Multicore fiber optic imaging reveals that astrocyte calcium activity in the mouse cerebral cortex is modulated by internal motivational state.

Astrocytes are a direct target of neuromodulators and can influence neuronal activity on broad spatial and temporal scales in response to a rise in cytosolic calcium. However, our knowledge about how astrocytes are recruited during different animal behaviors remains limited. To measure astrocyte activity calcium in vivo during normative behaviors, we utilize a high-resolution, long working distance multicore fiber optic imaging system that allows visualization of individual astrocyte calcium transients in the cerebral cortex of freely moving mice. We define the spatiotemporal dynamics of astrocyte calcium changes during diverse behaviors, ranging from sleep-wake cycles to the exploration of novel objects, showing that their activity is more variable and less synchronous than apparent in head-immobilized imaging conditions. In accordance with their molecular diversity, individual astrocytes often exhibit distinct thresholds and activity patterns during explorative behaviors, allowing temporal encoding across the astrocyte network. Astrocyte calcium events were induced by noradrenergic and cholinergic systems and modulated by internal state. The distinct activity patterns exhibited by astrocytes provides a means to vary their neuromodulatory influence in different behavioral contexts and internal states.

Multicore fiber optic imaging reveals that astrocyte calcium activity in the cerebral cortex is modulated by internal motivational state.

Astrocytes are a direct target of neuromodulators and can influence neuronal activity on broad spatial and temporal scales through their close proximity to synapses. However, our knowledge about how astrocytes are functionally recruited during different animal behaviors and their diverse effects on the CNS remains limited. To enable measurement of astrocyte activity patterns in vivo during normative behaviors, we developed a high-resolution, long working distance, multi-core fiber optic imaging platform that allows visualization of cortical astrocyte calcium transients through a cranial window in freely moving mice. Using this platform, we defined the spatiotemporal dynamics of astrocytes during diverse behaviors, ranging from circadian fluctuations to novelty exploration, showing that astrocyte activity patterns are more variable and less synchronous than apparent in head-immobilized imaging conditions. Although the activity of astrocytes in visual cortex was highly synchronized during quiescence to arousal transitions, individual astrocytes often exhibited distinct thresholds and activity patterns during explorative behaviors, in accordance with their molecular diversity, allowing temporal sequencing across the astrocyte network. Imaging astrocyte activity during self-initiated behaviors revealed that noradrenergic and cholinergic systems act synergistically to recruit astrocytes during state transitions associated with arousal and attention, which was profoundly modulated by internal state. The distinct activity patterns exhibited by astrocytes in the cerebral cortex may provide a means to vary their neuromodulatory influence in response to different behaviors and internal states.

The Inmate Who Continues to Seize: Delayed Diagnosis of Zolpidem Withdrawal Due to Functional Mimics.

Functional neurological disorder (FND) is a constellation of common neurological symptoms without exact organic pathophysiology. The disease arises from aberrant neural computation, and its diagnosis is made upon positive clinical features. FND has emerged as a challenge to healthcare, as clinicians often have limited instructions in assessing it during their career, mainly when there are preexisting organic entities. Here we discuss an inmate whose diagnosis of zolpidem withdrawal seizure is delayed due to co-existing functional mimics and eventually led to an unfavorable outcome. We also review and summarize the current consensus on FND diagnosis and management. Together this report highlights the importance of careful investigation in atypical clinical presentation, with the intent to improve care for both organic and functional neurological patients.

Deep-learning two-photon fiberscopy for video-rate brain imaging in freely-behaving mice.

