Mouse auditory cortex sub-fields receive neuronal projections from MGB subdivisions independently.

Mouse auditory cortex is composed of six sub-fields: primary auditory field (AI), secondary auditory field (AII), anterior auditory field (AAF), insular auditory field (IAF), ultrasonic field (UF) and dorsoposterior field (DP). Previous studies have examined thalamo-cortical connections in the mice auditory system and learned that AI, AAF, and IAF receive inputs from the ventral division of the medial geniculate body (MGB). However, the functional and thalamo-cortical connections between nonprimary auditory cortex (AII, UF, and DP) is unclear. In this study, we examined the locations of neurons projecting to these three cortical sub-fields in the MGB, and addressed the question whether these cortical sub-fields receive inputs from different subsets of MGB neurons or common. To examine the distributions of projecting neurons in the MGB, retrograde tracers were injected into the AII, UF, DP, after identifying these areas by the method of Optical Imaging. Our results indicated that neuron cells which in ventral part of dorsal MGB (MGd) and that of ventral MGB (MGv) projecting to UF and AII with less overlap. And DP only received neuron projecting from MGd. Interestingly, these three cortical areas received input from distinct part of MGd and MGv in an independent manner. Based on our foundings these three auditory cortical sub-fields in mice may independently process auditory information.

Perspective of Calcium Imaging Technology Applied to Acupuncture Research.

Acupuncture, a therapeutic treatment defined as the insertion of needles into the body at specific points (ie, acupoints), has growing in popularity world-wide to treat various diseases effectively, especially acute and chronic pain. In parallel, interest in the physiological mechanisms underlying acupuncture analgesia, particularly the neural mechanisms have been increasing. Over the past decades, our understanding of how the central nervous system and peripheral nervous system process signals induced by acupuncture has developed rapidly by using electrophysiological methods. However, with the development of neuroscience, electrophysiology is being challenged by calcium imaging in view field, neuron population and visualization in vivo. Owing to the outstanding spatial resolution, the novel imaging approaches provide opportunities to enrich our knowledge about the neurophysiological mechanisms of acupuncture analgesia at subcellular, cellular, and circuit levels in combination with new labeling, genetic and circuit tracing techniques. Therefore, this review will introduce the principle and the method of calcium imaging applied to acupuncture research. We will also review the current findings in pain research using calcium imaging from in vitro to in vivo experiments and discuss the potential methodological considerations in studying acupuncture analgesia.

Near-Infrared-Responsive Rare Earth Nanoparticles for Optical Imaging and Wireless Phototherapy.

Near-infrared (NIR) light is well-suited for the optical imaging and wireless phototherapy of malignant diseases because of its deep tissue penetration, low autofluorescence, weak tissue scattering, and non-invasiveness. Rare earth nanoparticles (RENPs) are promising NIR-responsive materials, owing to their excellent physical and chemical properties. The 4f electron subshell of lanthanides, the main group of rare earth elements, has rich energy-level structures. This facilitates broad-spectrum light-to-light conversion and the conversion of light to other forms of energy, such as thermal and chemical energies. In addition, the abundant loadable and modifiable sites on the surface offer favorable conditions for the functional expansion of RENPs. In this review, the authors systematically discuss the main processes and mechanisms underlying the response of RENPs to NIR light and summarize recent advances in their applications in optical imaging, photothermal therapy, photodynamic therapy, photoimmunotherapy, optogenetics, and light-responsive drug release. Finally, the challenges and opportunities for the application of RENPs in optical imaging and wireless phototherapy under NIR activation are considered.

Exploring the effect of photobiomodulation and gamma visual stimulation induced by 808 nm and visible LED in Alzheimer's disease mouse model.

Although photobiomodulation (PBM) and gamma visual stimulatqion (GVS) have been overwhelmingly explored in the recent time as a possible light stimulation (LS) means of Alzheimer's disease (AD) therapy, their effects have not been assessed at once. In our research, the AD mouse model was stimulated using light with various parameters [continuous wave (PBM) or 40 Hz pulsed visible LED (GVS) or 40 Hz pulsed 808 nm LED (PBM and GVS treatment)]]. The brain slices collected from the LS treated AD model mice were evaluated using (i) fluorescence microscopy to image thioflavine-S labeled amy-loid-ß (Aß) plaques (the main hallmark of AD), or (ii) two-photon excited fluorescence (TPEF) imaging of unlabeled Aß plaques, showing that the amount of Aß plaques was reduced after LS treatment. The imaging results correlated well with the results of Morris water maze (MWM) test, which demonstrated that the spatial learning and memory abilities of LS treated mice were noticeably higher than those of untreated mice. The LS effect was also assessed by in vivo nonlinear optical imaging, revealing that the cerebral amyloid angiopathy decreased spe-cifically as a result of 40 Hz pulsed 808 nm irradiation, on the contrary, the angiopathy reversed after visible 40 Hz pulsed light treatment. The obtained results provide useful reference for further optimization of the LS (PBM or GVS) parameters to achieve efficient phototherapy of AD.

