scholarly journals Coexistence of critical sensitivity and subcritical specificity can yield optimal population coding

2017 ◽  
Vol 14 (134) ◽  
pp. 20170207 ◽  
Author(s):  
Leonardo L. Gollo
Keyword(s):  
Dynamic Range ◽  
Heterogeneous Systems ◽  
External Input ◽  
Population Coding ◽  
Small Subset ◽  
Entire System ◽  
Critical Elements ◽  
Enhanced Sensitivity ◽  
Collective Response ◽  
Optimal Population

The vicinity of phase transitions selectively amplifies weak stimuli, yielding optimal sensitivity to distinguish external input. Along with this enhanced sensitivity, enhanced levels of fluctuations at criticality reduce the specificity of the response. Given that the specificity of the response is largely compromised when the sensitivity is maximal, the overall benefit of criticality for signal processing remains questionable. Here, it is shown that this impasse can be solved by heterogeneous systems incorporating functional diversity , in which critical and subcritical components coexist. The subnetwork of critical elements has optimal sensitivity, and the subnetwork of subcritical elements has enhanced specificity. Combining segregated features extracted from the different subgroups, the resulting collective response can maximize the trade-off between sensitivity and specificity measured by the dynamic-range-to-noise ratio. Although numerous benefits can be observed when the entire system is critical, our results highlight that optimal performance is obtained when only a small subset of the system is at criticality.

scholarly journals Optimal population coding by noisy spiking neurons

2010 ◽  
Vol 107 (32) ◽  
pp. 14419-14424 ◽  
Author(s):  
G. Tkacik ◽  
J. S. Prentice ◽  
V. Balasubramanian ◽  
E. Schneidman
Keyword(s):  
Population Coding ◽  
Spiking Neurons ◽  
Optimal Population

scholarly journals Optimal Short-Term Population Coding: When Fisher Information Fails

2002 ◽  
Vol 14 (10) ◽  
pp. 2317-2351 ◽  
Author(s):  
M. Bethge ◽  
D. Rotermund ◽  
K. Pawelzik
Keyword(s):  
Fisher Information ◽  
Dynamic Range ◽  
Mean Squared Error ◽  
Average Rate ◽  
Neuronal Response ◽  
Minimum Mean Square Error ◽  
Population Coding ◽  
Neuronal Firing ◽  
Tuning Curves ◽  
Efficient Coding

Efficient coding has been proposed as a first principle explaining neuronal response properties in the central nervous system. The shape of optimal codes, however, strongly depends on the natural limitations of the particular physical system. Here we investigate how optimal neuronal encoding strategies are influenced by the finite number of neurons N (place constraint), the limited decoding time window length T (time constraint), the maximum neuronal firing rate fmax (power constraint), and the maximal average rate fmax (energy constraint). While Fisher information provides a general lower bound for the mean squared error of unbiased signal reconstruction, its use to characterize the coding precision is limited. Analyzing simple examples, we illustrate some typical pitfalls and thereby show that Fisher information provides a valid measure for the precision of a code only if the dynamic range (fmin T, fmax T) is sufficiently large. In particular, we demonstrate that the optimal width of gaussian tuning curves depends on the available decoding time T. Within the broader class of unimodal tuning functions, it turns out that the shape of a Fisher-optimal coding scheme is not unique. We solve this ambiguity by taking the minimum mean square error into account, which leads to flat tuning curves. The tuning width, however, remains to be determined by energy constraints rather than by the principle of efficient coding.

Exhaustive Photon Reassignment™: A Method Offering Enhanced Sensitivity and Quantitative Accuracy for High Resolution Fluorescence Microscopy

1997 ◽  
Vol 3 (S2) ◽  
pp. 379-380
Author(s):  
Jennifer A. Kramer ◽  
Ramkumar K. Moorthy ◽  
William N. Casavan ◽  
David C. Hitrys
Keyword(s):  
High Resolution ◽  
Dynamic Range ◽  
Imaging System ◽  
Three Dimensional ◽  
Short Exposure ◽  
Enhanced Sensitivity ◽  
Quantitative Accuracy ◽  
University Of Massachusetts ◽  
The University ◽  
Contrast Image

