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Two‐photon high‐speed fluorescence calcium imaging stands as a mainstream technique in neuroscience for capturing neural activities with high spatiotemporal resolution. However, challenges arise from the inherent tradeoff between acquisition speed and image quality, grappling with a low signal‐to‐noise ratio (SNR) due to limited signal photon flux. Here, a contrast‐enhanced video‐rate volumetric system, integrating a tunable acoustic gradient (TAG) lens‐based high‐speed microscopy with a TAG‐SPARK denoising algorithm is demonstrated. The former facilitates high‐speed dense z‐sampling at sub‐micrometer‐scale intervals, allowing the latter to exploit the spatial redundancy of z‐slices for self‐supervised model training. This spatial redundancy‐based approach, tailored for 4D (xyzt) dataset, not only achieves >700% SNR enhancement but also retains fast‐spiking functional profiles of neuronal activities. High‐speed plus high‐quality images are exemplified by in vivo Purkinje cells calcium observation, revealing intriguing dendritic‐to‐somatic signal convolution, i.e., similar dendritic signals lead to reverse somatic responses. This tailored technique allows for capturing neuronal activities with high SNR, thus advancing the fundamental comprehension of neuronal transduction pathways within 3D neuronal architecture. [ABSTRACT FROM AUTHOR]

Background: The number and calibre of myelinated and unmyelinated fibres of the sacrococcygeal dorsal roots innervating the tail of rats were studied by means of light and electron microscopy.Materials and Methods: There were an estimated total of 12,500 myelinated and 25,500 unmyelinated dorsal root fibres innervating the tail of a rat.Results: The results showed that from the second sacral (S2) to the fourth sacral (S4) segment, the fibre diameter spectrum of myelinated fibres within each dorsal root was bimodal with two peaks at 5 microns and 10 microns, respectively. The first sacral (S1) segment was composed of numerous smaller-size myelinated fibres, thus forming a right-skewed distribution. The coccygeal (Co) segments showed a unimodal distribution peaking at 10 microns for the first (Co1) segment and gradually shifting to 7 microns for the third (Co3) segment. Overall, there was a continuous relative increase of the larger vs. the smaller myelinated fibres from the sacral to coccygeal segments. The fibre diameter of unmyelinated fibres of all these roots was unimodal with a single peak at 0.5 microns. The ratio of unmy- elinated to myelinated fibre numbers was on average 2.83 for the S1-S2 roots, 1.66 for the S3-S4 roots, and 1.24 for the coccygeal roots.Conclusions: The comparison of the left- and right-side nerve fibres show that there was no significant difference, thus implying a symmetrical sensory innervation of the rat's tail. [ABSTRACT FROM AUTHOR]

Optical imaging is a key modality for observing biological specimen with higher spatial resolution. However, scattering and absorption of light in tissues are inherent barriers in maximizing imaging depth in biological tissues. To achieve this goal, use of light at near‐infrared spectrum can improve the present situation. Here, the capability of saturated two‐photon saturated excitation (TP‐SAX) fluorescence microscopy to image at depths of >2.0 mm, with submicron resolution in transparent mouse brain imaging, is demonstrated. At such depths with scattering‐enlarged point spread function (PSF), we find that TP‐SAX is capable to provide spatial resolution improvement compared to its corresponding TPFM, which is on the other hand already providing a much improved resolution compared with single‐photon confocal fluorescence microscopy. With the capability to further improve spatial resolution at such deep depth with scattering‐enlarged PSF, TP‐SAX can be used for exquisite visualization of delicate cerebral neural structure in the scattering regime with a submicron spatial resolution inside intact mouse brain. In this study, the capability of saturated two‐photon excitation fluorescence microscopy (TP‐SAX) to image at depths of >2.0 mm, with submicron resolution in CALRITY treated mouse brain imaging, is demonstrated. We find that TP‐SAX is capable to provide spatial resolution improvement compared to its corresponding two‐photon fluorescence microscopy, which is on the other hand already providing a much improved resolution compared with single‐photon confocal fluorescence microscopy. [ABSTRACT FROM AUTHOR]

Cross-individual variability is considered the essence of biology, preventing precise mathematical descriptions of biological motion 1-7 like the physics law of motion. Here we report that the cerebellum shapes motor kinematics by encoding dynamic motor frequencies with remarkable numerical precision and cross-individual uniformity. Using in-vivo electrophysiology and optogenetics in mice, we confirmed that deep cerebellar neurons encoded frequencies via populational tuning of neuronal firing probabilities, creating cerebellar oscillations and motions with matched frequencies. The mechanism was consistently presented in self-generated rhythmic and non-rhythmic motions triggered by a vibrational platform, or skilled tongue movements of licking in all tested mice with cross-individual uniformity. The precision and uniformity allowed us to engineer complex motor kinematics with designed frequencies. We further validated the frequency-coding function of the human cerebellum using cerebellar electroencephalography recordings and alternating-current stimulation during voluntary tapping tasks. Our findings reveal a cerebellar algorithm for motor kinematics with precision and uniformity, the mathematical foundation for brain-computer interface for motor control., Competing Interests: Declaration of interests: All authors declare no competing interests.

