Autoshaped impulsivity: Some explorations with a neural network model.

This study evaluated the effect of delay and magnitude of reinforcement in Pavlovian contingencies, extending the understanding of the phenomenon of autoshaped impulsivity as described in Alcalá's thesis (2017) and Burgos and García-Leal (2015). The effects of adding a trace interval were analyzed on the maintained responses of impulsive choice, seen as the preference of a small and immediate reinforcer over a larger and delayed one, and the role of the contextual unit, as well as the inhibitory units according to the Diffuse Discrepancy Model. In the Simulation, the model with inhibitory units was used, trained in two signals with different delays and reinforcement magnitudes, and subsequently presented concurrently in choice tasks without reinforcement nor learning, using an ABA within-subject design. In general, the DD model successfully simulated the phenomenon of autoshaped impulsivity, consistent with studies from Alcalá's thesis (2017), Burgos and García-Leal (2015), and Picker and Poling (1982). It also predicted the elimination of this effect (autoshaped impulsivity) after introducing a trace interval. The observed results and their implications are discussed, as well as possible future studies with animals and humans.

Growth and Yield of Purple Kculli Corn Plants under Different Fertilization Schemes.

Globally, corn is the most economically important crop, surpassing other cereals of economic importance. However, the tillage methods, monoculture and the abuse of synthetic agrochemicals used in Mexico have led to the loss of fertility and soil yield. In this sense, the application of alternative fertilization methods based on chemical fertilizer, organic matter and biofertilizer, applied alone or in combination, can stimulate the defense systems of corn plants and increase their yield. Therefore, in this research, some fertilization schemes were tested on purple corn plants of the Kculli race through the evaluation of some growth and yield variables, as well as the subsequent evaluation of the chemical characteristics of the corn grain produced in each fertilization scheme. The results indicate highly significant differences (p ≤ 0.05) between treatments, for the different growth and yield variables studied. Of all the fertilization schemes evaluated, treatment T7 obtained the best grain yield of 6.19 ± 0.07 t ha-1, with respect to treatment T1 of 1.02 ± 0.01 t ha-1, as well as the highest protein content and starch quality. Being clear the positive effect of the adequate contribution of the macro and micronutrients used exerts on the corn crop in each of the fertilization schemes studied. On the other hand, the analysis carried out on the grains was found within the values reported by other authors.

Evidencia molecular de la infección por Trypanosoma cruzi TcI en Meccus pallidipennis capturados en el municipio de Tepecuacuilco, Guerrero.

No disponible.

The Real Problem with Hypothetical Constructs.

A recent discussion in this journal revolved around the issue of whether postulating internal clocks is harmful or beneficial to scientific psychology, and how. I argue that this and other discussions on the topic have yet to address the real problem: The concept of a hypothetical construct is unintelligible. Psychologists agree that all entities that constitute hypothetical constructs are unobservable, importantly different from observable entities, including overt behavior and its environment. The root issue at hand here, then, is the observable-unobservable distinction. Psychologists have implicitly but erroneously taken it for granted as sufficiently unproblematic to warrant meaningful discussions based on it, when in fact it is a pernicious untenable remnant of logical positivism. All previous discussions of hypothetical constructs in psychology have overlooked arguments against this view in the philosophy of science. These arguments are sufficiently compelling to at least question, if not cease altogether, talk of observability, unobservability, and HCs in psychology as useless, even harmful.

Corrigendum: Transitive Inference Remains Despite Overtraining on Premise Pair C+D.

[This corrects the article DOI: 10.3389/fpsyg.2018.01791.].

Selection by reinforcement: A critical reappraisal.

