Normalization of Voltage-Sensitive Dye Signal with Functional Activity Measures

In general, signal amplitude in optical imaging is normalized using the well-established ΔF/F method, where functional activity is divided by the total fluorescent light flux. This measure is used both directly, as a measure of population activity, and indirectly, to quantify spatial and spatiotemporal activity patterns. Despite its ubiquitous use, the stability and accuracy of this measure has not been validated for voltage-sensitive dye imaging of mammalian neocortex in vivo. In this report, we find that this normalization can introduce dynamic biases. In particular, the ΔF/F is influenced by dye staining quality, and the ratio is also unstable over the course of experiments. As methods to record and analyze optical imaging signals become more precise, such biases can have an increasingly pernicious impact on the accuracy of findings, especially in the comparison of cytoarchitechtonic areas, in area-of-activation measurements, and in plasticity or developmental experiments. These dynamic biases of the ΔF/F method may, to an extent, be mitigated by a novel method of normalization, ΔF/ΔFepileptiform. This normalization uses as a reference the measured activity of epileptiform spikes elicited by global disinhibition with bicuculline methiodide. Since this normalization is based on a functional measure, i.e. the signal amplitude of “hypersynchronized” bursts of activity in the cortical network, it is less influenced by staining of non-functional elements. We demonstrate that such a functional measure can better represent the amplitude of population mass action, and discuss alternative functional normalizations based on the amplitude of synchronized spontaneous sleep-like activity. These findings demonstrate that the traditional ΔF/F normalization of voltage-sensitive dye signals can introduce pernicious inaccuracies in the quantification of neural population activity. They further suggest that normalization-independent metrics such as waveform propagation patterns, oscillations in single detectors, and phase relationships between detector pairs may better capture the biological information which is obtained by high-sensitivity imaging

Assessing Interest and Awareness Among Japanese Medical Students in International Standardized Testing: The Introduction of the National Board of Medical Examiners (NBME) Comprehensive Basic Science Examination (CBSE) in Japan

Title: "Assessing Interest and Awareness Among Japanese Medical Students in International Standardized Testing: The Introduction of the National Board of Medical Examiners (NBME) Comprehensive Basic Science Examination (CBSE) in Japan" Authors and Affiliations: Emi Saegusa-Beecroft, M.D., Ph.D.1,2,4 Kentaroh Takagaki, M.D., Ph.D., B.Agr.3 Junji B. Machi, M.D., Ph.D., FACS1,2,4 1. Office of Global Health and International Medicine, John A, Burns School of Medicine, University of Hawai`i at Manoa 2. Department of Surgery, John A, Burns School of Medicine, University of Hawai`i at Manoa 3. Department of Anatomy and Systems Biology, Faculty of Medicine, University of Yamanashi, Japan 4. JrSr Corporation, Japan (A Non-profit Educational Organization) Introduction: Since 2016, the University of Hawaii John A. Burns School of Medicine, in partnership with the JrSr Corporation and 14 out of 82 medical schools in Japan, has been offering the Hawaii Medical Education Program (HMEP). This program offers clinical clerkships, workshops, on-demand course materials, and live online classes, all focused on global health and international medical standards. This study's primary goal was to examine the feasibility of rolling out the National Board of Medical Examiners (NBME) Comprehensive Basic Science (CBSE) and Clinical Science Examinations (CCSE) in Tokyo, potentially impacting the U.S. healthcare workforce, highlighted by Non-U.S. International Medical Graduates comprising 27.2 percent of all primary care positions in the 2023 U.S. match [1], with a particular focus on Hawai'i due to its significant Japanese heritage community (16.5%) [2]. Objectives: 1. To assess the level of interest among Japanese medical students in internationally standardized medical testing, specifically the USMLE Step 1 and NBME shelf examinations. 2. To present the implementation of the NBME CBSE and CCSE in Japan, affirming our HMEP program's direct role in this educational advancement. Methods: Using Google Forms, an online anonymous survey was conducted across 14 medical schools, with 1900 students on the HMEP mailing list (20% of medical students). Of those, 279 students (15%) were active participants, defined by direct participation in any of the HMEP curriculum. Participation was voluntary, and data were collected and analyzed by two independent researchers. Results: Out of 115 survey responses, 101 responses from medical students were retained (36% of active students), and the other responses from residents and faculty were excluded. Among the valid responses (n=99; 79 pre-clinical and 22 clerkship students), 98% expressed interest in participating in a testing-center-based NBME CBSE (n=97), with 23% strongly determined to take the exam (n=23). Only 1 student was not interested in the USMLE Step 1. While 55% (n=54) planned to take the Step 1 exam during medical school, 8% (n=8) intended to do so during post-graduate residency, and one third remained undecided (35%, n=35). Respondents cited various reasons for pursuing clinical training in the U.S., including experiencing advanced medical practice (64%, n=63), a desire to live in the U.S. (35%, n=35), perceived higher physician compensation (26%, n=26), a desire to see the world (83%, n=82), a passion for global healthcare and international medicine (60%, n=59), and the belief in potential career advantages within Japan (22%, n=22). Regarding the USMLE Step 1, 47.5% (n=47) faced challenges in balancing exam preparation with extracurricular activities and their busy Japanese medical curriculum, while 62% (n=61) found gathering information for effective preparation challenging. Discussion: Survey results show strong interest for the NBME CBSE and CCSE at testing centers among Japan's medical students. A majority wish to train in the U.S., aiming for the USMLE. Although this study was limited by its voluntary nature, the survey offers insights into the ambitions and barriers of the responders who are highly-motivated students pursuing international medical careers, who may stand to benefit from new center-based exams, particularly for U.S. residencies. Conclusion: The introduction of NBME Shelf Examinations in Japan by the HMEP marks a significant milestone in aligning Japanese medical education with international standards. This initiative is a substantial contribution to the modernization of medical education in Japan. It addresses the strong demand from students aiming for international medical careers and enhances proficiency in professional English communication. The successful implementation of these examinations is anticipated to profoundly impact the global healthcare workforce, including in the U.S., by producing a generation of medical professionals equipped with global competencies and perspectives. Target Audience: International Medical Students, Medical School Faculty, Medical School Administrators, Medical Education Researchers. References: [1]https://www.nrmp.org/wp-content/uploads/2023/05/2023-Main-Match-Results-and-Data-Book-FINAL.pdf [2] 2020 Unites States Census<p/

