Shortening of Subjective Visual Intervals Followed by Repetitive Stimulation

Our previous research demonstrated that repetitive tone stimulation shortened the perceived duration of the preceding auditory time interval. In this study, we examined whether repetitive visual stimulation influences the perception of preceding visual time intervals. Results showed that a time interval followed by a high-frequency visual flicker was perceived as shorter than that followed by a low-frequency visual flicker. The perceived duration decreased as the frequency of the visual flicker increased. The visual flicker presented in one hemifield shortened the apparent time interval in the other hemifield. A final experiment showed that repetitive tone stimulation also shortened the perceived duration of preceding visual time intervals. We concluded that visual flicker shortened the perceived duration of preceding visual time intervals in the same way as repetitive auditory stimulation shortened the subjective duration of preceding tones

c-Fos Expression during Temporal Order Judgment in Mice

The neuronal mechanisms for ordering sensory signals in time still need to be clarified despite a long history of research. To address this issue, we recently developed a behavioral task of temporal order judgment in mice. In the present study, we examined the expression of c-Fos, a marker of neural activation, in mice just after they carried out the temporal order judgment task. The expression of c-Fos was examined in C57BL/6N mice (male, n = 5) that were trained to judge the order of two air-puff stimuli delivered bilaterally to the right and left whiskers with stimulation intervals of 50–750 ms. The mice were rewarded with a food pellet when they responded by orienting their head toward the first stimulus (n = 2) or toward the second stimulus (n = 3) after a visual “go” signal. c-Fos-stained cell densities of these mice (test group) were compared with those of two control groups in coronal brain sections prepared at bregma −2, −1, 0, +1, and +2 mm by applying statistical parametric mapping to the c-Fos immuno-stained sections. The expression of c-Fos was significantly higher in the test group than in the other groups in the bilateral barrel fields of the primary somatosensory cortex, the left secondary somatosensory cortex, the dorsal part of the right secondary auditory cortex. Laminar analyses in the primary somatosensory cortex revealed that c-Fos expression in the test group was most evident in layers II and III, where callosal fibers project. The results suggest that temporal order judgment involves processing bilateral somatosensory signals through the supragranular layers of the primary sensory cortex and in the multimodal sensory areas, including marginal zone between the primary somatosensory cortex and the secondary sensory cortex

Low-temperature specific heat study of antiferromagnetic transition in ternary rare-earth metal silicide R5Ir4Si10 (R = Tb, Dy, Ho, Er)

金沢大学理工研究域数物科学系We investigated antiferromagnetic transitions of R5lr4Si10 (R = Tb, Dy, Ho, Er) by measuring the low-temperature specific heat. The antiferromagnetic transition temperature TN is precisely determined. TN is l0.7 K for R = Tb, TN is 5.8 K for R = Dy, TN is 5.1 K for R = Ho and TN is 3.5 K for R = Er, respectively. These results suggest that the antiferromagnetic transition of the ternary rare-earth metal silicide R5lr4Si10 is dominated by the exchange interaction between R3+ ions like as the antiferromagnetic transitions in the ternary rare-earth metal compounds RCu2Ge2 (R = rare-earth metal). In addition, we report the upturn of the specific heat below 1.5 K observed for R = Tb and Ho. © 2006 Elsevier B.V. All rights reserved

FIELD MEASUREMENT AND MODELLING OF THE MATERIAL CYCLE IN THE CULTIVATION POND OF PENAEID SHRIMP PENAEUS JAPONICUS

ABSTRACT Field measurement and modelling of the material cycle are carried out for the cultivation pond of penaeid shrimp Penaeus japonicus. The main purpose of the present study is to investigate the sustainability of coastal shrimp aquaculture, which is increasingly being questioned due to many problems like disease, excessive nutrient enrichment, and low levels of dissolved oxygen tension. Despite the great economic importance of shrimps and their suitability to aquaculture, little is known about the material cycle through the cultivation pond. Additionally, the collapse of shrimp aquaculture in most tropical countries may be attributed to the lack of ecological, biological, and environmental understanding. Hence field measurement of water quality is conducted in the shrimp cultivation pond, which locates in the Kyushu district of Japan. Various environmental factors such as water temperature, salinity, and the concentrations of dissolved oxygen, nutrients, and chlorophyll a are monitored for the water in the pond and that drawn from the outer sea during November and December of 2006. In addition to field measurement, one dimensional numerical model is developed for the shrimp cultivation pond to understand the material cycle through the pond in a quantitative manner. The numerical model consists of physical, lower trophic-level ecosystem, and shrimp growth submodels. The numerical values of physical and physiological parameters are calibrated to achieve the best agreement between observed and simulated results. By integrating results from field measurement and numerical simulation, it is revealed that the quality of water in the cultivation pond is quite different from that drawn from the outer sea. In particular the concentration of chlorophyll a is much higher in the cultivation pond due to large primary production. The results of the numerical simulation show that the high productivity is attributed partly to the activities of shrimps. The information from field measurement and the simulated results of the developed numerical model are useful to optimize the food quantity and quality, the population density of shrimps, and the design of watermills or the other equipments to improve the water quality for sustainable use of coastal shrimp cultivation pond