This essay is a critical reappraisal of the idea of ontogenetic selection by reinforcement, according to which learning, specifically conditioning, in the individual animal is deeply analogous to phylogenetic evolution by natural selection. I focus on two general versions of this idea. The traditional Skinnerian version restricts the idea to operant conditioning and excludes Pavlovian conditioning, based on a sharp dichotomy between the two types of conditioning. The other version extends the idea to Pavlovian conditioning, based on a unified principle of reinforcement that applies to both types of conditioning, and linked to a neural-network model. I criticize both versions on the same grounds, for being: 1) unable to capture Pavlovian conditioning; 2) unnecessary to formulate said model and use it for explanation and prediction (its combination with a genetic algorithm allows for a substantive contact with the theory of evolution by selection, without the idea of selection by reinforcement), and 3) metaphysically unsound. Non-selectionist accounts of conditioning are not only possible but also more intelligible, explanatory, and heuristic.

Suing for Peace in the War Against Mentalism.

The antimentalists' war against mentalism has not vanquished it. To examine why, we focus on two theses-mind as causal and internal-and three standard attacks against mentalism as defined by both theses: 1) mentalism implies dualism; 2) mind is unobservable, which hinders its scientific study; and 3) mentalism is impractical. These salients fail because: 1) if the mind is causal and internal, it must be material; 2) the observable/unobservable distinction is too problematic, with antimentalists equivocal about where to draw that line, with some even embracing publicly unobservable behavior as causally relevant; and 3) mentalism has not been demonstrated to be less practical than antimentalism. For the war on mentalism to succeed, stronger attacks must be devised, both scientific and philosophical. We contemplate some possibilities, while expressing doubts as to the wisdom of continuing the war. Peace may be better than war, and the resulting intellectual commerce may be good for both sides.

Transitive Inference Remains Despite Overtraining on Premise Pair C+D.

Transitive inference (TI) has been studied in humans and several animals such as rats, pigeons and fishes. Using different methods for training premises it has been shown that a non-trained relation between stimuli can be stablished, so that if A > B > C > D > E, then B > D. Despite the widely reported cases of TI, the specific mechanisms underlying this phenomenon remain under discussion. In the present experiment pigeons were trained in a TI procedure with four premises. After being exposed to all premises, the pigeons showed a consistent preference for B over D during the test. After overtraining C+D- alone, B was still preferred over D. However, the expected pattern of training performance (referred to as serial position effect) was distorted, whereas TI remained unaltered. The results are discussed regarding value transfer and reinforcement contingencies as possible mechanisms. We conclude that reinforcement contingencies can affect training performance without altering TI.

Is a Nervous System Necessary for Learning?

In this article, I propose some elements for a conceptual foundation for a negative answer to the titular question, based on a historical conceptual analysis of some definitions of "learning" in the specialized literature. I intend such a foundation to include learning in living organisms as well as inorganic machines. After analyzing several behavioral and nonbehavioral definitions, I argue that although most of the former favor a negative answer, they tend to be restricted to living organisms and thus exclude inorganic machine learning. They also face the yet-unresolved issue of behavioral silence, which makes behavior not defining of learning. Some nonbehavioral neurobiological definitions favor an affirmative, others a negative answer, but still exclude inorganic machines. Nonneurobiological definitions are more suitable, but they commit us to some form of computationalism (Turing machine or connectionist) about learning, which is premature. I thus propose elements for an alternative definition of "learning" without such commitment. The elements are elaborations of the notions of learning as a kind of causal interaction between causal stochastic environmental and internal processes, and minimal learner as a kind of abstract system that shares certain internal structural and functional features with animals, spinal vertebrates, bacteria, plants, and inorganic machines.

Unified principle of reinforcement in a neural-network model: Reply to N. T. Calvin and J. J. McDowell.

An article published in Behavioural Processes (Calvin and McDowell, 2015) contemplated that the approach to neural networks developed by the present authors cannot simulate certain behavioral findings, notably the Kamin blocking effect and successive conditioning. Here we demonstrate that these concerns are unwarranted as an overall characterization of the approach. In addition, several other more general issues identified in the target article are addressed as well. These include the determination of network architectures, the assignment-of-credit problem, the potential for catastrophic interference, and the falsifiability of the model.