Imaging assessment of photosensitizer emission induced by radionuclide-derived Cherenkov radiation using charge-coupled device optical imaging and long-pass filters.

BACKGROUND: Radionuclides produce Cherenkov radiation (CR), which can potentially activate photosensitizers (PSs) in phototherapy. Several groups have studied Cherenkov energy transfer to PSs using optical imaging; however, cost-effectively identifying whether PSs are excited by radionuclide-derived CR and detecting fluorescence emission from excited PSs remain a challenge. Many laboratories face the need for expensive dedicated equipment. AIM: To cost-effectively confirm whether PSs are excited by radionuclide-derived CR and distinguish fluorescence emission from excited PSs. METHODS: The absorbance and fluorescence spectra of PSs were measured using a microplate reader and fluorescence spectrometer to examine the photo-physical properties of PSs. To mitigate the need for expensive dedicated equipment and achieve the aim of the study, we developed a method that utilizes a charge-coupled device optical imaging system and appropriate long-pass filters of different wavelengths (manual sequential application of long-pass filters of 515, 580, 645, 700, 750, and 800 nm). Tetrakis (4-carboxyphenyl) porphyrin (TCPP) was utilized as a model PS. Different doses of copper-64 (64CuCl2) (4, 2, and 1 mCi) were used as CR-producing radionuclides. Imaging and data acquisition were performed 0.5 h after sample preparation. Differential image analysis was conducted by using ImageJ software (National Institutes of Health) to visually evaluate TCPP fluorescence. RESULTS: The maximum absorbance of TCPP was at 390-430 nm, and the emission peak was at 670 nm. The CR and CR-induced TCPP emissions were observed using the optical imaging system and the high-transmittance long-pass filters described above. The emission spectra of TCPP with a peak in the 645-700 nm window were obtained by calculation and subtraction based on the serial signal intensity (total flux) difference between 64CuCl2 + TCPP and 64CuCl2. Moreover, the differential fluorescence images of TCPP were obtained by subtracting the 64CuCl2 image from the 64CuCl2 + TCPP image. The experimental results considering different 64CuCl2 doses showed a dose-dependent trend. These results demonstrate that a bioluminescence imaging device coupled with different long-pass filters and subtraction image processing can confirm the emission spectra and differential fluorescence images of CR-induced TCPP. CONCLUSION: This simple method identifies the PS fluorescence emission generated by radionuclide-derived CR and can contribute to accelerating the development of Cherenkov energy transfer imaging and the discovery of new PSs.

In vivo skin optical clearing for improving imaging and light-induced therapy: a review.

Significance: Skin is the largest organ and also the first barrier of body. Skin diseases are common, and cutaneous microcirculation is relative to various diseases. Researchers attempt to develop novel imaging techniques to obtain the complex structure, components, and functions of skin. Modern optical techniques provide a powerful tool with non-invasiveness, but the imaging performance suffers from the turbid character of skin. In vivo skin optical clearing technique has been proposed to reduce tissue scattering and enhance penetration depth of light and became a hot topic of research. Aim: The aim of this review is to provide a comprehensive overview of recent development of in vivo skin optical clearing methods, how in vivo skin optical clearing enhances imaging performance, and its applications in study and light therapy of various diseases. Approach: Based on the references published over the last decade, the important milestones on the mechanism, methods, and its fundamental and clinical applications of in vivo skin optical clearing technique are provided. Results: With the deepening understanding of skin optical clearing mechanisms, efficient in vivo skin optical clearing methods were constantly screened out. These methods have been combined with various optical imaging techniques to improve imaging performances and acquire deeper and finer skin-related information. In addition, in vivo skin optical clearing technique has been widely applied in assisting study of diseases as well as achieving safe, high-efficiency light-induced therapy. Conclusions: In the last decade, in vivo skin optical clearing technique has developed rapidly and played an important role in skin-related studies.

