뉴럴 디코딩의 원리와 최신 연구 동향 소개

김광수,안정열,차성광,구교인,구용숙 대한의용생체공학회 2017 의공학회지 Vol.38 No.6

The neural decoding is a procedure that uses spike trains fired by neurons to estimate features of original stimulus. This is a fundamental step for understanding how neurons talk each other and, ultimately, how brains manage information. In this paper, the strategies of neural decoding are classified into three methodologies: rate decoding, temporal decoding, and population decoding, which are explained. Rate decoding is the firstly used and simplest decoding method in which the stimulus is reconstructed from the numbers of the spike at given time (e. g. spike rates). Since spike number is a discrete number, the spike rate itself is often not continuous and quantized, therefore if the stimulus is not static and simple, rate decoding may not provide good estimation for stimulus. Temporal decoding is the decoding method in which stimulus is reconstructed from the timing information when the spike fires. It can be useful even for rapidly changing stimulus, and our sensory system is believed to have temporal rather than rate decoding strategy. Since the use of large numbers of neurons is one of the operating principles of most nervous systems, population decoding has advantages such as reduction of uncertainty due to neuronal variability and the ability to represent a stimulus attributes simultaneously. Here, in this paper, three different decoding methods are introduced, how the information theory can be used in the neural decoding area is also given, and at the last machinelearning based algorithms for neural decoding are introduced.

Development of a Post-vitrectomy Injection of N-methyl-N-nitrosourea as a Localized Retinal Degeneration Rabbit Model

안소민,Jungryul Ahn,차성광,윤철민,박태관,구용숙,김성우 한국뇌신경과학회 2019 Experimental Neurobiology Vol.28 No.1

Since genetic models for retinal degeneration (RD) in animals larger than rodents have not been firmly established to date, we sought in the present study to develop a new rabbit model of drug-induced RD. First, intravitreal injection of N-methyl-N-nitrosourea (MNU) without vitrectomy in rabbits was performed with different doses. One month after injection, morphological changes in the retinas were identified with ultra-wide-field color fundus photography (FP) and fundus autofluorescence (AF) imaging as well as spectral-domain optical coherence tomography (OCT). Notably, the degree of RD was not consistently correlated with MNU dose. Then, to check the effects of vitrectomy on MNU-induced RD, the intravitreal injection of MNU after vitrectomy in rabbits was also performed with different doses. In OCT, while there were no significant changes in the retinas for injections up to 0.1 mg (i.e., sham, 0.05 mg, and 0.1 mg), outer retinal atrophy and retinal atrophy of the whole layer were observed with MNU injections of 0.3 mg and 0.5 mg, respectively. With this outcome, 0.2 mg MNU was chosen to be injected into rabbit eyes (n=10) at two weeks after vitrectomy for further study. Six weeks after injection, morphological identification with FP, AF, OCT, and histology clearly showed localized outer RD - clearly bordered non-degenerated and degenerated outer retinal area - in all rabbits. We suggest our post-vitrectomy MNU-induced RD rabbit model could be used as an interim animal model for visual prosthetics before the transition to larger animal models.

Synchrony of Spontaneous Burst Firing between Retinal Ganglion Cells Across Species

안정열,Huu Lam Phan,차성광,구교인,유용석,구용숙 한국뇌신경과학회 2020 Experimental Neurobiology Vol.29 No.4