Confocal microscopy is a technique that allows researchers to obtain a highly resolved, high-contrast image of a focal plane in a fluorescent specimen by excluding or rejecting light emanating from out-of-focus planes. However, the basic design of confocals results in limitations for many biologists. It is often difficult to avoid photobleaching of specimens, to visualize fine or faintly-labeled structures, or to acquire high-quality images using short exposure times. The photomultiplier tubes used as the amplification detectors in these systems are restricted to a dynamic range of 8 bits (255 intensity levels), produce noise, and are not quantitatively linear detectors.Members of the Biomedical Imaging Group at the University of Massachusetts Medical School in Worcester, MA have spent the last fifteen years developing and perfecting a digital imaging system that helps scientists overcome these problems. Scanalytics is the exclusive worldwide licensee of this patented technology which allows researchers to obtain high-resolution, quantitatively accurate three-dimensional images of fluorescent specimens

scholarly journals Neuronal hyperexcitability in the ventral posterior thalamus of neuropathic rats: modality selective effects of pregabalin

2016 ◽  
Vol 116 (1) ◽  
pp. 159-170 ◽  
Author(s):  
Ryan Patel ◽  
Anthony H. Dickenson
Keyword(s):  
Dynamic Range ◽  
Spinal Nerve ◽  
Population Coding ◽  
Mechanical Stimuli ◽  
Spinothalamic Tract ◽  
Noxious Heat ◽  
Posterior Thalamus ◽  
Central Processing ◽  
Wdr Neurons

Neuropathic pain represents a substantial clinical challenge; understanding the underlying neural mechanisms and back-translation of therapeutics could aid targeting of treatments more effectively. The ventral posterior thalamus (VP) is the major termination site for the spinothalamic tract and relays nociceptive activity to the somatosensory cortex; however, under neuropathic conditions, it is unclear how hyperexcitability of spinal neurons converges onto thalamic relays. This study aimed to identify neural substrates of hypersensitivity and the influence of pregabalin on central processing. In vivo electrophysiology was performed to record from VP wide dynamic range (WDR) and nociceptive-specific (NS) neurons in anesthetized spinal nerve-ligated (SNL), sham-operated, and naive rats. In neuropathic rats, WDR neurons had elevated evoked responses to low- and high-intensity punctate mechanical stimuli, dynamic brushing, and innocuous and noxious cooling, but less so to heat stimulation, of the receptive field. NS neurons in SNL rats also displayed increased responses to noxious punctate mechanical stimulation, dynamic brushing, noxious cooling, and noxious heat. Additionally, WDR, but not NS, neurons in SNL rats exhibited substantially higher rates of spontaneous firing, which may correlate with ongoing pain. The ratio of WDR-to-NS neurons was comparable between SNL and naive/sham groups, suggesting relatively few NS neurons gain sensitivity to low-intensity stimuli leading to a “WDR phenotype.” After neuropathy was induced, the proportion of cold-sensitive WDR and NS neurons increased, supporting the suggestion that changes in frequency-dependent firing and population coding underlie cold hypersensitivity. In SNL rats, pregabalin inhibited mechanical and heat responses but not cold-evoked or elevated spontaneous activity.

scholarly journals Facial injections of pruritogens or algogens elicit distinct behavior responses in rats and excite overlapping populations of primary sensory and trigeminal subnucleus caudalis neurons

2011 ◽  
Vol 106 (3) ◽  
pp. 1078-1088 ◽  
Author(s):  
Amanda Klein ◽  
Mirela Iodi Carstens ◽  
E. Carstens
Keyword(s):  
Dynamic Range ◽  
Allyl Isothiocyanate ◽  
Population Coding ◽  
Second Order ◽  
Mustard Oil ◽  
Sprague Dawley ◽  
Wide Dynamic Range ◽  
Sprague Dawley Rats ◽  
Dose Dependent ◽  
Trigeminal Subnucleus Caudalis