Scanning two-photon (2P) fiberscopes (also termed endomicroscopes) have the potential to transform our understanding of how discrete neural activity patterns result in distinct behaviors, as they are capable of high resolution, sub cellular imaging yet small and light enough to allow free movement of mice. However, their acquisition speed is currently suboptimal, due to opto-mechanical size and weight constraints. Here we demonstrate significant advances in 2P fiberscopy that allow high resolution imaging at high speeds (26 fps) in freely-behaving mice. A high-speed scanner and a down-sampling scheme are developed to boost imaging speed, and a deep learning (DL) algorithm is introduced to recover image quality. For the DL algorithm, a two-stage learning transfer strategy is established to generate proper training datasets for enhancing the quality of in vivo images. Implementation enables video-rate imaging at ~26 fps, representing 10-fold improvement in imaging speed over the previous 2P fiberscopy technology while maintaining a high signal-to-noise ratio and imaging resolution. This DL-assisted 2P fiberscope is capable of imaging the arousal-induced activity changes in populations of layer2/3 pyramidal neurons in the primary motor cortex of freely-behaving mice, providing opportunities to define the neural basis of behavior.

Multicolor fiber-optic two-photon endomicroscopy for brain imaging.

Visualizing activity patterns of distinct cell types during complex behaviors is essential to understand complex neural networks. It remains challenging to excite multiple fluorophores simultaneously so that different types of neurons can be imaged. In this Letter, we report a multicolor fiber-optic two-photon endomicroscopy platform in which two pulses from a Ti:sapphire laser and an optical parametric oscillator were synchronized and delivered through a single customized double-clad fiber to excite multiple chromophores. A third virtual wavelength could also be generated by spatial-temporal overlapping of the two pulses. The performance of the fiber-optic multicolor two-photon endomicroscope was demonstrated by in vivo imaging of a mouse cerebral cortex with "Brainbow" labeling.

Throughput-Speed Product Augmentation for Scanning Fiber-Optic Two-Photon Endomicroscopy.

Compactness, among several others, is one unique and very attractive feature of a scanning fiber-optic two-photon endomicroscope. To increase the scanning area and the total number of resolvable pixels (i.e., the imaging throughput), it typically requires a longer cantilever which, however, leads to a much undesired, reduced scanning speed (and thus imaging frame rate). Herein we introduce a new design strategy for a fiber-optic scanning endomicroscope, where the overall numerical aperture (NA) or beam focusing power is distributed over two stages: 1) a mode-field focuser engineered at the tip of a double-clad fiber (DCF) cantilever to pre-amplify the single-mode core NA, and 2) a micro objective of a lower magnification (i.e.,  âˆ¼ 2× in this design) to achieve final tight beam focusing. This new design enables either an ~9-fold increase in imaging area (throughput) or an ~3-fold improvement in imaging frame rate when compared to traditional fiber-optic endomicroscope designs. The performance of an as-designed endomicroscope of an enhanced throughput-speed product was demonstrated by two representative applications: (1) high-resolution imaging of an internal organ (i.e., mouse kidney) in vivo over a large field of view without using any fluorescent contrast agents, and (2) real-time neural imaging by visualizing dendritic calcium dynamics in vivo with sub-second temporal resolution in GCaMP6m-expressing mouse brain. This cascaded NA amplification strategy is universal and can be readily adapted to other types of fiber-optic scanners in compact linear or nonlinear endomicroscopes.

Focus scanning with feedback-control for fiber-optic nonlinear endomicroscopy.

Fiber-optic endomicroscopes open new avenues for the application of non-linear optics to novel in vivo applications. To achieve focus scanning in vivo, shape memory alloy (SMA) wires have been used to move optical elements in miniature endomicroscopes. However, this method has various limitations, making it difficult to achieve accurate and reliable depth scanning. Here we present a feedback-controlled SMA depth scanner. With a Hall effect sensor, contraction of the SMA wire can be tracked in real time, rendering accurate and robust control of motion. The SMA depth scanner can achieve up to 490 µm travel and with open-loop operation, it can move more than 350 µm within one second. With the feedback loop engaged, submicron positioning accuracy was achieved along with superior positioning stability. The high-precision positioning capability of the SMA depth scanner was verified by depth-resolved nonlinear endomicroscopic imaging of mouse brain samples.

Sexually dimorphic effect of catechol-O-methyltransferase val158met polymorphism on clinical response to fluoxetine in major depressive patients.