Advances in the prevention and treatment of breast cancer-related lymphedema.

PURPOSE: Breast cancer-related lymphedema (BCRL) represents a lifelong risk for breast cancer survivors and once acquired becomes a lifelong burden. This review summarizes current BCRL prevention and treatment strategies. FINDINGS: Risk factors for BCRL have been extensively studied and their identification has affected breast cancer treatment practice, with sentinel lymph node removal now standard of care for patients with early stage breast cancer without sentinel lymph node metastases. Early surveillance and timely management aim to reduce BCRL incidence and progression, and are further facilitated by patient education, which many breast cancer survivors report not having adequately received. Surgical approaches to BCRL prevention include axillary reverse mapping, lymphatic microsurgical preventative healing (LYMPHA) and Simplified LYMPHA (SLYMPHA). Complete decongestive therapy (CDT) remains the standard of care for patients with BCRL. Among CDT components, facilitating manual lymphatic drainage (MLD) using indocyanine green fluorescence lymphography has been proposed. Intermittent pneumatic compression, nonpneumatic active compression devices, and low-level laser therapy appear promising in lymphedema management. Reconstructive microsurgical techniques such as lymphovenous anastomosis and vascular lymph node transfer are growing surgical considerations for patients as well as liposuction-based procedures for addressing fatty fibrosis formation from chronic lymphedema. Long-term self-management adherence remains problematic, and lack of diagnosis and measurement consensus precludes a comparison of outcomes. Currently, no pharmacological approaches have proven successful. CONCLUSION: Progress in prevention and treatment of BCRL continues, requiring advances in early diagnosis, patient education, expert consensus and novel treatments designed for lymphatic rehabilitation following insults.

Optical diagnostic imaging and therapy for thyroid cancer.

Thyroid cancer, as one of the most common endocrine cancers, has seen a surge in incidence in recent years. This is most likely due to the lack of specificity and accuracy of its traditional diagnostic modalities, leading to the overdiagnosis of thyroid nodules. Although there are several treatment options available, they are limited to surgery and 131I radiation therapy that come with significant side effects and hence cannot meet the treatment needs of anaplastic thyroid carcinoma with very high malignancy. Optical imaging that utilizes optical absorption, refraction and scattering properties, not only observes the structure and function of cells, tissues, organs, or even the whole organism to assist in diagnosis, but can also be used to perform optical therapy to achieve targeted non-invasive and precise treatment of thyroid cancer. These applications of screening, diagnosis, and treatment, lend to optical imaging's promising potential within the realm of thyroid cancer surgical navigation. Over the past decade, research on optical imaging in the diagnosis and treatment of thyroid cancer has been growing year by year, but no comprehensive review on this topic has been published. Here, we review key advances in the application of optical imaging in the diagnosis and treatment of thyroid cancer and discuss the challenges and potential for clinical translation of this technology.

Intravital optical imaging for immune cell tracking after photoimmunotherapy with plasmonic gold nanostars.

Bladder cancer has been ranked as one of the most commonly occurring cancers in men and women with approximately half of the diagnoses being the late stage and/or metastatic diseases. We have developed a novel cancer treatment by combining gold nanostar-mediated photothermal therapy with checkpoint inhibitor immunotherapy to treat bladder cancer. Experiment results with a murine animal model demonstrated that our developed photoimmunotherapy therapy is more efficacious than any individual studied treatment. In addition, we used intravital optical imaging with a dorsal skinfold window chamber animal model to study immune responses and immune cell accumulation in a distant tumor following our photoimmunotherapy. The mice used have the CX3CR1-GFP receptor on monocytes, natural killer cells, and dendritic cells allowing us to dynamically track their presence by fluorescence imaging. Our proof-of-principle study results showed that the photoimmunotherapy triggered anti-cancer immune responses to generate anti-cancer immune cells which accumulate in metastatic tumors. Our study results illustrate that intravital optical imaging is an efficient and versatile tool to investigate immune responses and mechanisms of photoimmunotherapy in future studies.

Skin optical clearing enabled by dissolving hyaluronic acid microneedle patches.