Primary somatosensory cortex (SI) is a key area in the processing of nociceptor inputs to our consciousness. To clarify the columnar and laminar organization of SI for pain processing, we compared spatiotemporal changes in neuronal activities of the primary sensorimotor cortex (SmI) of the rat in response to noxious laser heat stimulation applied to the mid-tail. Longitudinal and vertical array microelectrodes were chronically implanted in the cerebral cortex. Evoked neuronal activities, including intracortical local field potentials (LFP) and ensemble single-unit activity (SU) around SmI were simultaneously recorded. The effect of pentobarbital on the neuronal responses was evaluated in comparison with the neuronal responses in conscious animals to explore the potential substrate of nociceptive processing in the conscious state. The results from the experiment with longitudinal microelectrode arrays indicated that noxious stimulation induced a neuronal response which was spread widely around the SmI of the conscious rat, and the range of neuronal responses was limited to the tail region of the SmI under anesthesia. The results from the experiment with vertical microelectrode arrays showed the universal neuronal responses through all cortical layers of the SmI in conscious rats, and sodium pentobarbital suppressed these neuronal responses in the supragranular layers significantly relative to the deeper layers and basal activity. These results imply that a wider range of cortical activation, both in the horizontal or vertical dimension, might be important for nociceptive processing in the conscious state.

The orofacial sensorimotor cortex is known to play a role in motor learning. However, how motor learning changes the dynamics of neuronal activity and whether these changes differ between orofacial primary motor (MIo) and somatosensory (SIo) cortices remain unknown. To address these questions, we used chronically implanted microelectrode arrays to track learning-induced changes in the activity of simultaneously recorded neurons in MIo and SIo as two naive monkeys (Macaca mulatta) were trained in a novel tongue-protrusion task. Over a period of 8-12 d, the monkeys showed behavioral improvements in task performance that were accompanied by rapid and long-lasting changes in neuronal responses in MIo and SIo occurring in parallel: (1) increases in the proportion of task-modulated neurons, (2) increases in the mutual information between tongue-protrusive force and spiking activity, (3) reductions in the across-trial firing rate variability, and (4) transient increases in coherent firing of neuronal pairs. More importantly, the time-resolved mutual information in MIo and SIo exhibited temporal alignment. While showing parallel changes, MIo neurons exhibited a bimodal distribution of peak correlation lag times between spiking activity and force, whereas SIo neurons showed a unimodal distribution. Moreover, coherent activity between pairs of MIo neurons was higher and centered around force onset compared with pairwise coherence of SIo neurons. Overall, the results suggest that the neuroplasticity in MIo and SIo occurring in parallel serves as a substrate for linking sensation and movement during sensorimotor learning, whereas the differing dynamic organizations reflect specific ways to control movement parameters as learning progresses.

Loss of teeth or dental attrition is a common clinical occurrence associated with altered somatosensation and impaired oral motor behavior (e.g., mastication, deglutition, phonation). Oral rehabilitation aims at restoring these sensorimotor functions to improve patients' quality of life. Recent studies have implicated neuroplastic changes within the primary motor cortex (M1) in the control of limb motor behaviors following manipulations of sensory inputs to or motor outputs from the central nervous system as well as in learning and adaptation processes. However, limited data are available of the neuroplastic capabilities of face-M1 in relation to orofacial motor functions. The overall objective of our series of studies was to use intracortical microstimulation (ICMS) and recordings of evoked muscle electromyographic activity to test if neuroplastic changes occur in the ICMS-defined motor representations of the tongue-protrusive (genioglossus, GG) and jaw-opening (anterior digastric, AD) muscles within the rat face-M1 and adjacent face primary somatosensory cortex (face-S1) following several different types of intraoral manipulations. We found that a change in diet consistency was not associated with statistically significant changes in AD and GG motor representations. However, incisor extraction resulted, one week later, in a significantly increased AD representation within the contralateral face-M1 and face-S1, and incisor trimming produced time-dependent changes in the AD motor representation. These novel findings underscore the neuroplastic capabilities of the face sensorimotor cortex and point to its possible role in adaptation to an altered peripheral state or altered sensorimotor behavior. Further insights into the neuroplastic capabilities of the face sensorimotor cortex promise to improve therapeutic strategies aimed at the restoration of oral functions, particularly in patients suffering from orofacial sensorimotor deficits or pain., (Copyright © 2011 Elsevier B.V. All rights reserved.)