Synchronization of spontaneous eyeblinks while viewing video stories

Blinks are generally suppressed during a task that requires visual attention and tend to occur immediately before or after the task when the timing of its onset and offset are explicitly given. During the viewing of video stories, blinks are expected to occur at explicit breaks such as scene changes. However, given that the scene length is unpredictable, there should also be appropriate timing for blinking within a scene to prevent temporal loss of critical visual information. Here, we show that spontaneous blinks were highly synchronized between and within subjects when they viewed the same short video stories, but were not explicitly tied to the scene breaks. Synchronized blinks occurred during scenes that required less attention such as at the conclusion of an action, during the absence of the main character, during a long shot and during repeated presentations of a similar scene. In contrast, blink synchronization was not observed when subjects viewed a background video or when they listened to a story read aloud. The results suggest that humans share a mechanism for controlling the timing of blinks that searches for an implicit timing that is appropriate to minimize the chance of losing critical information while viewing a stream of visual events

Elastic microfibril distribution in the cornea: Differences between normal and keratoconic stroma

The optical and biomechanical properties of the cornea are largely governed by the collagen-rich stroma, a layer that represents approximately 90% of the total thickness. Within the stroma, the specific arrangement of superimposed lamellae provides the tissue with tensile strength, whilst the spatial arrangement of individual collagen fibrils within the lamellae confers transparency. In keratoconus, this precise stromal arrangement is lost, resulting in ectasia and visual impairment. In the normal cornea, we previously characterised the three-dimensional arrangement of an elastic fiber network spanning the posterior stroma from limbus-to-limbus. In the peripheral cornea/limbus there are elastin-containing sheets or broad fibers, most of which become microfibril bundles (MBs) with little or no elastin component when reaching the central cornea. The purpose of the current study was to compare this network with the elastic fiber distribution in post-surgical keratoconic corneal buttons, using serial block face scanning electron microscopy and transmission electron microscopy. We have demonstrated that the MB distribution is very different in keratoconus. MBs are absent from a region of stroma anterior to Descemet's membrane, an area that is densely populated in normal cornea, whilst being concentrated below the epithelium, an area in which they are absent in normal cornea. We contend that these latter microfibrils are produced as a biomechanical response to provide additional strength to the anterior stroma in order to prevent tissue rupture at the apex of the cone. A lack of MBs anterior to Descemet's membrane in keratoconus would alter the biomechanical properties of the tissue, potentially contributing to the pathogenesis of the disease

An easy-to-implement, non-invasive head restraint method for monkey fMRI

Tanaka R., Watanabe K., Suzuki T., et al. An easy-to-implement, non-invasive head restraint method for monkey fMRI. NeuroImage 285, 120479 (2024); https://doi.org/10.1016/j.neuroimage.2023.120479.Functional magnetic resonance imaging (fMRI) in behaving monkeys has a strong potential to bridge the gap between human neuroimaging and primate neurophysiology. In monkey fMRI, to restrain head movements, researchers usually surgically implant a plastic head-post on the skull. Although time-proven to be effective, this technique could create burdens for animals, including a risk of infection and discomfort. Furthermore, the presence of extraneous objects on the skull, such as bone screws and dental cement, adversely affects signals near the cortical surface. These side effects are undesirable in terms of both the practical aspect of efficient data collection and the spirit of “refinement” from the 3R's. Here, we demonstrate that a completely non-invasive fMRI scan in awake monkeys is possible by using a plastic head mask made to fit the skull of individual animals. In all of the three monkeys tested, longitudinal, quantitative assessment of head movements showed that the plastic mask has effectively suppressed head movements, and we were able to obtain reliable retinotopic BOLD signals in a standard retinotopic mapping task. The present, easy-to-make plastic mask has a strong potential to simplify fMRI experiments in awake monkeys, while giving data that is as good as or even better quality than that obtained with the conventional head-post method

Atypical gaze patterns in children and adults with autism spectrum disorders dissociated from developmental changes in gaze behaviour

Eye tracking has been used to investigate gaze behaviours in individuals with autism spectrum disorder (ASD). However, traditional analysis has yet to find behavioural characteristics shared by both children and adults with ASD. To distinguish core ASD gaze behaviours from those that change with development, we examined temporo-spatial gaze patterns in children and adults with and without ASD while they viewed video clips. We summarized the gaze patterns of 104 participants using multidimensional scaling so that participants with similar gaze patterns would cluster together in a two-dimensional plane. Control participants clustered in the centre, reflecting a standard gaze behaviour, whereas participants with ASD were distributed around the periphery. Moreover, children and adults were separated on the plane, thereby showing a clear effect of development on gaze behaviours. Post hoc frame-by-frame analyses revealed the following findings: (i) both ASD groups shifted their gaze away from a speaker earlier than the control groups; (ii) both ASD groups showed a particular preference for letters; and (iii) typical infants preferred to watch the mouth rather than the eyes during speech, a preference that reversed with development. These results highlight the importance of taking the effect of development into account when addressing gaze behaviours characteristic of ASD

Developmental genetic bases behind the independent origin of the tympanic membrane in mammals and diapsids

International audienceThe amniote middle ear is a classical example of the evolutionary novelty. Although paleontological evidence supports the view that mammals and diapsids (modern reptiles and birds) independently acquired the middle ear after divergence from their common ancestor, the developmental bases of these transformations remain unknown. Here we show that lower-to-upper jaw transformation induced by inactivation of the Endothelin1-Dlx5/6 cascade involving Goosecoid results in loss of the tympanic membrane in mouse, but causes duplication of the tympanic membrane in chicken. Detailed anatomical analysis indicates that the relative positions of the primary jaw joint and first pharyngeal pouch led to the coupling of tympanic membrane formation with the lower jaw in mammals, but with the upper jaw in diapsids. We propose that differences in connection and release by various pharyngeal skeletal elements resulted in structural diversity, leading to the acquisition of the tympanic membrane in two distinct manners during amniote evolution