Sleep spindles are rhythmic patterns of neuronal activity generated within the thalamocortical circuit. Although spindles have been hypothesized to protect sleep by reducing the influence of external stimuli, it remains to be confirmed experimentally whether there is a direct relationship between sleep spindles and the stability of sleep. We have addressed this issue by using in vivo photostimulation of the thalamic reticular nucleus of mice to generate spindle oscillations that are structurally and functionally similar to spontaneous sleep spindles. Such optogenetic generation of sleep spindles increased the duration of non-rapid eye movement (NREM) sleep. Furthermore, the density of sleep spindles was correlated with the amount of NREM sleep. These findings establish a causal relationship between sleep spindles and the stability of NREM sleep, strongly supporting a role for the thalamocortical circuit in sleep regulation.sleep rhythms | sleep protection S leep spindles are characteristic EEG rhythms observed during non-rapid eye movement (NREM) sleep. It is characterized by periodic waxing and waning and 7-to 15-Hz oscillations with durations ranging from 0.5 to 3 s (1-3), and is often used as an EEG marker of NREM sleep. Sleep spindles are hypothesized to originate from the thalamic reticular nucleus (TRN) (4, 5), where the rhythmic burst activity of TRN neurons could initiate spindle oscillations within the whole thalamocortical circuit. When it has been initiated, this oscillation is self-maintained by the reciprocal interactions among cortical, thalamocortical (TC), and TRN neurons during NREM sleep (4, 6, 7). Sleep spindles are of particular interest because they are known to be involved in several sleep-dependent physiological and cognitive processes, such as memory consolidation and neuronal plasticity (7-10). Moreover, a growing amount of evidence suggests that sleep spindles serve a sleep-protecting function by modulating the degree of sensory transmission through the thalamus (11). Patients with hypersomnia show increased spindle density (SD) compared with control (12), and KO mice whose sleep spindles are reduced as a result of impaired thalamocortical oscillations experience sleep disturbances during NREM sleep (13-16). Further, individuals with a higher spindle rate are more tolerant to noise that occurs during sleep (17). Despite considerable evidence hinting at the sleepprotecting function of sleep spindles, no experimental studies have yet demonstrated a direct causal relationship between sleep spindles and the stability of sleep. A recent study found that optogenetic stimulation of TRN induced burst firing in TC neurons, which were hypothesized to underlie the occurrence of neocortical sleep spindles (18). However, because sleep spindles also occur spontaneously, it was not clear whether sleep spindles were driven by optogenetic stimulation of the TRN.To experimentally examine the sleep-protecting function of sleep spindles, we used Channelrhodopsin2 (ChR2) transgenic (tg) mice to bilaterally ...

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Microelectrodes are widely used for monitoring neural activities in various neurobiological studies. The size of the neural electrode is an important factor in determining the signal-to-noise ratio (SNR) of recorded neural signals and, thereby, the recording sensitivity. Here, it is demonstrated that commercial tungsten microelectrodes can be modified with carbon nanotubes (CNTs), resulting in a highly sensitive recording ability. The impedance with the respect to surface area of the CNT-modified electrodes (CNEs) is much less than that of tungsten microelectrodes because of their large electrochemical surface area (ESA). In addition, the noise level of neural signals recorded by CNEs is significantly less. Thus, the SNR is greater than that obtained using tungsten microelectrodes. Importantly, when applied in a mouse brain in vivo, the CNEs can detect action potentials five times more efficiently than tungsten microelectrodes. This technique provides a significant advance in the recording of neural signals, especially in brain regions with sparse neuronal densities.

For synchrotron X-ray micro-imaging of micro-scale biological flows in organisms, the development of a suitable flow-sensing tracer is essential for visualizing opaque flows quantitatively. In order to achieve this development in this study, the techniques employed in three different research fields were integrated namely, X-ray optics for enhancing X-ray concentration, fluid dynamics to satisfy the flow traceability and drug delivery system to fabricate bio-compatible microcapsules. On the front burner, we need a special sensor which can be well observed in X-ray micro-imaging and follow working fluid as well. As a result, bio-compatible micro-scale microcapsule sensors that perform the role of spherical micro lenses were developed. These novel microcapsules exhibit not only much improved contrast enhancement but also better performance as sensor tracers in micro-scale flows, compared to conventional solid particles.