No abstract

Despite growing scientific interest in the placebo effect and increasing understanding of neurobiological mechanisms, theoretical modeling of the placebo response remains poorly developed. The most extensively accepted theories are expectation and conditioning, involving both conscious and unconscious information processing. However, it is not completely understood how these mechanisms can shape the placebo response. We focus here on neural processes which can account for key properties of the response to substance intake. It is shown that placebo response can be conceptualized as a reaction of a distributed neural system within the central nervous system. Such a reaction represents an integrated component of the response to open substance administration (or to substance intake) and is updated through “unconditioned stimulus (UCS) revaluation learning”. The analysis leads to a theorem, which proves the existence of two distinct quantities coded within the brain, these are the expected or prediction outcome and the reactive response. We show that the reactive response is updated automatically by implicit revaluation learning, while the expected outcome can also be modulated through conscious information processing. Conceptualizing the response to substance intake in terms of UCS revaluation learning leads to the theoretical formulation of a potential neuropharmacological treatment for increasing unlimitedly the effectiveness of a given drug.

Nowadays, the experimental study of emotional learning is commonly based on classical conditioning paradigms and models, which have been thoroughly investigated in the last century. Unluckily, models based on classical conditioning are unable to explain or predict important psychophysiological phenomena, such as the failure of the extinction of emotional responses in certain circumstances (for instance, those observed in evaluative conditioning, in post-traumatic stress disorders and in panic attacks). In this manuscript, starting from the experimental results available from the literature, a computational model of implicit emotional learning based both on prediction errors computation and on statistical inference is developed. The model quantitatively predicts (a) the occurrence of evaluative conditioning, (b) the dynamics and the resistance-to-extinction of the traumatic emotional responses, (c) the mathematical relation between classical conditioning and unconditioned stimulus revaluation. Moreover, we discuss how the derived computational model can lead to the development of new animal models for resistant-to-extinction emotional reactions and novel methodologies of emotions modulation.

There is an increasing need to apply emerging technologies in knowledge-based management system. This proposed system captures the knowledge of experts and the knowledge acquired for designing a new systems. Wind Tunnel Test data of missiles has been taken into consideration for knowledge management. Interpolation and Extrapolation of missile test data has been attempted using neural network technique General Regression Neural Networks training algorithm. The results produced by neural network training methodologies are validated with the existing test data. The knowledge extraction using neural network is found suitable for interpolation and to some extent for extrapolation, thereby reducing the cost as well as number of test runs in Wind Tunnel Test.

It is well known from the technical literature that non-conscious perception of emotional stimuli\ud affects behavior, perception, and even decision making [e.g., see Ref. (1) for a comprehensive\ud review]. Non-conscious perception can be obtained by inducing sensory unawareness, e.g., through\ud backward masking and binocular rivalry (1). Experiments adopting such paradigms have evidenced\ud that non-consciously perceived emotional stimuli elicit activity in the amygdala, superior colliculus,\ud basal ganglia, and pulvinar. More specifically, it has been shown that a subcortical fast route exists\ud between the thalamus and the amygdala, which, in turn, project onto different cortical and subcortical\ud structures [e.g., onto the nucleus accumbens, NAcc, when appetitive stimuli are perceived (2)].\ud These findings agree with the hypothesis about amygdala functionality proposed by LeDoux (3, 4).\ud In fact, LeDoux has hypothized the existence of a thalamic pathway to the amygdala; such a pathway\ud would allow to automatically detect evolutionary prepared visual stimuli (such as emotional faces,\ud sexual-related stimuli, spiders, snakes, and injuries). Note that this model is also supported by other\ud results acquired by different researchers that have employed masking in normal participants (5, 6)\ud or have observed brain activity in patients affected by cortical blindness (7, 8). According to this\ud model about amygdala functionality, the superior colliculus stimulates the pulvinar nucleus of the\ud thalamus, which then arouses the amygdala (4, 9, 10). This suggests that salient features representing\ud biologically prepared stimuli could be stored in the amygdala since birth. From an evolutionary perspective,\ud this can be related to the fact that fast and implicit (or unconscious) reactions are needed in\ud dangerous and highly dynamical environments. Moreover, even ontogenetic stimuli (e.g., weapons)\ud are encoded within the amygdala through implicit learning during life (11, 12). These data evidence\ud the importance of subcortical regions associated with implicit emotional processing. In fact, since\ud the brain structure works like a hierarchical network (13) in which the limbic system represents a\ud lower hierarchical level with respect to the higher cortical structure, it is likely that the overall perception\ud and emotional appraisal are influenced by low-level evaluations. More specifically, the signals\ud coming from lower and higher hierarchical levels determine prediction errors (or error signals) at\ud intermediate levels; such error signals propagate through the entire hierarchical structure, determining\ud cognitive perception, causes attributions, emotional evaluations, actions, and behaviors (14).\ud Hence, if subcortical limbic-brainstem regions are defective, all the network hierarchy functioning\ud will be compromised. As a matter of fact, a dysfunction in the limbic-brainstem regions is associated\ud with various psychiatric disorders with higher cognitive deficits including auti...