories is correlated with other cognitive functions such as “lying” or “confabulation”.
Carnitine is known for its role in the transport of long-chain fatty acids into the mitochondrial matrix for subsequent β-oxidation. In addition, carnitine acts as an acceptor of excess acetyl-CoA and forms acetylcarnitine to relieve inhibition of pyruvate dehydrogenase. Recent studies have demonstrated that carnitine acetylation is essential for glucose homeostasis, and its dysfunction induces metabolic failure. Furthermore, it has been suggested that acetylcarnitine might be exported from skeletal muscle into the blood. Considering that acetylcarnitine is a bioactive molecule involved in glucose metabolism and neuroprotection, we expect that acetylcarnitine production is beneficial to the body. In this article, we reviewed recent knowledge on the role of carnitine acetylation in glucose metabolism within skeletal muscle. Furthermore, this article introduces acetylcarnitine as a physiologically active substance and discusses carnitine dynamics during exercise.
In daily life, voluntary movements accompany the appropriate whole-body configurations and orientations in relation to the force of gravity. To produce skilled motor behavior, it is necessary to concurrently maintain an upright stance. There are two main aspects to postural control, namely, compensatory postural reaction by means of sensory feedback mechanisms, and anticipatory postural adjustments by means of feedforward mechanisms. The cerebellum has been suggested to be the brain region principally responsible for these postural control mechanisms. In this report, we review the effects of lesions of the cerebellum on postural control in human patients and in a mouse model of a human inherited disease.
For developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in healthy adults, a minimum of 30 min of moderate-intensity physical activity or 20 min of vigorous-intensity physical activity per exercise day is recommended. However, many adults are still physically inactive because of the lack of time and facilities, bad weather, and other factors. Therefore, it is important to develop a type of exercise that is effective for health promotion and easy to do in daily life. An exercise with stairs is likely to satisfy this aim. Using data from previous studies, we produced the following formula to predict the intensity (oxygen consumption) during stair-ascending exercise. Oxygen consumption (ml/kg/min) = 2.03 x [moving speed for vertical direction in m/min] + 3.7. Previous intervention studies of exercise using stairs show that stair-ascending exercise improves fitness and health, but is too intense for unfit and/or elderly adults. Stair exercise can be performed more easily if it comprises ascending and descending stairs alternately using a short flight of stairs. Our data suggest that stair-ascending/descending exercise expands the availability of stair exercise for health promotion.
Corticospinal excitability is known to be modulated during voluntary muscle contraction of distal limbs. Although a large number of studies have demonstrated the variety of modulations in corticospinal excitability during distal limb movement, those interlimb neural interactions in corticospinal excitability have not been fully understood. Here, we mainly review previous studies that used transcranial magnetic stimulation (TMS) to report the modulation of corticospinal excitability during distal limb movement, and discuss related neural mechanisms and functional implications. Corticospinal modulation, produced across the limbs, was observed regardless of the combination of limbs (i.e., upper limbs, upper and lower limbs, and lower limbs). The pattern of modulation depended on the strength and the modality of muscle contraction in the active limb. Discrete forceful isometric contraction tended to facilitate corticospinal excitability in the tested muscle of the opposite limb. However, isotonic muscle contraction tended to show suppression or movement phase-locked specific facilitation. In association with the involvement of modulation in spinal motoneuronal and intracortical motor circuitry, it was suggested that different neural mechanisms mediate each pattern of corticospinal modulation.
The authors detected the discrete spike potentials during contraction from surface electrodes fixed on the skin surface over the m. vastus medialis, and the spikes could always be detected with almost the same wave-form by putting the electrode on at the same point. Therefore, its electrical source in the muscle could be searched by detection of the existence of the synchronized motor unit action potential using an intramuscular electrode with surface spikes. The electrical source of the surface spikes originated from single motor unit action potential in the muscle (surface MUAP). By analyzing the surface MUAP wave-form employing both mono- and bipolar recording methods, surface MUAP allowed us to decide the position of the neuro-muscular junction and apparent path of muscle fibers on the skin surface. Marking the position of the neuro-muscular junction on the skin permits the reproducible recording of the MUAP wave-form of the same motor unit between the different experiments. Including the detection of the excitability of the spinal α-motoneuron, surface MUAP wave-form analysis would be a useful tool to investigate the structural change, such as length change of muscle fibers with the joint angle, and membrane property such as supernormal conduction velocity or supernormal phase in membrane potential at severe condition (lowered muscle temperature) in a single motor unit in situ human muscle. It emphasizes that the surface MUAP detection method is safe for a subject without any invasive damages such as an inserted electrode.