BACKGROUND: Essential in dopamine degradation, it was suggested that catechol-O-methyltransferase (COMT) might be involved in the action of antidepressants and may therefore be a promising candidate for antidepressant pharmacogenetic studies. METHODS: COMT Val158met polymorphism was genotyped in 334 Chinese major depressive disorder (MDD) patients who were treated with fluoxetine for at least 4 weeks. Clinical response was evaluated using the 21-item Hamilton Rating Scale for Depression (HAM-D(21)). In the analysis of association, response was defined as >or=50% decrease in HAM-D(21) score after treatment and then further clarified by intra-individual changes in HAM-D(21) score. RESULTS: We found that the COMT val158met polymorphism was not associated with 4-week fluoxetine therapeutic response; however, association analysis showed that patients with the COMT(Val/Val) genotype had poorer responses in the eighth week (CLUMP T1 P=0.020) and consistently showed significantly smaller reductions in HAM-D(21) scores in the eighth week (P=0.027). Further stratification based on gender revealed an isolated effect of the COMT genotype in males (P=0.035) but not in females (P=0.650) in percent reduction in HAM-D(21) scores in the eighth week. LIMITATIONS: There was a lack of placebo control and the serum fluoxetine concentration was not taken into account. CONCLUSIONS: This identified association between the COMT genetic variation and antidepressant response may be useful either as a clinical predictor in the future.

Association study of brain-derived neurotrophic factor and apolipoprotein E polymorphisms and cognitive function in aged males without dementia.

Genetic factors for inter-individual variation in cognition have been arousing great interest among researchers. Among the many associated genes, brain-derived neurotrophic factor (BDNF) and apolipoprotein E (APOE), as two of the most frequently studied, might be good prospects for cognitive genetics. Thus, the aim of this study was to investigate both the isolated and cooperative effect of BDNF and APOE on normal cognitive ageing. A homogeneous population of Chinese aged males (N=161) were genotyped for functional genetic variants of BDNF (BDNF-G196A) and APOE (APOE-epsilon4) and assessed by a comprehensive neuropsychological measurement (Cognitive Abilities Screening Instrument Chinese version; CASI C-2.0). Thereafter genotypic group differences of BDNF and APOE in CASI cognitive profiles were tested. Results from the present study suggest the possible influence of APOE on specific cognitive domains (CASI orientation and language domains; p=0.010 and 0.028, respectively), whereas there was no significant role of BDNF, either solely or with APOE, in cognition in the elderly. Our findings suggest a possible association between APOE-epsilon4 and specific cognitive domains in the aged male, whereas the functional genetic variant of BDNF (BDNF-G196A) played no significant role in normal cognitive ageing.

Evidence for association between genetic variants of p75 neurotrophin receptor (p75NTR) gene and antidepressant treatment response in Chinese major depressive disorder.

The p75 neurotrophin receptor (p75(NTR)) is an essential component of neurotrophin system, and has been implicated in the pathogenesis of major depressive disorder (MDD) and in the mechanism of antidepressant action. This study aimed to delineate the association between phenotype (MDD susceptibility and antidepressant response) and genotype (p75(NTR) common genetic variants) in a Chinese population. A total of 228 MDD patients and 402 unrelated controls were recruited. Subjects took selective serotonin reuptake inhibitors (SSRIs) and responders were defined as those with at least a 50% decrease in score of the Hamilton Rating Scale for Depression (HAM-D) from baseline. Five p75(NTR) polymorphisms were genotyped and their association with MDD or treatment response was assessed by haplotype and single marker analysis. No significant association with MDD was discovered in single locus or haplotype analyses. With regard to the therapeutic outcome, however, one missense polymorphism (S250L) showed association in both genotype distribution (P = 0.039) and allele frequency (P = 0.012). Haplotype analysis also revealed that p75(NTR) TCT carriers had a more unfavorable response to therapy (P = 0.010). Our exploratory study has demonstrated the association between p75(NTR) and SSRI response for the first time, which may assist in individualized therapy for MDD patients in the future.