The equivalence of information-theoretic and likelihood-based methods for neural dimensionality reduction

Stimulus dimensionality-reduction methods in neuroscience seek to identify a low-dimensional space of stimulus features that affect a neuron's probability of spiking. One popular method, known as maximally informative dimensions (MID), uses an information-theoretic quantity known as "single-spike information" to identify this space. Here we examine MID from a model-based perspective. We show that MID is a maximum-likelihood estimator for the parameters of a linear-nonlinear-Poisson (LNP) model, and that the empirical single-spike information corresponds to the normalized log-likelihood under a Poisson model. This equivalence implies that MID does not necessarily find maximally informative stimulus dimensions when spiking is not well described as Poisson. We provide several examples to illustrate this shortcoming, and derive a lower bound on the information lost when spiking is Bernoulli in discrete time bins. To overcome this limitation, we introduce model-based dimensionality reduction methods for neurons with non-Poisson firing statistics, and show that they can be framed equivalently in likelihood-based or information-theoretic terms. Finally, we show how to overcome practical limitations on the number of stimulus dimensions that MID can estimate by constraining the form of the non-parametric nonlinearity in an LNP model. We illustrate these methods with simulations and data from primate visual cortex

Temporal structure in neuronal activity during working memory in Macaque parietal cortex

A number of cortical structures are reported to have elevated single unit firing rates sustained throughout the memory period of a working memory task. How the nervous system forms and maintains these memories is unknown but reverberating neuronal network activity is thought to be important. We studied the temporal structure of single unit (SU) activity and simultaneously recorded local field potential (LFP) activity from area LIP in the inferior parietal lobe of two awake macaques during a memory-saccade task. Using multitaper techniques for spectral analysis, which play an important role in obtaining the present results, we find elevations in spectral power in a 50--90 Hz (gamma) frequency band during the memory period in both SU and LFP activity. The activity is tuned to the direction of the saccade providing evidence for temporal structure that codes for movement plans during working memory. We also find SU and LFP activity are coherent during the memory period in the 50--90 Hz gamma band and no consistent relation is present during simple fixation. Finally, we find organized LFP activity in a 15--25 Hz frequency band that may be related to movement execution and preparatory aspects of the task. Neuronal activity could be used to control a neural prosthesis but SU activity can be hard to isolate with cortical implants. As the LFP is easier to acquire than SU activity, our finding of rich temporal structure in LFP activity related to movement planning and execution may accelerate the development of this medical application.Comment: Originally submitted to the neuro-sys archive which was never publicly announced (was 0005002

RANCANG BANGUN SISTEM PENGUNCI OTOMATIS DENGAN KENDALI AKSES MENGGUNAKAN RFID CARD DAN PASSWORD BERBASIS MIKROKONTROLER ATMEGA 16

ABSTRAKKecanggihan teknologi semakin berkembang dalam berbagai bidang kehidupan. Hal ini ditandai dengan banyak bermunculan peralatan elektronik yang bermacam-macam bentuk dan fungsinya. Kemajuan teknologi elektronika turut membantu dalam pengembangan sistem keamanan yang lebih baik. Salah satu aplikasi sistem keamanan adalah untuk pengaman pengunci loker menggunakan kartu RFID dan password . Kunci pengaman pada pintu loker ini dirancang dengan menggunakan sistem ganda yang bertujuan agar pintu loker hanya dapat dibuka dengan menggunakan kartu RFID dan password. Kartu RFID berfungsi sebagai identitas loker dan password sebagai kunci elektroniknya. Setiap kartu RFID memiliki ID chip yang berbeda-beda sehingga tidak mudah untuk diduplikasi.Tujuan dari pembuatan alat ini adalah untuk merancang dan membuat pengunci loker otomatis membuka atau menutup pintu loker dengan kendali akses menggunakan kartu RFID dan password berbasis mikrokontroler ATmega 16. Kata Kunci : RFID, Password, Sistem Pengunci Loker Otomatis, Mikrokontroler ATmega 16.ABSTRACTTechnological sophistication is growing in many areas of life. It is characterized by many emerging electronic equipment that a variety of forms and functions. Advances of technology electronics helped in the development of better security systems. One of application is the security system used for safety locker locks using RFID card and password. The safety lock on the locker door is designed by using a dual system that aims the doors of locker which can only be opened by using RFID card and password. RFID card locker serves as the identity and password as the electronic lock. Each RFID card have different id chips, so it is not easy to duplicate. The purpose of making this tool is to design and make a locker lock open or closes the door of locker automatically with access control using RFID card and password.Key words : RFID, Password, Automatic Locker Lock System, Mikrokontroler ATmega 16

Modelling the Dynamics of a Renewable Resource under Harvesting with Taxation as a Control Variable

The present paper describes a model of resource biomass and population with a non-linear catch rate function on resource biomass. The harvesting effort is assumed to be a dynamical variable. Tax on per unit harvested resource biomass is used as a tool to control exploitation of the resource. Pontryagin’s Maximum Principle is used to find the optimal control to maintain the resource biomass and population at an optimal level. A numerical simulation is also carried out to support the analytical results

Problemi umjetnog osjemenjivanja jednogrbe deve - izostanak ovulacije i zadržavanje spermija u želatinoznoj spermi.

