The cerebellum could solve the motor error problem through error increase prediction

We present a cerebellar architecture with two main characteristics. The first one is that complex spikes respond to increases in sensory errors. The second one is that cerebellar modules associate particular contexts where errors have increased in the past with corrective commands that stop the increase in error. We analyze our architecture formally and computationally for the case of reaching in a 3D environment. In the case of motor control, we show that there are synergies of this architecture with the Equilibrium-Point hypothesis, leading to novel ways to solve the motor error problem. In particular, the presence of desired equilibrium lengths for muscles provides a way to know when the error is increasing, and which corrections to apply. In the context of Threshold Control Theory and Perceptual Control Theory we show how to extend our model so it implements anticipative corrections in cascade control systems that span from muscle contractions to cognitive operations.Comment: 34 pages (without bibliography), 13 figure

Learning and generation of temporal sequences in the neocortex

The temporal structure of neuronal activity plays a fundamental role in brain function. In addition to the compelling structure found in birdsong, repeating temporal sequences have been experimentally observed in the mammalian neocortex, both at the levels of local field potentials and individual neurons.\ud \ud The mechanisms underlying the learning and generation of temporal sequences are currently unknown. An attractive idea is that time-asymmetric Hebbian mechanisms capture the temporal structure of afferent signals by selectively strengthening the connections between sequentially activated neuronal populations. We explore some consequences of this idea using a simplified model of neocortex.\ud \ud Our model uses excitatory and inhibitory firing rate variables, along with adaptation and time-asymmetric Hebbian plasticity to create a versatile pattern generator which can store and reconstruct input sequences. We study several related properties of this model, mainly: 1) the formation of intersecting and complex sequences, 2) how the structure in the connection matrix affects the dynamics of the system and the symmetries observed in the activity of the network, 3) pathological behaviors due to abnormalities in plasticity and inhibition; the possible relation with epilepsy

A differential Hebbian framework for biologically-plausible motor control

In the realm of motor control, artificial agents cannot match the performance of their biological counterparts. We thus explore a neural control architecture that is both biologically plausible, and capable of fully autonomous learning. The architecture consists of feedback controllers that learn to achieve a desired state by selecting the errors that should drive them. This selection happens through a family of differential Hebbian learning rules that, through interaction with the environment, can learn to control systems where the error responds monotonically to the control signal. We next show that in a more general case, neural reinforcement learning can be coupled with a feedback controller to reduce errors that arise non-monotonically from the control signal. The use of feedback control reduces the complexity of the reinforcement learning problem, because only a desired value must be learned, with the controller handling the details of how it is reached. This makes the function to be learned simpler, potentially allowing to learn more complex actions. We discuss how this approach could be extended to hierarchical architectures.Comment: 35 pages, 10 figures. Appendix: 9 pages, 2 figure

WORKING MEMORY AND TEMPORAL PATTERNS: THE IMPLICATIONS OF NEURAL POPULATIONS

Working memory, the ability to temporarily retain information which will be used to guidesubsequent behavior, is a central component of our cognitive abilities. Almost 40 years ago,electrophysiological experiments in monkeys established that persistent activity may be theneuronal substrate of working memory. Many computational models have been proposedin order to explain persistent activity, with recurrent connections playing a prominent rolein many of these. No model, however, has captured all the important features in workingmemory networks. This work presents three related models which seek to understand someof these features. In particular, the first model explores the formation of firing rate patternsduring the delay period of working memory tasks; the second model explores the dynamicsof working memory networks with reduced inhibition, and their possible role in epilepsy;the third model explores the formation of temporal sequences and closed loops of activity.The three models assume the existence of densely connected neural populations (such asminicolumns), which respond similarly to the same stimuli. Another common feature is therole of dynamic synapses: the first two models rely on synaptic facilitation, whereas thethird uses temporally asymmetric Hebbian plasticity

Draculab: A Python Simulator for Firing Rate Neural Networks With Delayed Adaptive Connections

Draculab is a neural simulator with a particular use scenario: firing rate units with delayed connections, using custom-made unit and synapse models, possibly controlling simulated physical systems. Draculab also has a particular design philosophy. It aims to blur the line between users and developers. Three factors help to achieve this: a simple design using Python's data structures, extensive use of standard libraries, and profusely commented source code. This paper is an introduction to Draculab's architecture and philosophy. After presenting some example networks it explains basic algorithms and data structures that constitute the essence of this approach. The relation with other simulators is discussed, as well as the reasons why connection delays and interaction with simulated physical systems are emphasized