Immune protection against Trypanosoma cruzi induced by TcVac4 in a canine model.

Chagas disease, caused by Trypanosoma cruzi, is endemic in southern parts of the American continent. Herein, we have tested the protective efficacy of a DNA-prime/T. rangeli-boost (TcVac4) vaccine in a dog (Canis familiaris) model. Dogs were immunized with two-doses of DNA vaccine (pcDNA3.1 encoding TcG1, TcG2, and TcG4 antigens plus IL-12- and GM-CSF-encoding plasmids) followed by two doses of glutaraldehyde-inactivated T. rangeli epimastigotes (TrIE); and challenged with highly pathogenic T. cruzi (SylvioX10/4) isolate. Dogs given TrIE or empty pcDNA3.1 were used as controls. We monitored post-vaccination and post-challenge infection antibody response by an ELISA, parasitemia by blood analysis and xenodiagnosis, and heart function by electrocardiography. Post-mortem anatomic and pathologic evaluation of the heart was conducted. TcVac4 induced a strong IgG response (IgG2>IgG1) that was significantly expanded post-infection, and moved to a nearly balanced IgG2/IgG1 response in chronic phase. In comparison, dogs given TrIE or empty plasmid DNA only developed high IgG titers with IgG2 predominance in response to T. cruzi infection. Blood parasitemia, tissue parasite foci, parasite transmission to triatomines, electrocardiographic abnormalities were significantly lower in TcVac4-vaccinated dogs than was observed in dogs given TrIE or empty plasmid DNA only. Macroscopic and microscopic alterations, the hallmarks of chronic Chagas disease, were significantly decreased in the myocardium of TcVac4-vaccinated dogs. We conclude that TcVac4 induced immunity was beneficial in providing resistance to T. cruzi infection, evidenced by control of chronic pathology of the heart and preservation of cardiac function in dogs. Additionally, TcVac4 vaccination decreased the transmission of parasites from vaccinated/infected animals to triatomines.

Autoshaped choice in artificial neural networks: implications for behavioral economics and neuroeconomics.

An existing neural network model of conditioning was used to simulate autoshaped choice. In this phenomenon, pigeons first receive an autoshaping procedure with two keylight stimuli X and Y separately paired with food in a forward-delay manner, intermittently for X and continuously for Y. Then pigeons receive unreinforced choice test trials of X and Y concurrently present. Most pigeons choose Y. This preference for a more valuable response alternative is a form of economic behavior that makes the phenomenon relevant to behavioral economics. The phenomenon also suggests a role for Pavlovian contingencies in economic behavior. The model used, in contrast to others, predicts autoshaping and automaintenance, so it is uniquely positioned to predict autoshaped choice. The model also contemplates neural substrates of economic behavior in neuroeconomics, such as dopaminergic and hippocampal systems. A feedforward neural network architecture was designed to simulate a neuroanatomical differentiation between two environment-behavior relations X-R1 and Y-R2, [corrected] where R1 and R2 denote two different emitted responses (not unconditionally elicited by the reward). Networks with this architecture received a training protocol that simulated an autoshaped-choice procedure. Most networks simulated the phenomenon. Implications for behavioral economics and neuroeconomics, limitations, and the issue of model appraisal are discussed.

Testing the efficacy of a multi-component DNA-prime/DNA-boost vaccine against Trypanosoma cruzi infection in dogs.