An artificial insemination study was conducted on 17 female camels which were administered human Chorionic Gonadotrophin (hCG) to induce ovulation after confirming a follicle in the ovaries using sonography. The animals were inseminated with either diluted-cooled or fresh undiluted semen. No female camel could be impregnated with diluted and cooled semen, while pregnancy rate was low with neat undiluted semen. To ascertain possible causes of low conception rate, plasma progesterone (P4) profiles were monitored. Criteria adopted for interpretation of these profiles were as follows: P4 levels below 1 ng/ml on days 5-8 was considered to indicate failure to ovulate; a single peak of 1ng/ml on days 5-8 followed by a decline on day 12 was considered to indicate ovulation. However, failure of fertilization and P4 levels of more than 1 ng/ml on days 5-8 and day 12 followed by a decline was considered to indicate successful ovulation and fertilization, but failure of embryo survival. Consistently higher levels of P4 were considered to be indicative of pregnancy. Using these criteria, 5 of 33 inseminations were diagnosed as pregnant, while profiles of 17 of 33, 8 of 33 and 3 of 33 were indicative of failure of ovulation, failure of fertilization and failure of embryo survival, respectively. A high incidence of failure of ovulation may be due to oversized follicles or follicles in which degenerative processes might have been initiated prior to administration of hCG. High failure of fertilization may be due to a viscous form of camel semen, which may play a role as a sperm reservoir and protect the viability of spermatozoa in the female genital tract by entrapping sperm. Insemination with diluted and cooled semen may disturb the protection, resulting in failure of conception. It is concluded that the high incidence of ovulation failure and failure to deposit sperm in its natural entrapped viscous form are the major problems for development of AI in the camel. Further improvement may be expected, if we are able to standardize the appropriate insemination time around peri ovulatory time, and appropriate follicular size, which responds to hCG.Umjetno osjemenjivanje provedeno je na 17 deva kojima je dan ljudski korionski gonadotropin (hCG) u svrhu poticanja ovulacije. Prethodno je ultrazvučnom metodom ustanovljen folikul na jajnicima pretraženih deva. Deve su osjemenjene ili razrijeđenom i rashlađenom ili svježom, nerazrijeđenom spermom. Nijedna deva nije bila oplođena nakon osjemenjivanja razrijeđenom i rashlađenom spermom, a nakon osjemenjivanja nerazrijeđenom spermom stopa oplođenosti bila je niska. Radi utvrđivanja mogućih uzroka niske stope koncepcije, utvrđivana je razina progesterona u plazmi (P4). Razina P4 ispod 1 ng/ml u razdoblju 5 do 8 dana smatrala se pokazateljem izostanka ovulacije. Jednokratni porast od 1 ng/ml tijekom 5-8 dana nakon kojeg je slijedio pad 12. dana, smatrao se pokazateljem ovulacije s neuspjelom oplodnjom. P4 razine veće od 1 ng/ml tijekom razdoblja 5 do 8 dana, uključujući 12. dan nakon kojeg slijedi opadanje smatrale su se uspješnom ovulacijom i oplodnjom ali neuspjelim preživljavanjem embrija. Postojano visoke razine P4 smatrale su se pokazateljem gravidnosti. Prema navedenim kriterijima, pet od 33 osjemenjivanja rezultirala su gravidnošću. U 17 od 33 osjemenjivanja izostala je ovulacija. U 8 od 33 osjemenjivanja nije došlo do oplodnje, a u tri od 33 osjemenjnivanja embrij nije preživio. Učestala pojavnost izostanka ovulacije mogla bi se povezati s prevelikim folikulima ili folikulima u kojih su degenerativni procesi započeli prije davanja hCG. Visoka učestalost neuspjele oplodnje, mogla bi se povezati s viskoznošću sperme, zbog koje su spermiji u genitalnom traktu deve zaštićeniji i lakše preživljavaju. Osjemenjivanje s razrijeđenom i rashlađenom spermom može poremetiti navedene zaštitne mehanizme i dovesti do slabije oplođenosti. Može se zaključiti da je učestalo izostajanje ovulacije i nemogućnost polaganja sperme u njezinom prirodno viskoznom obliku glavni problem za razvoj umjetnog osjemenjivanja deva. Daljnji napredak se može očekivati ako se standardizira prikladno vrijeme osjemenjivanja (periovulatorno vrijeme), te utvrdi veličina folikula koja najbolje odgovara na aplikaciju hCG

Error Analysis in Spin Measurement using Synchro-ballistic Method and its Improvement