Optical imaging and phototherapy are of great significance in the detection, diagnosis, and therapy of diseases. Depth of light in the skin tissues in optical imaging and phototherapy can be significantly improved with the assistance of optical clearing technology by weakening the scattering from the refractive indexes inhomogeneity among skin constituents. However, the barrier of the stratum corneum restricts the penetration of optical clearing agents into deep tissues and limits the optical clearing effects. Herein, we develop an optical clearing strategy by using dissolving microneedle (MN) patches made of hyaluronic acid (HA), which can effortlessly and painlessly penetrate the stratum corneum to reach the epidermis and dermis. By using the HA MN patches, the transmittance of skin tissues is improved by about 12.13 %. We show that the HA MN patches enhance the clarity of blood vessels to realize naked-eyes observation. Moreover, a simulated subcutaneous tumor cells experiment also verifies that the optical clearing effects of the HA MN patch efficiently boost the efficiency of the photodynamic killing of tumor cells by 26.8 %. As a courageous attempt, this study provides a promising avenue to improve the optical clearing effects for further clinical application of optical imaging and phototherapy.

Multi-Modal Optical Imaging and Combined Phototherapy of Nasopharyngeal Carcinoma Based on a Nanoplatform.

Nasopharyngeal carcinoma (NPC) is a common malignant tumor of the head and neck with a high incidence rate worldwide, especially in southern China. Phototheranostics in combination with nanoparticles is an integrated strategy for enabling simultaneous diagnosis, real-time monitoring, and administration of precision therapy for nasopharyngeal carcinoma (NPC). It has shown great potential in the field of cancer diagnosis and treatment owing to its unique noninvasive advantages. Many Chinese and international research teams have applied nano-targeted drugs to optical diagnosis and treatment technology to conduct multimodal imaging and collaborative treatment of NPC, which has become a hot research topic. In this review, we aimed to introduce the recent developments in phototheranostics of NPC based on a nanoplatform. This study aimed to elaborate on the applications of nanoplatform-based optical imaging strategies and treatment modalities, including fluorescence imaging, photoacoustic imaging, Raman spectroscopy imaging, photodynamic therapy, and photothermal therapy. This study is expected to provide a scientific basis for further research and development of NPC diagnosis and treatment.

Phytoglycogen Encapsulation of Lanthanide-Based Nanoparticles as an Optical Imaging Platform with Therapeutic Potential.

Lanthanide-based upconverting nanoparticles (UCNPs) are largely sought-after for biomedical applications ranging from bioimaging to therapy. A straightforward strategy is proposed here using the naturally sourced polymer phytoglycogen to coencapsulate UCNPs with hydrophobic photosensitizers as an optical imaging platform and light-induced therapeutic agents. The resulting multifunctional sub-micrometer-sized luminescent beads are shown to be cytocompatible as carrier materials, which encourages the assessment of their potential in biomedical applications. The loading of UCNPs of various elemental compositions enables multicolor hyperspectral imaging of the UCNP-loaded beads, endowing these materials with the potential to serve as luminescent tags for multiplexed imaging or simultaneous detection of different moieties under near-infrared (NIR) excitation. Coencapsulation of UCNPs and Rose Bengal opens the door for potential application of these microcarriers for collagen crosslinking. Alternatively, coloading UCNPs with Chlorin e6 enables NIR-light triggered generation of reactive oxygen species. Overall, the developed encapsulation methodology offers a straightforward and noncytotoxic strategy yielding water-dispersible UCNPs while preserving their bright and color-tunable upconversion emission that would allow them to fulfill their potential as multifunctional platforms for biomedical applications.

NIR-II phototherapy agents with aggregation-induced emission characteristics for tumor imaging and therapy.

As one of the major public health concerns, malignant tumors threaten people's lives. With the increasing demand for early accurate diagnosis and the safe treatment of tumors, non-invasive optical imaging (including fluorescence imaging and photoacoustic imaging) and phototherapy (including photothermal therapy and photodynamic therapy) have received much attention. In particular, light in the near-infrared second region (NIR-II) has been attracting research interest, owing to its deep penetration, minimal tissue autofluorescence, and decreased tissue absorption and scattering. Among all biological materials, organic nanomaterials with aggregation-induced emission (AIE) properties have attracted significant attention, owing to various incomparable advantages, such as high brightness, good photostability, tunable photophysical properties, and good biosafety. To modulate the working optical region of AIE molecules to the NIR-II region, many researchers have tried a variety of methods in recent years, and the focus of this review is to summarize the three most common methods from the perspective of molecular design strategies. In addition, this article briefly reviews the recent five-year progress of NIR-II AIE luminophores in tumor imaging and phototherapy applications. The research status is also summarized and prospected, with the hope of contributing to further research.

