Geometric transformation adaptive optics (GTAO) for volumetric deep brain imaging through gradient-index lenses.

The advance of genetic function indicators has enabled the observation of neuronal activities at single-cell resolutions. A major challenge for the applications on mammalian brains is the limited optical access depth. Currently, the method of choice to access deep brain structures is to insert miniature optical components. Among these validated miniature optics, the gradient-index (GRIN) lens has been widely employed for its compactness and simplicity. However, due to strong fourth-order astigmatism, GRIN lenses suffer from a small imaging field of view, which severely limits the measurement throughput and success rate. To overcome these challenges, we developed geometric transformation adaptive optics (GTAO), which enables adaptable achromatic large-volume correction through GRIN lenses. We demonstrate its major advances through in vivo structural and functional imaging of mouse brains. The results suggest that GTAO can serve as a versatile solution to enable large-volume recording of deep brain structures and activities through GRIN lenses.

Optical gearbox enabled versatile multiscale high-throughput multiphoton functional imaging.

To understand the function and mechanism of biological systems, it is crucial to observe the cellular dynamics at high spatiotemporal resolutions within live animals. The recent advances in genetically encoded function indicators have significantly improved the response rate to a near millisecond time scale. However, the widely employed in vivo imaging systems often lack the temporal solution to capture the fast biological dynamics. To broadly enable the capability of high-speed in vivo deep-tissue imaging, we developed an optical gearbox. As an add-on module, the optical gearbox can convert the common multiphoton imaging systems for versatile multiscale high-throughput imaging applications. In this work, we demonstrate in vivo 2D and 3D function imaging in mammalian brains at frame rates ranging from 50 to 1000 Hz. The optical gearbox's versatility and compatibility with the widely employed imaging components will be highly valuable to a variety of deep tissue imaging applications.

Monolithic 3D phase profile formation in glass for spatial and temporal control of optical waves.

Optical manufacturing technologies play a central role in modern science and engineering. Progress on both subtractive and additive fabrications is transforming the implementation of optical technologies. Despite the recent advances, modern fabrication still faces challenges in the accuracy, dimension, durability, intensity, and wavelength range. Here we present a direct monolithic 3D phase profile formation in glass and demonstrate its versatile applications for high-accuracy spatial and temporal control of optical waves in the extreme wavelength and intensity domains, direct fabrication of microlenses, and in situ aberration correction for refractive components. These advances and flexibilities will provide a new dimension for high-performance optical design and manufacture and enable novel applications in a broad range of disciplines.

High resolution ultrasonic neural modulation observed via in vivo two-photon calcium imaging.

Neural modulation plays a major role in delineating the circuit mechanisms and serves as the cornerstone of neural interface technologies. Among the various modulation mechanisms, ultrasound enables noninvasive label-free deep access to mammalian brain tissue. To date, most if not all ultrasonic neural modulation implementations are based on ∼1 MHz carrier frequency. The long acoustic wavelength results in a spatially coarse modulation zone, often spanning over multiple function regions. The modulation of one function region is inevitably linked with the modulation of its neighboring regions. Moreover, the lack of in vivo cellular resolution cell-type-specific recording capabilities in most studies prevents the revealing of the genuine cellular response to ultrasound. To significantly increase the spatial resolution, we explored the application of high-frequency ultrasound. To investigate the neuronal response at cellular resolutions, we developed a dual-modality system combining in vivo two-photon calcium imaging and focused ultrasound modulation. The studies show that the ∼30 MHz ultrasound can suppress the neuronal activity in awake mice at 100-µm scale spatial resolutions, paving the way for high-resolution ultrasonic neural modulation. The dual-modality in vivo system validated through this study will serve as a general platform for studying the dynamics of various cell types in response to ultrasound.

Clear optically matched panoramic access channel technique (COMPACT) for large-volume deep brain imaging.

To understand neural circuit mechanisms underlying behavior, it is crucial to observe the dynamics of neuronal structure and function in different regions of the brain. Since current noninvasive imaging technologies allow cellular-resolution imaging of neurons only within ~1 mm below the cortical surface, the majority of mouse brain tissue remains inaccessible. While miniature optical imaging probes allow access to deep brain regions, cellular-resolution imaging is typically restricted to a small tissue volume. To increase the tissue access volume, we developed a clear optically matched panoramic access channel technique (COMPACT). With probe dimensions comparable to those of common gradient-index lenses, COMPACT enables a two to three orders of magnitude greater tissue access volume. We demonstrated the capabilities of COMPACT by multiregional calcium imaging in mice during sleep. We believe that large-volume in vivo imaging with COMPACT will be valuable to a variety of deep tissue imaging applications.

Pupil plane actuated remote focusing for rapid focal depth control.

Laser scanning is widely employed in imaging and material processing. Common laser scanners are often fast for 2D transverse scanning. Rapid focal depth control is highly desired in many applications. Although remote focusing has been developed to achieve fast focal depth control, the implementation is limited by the laser damage to the actuator near laser focus. Here, we present a new method named pupil plane actuated remote focusing, which enables sub-millisecond response time while avoiding laser damage. We demonstrate its application by implementing a dual-plane two-photon laser scanning fluorescence microscope for in vivo recording of calcium transient of neurons in mouse neocortex.