Neurons communicate with other neurons in response to environmental changes. Their goal is to transmit information to their targets reliably. A burst, which consists of multiple spikes within a short time interval, plays an essential role in enhancing the reliability of information transmission through synapses. In the visual system, retinal ganglion cells (RGCs), the output neurons of the retina, show bursting activity and transmit retinal information to the lateral geniculate neuron of the thalamus. In this study, to extend our interest to the population level, the burstings of multiple RGCs were simultaneously recorded using a multi-channel recording system. As the first step in network analysis, we focused on investigating the pairwise burst correlation between two RGCs. Furthermore, to assess if the population bursting is preserved across species, we compared the synchronized bursting of RGCs between marmoset monkey (callithrix jacchus), one species of the new world monkeys and mouse (C57BL/6J strain). First, monkey RGCs showed a larger number of spikes within a burst, while the inter-spike interval, burst duration, and inter-burst interval were smaller compared with mouse RGCs. Monkey RGCs showed a strong burst synchronization between RGCs, whereas mouse RGCs showed no correlated burst firing. Monkey RGC pairs showed significantly higher burst synchrony and mutual information than mouse RGC pairs did. Comprehensively, through this study, we emphasize that two species have a different bursting activity of RGCs and different burst synchronization suggesting two species have distinctive retinal processing.

원발성 간암에서 PIVKA-II 및 Lens Culinaris Agglutinin-A 반응성 Alpha-fetoprotein(AFP-L3)의 임상적 유용성

배시현,박두호,양진모,박영민,차상복,최종영,성광용,조세현,정규원,선희식,김부성,최상욱,변병훈,한남익 대한간학회 2000 Clinical and Molecular Hepatology(대한간학회지) Vol.6 No.2

Background/Aims: Des-γ-carboxy prothrombin(DCP), a protein induced by vitamin K absence or antagonist-II(PIVKA-II), and Lens culinaris agglutinin-A reactive AFP-L3 have been reported to be useful markers for the diagnosis of hepatocellular carcinoma (HCC). In the present study, both the PIVKA-II and AFP-L3 were analyzed and compared with a conventional AFP to determine its usefulness, specificity and sensitivity in the diagnosis of HCC. Methods: Sera were collected from 108 patients consisting of 17 patients with chronic hepatitis, 22 patients with liver cirrhosis and 69 patients with HCC. The AFP-L3 was determined by an lectin affinity electrophoresis coupled with an antibody-affinity blotting. Level of DCP was measured by an enzyme immunoassay with an anti-DCP monoclonal antibody. Results: The sensitivity and specificity of PIVKA-II and AFP L3 were 49.3% and 89.5%, and 32.5% and 85.7%, respectively. No significant correlation was found between the PIVKA-II or AFP L3 and serum AFP. No correlation was found etween the PIVKA-II or AFP L3 and the characteristics of HCC. Conclusion: The determination of plasma DCP and AFP L3 levels combined with AFP levels may be useful especially for the differential diagnosis between HCC and chronic liver diseases without HCC.(Korean J HepatoBackground/Aims: Des-γ-carboxy prothrombin(DCP), a protein induced by vitamin K absence or antagonist-II(PIVKA-II), and Lens culinaris agglutinin-A reactive AFP-L3 have been reported to be useful markers for the diagnosis of hepatocellular carcinoma (HCC). In the present study, both the PIVKA-II and AFP-L3 were analyzed and compared with a conventional AFP to determine its usefulness, specificity and sensitivity in the diagnosis of HCC. Methods: Sera were collected from 108 patients consisting of 17 patients with chronic hepatitis, 22 patients with liver cirrhosis and 69 patients with HCC. The AFP-L3 was determined by an lectin affinity electrophoresis coupled with an antibody-affinity blotting. Level of DCP was measured by an enzyme immunoassay with an anti-DCP monoclonal antibody. Results: The sensitivity and specificity of PIVKA-II and AFP-L3 were 49.3% and 89.5%, and 32.5% and 85.7%, respectively. No significant correlation was found between the PIVKA-II or AFP-L3 and serum AFP. No correlation was found etween the PIVKA-II or AFP L3 and the characteristics of HCC. Conclusion: The determination of plasma DCP and AFP-L3 levels combined with AFP levels may be useful especially for the differential diagnosis between HCC and chronic liver diseases without HCC.(Korean J Hepatol 2000;6:205-214)l 2000;6:205-214)