The Fluorescent Effect of Withania Somnifera Chitosan Nanocomposite as an Effective Contrast Agent for Cancer Theragnostic: Experimental Study in Vitro.

Nanomedicine and fluorescent optical imaging are effective in early cancer detection. The current study synthesized biocompatible nanocomposites from natural biomaterials towards inexpensive and safe cancer theragnostic. Two forms of nanocomposites were synthesized using the ionic gelation method: 1. Chitosan/ Withania Somnifera /tripolyphosphate nanocomposites, 2. Withania Somnifera/Chitosan nanocomposites. The nanocomposites were characterized by dynamic light scattering, zeta potential, and the transmission electron microscope. Fourier transform infrared spectroscopy analyzed the Withania Somnifera root water extract, Chitosan, and the synthesized nanocomposites. The cytotoxicity of the nanocomposites was investigated against the colon cancer cells (Caco2 cells) in the absence and the presence of laser (665 nm, 5 mW) irradiation. MTT assay evaluated the cytotoxicity, and Trypan blue assay assessed the cell viability. Cancerous cells were photographed under the inverted microscope in the presence and the absence of laser irradiation. Results were analyzed statistically using one-way variance (ANOVA) analysis with Bonferroni post-Hoc multiple two-group comparisons. The characterization results ensured the successful synthesis of Withania Somnifera/Chitosan nanocomposites. The results showed an increase in the cytotoxicity against colon carcinoma and a decrease in cell viability in the presence and absence of Near-infrared laser irradiation under the action of nanocomposites. The cytotoxicity of the synthesized nanocomposites increased by exposing the cells to the laser. The shining light of the nanocomposites appeared on the cells photographed under the inverted microscope. The synthesized natural nanocomposites promise systemic cytotoxicity will be efficient in molecular imaging in vivo applications.

Iron oxide nanoparticles conjugated with organic optical probes for in vivo diagnostic and therapeutic applications.

The role and scope of functional inorganic nanoparticles in biomedical research is well established. Among these, iron oxide nanoparticles (IONPs) have gained maximum attention as they can provide targeting, imaging and therapeutic capabilities. Furthermore, incorporation of organic optical probes with IONPs can significantly enhance the scope and viability of their biomedical applications. Combination of two or more such applications renders multimodality in nanoparticles, which can be exploited to obtain synergistic benefits in disease detection and therapy viz theranostics, which is a key trait of nanoparticles for advanced biomedical applications. This review focuses on the use of IONPs conjugated with organic optical probe/s for multimodal diagnostic and therapeutic applications in vivo.

Multiple Visuotopically Organized Subdivisions of the Lateral Pulvinar/Central Lateral Inferior Pulvinar Project into Thin and Thick Stripe Compartments of V2 in Macaques.

The lateral and central lateral inferior pulvinar (PL/PIcl) of primates has been implicated in playing an important role in visual processing, but its physiological and anatomical characteristics remain to be elucidated. It has been suggested that there are two complete visuotopic maps in the PL/PIcl, each of which sends afferents into V2 and V4 in primates. Given that functionally distinct thin and thick stripes of V2 both receive inputs from the PL/PIcl, this raises the possibility of a presence of parallel segregated pathways within the PL/PIcl. To address this question, we selectively injected three types of retrograde tracers (CTB-488, CTB-555, and BDA) into thin or thick stripes in V2 and examined labeling in the PL/PIcl in macaques. As a result, we found that every cluster of retrograde labeling in the PL/PIcl included all three types of signals next to each other, suggesting that thin stripe- and thick stripe-projecting compartments are not segregated into domains. Unexpectedly, we found at least five topographically organized retrograde labeling clusters in the PL/PIcl, indicating the presence of more than two V2-projecting maps. Our results suggest that the PL/PIcl exhibits greater compartmentalization than previously thought. They may be functionally similar but participate in multiple cortico-pulvinar-cortical loops.

Electroacupuncture activates inhibitory neural circuits in the somatosensory cortex to relieve neuropathic pain.

Electroacupuncture (EA) has been accepted to effectively relieve neuropathic pain. Current knowledge of its neural modulation mainly covers the spinal cord and subcortical nuclei, with little evidence from the cortical regions. Using in vivo two-photon imaging in mice with chronic constriction injury, we found that EA treatment systemically modulated the Ca2+ activity of neural circuits in the primary somatosensory cortex, including the suppression of excitatory pyramidal neurons, potentiation of GABAergic somatostatin-positive interneurons, and suppression of vasoactive intestinal peptide-positive interneurons. Furthermore, EA-mediated alleviation of pain hypersensitivity and cortical modulation were dependent on the activation of endocannabinoid receptor 1. These findings collectively reveal a cortical circuit involved in relieving mechanical or thermal hypersensitivity under neuropathic pain and identify one molecular pathway directing analgesic effects of EA.