Measurement, modeling, and prediction of temperature rise due to optogenetic brain stimulation

Optogenetics is one of the most important techniques in neurophysiology, with potential clinical applications. However, the strong light needed may cause harmful temperature rises. So far, there are no methods to reliably estimate brain heating and safe limits in actual optogenetic experiments. We used thermal imaging to directly measure such temperature rises at the surface of live mouse brains during laser illumination with wavelengths and intensities typical for optogenetics. We then modeled the temperature rise with a simple logarithmic model. Our results indicate that previous finite-element models can underestimate temperature increases by an order of magnitude. We validate our empirical model by predicting the temperature rise caused by pulsed stimulation paradigms. These predictions fit closely to the empirical data and constitute a better estimate of real temperature increases. Additionally, we provide a web-based app for easy calculation that can be used as a tool for safe design of optogenetic experiments

Fabrication of MEMS-based 3D-μECoG-MEAs

The microfabrication and packaging of novel, three-dimensional, polyimide-based, highly flexible, microscale electrocorticography multi-electrode arrays for enhanced epicortical recording of local field potentials is presented. A polyimide foil embeds metallic structures relating to 32 taper-type electrode sites, contact pads as well as interconnecting conductor paths which are integrated in the planar portion of the electrode substrate material. Circular exposed and, thus, active electrode sites are 50 μm in diameter and employed center-to-center pitches range from 250 μm to 1 mm, respectively. As-fabricated 3D-μECoG-MEAs provide taper heights of approximately 4 μm as well as 59 μm being distinguished by characteristic impedances of about 368.9 kΩ at 1 kHz measured in saline electrolyte. The applied packaging strategies favor flip-chip bonding and vapor phase soldering of the polymer substrates to customized printed circuit boards

Fabrication of MEMS-based 3D-μECoG-MEAs

The microfabrication and packaging of novel, three-dimensional, polyimide-based, highly flexible, microscale electrocorticography multi-electrode arrays for enhanced epicortical recording of local field potentials is presented. A polyimide foil embeds metallic structures relating to 32 taper-type electrode sites, contact pads as well as interconnecting conductor paths which are integrated in the planar portion of the electrode substrate material. Circular exposed and, thus, active electrode sites are 50 μm in diameter and employed center-to-center pitches range from 250 μm to 1 mm, respectively. As-fabricated 3D-μECoG-MEAs provide taper heights of approximately 4 μm as well as 59 μm being distinguished by characteristic impedances of about 368.9 kΩ at 1 kHz measured in saline electrolyte. The applied packaging strategies favor flip-chip bonding and vapor phase soldering of the polymer substrates to customized printed circuit boards

Identifying mesoscopic activity patterns in auditory category discrimination task

The capability to discriminate stimulus categories is required for complex cognitive processes and it is a feature present in different organisms. In the case of Mongolian gerbils, it has been shown that their primary auditory cortex is necessary for the formation of auditory categories with FM sweeps [1], since after cortex ablation the animals are not able to discriminate these stimulus categories, although still capable of discriminating pure tones. This indicates that the formation of categories is reflected in neuronal activity in this cortical area. Moreover, spatiotemporal patterns have been shown to occur in recordings with surface electrodes (electrocorticogram or ECoG) at the mesoscopic local field potential (LFP) level [2], indicating such a category formation. We hypothesize that we can also identify patterns of neuronal unit activity pertaining to specific categories when the animals are performing auditory category discrimination tasks, both at the level of single units (spikes, microscopic) and at LFP level (mesoscopic).Here we present a study which also serves as the first step towards an upcoming optogenetics study where the behavior of the animal will be manipulated by optical stimulation. We show that indeed we were able to find behavior related marked states, albeit here in the LFP signal from deeply inserted electrodes as opposed to the former study with ECoG signal (surface electrodes). These marked states were first identified in [2] as specific trajectories of neuronal activities (derived from parallel ECoG data) in the high-dimensional space, each indicating a particular category of the auditory stimuli. The experiment consists, as in [2], of an auditory category discrimination task where Mongolian gerbils are presented with either ‘rising’ or ‘falling’ frequency modulated sweeps (GO or NO GO stimuli, respectively) in a shuttlebox paradigm. If the animal receives a GO stimulus, it should shuttle within 4 seconds, otherwise it is shocked until it does. Conversely, in a NO GO trial, it does not get shocked if it stays put for 4 seconds, but will be shocked if it incorrectly shuttles. Throughout the trials recordings of electrophysiological signals were performed with a custom made set of tetrodes (3-8). LFPs and spikes were extracted from the recorded signals. We analyzed parallel LFP recordings for marked states with the same method as proposed in [2] but newly implemented in Python to be compatible with the open source data analysis toolbox Elephant developed at INM-6 [3]. With this method we were able to reproduce prior findings [2] by detecting marked states, i.e. they differed substantially between trials of GO stimulus and NO GO stimulus. Our next goal is to test if we find similar states in the parallel spiking activities, e.g. in the form of spatio-temporal patterns [4]. Of particular interest will be if and how the marked states identified in the mesoscopic signals (LFP) relate to the states identified at the microscopic level (spike data)