Error analysis of spin measurement using synchro-ballistic method is presented in this paper. Error in the spin measurement varies as the projections of marker move away from axis of symmetry, and the reason for variation of error is explained. An improvement to synchro-ballistic method is proposed for spin measurement, which reduces the error in measured spin, and an algorithm for implementation of same is provided. Results of improved synchro-ballistic method are compared with the theoretical estimation of spin from muzzle velocity

Probabilistic Tensor Decomposition of Neural Population Spiking Activity

The firing of neural populations is coordinated across cells, in time, and across experimental conditions or repeated experimental trials, and so a full understanding of the computational significance of neural responses must be based on a separation of these different contributions to structured activity. Tensor decomposition is an approach to untangling the influence of multiple factors in data that is common in many fields. However, despite some recent interest in neuroscience, wider applicability of the approach is hampered by the lack of a full probabilistic treatment allowing principled inference of a decomposition from non-Gaussian spike-count data. Here, we extend the Polya-Gamma (PG) augmentation, previously used in sampling-based Bayesian inference, to implement scalable variational inference in non-conjugate spike-count models. Using this new approach, we develop techniques related to automatic relevance determination to infer the most appropriate tensor rank, as well as to incorporate priors based on known brain anatomy such as the segregation of cell response properties by brain area. We apply the model to neural recordings taken under conditions of visual-vestibular sensory integration, revealing how the encoding of self- and visual-motion signals is modulated by the sensory information available to the animal

Low current Cd4+T cell count: prediction, for persistent herpetic gingivostomatitis in HIV-positive patients under antiretroviral therapy

Background: Oral viral lesions associated with HIV infection are important since they affect the quality of life of the patient and are useful markers of disease progression and immunosuppression. The purpose of this study was to correlate the persistence of herpetic gingivostomatitis lesions with the current CD4+ T cell count for adherence of HIV-infected individuals to anti retroviral therapy (ART) and antiviral therapy.Methods: 302 HIV +ve patients developing oral ulcers were included in this study. The herpes simplex viral infections associated with the oral manifestations were detected through Immuno histochemical staining. The quantitative analysis of oral ulceration was done by using mucositis index.CD4T cell count was correlated with clinical manifestations of extensiveness of oral ulcers, acute febrile condition and other constitutional symptoms during follow up of cases for the treatment with anti viral therapies.Results: Association of herpes simplex viral infections was found in 72 out of 302 HIV+ ve cases. All the HSV +ve patients developed extensive oral mucsal lesions during the 1st week. Extensive lesions developed within 7 days in patients with CD4 count 500, manifestation of mucosal ulcers due to acute herpetic gingivostomatitis was limited to a period of 1 to 2 weeks. Patients with CD4 count >200 <500 did not follow a definite pattern.Conclusions: Persistent oropharyngeal mucosal ulcers along with acute febrile condition due to herpes simplex virus infection are associated with low CD4 T cell count in HIV + patients under antiretroviral therapy

Study of Radiophotoluminescence of Eu Doped CaSO4 Phosphor for Gamma Dosimetric Applications

CaSO4:Eu phosphor is synthesised by acid distillation method with varying synthesis parameters for studying its Radiophotoluminescence (RPL) properties for gamma absorbed dose measurements. Five phosphor samples are prepared by varying quantity of solvent, distillation temperature and reaction time. XRD, SEM, particle size analysis and photoluminescence studies are carried out. The characterisation study shows polycrystalline luminescent particles of average size varying from 35 μm to 55 μm. Characteristic emission of Eu3+ is observed around 590, 615 and 620 nm at 242 nm excitation. Gamma dose response of maximum Eu3+ PL intensity sample is studied in the range 10 cGy to 1000 cGy using Co-60 source. Gamma radiation exposure induces conversion of Eu3+ to Eu2+ giving luminescence at 385 nm with 320 nm excitation. Repetitive measurements of gamma exposed samples are carried out and no significant fading is observed within one week of post-irradiation. The phosphor has the potential to be used for gamma dosimetry

Prior context in audition informs binding and shapes simple features

A perceptual phenomenon is reported, whereby prior acoustic context has a large, rapid and long-lasting effect on a basic auditory judgement. Pairs of tones were devised to include ambiguous transitions between frequency components, such that listeners were equally likely to report an upward or downward ‘pitch’ shift between tones. We show that presenting context tones before the ambiguous pair almost fully determines the perceived direction of shift. The context effect generalizes to a wide range of temporal and spectral scales, encompassing the characteristics of most realistic auditory scenes. Magnetoencephalographic recordings show that a relative reduction in neural responsivity is correlated to the behavioural effect. Finally, a computational model reproduces behavioural results, by implementing a simple constraint of continuity for binding successive sounds in a probabilistic manner. Contextual processing, mediated by ubiquitous neural mechanisms such as adaptation, may be crucial to track complex sound sources over time