Siglecs are a family of vertebrate glycan-recognition proteins belonging to the immunoglobulin superfamily, which recognize oligosaccharides containing acidic sugars called sialic acid. Most Siglecs are primarily expressed on leukocytes, and have crucial roles in regulating the viability and activity of the cells that express them. While most Siglecs associate with tyrosine phosphatases and negatively regulate immune cells, a small subset of Siglecs associate with an adapter molecule and recruit tyrosine kinase, triggering a signaling cascade leading to the activation of immune cells. Recent studies revealed that activating-type Siglecs are involved in various aspects of biology, such as defense against pathogens, bone homeostasis, and possibly cancer. Genetic polymorphisms of activating-type Siglecs might be associated with modern diseases caused by changes in human lifestyle and our extended lifespan, and deserve investigation from various angles.
Lower-body plyometric exercises are jumping-type exercises that use an individual’s body weight or a relatively low external load as resistance. In various sports training regimens, lower-body plyometric training is used to improve athletic performance in tasks that require high power generation such as jumping and sprint running. Over the past three decades, numerous studies have investigated the effectiveness of lower-body plyometric training for athletic and neuromuscular performance. The study findings indicated that lower-body plyometric training is effective for improving athletic performance in a wide range of activities. In addition, recent studies have provided knowledge about the adaptation of muscle and tendon components to lower-body plyometric training. These studies showed that neural as well as functional and/or geometrical adaptations occur after plyometric training. However, many issues remain to be fully elucidated. This short review will introduce these recent findings of the effects of lower-body plyometric training on athletic performance and muscle–tendon properties.
Growing evidence has shown that skeletal muscle secretes several bioactive proteins from muscle cells into extracellular fluid. The secretion of several proteins, whose levels increase in response to exercise, can regulate the functions of several organs via autocrine, paracrine, and endocrine actions, and mediate exercise-induced benefits such as metabolic improvement, muscle building, and anti-inflammation. This is known as the myokine theory. Recently, we found a novel myokine, secreted protein acidic and rich in cysteine (SPARC), a member of the matricellular protein family that essentially modulates cell-cell and cell-matrix interactions. The secreted SPARC has been shown to prevent colon tumorigenesis via an apoptotic effect in in vitro and in vivo studies. Therefore, the muscle-secreted protein SPARC can support underlying mechanisms of epidemiological studies that suggest that habitual exercise can prevent the incidence of colon cancer. Many different types of studies have suggested that many other factors including proteins, metabolites, and microRNAs secreted from muscle have yet to be identified. These secretory factors may be biomarkers that reflect muscular function and beneficial adaptation achieved by exercise, along with the underlying mechanisms of beneficial effects.
In homeothermic animals, metabolic heat production in the brain is higher than in other tissues. However, cerebral tissue is susceptible to heat. Several animals have mechanisms that selectively cool the brain during hyperthermia (i.e., selective brain cooling [SBC]). Carotid retes have been well documented in artiodactyls (hoofed animals) and felids (cats) as mechanisms of SBC. SBC has also been found in some species without carotid retes, such as horses and squirrel monkeys. However, the presence of SBC in humans remains controversial. Brain temperature cannot be directly measured in healthy subjects; therefore, tympanic temperature has been used to estimate brain temperature. However, tympanic temperature is reportedly affected by facial skin temperature. We recently investigated the effect of facial fanning on tympanic and esophageal temperature in normothermic and hyperthermic humans. The results showed that tympanic temperature is not affected by the facial skin temperature under normothermic conditions and that facial fanning may induce SBC under hyperthermic conditions. Regional differences in thermal comfort are present over the body surface in humans, i.e. humans prefer a cool head in the heat and a warm abdomen in the cold. Therefore, preference for a low facial temperature may activate SBC. Several recent studies have demonstrated that whole-brain temperature can be measured noninvasively with proton magnetic resonance spectroscopy. The existence of a thermal gradient within the brain has been suggested. Studies measuring whole-brain temperature will reveal the details of human SBC.