Jitter suppression for resonant galvo based high-throughput laser scanning systems.

Laser scanning has been widely used in material processing and optical imaging. Among the established scanners, resonant galvo scanners offer high scanning throughput and 100% duty cycle and have been employed in various laser scanning microscopes. However, the common applications of resonant galvo often suffer from position jitters which could introduce substantial measurement artifacts. In this work, we systematically quantify the impact of position sensor, data acquisition system and air turbulence and provide a simple solution to achieve jitter free high-throughput measurement.

Line scanning mechanical streak camera for phosphorescence lifetime imaging.

Phosphorescence lifetime measurement holds great importance in life sciences and material sciences. Due to the long lifetime of phosphorescence emission, conventional approaches based on point scanning time-domain recording suffer from long recording time and low signal-to-noise ratio (SNR). To overcome these difficulties, we developed a line scanning mechanical streak camera for parallel and high SNR imaging. This design offers three key advantages. First, hundreds to thousands of pixels can be recorded simultaneously at high throughput. Second, hundreds of excitation can be accumulated on a single camera frame and read out at once with high quantum efficiency (QE) and low read noise. Third, the system is very simple, only requiring a camera and a scanner. Using a confocal line scanning configuration, we imaged samples of various lifetime ranging from tens of nanoseconds to hundreds of microseconds, which demonstrated the versatility and advantages of this method.

Contrast gain through simple illumination control for wide-field fluorescence imaging of scattering samples.

Wide field fluorescence microscopy is the most commonly employed fluorescence imaging modality. However, a major drawback of wide field imaging is the very limited imaging depth in scattering samples. By experimentally varying the control of illumination, we found that the optimized illumination profile can lead to large contrast improvement for imaging at a depth beyond four scattering path lengths. At such imaging depth, we found that the achieved image signal-to-noise ratio can rival that of confocal measurement. As the employed illumination control is very simple, the method can be broadly applied to a wide variety of wide field fluorescence imaging systems.

Large-scale femtosecond holography for near simultaneous optogenetic neural modulation.

For better understanding of brain functions, optogenetic neural modulation has been widely employed in neural science research. For deep tissue in vivo applications, large-scale two-photon based near simultaneous 3D laser excitation is needed. Although 3D holographic laser excitation is nowadays common practice, the inherent short coherence length of the commonly used femtosecond pulses fundamentally restricts the achievable field-of-view. Here we report a technique for near simultaneous large-scale femtosecond holographic 3D excitation. Specifically, we achieved two-photon excitation over 1.3 mm field-of-view within 1.3 milliseconds, which is sufficiently fast even for spike timing recording. The method is scalable and compatible with the commonly used two-photon sources and imaging systems in neuroscience research.

Neonatal Maternal Separation Impairs Prefrontal Cortical Myelination and Cognitive Functions in Rats Through Activation of Wnt Signaling.

Adverse early-life experience such as depriving the relationship between parents and children induces permanent phenotypic changes, and impairs the cognitive functions associated with the prefrontal cortex (PFC). However, the underlying mechanism remains unclear. In this work, we used rat neonatal maternal separation (NMS) model to illuminate whether and how NMS in early life affects cognitive functions, and what the underlying cellular and molecular mechanism is. We showed that rat pups separated from their dam 3 h daily during the first 3 postnatal weeks alters medial prefrontal cortex (mPFC) myelination and impairs mPFC-dependent behaviors. Myelination appears necessary for mPFC-dependent behaviors, as blockade of oligodendrocytes (OLs) differentiation or lysolecithin-induced demyelination, impairs mPFC functions. We further demonstrate that histone deacetylases 1/2 (HDAC1/2) are drastically reduced in NMS rats. Inhibition of HDAC1/2 promotes Wnt activation, which negatively regulates OLs development. Conversely, selective inhibition of Wnt signaling by XAV939 partly rescue myelination arrestment and behavior deficiency caused by NMS. These findings indicate that NMS impairs mPFC cognitive functions, at least in part, through modulation of oligodendrogenesis and myelination. Understanding the mechanism of NMS on mPFC-dependent behaviors is critical for developing pharmacological and psychological interventions for child neglect and abuse.

ß1-and ß2-adrenoceptors in hippocampal CA3 region are required for long-term memory consolidation in rats.

The existence of ß-adrenoceptors (ARs) in the hippocampus and the importance of ß-ARs in regulating synaptic plasticity and learning/memory function are well documented. As known, ß-ARs in area cornu ammonis 1 (CA1) are involved in regulating memory consolidation. However, little is known about the functional roles of the ß-ARs subtypes, ß1- and ß2-ARs, in the hippocampal cornu ammonis 3 (CA3) region. To address this question, we firstly locally infused the ß1- or ß2-ARs antagonist into the CA3 region and observed that blockage of either ß1-AR or ß2-AR impaired long-term contextual fear memory and water-maze spatial memory. We also found that, following the contextual fear conditioning, the expression of ß1-AR in the CA3 region significantly increased, whereas ß2-AR was unchanged. Then intra-CA3 infusion of recombinant lentiviral RNAi vectors for ß1 or ß2-ARs also produced deficit in contextual memory consolidation. Taken together, the results suggested that the ß1- and ß2-ARs in the CA3 region were involved in hippocampus dependent memory consolidation.