No abstract

Although low executive functioning is a risk factor for vehicle crashes among elderly drivers, the neural basis of individual differences in this cognitive ability remains largely unknown. Here we aimed to examine regional frontal gray matter volume associated with executive functioning in normal aging individuals, using voxel-based morphometry (VBM). To this end, 39 community-dwelling elderly volunteers who drove a car on a daily basis participated in structural magnetic resonance imaging, and completed two questionnaires concerning executive functioning and risky driving tendencies in daily living. Consequently, we found that participants with low executive function capacity were prone to risky driving. Furthermore, VBM analysis revealed that lower executive function capacity was associated with smaller gray matter volume in the supplementary motor area (SMA). Thus, the current data suggest that SMA volume is a reliable predictor of individual differences in executive function capacity as a risk factor for vehicle crashes among elderly persons. The implication of our results is that regional frontal gray matter volume might underlie the variation in driving tendencies among elderly drivers. Therefore, detailed driving behavior assessments might be able to detect early neurodegenerative changes in the frontal lobe in normal aging adults.

SUMMARY A delayed response caused by sleepiness can result in severe car accidents. Previous studies suggest that slow eye movement (SEM) is a sleep-onset index related to delayed response. This study was undertaken to verify that SEM detection is effective for preventing sleep-related accidents. We propose a real-time detection algorithm of SEM based on feature-extracted parameters of electrooculogram (EOG), i.e. amplitude and mean velocity of eye movement. In Experiment 1, 12 participants (33.5 ± 7.3 years) performed an auditory detection task with EOG measurement to determine the threshold parameters of the proposed algorithm. Consequently, the valid threshold parameters were determined, respectively, as >5°and <30°s. In Experiment 2, 11 participants (32.8 ± 7.2 years) performed a simulated car-following task to verify that the SEM detection is effective for preventing sleep-related accidents. Accidents in the SEM condition were significantly more numerous than in the non-SEM condition (P < 0.01, one-way repeated-measures anova followed by Scheffe´Õs test). Furthermore, no accident occurred in the SEM condition with a warning generated using the proposed algorithm. Results also demonstrate clearly that the SEM detection can prevent sleep-related accidents effectively in this simulated driving task.

No abstract

No abstract

SUMMARYThe goals of this study were to model the secondary ow components of in ow boundary conditions and examine the e ects of in ow boundary conditions on cerebral haemodynamics. Finite element simulations were conducted for the curved pipe model and the results were compared with PIV measurements. The vortex structures of secondary ow were modelled in terms of the Dean number, which is a function of curvature and the Reynolds number. The modelled secondary ow was superimposed on the axial velocity proÿle obtained by ultrasound as the in ow boundary condition. The image-based simulation was performed for an aneurysm of the middle cerebral artery using the modelled in ow boundary conditions. Results of in ow models with and without secondary ow are compared and show di erences in ow patterns and wall shear stress distributions depending on the in ow model.

Based on physiological responses, a model of the auditory-brain system may be proposed. The model consists of the autocorrelation mechanisms, the interaural cross-correlation mechanism between the two auditory pathways, and the specialization of human cerebral hemispheres for temporal and spatial factors of sound field. The specialization of the human cerebral hemisphere may relate to the highly independent contribution between the spatial and temporal criteria of sound fields on subjective preference judgments. In addition, based on the model, any other subjective attributes of sound fields can be described in terms of processes of the auditory pathways and the brain. For example, the phenomena of missing fundamental, loudness and coloration, the threshold of perception, and preferred delay of a single reflection are well described by the autocorrelation mechanism. The subjective diffuseness and ASW are described by the interaural crosscorrelation function. Even so-called ‘‘cocktail party effects’’ may well be explained by such specialization of the human brain, because speech is processed in the left hemisphere, and the directional spatial information is mainly processed in the right hemisphere. [Work was partially supported by the Ministry of Education, Grant-in-Aid for Scientific Research (C), 9838022, 1997.]

No abstract