Pancreatic β cells express glucose transporter-2 (GLUT2) on the cell surface as a glucose sensor molecule for appropriate insulin secretion. Disappearance of GLUT2 from the β cell surface is one of the early markers of the onset of type 2 diabetes, though the molecular mechanism has not been well understood. Glycobiology and mouse genetics revealed that GnT-IV is a glycosyltransferase indispensable for increasing the N-glycan branch complexity of GLUT2, which provides carbohydrate epitopes bound to galectin-9 on the β cell surface. The engagement of galectin-9 with GLUT2 regulates remodeling of GLUT2 clusters among cell surface membrane sub-domains, to control glucose transport activities, and prevents endocytosis to increase cell surface residency of GLUT2 that contributes to sustaining the glucose sensor function of β cells. The pathophysiological pathway to diet- and obesity-associated diabetes has recently been revealed, in which a high-fat diet leading to diabetes recapitulated the free-fatty acid induced-oxidative stress in human and mouse pancreatic β cells that induced nuclear exclusion of transcription factors and, subsequently, attenuated GnT-IVa-dependent GLUT2 glycosylation. Engineering and characterizing of transgenic mice overexpressing GnT-IVa in pancreatic β cells revealed that maintenance of GnT-IVa-dependent protein glycosylation prevents high fat diet-induced β cell dysfunction and ameliorates the onset of type 2 diabetes. These findings indicate that GnT-IV-mediated organization of cell surface GLUT2 is a fundamental process to modulate insulin secretion responses to fluctuating extracellular glucose levels, a paradigm that can be practically applied to better understand the pathogenesis of type 2 diabetes and development of drugs.
Satellite cells are skeletal muscle tissue stem cells located between the basal lamina and sarcolemma of myofibres and play crucial roles in adult muscle repair and regeneration as well as postnatal muscle growth. More and more findings indicate that satellite cells exist as a genetically and functionally heterogeneous population among muscles, which is not only based on fibre types, but also embryonic origin. Satellite cells are also a heterogeneous population even within a single myofibre. Only a small population of satellite cells possesses “stemness” and exhibits remarkable regeneration with a high self-renewal ability when transplanted into injured muscles. Recent studies have shed light on the cellular and molecular characteristics of satellite cell heterogeneity including Pax7+Myf5- cells, satellite-side population cells, Pax7-nGFPhigh cells, and slow-dividing cells. Here, we review recent progress in our understanding of the heterogeneity and stem cell hierarchies in the satellite cell population.
The visual system conducts parallel and hierarchical signal processing for each aspect of visual information. The different signals are then integrated at appropriate stages to generate unified visual percepts. This ability is a remarkable accomplishment considering that the retinal image is constantly moved by self-motion including movements of body, head, and eyes, so that it contains information about movement from external objects and the observer himself. Our eyes alternate fixation and saccade (rapid and jerky eye movement used to scan the world around us). Therefore, the visual system needs to discriminate this information for an individual to accurately interpret his environment and to prevent the visual images from blurring and bouncing during saccades. In this review, we discuss how the visual system solves these problems at the single neuron level. Results indicate that our visual motion perception is built on the integration of different aspects of visual signals, multisensory signals, and sensory-motor signals along a hierarchy of visual motion information processing.
In general, exercise and/or sports are effective for bone health. Bone metabolism is influenced by several environmental factors, especially mechanical loading and nutrition. It is well known that the bone mass in athletes is higher than that of people having a sedentary lifestyle. Mechanical loading leads to an increase in bone mass, whereby it helps in strengthening. However, in some cases athletes might have lower bone mass. Insufficient dietary intake and an imbalanced nutritional status cause an inhibition of bone formation and activation of bone resorption. A higher than necessary Ca intake is important for improving bone metabolism. An adequate protein intake level, not too high or low, might be effective for bone maintenance. In addition, low energy availability could be leading to low bone mass. It might be possible to say that exercise is not effective for improving bone metabolism in an inadequate and/or imbalanced nutritional condition. A moderate level of physical activity, not an excess level, and appropriate nutrient intake are both necessary for bone health.