Lo propio y lo ajeno en narraciones sobre brujería del noreste de México

The stories about witchcraft in northeastern of Mexico always present how some situations that seem daily and normal end up covering up their true reality that is negative and harmful, that is, people, things or situations that seem good, in reality they are evil situations. The cover-up mentioned above occurs in an irruption of the alien in the own, where the alien is that which does not belong to the daily reality of the speaker and that is therefore considered as threatening and dangerous. The own usually appears as the daily, the usual and ordinary in the lives of these people. This paper shows the linguistic expressions with which the own, the alien and that inversion of the reality of the speakers of the southeast of the Mexican state of Coahuila are referred to in a series of 21 oral narratives on witchcraft. These references use differences between fright, fear, terror and horror to discursively express this process. When the borders between the own and the alien are blurred, the linguistic expressions return to these narratives in horror stories and raise the notion, from witchcraft, of an upside down world.Las narraciones sobre brujería en el noreste de México presentan siempre cómo algunas situaciones que parecen normales y cotidianas terminan encubriendo su verdadera realidad que es negativa y dañina, es decir, personas, cosas o situaciones que parecen buenas, en realidad son situaciones malas. El encubrimiento antes señalado se da en una irrupción de lo ajeno en lo propio, en donde lo ajeno es aquello que no pertenece a la realidad cotidiana del hablante y que por ello se considera como amenazante y peligroso. Lo propio suele aparecer como lo cotidiano, lo habitual y ordinario en la vida de estas personas. En este trabajo se muestran las expresiones lingüísticas con las que se refiere lo propio, lo ajeno y esa inversión de la realidad de los hablantes del sureste del estado mexicano de Coahuila en una serie de 21 narraciones orales sobre brujería. Estas referencias se sirven de las diferencias entre el susto, miedo, terror y horror para expresar discursivamente este proceso. Al difuminarse las fronteras entre lo propio y lo ajeno, las expresiones lingüísticas vuelven a estas narraciones en relatos de horror y plantean la noción, desde la brujería, de un mundo al revés

Numerical and Experimental Analysis of Sound Suppressor for a 5.56 mm Calibre

A sound suppressor is an internal or external device coupled to the barrel of a firearm. Its development has been historically related to the negative effects produced by the noise. This article presents the numerical and experimental analysis of a sound suppressor for a 5.56 mm caliber rifle. It was designed, manufactured, and tested inside a shooting tunnel for 911 m/s and 344 m/s velocities. Three geometric configurations with curved deflectors, conical deflectors, and finally with a reactive spiral capable of dissipating the acoustic wave were compared considering reactive and dissipative systems. The attenuation of the sound inside the silencer depends directly on the reduction of the projectile wave velocity and the deflagration of the gases at the instant of firing. Then the MIL-STD-1474E standard was used to carry out the experiments. The results in the computational numerical simulation show an average value of 143 dB for the considered three models, the Sound Pressure Level in the reactive core model decreased by 25% with respect to other proposals, which have an average value of 141 dB. These results can be useful to improve in the design of sound suppressors based on the needs of the users and under the specific characteristics of each weapon ballistic.&nbsp

School environment as a mediating variable between family support and social wellbeing in high school students

Educational institutions are crucial environments to promote students’ wellbeing. This introduces major challenges into the processes of executing and evaluating programmes such as the ones focused on achieving bullying-free schools. The concept of social wellbeing that is used throughout the present paper is associated to the subjective sense of action in the social construction and understanding of reality. The primary objective was to examine the relationship between Family Support (FS) and Social Wellbeing (SW) of high school education students in the state of Sonora, Mexico, as well as the effect of potential mediation of the School Environment (SE). This research was carried out with a cross-sectional sample of 265 teenagers (average age = 16 years old, SD=1.35), who responded to a self-report scale developed for this research study. The structural model has shown a high predictive power of SE as a mediating variable between FS and SW. Furthermore, both immediate contexts of students, i.e. family and school, were found to be relevant to their emotions and SW, which translates into a lower probability of being a victim of bullying. Therefore, we discuss a concept of SW seen from a perspective related to emotions, where material, economic, and/or monetary factors are not a priority.peer-reviewe

Evolution of substrate specificity in a retained enzyme driven by gene loss.

The connection between gene loss and the functional adaptation of retained proteins is still poorly understood. We apply phylogenomics and metabolic modeling to detect bacterial species that are evolving by gene loss, with the finding that Actinomycetaceae genomes from human cavities are undergoing sizable reductions, including loss of L-histidine and L-tryptophan biosynthesis. We observe that the dual-substrate phosphoribosyl isomerase A or priA gene, at which these pathways converge, appears to coevolve with the occurrence of trp and his genes. Characterization of a dozen PriA homologs shows that these enzymes adapt from bifunctionality in the largest genomes, to a monofunctional, yet not necessarily specialized, inefficient form in genomes undergoing reduction. These functional changes are accomplished via mutations, which result from relaxation of purifying selection, in residues structurally mapped after sequence and X-ray structural analyses. Our results show how gene loss can drive the evolution of substrate specificity from retained enzymes