Diagnostic imaging in near-infrared photoimmunotherapy using a commercially available camera for indocyanine green.

Near-infrared photoimmunotherapy (NIR-PIT) is a new type of cancer treatment, which was recently approved in Japan for patients with inoperable head and neck cancer. NIR-PIT utilizes antibody-IRDye700DX (IR700) conjugates and NIR light at a wavelength of 690 nm. NIR light exposure leads to physicochemical changes in the antibody-IR700 conjugate cell receptor complex, inducing rapid necrotic cell death. Just as fluorescence guided surgery is useful for surgeons to resect tumors completely, real-time information of tumor locations would help clinicians irradiate NIR light more precisely. IR700 is a fluorescence dye that emits at 702 nm; however, there is no clinically available device optimized for detecting this fluorescence. On the other hand, many indocyanine green (ICG) fluorescence imaging devices have been approved for clinical use. Therefore, we investigated whether LIGHTVISION, one of the clinically available ICG cameras, could be employed for tumor detection. We hypothesized that irradiation with even low-power 690-nm laser light, attenuated by 99% with a neutral-density filter, could be detected with LIGHTVISION without fluorescence decay or therapeutic effect because of the long emission tail of IR700 beyond 800 nm (within the detection range of LIGHTVISION). We demonstrated that the LIGHTVISION camera, originally designed for ICG detection, can detect the tail of IR700 fluorescence in real time, thus enabling the visualization of target tumors.

Fluorescence Imaging of Tumor-Accumulating Antibody-IR700 Conjugates Prior to Near-Infrared Photoimmunotherapy (NIR-PIT) Using a Commercially Available Camera Designed for Indocyanine Green.

Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed cancer treatment that uses antibody-IRDye700DX (IR700) conjugates and was recently approved in Japan for patients with inoperable head and neck cancer. Exposure of the tumor with NIR light at a wavelength of 690 nm leads to physicochemical changes in the antibody-IR700 conjugate-cell receptor complex, resulting in increased hydrophobicity and damage to the integrity of the cell membrane. However, it is important that the tumor be completely exposed to light during NIR-PIT, and thus, a method to provide real-time information on tumor location would help clinicians direct light more accurately. IR700 is a fluorophore that emits at 702 nm; however, there is no clinically available device optimized for detecting this fluorescence. On the other hand, many indocyanine green (ICG) fluorescence imaging devices have been approved for clinical use in operating rooms. Therefore, we investigated whether LIGHTVISION, one of the clinically available ICG cameras, could be employed for NIR-PIT target tumor detection. Due to the limited benefits of adding IR700 molecules, the additional conjugation of IRDye800CW (IR800) or ICG-EG4-Sulfo-OSu (ICG-EG4), which has an overlapping spectrum with ICG, to trastuzumab-IR700 conjugates was performed. Conjugation of second NIR dyes did not interfere the efficacy of NIR-PIT. The dual conjugation of IR800 and IR700 to trastuzumab clearly visualized target tumors with LIGHTVISION by detecting emission light of IR800. We demonstrated that the conjugation of second NIR dyes enables us to provide a real-time feedback of tumor locations prior to NIR-PIT.

Densities and numbers of calbindin and parvalbumin positive neurons across the rat and mouse brain.

The calcium-binding proteins parvalbumin and calbindin are expressed in neuronal populations regulating brain networks involved in spatial navigation, memory processes, and social interactions. Information about the numbers of these neurons across brain regions is required to understand their functional roles but is scarcely available. Employing semi-automated image analysis, we performed brain-wide analysis of immunohistochemically stained parvalbumin and calbindin sections and show that these neurons distribute in complementary patterns across the mouse brain. Parvalbumin neurons dominate in areas related to sensorimotor processing and navigation, whereas calbindin neurons prevail in regions reflecting behavioral states. We also find that parvalbumin neurons distribute according to similar principles in the hippocampal region of the rat and mouse brain. We validated our results against manual counts and evaluated variability of results among researchers. Comparison of our results to previous reports showed that neuron numbers vary, whereas patterns of relative densities and numbers are consistent.