scholarly journals Artificial Complex Cells via the Tropical Semiring

2007 ◽  
Author(s):  
Lior Wolf ◽  
Moshe Guttmann
Keyword(s):  
Complex Cells ◽  
Tropical Semiring

Languages Accepted by Weighted Restarting Automata*

2021 ◽  
Vol 180 (1-2) ◽  
pp. 151-177
Author(s):  
Qichao Wang
Keyword(s):  
General Class ◽  
Formal Languages ◽  
Input Word ◽  
Additional Requirement ◽  
Tropical Semiring

Weighted restarting automata have been introduced to study quantitative aspects of computations of restarting automata. In earlier works we studied the classes of functions and relations that are computed by weighted restarting automata. Here we use them to define classes of formal languages by restricting the weight associated to a given input word through an additional requirement. In this way, weighted restarting automata can be used as language acceptors. First, we show that by using the notion of acceptance relative to the tropical semiring, we can avoid the use of auxiliary symbols. Furthermore, a certain type of word-weighted restarting automata turns out to be equivalent to non-forgetting restarting automata, and another class of languages accepted by word-weighted restarting automata is shown to be closed under the operation of intersection. This is the first result that shows that a class of languages defined in terms of a quite general class of restarting automata is closed under intersection. Finally, we prove that the restarting automata that are allowed to use auxiliary symbols in a rewrite step, and to keep on reading after performing a rewrite step can be simulated by regular-weighted restarting automata that cannot do this.

scholarly journals Origin of the Eukaryotic Cell

2017 ◽  
Vol 01 (02) ◽  
pp. 108-120 ◽  
Author(s):  
Nick Lane
Keyword(s):  
Protein Synthesis ◽  
Host Cell ◽  
Genome Size ◽  
Energy Savings ◽  
Nuclear Genome ◽  
Eukaryotic Cell ◽  
Eukaryotic Cells ◽  
Bacterial Genomes ◽  
Complex Cells ◽  
Life On Earth

All complex life on Earth is composed of ‘eukaryotic’ cells. Eukaryotes arose just once in 4 billion years, via an endosymbiosis — bacteria entered a simple host cell, evolving into mitochondria, the ‘powerhouses’ of complex cells. Mitochondria lost most of their genes, retaining only those needed for respiration, giving eukaryotes ‘multi-bacterial’ power without the costs of maintaining thousands of complete bacterial genomes. These energy savings supported a substantial expansion in nuclear genome size, and far more protein synthesis from each gene.

scholarly journals Encoding of Binocular Disparity by Complex Cells in the Cat's Visual Cortex

1997 ◽  
Vol 77 (6) ◽  
pp. 2879-2909 ◽  
Author(s):  
Izumi Ohzawa ◽  
Gregory C. Deangelis ◽  
Ralph D. Freeman
Keyword(s):  
Visual Cortex ◽  
Striate Cortex ◽  
Binocular Disparity ◽  
Substantial Reduction ◽  
Energy Model ◽  
Simple Type ◽  
Correspondence Problem ◽  
Complex Cell ◽  
Stimulus Contrast ◽  
Complex Cells

Ohzawa, Izumi, Gregory C. DeAngelis, and Ralph D. Freeman. Encoding of binocular disparity by complex cells in the cat's visual cortex. J. Neurophysiol. 77: 2879–2909, 1997. To examine the roles that complex cells play in stereopsis, we have recorded extracellularly from isolated single neurons in the striate cortex of anesthetized paralyzed cats. We measured binocular responses of complex cells using a comprehensive stimulus set that encompasses all possible combinations of positions over the receptive fields for the two eyes. For a given position combination, stimulus contrast could be the same for the two eyes (2 bright or 2 dark bars) or opposite (1 bright and 1 dark). These measurements provide a binocular receptive field (RF) profile that completely characterizes complex cell responses in a joint domain of left and right stimulus positions. Complex cells typically exhibit a strong selectivity for binocular disparity, but are only broadly selective for stimulus position. For most cells, selectivity for disparity is more than twice as narrow as that for position. These characteristics are highly desirable if we assume that a disparity sensor should exhibit position invariance while encoding small changes in stimulus depth. Complex cells have nearly identical binocular RFs for bright and dark stimuli as long as the sign of stimulus contrast is the same for the two eyes. When stimulus contrast is opposite, the binocular RF also is inverted such that excitatory subregions become suppressive. We have developed a disparity energy model that accounts for the behavior of disparity-sensitive complex cells. This is a hierarchical model that incorporates specific constraints on the selection of simple cells from which a complex cell receives input. Experimental data are used to examine quantitatively predictions of the model. Responses of complex cells generally agree well with predictions of the disparity energy model. However, various types of deviations from the predictions also are found, including a highly elongated excitatory region beyond that supported by a single energy mechanism. Complex cells in the visual cortex appear to provide a next level of abstraction in encoding information for stereopsis based on the activity of a group of simple-type subunits. In addition to exhibiting narrow disparity tuning and position invariance, these cells seem to provide a partial solution to the stereo correspondence problem that arises in complex natural scenes. Based on their binocular response properties, these cells provide a substantial reduction in the complexity of the correspondence problem.

scholarly journals Spatio-temporal requirements for direction selectivity in area 18 and PMLS complex cells

2005 ◽  
Vol 45 (13) ◽  
pp. 1769-1779 ◽  
Author(s):  
Ildikó Vajda ◽  
Martin J.M. Lankheet ◽  
Wim A. van de Grind
Keyword(s):  
Direction Selectivity ◽  
Complex Cells ◽  
Area 18 ◽  
Spatio Temporal

scholarly journals Identification of SRC, LCK, ABL, JAK1 genes exrression in lymphohemopoietic complex cells on fetal material application

2016 ◽  
Vol 0 (1 (1)) ◽  
pp. 40-46
Author(s):  
Анатолій Миколайович Гольцев ◽  
Олена Дмитрівна Луценко ◽  
Катерина Євгенівна Ямпольська ◽  
Максим Вадимович Останков ◽  
Миколай Олександрович Бондарович
Keyword(s):  
Complex Cells
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