BACKGROUND: Trypanosoma cruzi, the etiologic agent of Chagas Disease, is a major vector borne health problem in Latin America and an emerging infectious disease in the United States. METHODS: We tested the efficacy of a multi-component DNA-prime/DNA-boost vaccine (TcVac1) against experimental T. cruzi infection in a canine model. Dogs were immunized with antigen-encoding plasmids and cytokine adjuvants, and two weeks after the last immunization, challenged with T. cruzi trypomastigotes. We measured antibody responses by ELISA and haemagglutination assay, parasitemia and infectivity to triatomines by xenodiagnosis, and performed electrocardiography and histology to assess myocardial damage and tissue pathology. RESULTS: Vaccination with TcVac1 elicited parasite-and antigen-specific IgM and IgG (IgG2>IgG1) responses. Upon challenge infection, TcVac1-vaccinated dogs, as compared to non-vaccinated controls dogs, responded to T. cruzi with a rapid expansion of antibody response, moderately enhanced CD8(+) T cell proliferation and IFN-γ production, and suppression of phagocytes' activity evidenced by decreased myeloperoxidase and nitrite levels. Subsequently, vaccinated dogs controlled the acute parasitemia by day 37 pi (44 dpi in non-vaccinated dogs), and exhibited a moderate decline in infectivity to triatomines. TcVac1-immunized dogs did not control the myocardial parasite burden and electrocardiographic and histopatholgic cardiac alterations that are the hallmarks of acute Chagas disease. During the chronic stage, TcVac1-vaccinated dogs exhibited a moderate decline in cardiac alterations determined by EKG and anatomo-/histo-pathological analysis while chronically-infected/non-vaccinated dogs continued to exhibit severe EKG alterations. CONCLUSIONS: Overall, these results demonstrated that TcVac1 provided a partial resistance to T. cruzi infection and Chagas disease, and provide an impetus to improve the vaccination strategy against Chagas disease.

Pavlovian conditioning: pigeon nictitating membrane.

A new Pavlovian conditioning preparation was developed using the nictitating membrane of the restrained pigeon. Either visual or auditory stimuli served as conditioned stimuli (CSs) with an unconditioned stimulus (US) of a puff of air to the cornea. Movement of the nictitating membrane constituted the conditioned and unconditioned responses (CR and UR). Conditioning was studied with the Kamin blocking procedure. In agreement with findings from other conditioning preparations, responding to the redundant stimulus was attenuated relative to a stimulus that received the same number of CS-US pairings in a compound-conditioning procedure. Although response attenuation occurred, substantial individual variation was observed within the blocking procedure, a finding with some precedent in the experimental literature. Theoretical analysis and neural-network simulations indicate that inter-subject variation in response attenuation may result from differences in the extent to which contextual stimuli contribute to the functional CS.

Prevalence of Trypanosoma cruzi in dogs (Canis familiaris) and triatomines during 2008 in a sanitary region of the State of Mexico, Mexico.

American trypanosomiasis is a public health problem in Latin America and southern parts of the United States. Infection in triatomines (vector) and domestic dogs (reservoir host) is a good indicator of Trypanosoma cruzi circulation and human risk of infection. The State of Mexico, Mexico, has been considered free of T. cruzi, and no detailed epidemiologic study has been conducted to assess the intricacies of the transmission cycle of the parasite in the region. Such studies would enhance our understanding of the epidemiology of T. cruzi infection in this geographic region and provide regional sanitary authorities with stronger fundamental knowledge for making decisions and allocating funds for Chagas disease control programs in the State of Mexico. The objective of this study was to determine the prevalence of T. cruzi infection in dogs (seroprevalence) and triatomines (fecal parasites) in a previously identified, discrete endemic region of parasite circulation and to widen our studies in the Tejupilco Sanitary Region located in the southern part of the State of Mexico. Dog blood samples (n=102) were analyzed for the presence of anti-T. cruzi antibodies by two assays, namely indirect hemagglutination assay and enzyme-linked immunosorbent assay. Triatomines (n=88) were collected and fecal aliquots were analyzed for the presence of parasites by light microscopy. Average seroprevalence in dogs in the Tejupilco Sanitary region was 24.5%, and the overall triatomine infection rate was 34.01%. Triatoma pallidipennis was the only triatomine species found in this region. Our data demonstrate that T. cruzi is actively circulating in the Tejupilco Sanitary Region and emphasize the requirement for epidemiologic surveillance programs throughout the putative endemic areas of the State of Mexico.