In the present study, we investigated whether intradermal cheek injection of pruritogens or algogens differentially elicits hindlimb scratches or forelimb wipes in Sprague-Dawley rats, as recently reported in mice. We also investigated responses of primary sensory trigeminal ganglion (TG) and dorsal root ganglion (DRG) cells, as well as second-order neurons in trigeminal subnucleus caudalis (Vc), to pruritic and algesic stimuli. 5-HT was the most effective chemical to elicit dose-dependent bouts of hindlimb scratches directed to the cheek, with significantly less forelimb wiping, consistent with itch. Chloroquine also elicited significant scratching but not wiping. Allyl isothiocyanate (AITC; mustard oil) elicited dose-dependent wiping with no significant scratching. Capsaicin elicited equivalent numbers of scratch bouts and wipes, suggesting a mixed itch and pain sensation. By calcium imaging, ∼6% of cultured TG and DRG cells responded to 5-HT. The majority of 5-HT-sensitive cells also responded to chloroquine, AITC, and/or capsaicin, and one-third responded to histamine. Using a chemical search strategy, we identified single units in Vc that responded to intradermal cheek injection of 5-HT. Most were wide dynamic range (WDR) or nociceptive specific (NS), and a few were mechanically insensitive. The large majority additionally responded to AITC and/or capsaicin and thus were not pruritogen selective. These results suggest that primary and second-order neurons responsive to pruritogens and algogens may utilize a population coding mechanism to distinguish between itch and pain, sensations that are behaviorally manifested by distinct hindlimb scratching and forelimb wiping responses.

scholarly journals Optimal Population Coding, Revisited

2011 ◽  
Author(s):  
Philipp Berens ◽  
Alexander Ecker ◽  
Sebastian Gerwinn ◽  
Andreas Tolias ◽  
Matthias Bethge
Keyword(s):  
Population Coding ◽  
Optimal Population

2152–69: The First Image from the Australia Telescope

1990 ◽  
Vol 8 (3) ◽  
pp. 252-253 ◽  
Author(s):  
R. P. Norris ◽  
M. J. Kesteven ◽  
R. A. Sramek ◽  
W. E. Wilson ◽  
J. W. Brooks ◽  
...  
Keyword(s):  
Radio Galaxy ◽  
Dynamic Range ◽  
High Dynamic Range ◽  
Small Subset ◽  
The Future ◽  
High Dynamic ◽  
Compact Array

AbstractAlthough only three antennas of the Australia Telescope Compact Array are currently operational, we have made use of the technique of bandwidth synthesis to make an image of the radio galaxy 2152 – 69. The three baselines were used to observe the source at three different frequencies, effectively resulting in nine baselines, which have been used to produce an image with a surprisingly high dynamic range, and with a slightly higher resolution than any existing image.The production of such a worthwhile result, despite being made with a small subset of the capabilities of the Australia Telescope, bodes well for the future operation of the instrument.

scholarly journals Functional diversity among sensory neurons from efficient coding principles

2017 ◽  
Author(s):  
Julijana Gjorgjieva ◽  
Markus Meister ◽  
Haim Sompolinsky
Keyword(s):  
Mutual Information ◽  
Sensory Neurons ◽  
Population Coding ◽  
Natural Stimulus ◽  
Neural Signal ◽  
Efficient Coding ◽  
Signal Stimulus ◽  
Optimal Linear ◽  
Optimal Population ◽  
Two Measures

AbstractIn many sensory systems the neural signal is coded by the coordinated response of heterogeneous populations of neurons. What computational benefit does this diversity confer on information processing? We derive an efficient coding framework assuming that neurons have evolved to communicate signals optimally given natural stimulus statistics and metabolic constraints. Incorporating nonlinearities and realistic noise, we study optimal population coding of the same sensory variable using two measures: maximizing the mutual information between stimuli and responses, and minimizing the error incurred by the optimal linear decoder of responses. Our theory is applied to a commonly observed splitting of sensory neurons into ON and OFF that signal stimulus increases or decreases, and to populations of monotonically increasing responses of the same type, ON. Depending on the optimality measure, we make different predictions about how to optimally split a population into ON and OFF, and how to allocate the firing thresholds of individual neurons given realistic stimulus distributions and noise, which accord with certain biases observed experimentally.

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