Locomotor function is affected by neurological disorders such as stroke and spinal cord injury. Based on the results of animal studies, locomotor training with body weight unloading toward neuroplastic changes to improve walking function is conducted. However, in patients with severely impaired locomotor function, manual assistance by physical therapists is needed for stepping movements during locomotor training. Manual assistance places a heavy burden on therapists; therefore, various robots for locomotor training have been developed. One of these robots, Robot Suit HAL®, is a wearable robot developed in Japan that can produce assistive torque for stepping via actuators on the hip and knee joints. In this short review, information on robotic devices for locomotor training will be presented, and then recent results from feasibility studies using HAL for patients with neurological disorders will be explained.
This review article deals with the facilitatory and beneficial effects of nonconscious perception on motor responses and actions in both primitive and real-world situations. First, the effects of nonconscious perception on motor responses in somatosensory and visual simple reaction time (RT) tasks with backward masking were examined. This showed that simple RTs were facilitated by the perception of given stimuli even if the performers were unaware of them under backward masking. Second, the so-called speed contagion effects on simple motor responses were examined, indicating that a prior observation of another individual’s fast motor actions facilitated simple RTs. Finally, evidence for the facilitatory effects of nonconscious perception on real-world situations was examined. This showed that penalty kicks may often be targeted toward the wider space in a goal area subdivided by the standing position of the goalkeeper, despite the lack of conscious awareness of which side was wider. These findings suggest that our perceptual judgment and motor control in both simple/primitive and real-world conditions are probably influenced in part by nonconscious and nonattended perception of stimuli provided in the environment. This is despite the fact that we tend to have the impression that our own behaviors are primarily governed by the conscious awareness of environmental conditions. Nonconscious perception may be primarily involved in our perceptual and motor actions and probably plays a role in advancing motor learning and control in daily activities and sports.
We compared the physical activity level (PAL) and training and non-training physical activity (PA) between rhythmic gymnasts and lacrosse players. In addition, we aimed to clarify the contribution of training and non-training PA to the PAL. Our study subjects were 11 female rhythmic gymnasts and 11 female lacrosse players. PAL was calculated from the total energy expenditure (TEE) as assessed by the doubly labeled water (DLW) method, and the resting metabolic rate (RMR) was measured using indirect calorimetry. Daily PA and sleep durations were assessed using an activity diary. The intensity (metabolic equivalent, MET) of non-training PA was measured using a tri-axial accelerometer. The amount (MET･h) of training was calculated by subtracting the amount of PA and sleep outside of training from the TEE. There were no significant differences in PAL between rhythmic gymnasts (2.59 ± 0.63) and lacrosse players (2.43 ± 0.46). Rhythmic gymnasts had a longer duration and larger amount of training PA and a shorter duration and smaller amount of non-training PA than did lacrosse players. The mean intensities of training and non-training PA were not significantly different between the groups. PAL was positively correlated with the amount of training in both rhythmic gymnasts (γs = 0.818) and lacrosse players (γs = 0.882). There were no significant relationships between PAL and non-training PA in both groups. Our results indicate that the amount of training strongly affects PAL in these athletes.
Respiratory gas collection and analysis with indirect calorimetry allows assessment of energy and substrate use during rest and exercise and aerobic capacity. We have developed a novel system for simultaneous multiple-subject measurement of respiratory gas exchange during rest and exercise for up to five subjects, and validated the system with a series of experiments. Thirteen healthy young men (mean age 22 ± 2 years, height 172 ± 6 cm, weight 67.1 ± 11.6 kg) participated in this study. Memory problems of the mass spectrometer, which are caused by switching analyzed gases of different compositions between channels, was sufficiently eliminated with a washout of 2 s (seconds) with errors of less than 0.3% for O2 and less than 0.4% for CO2. The high-response mass spectrometer and specially designed mixing chamber enabled correct estimation of metabolic measurements, even for gas concentration data from a non-continuous flow of any given 1s of every 10-s interval (spot-sampling method). Diet-induced thermogenesis (DIT) and oxygen consumption (VO2) during maximal incremental exercise were not significantly different between the novel and Douglas bag methods (P = 0.61 and P = 0.56, respectively). The limit of agreement of DIT and VO2 during maximal incremental exercise between the two methods were 2.8 ± 43.6% and 0.9 ± 4.8%, respectively. We concluded that the newly developed system has reasonable validity over a wide range.
We would like add two references, from which Fig.3 and Fig.4 are cited. We were able to finally find out these old book and old journal after writing the review. So we would like to add the literatures.