Some structural determinants of Pavlovian conditioning in artificial neural networks.

This paper investigates the possible role of neuroanatomical features in Pavlovian conditioning, via computer simulations with layered, feedforward artificial neural networks. The networks' structure and functioning are described by a strongly bottom-up model that takes into account the roles of hippocampal and dopaminergic systems in conditioning. Neuroanatomical features were simulated as generic structural or architectural features of neural networks. We focused on the number of units per hidden layer and connectivity. The effect of the number of units per hidden layer was investigated through simulations of resistance to extinction in fully connected networks. Large networks were more resistant to extinction than small networks, a stochastic effect of the asynchronous random procedure used in the simulator to update activations and weights. These networks did not simulate second-order conditioning because weight competition prevented conditioning to a stimulus after conditioning to another. Partially connected networks simulated second-order conditioning and devaluation of the second-order stimulus after extinction of a similar first-order stimulus. Similar stimuli were simulated as nonorthogonal input-vectors.

A simultaneous procedure facilitates acquisition under an optimal interstimulus interval in artificial neural networks and rats.

In a computer simulation, a neural network first received a simultaneous procedure, where the interstimulus interval (ISI) was 0 time-steps (ts). Output activations were near zero under this procedure. The network then received a forward-delay procedure where the ISI was 8 ts. Output activations increased to the near-maximum level faster than those of a control network that first received an explicitly unpaired procedure. Comparable results were obtained with rats that first received trials where a retractable lever was presented for 3s concurrently with access to water. Low-lever pressing was observed under this procedure. The rats then received trials where the lever was followed 15s after by water. Lever pressing appeared faster than a control group that received the 15-s ISI after an explicitly unpaired procedure. The model used in the simulation explains these results as connection-weight increments that promote little output activations in a simultaneous procedure, but facilitate acquisition in an optimal ISI.

Autoshaping and automaintenance: a neural-network approach.

This article presents an interpretation of autoshaping, and positive and negative automaintenance, based on a neural-network model. The model makes no distinction between operant and respondent learning mechanisms, and takes into account knowledge of hippocampal and dopaminergic systems. Four simulations were run, each one using an A-B-A design and four instances of feedfoward architectures. In A, networks received a positive contingency between inputs that simulated a conditioned stimulus (CS) and an input that simulated an unconditioned stimulus (US). Responding was simulated as an output activation that was neither elicited by nor required for the US. B was an omission-training procedure. Response directedness was defined as sensory feedback from responding, simulated as a dependence of other inputs on responding. In Simulation 1, the phenomena were simulated with a fully connected architecture and maximally intense response feedback. The other simulations used a partially connected architecture without competition between CS and response feedback. In Simulation 2, a maximally intense feedback resulted in substantial autoshaping and automaintenance. In Simulation 3, eliminating response feedback interfered substantially with autoshaping and automaintenance. In Simulation 4, intermediate autoshaping and automaintenance resulted from an intermediate response feedback. Implications for the operant-respondent distinction and the behavior-neuroscience relation are discussed.

Neural-network simulations of two context-dependence phenomena.

This paper describes simulations of two context-dependence phenomena in Pavlovian conditioning, using a neural-network model that draws on knowledge from neuroscience and makes no distinction between operant and respondent learning mechanisms. One phenomenon is context specificity or the context-shift effect, the decrease of conditioned responding (CR) when the conditioned stimulus (CS) is tested in a context different from the one in which it had been paired with the unconditioned stimulus (US). The other effect is renewal, the recovery of CR in the training context after extinction in another context. For specificity (simulation 1), two neural networks were first given 200 CS-US pairings in a context. Then, the CS was tested either in the training context or a new context. Output activations in the new context were substantially lower. For renewal (simulation 2), two networks were first given 200 CS-US pairings in a context, then 100 extinction trials in either the same context or a new one, and then tested back in the training context. Output activations during the test phase were substantially higher after extinction in a new context. The results are interpreted in terms of the dynamics of activations and weights.