A modeling study suggesting how a reduction in the context-dependent input on CA1 pyramidal neurons could generate schizophrenic behavior.
ABSTRACT The neural mechanisms underlying schizophrenic behavior are unknown and very difficult to investigate experimentally, although a few experimental and modeling studies suggested possible causes for some of the typical psychotic symptoms related to this disease. The brain region most involved in these processes seems to be the hippocampus, because of its critical role in establishing memories for objects or events in the context in which they occur. In particular, a hypofunction of the N-methyl-D-aspartate (NMDA) component of the synaptic input on the distal dendrites of CA1 pyramidal neurons has been suggested to play an important role for the emergence of schizophrenic behavior. Modeling studies have investigated this issue at the network and cellular level. Here, starting from the experimentally supported assumption that hippocampal neurons are very specific, sparse, and invariant in their firing, we explore an experimentally testable prediction at the single neuron level. The model shows how and to what extent a pathological hypofunction of a context-dependent distal input on a CA1 neuron can generate hallucinations by altering the normal recall of objects on which the neuron has been previously tuned. The results suggest that a change in the context during the recall phase may cause an occasional but very significant change in the set of active dendrites used for feature recognition, leading to a distorted perception of objects.
Conference Proceeding: Simple CAD formulas of edge-compensated microstrip lines[show abstract] [hide abstract]
ABSTRACT: The proximity effects of microstrip lines near a substrate edge are estimated by using the rectangular boundary division method for effectively designing high-packing-density MMICs (monolithic microwave integrated circuits). Simple CAD (computer-aided design) formulas of edge-compensated microstrip lines (ECM lines) are introduced which can be applied to circumvent the proximity effects on the characteristic impedance. The practical design parameters of the ECM lines are given in the form of numerical data and simple polynomials for CAD work with a curve-fitting procedure. Results of capacitance measurements are compared with this theoryMicrowave Symposium Digest, 1989., IEEE MTT-S International; 07/1989
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ABSTRACT: Recent advances in theoretical neuroscience have provided new insights into information processing within large brain-like networks operating in an uncertain world. The computational framework can overcome some of the complexity within the object of study by predicting how basic changes in neural architecture may lead to systems-level changes that translate into changes in behavior. Computational models offer ways to unify basic neurochemical ﬁndings with data from more macroscopic levels and to start to apply these ﬁndings to cognitive sciences and psychiatry. Some of these approaches have been used to investigate the underlying mechanisms of subjective experiences, such as hallucinations, which can spontaneously emerge into consciousness in the absence of any corresponding external stimuli. This chapter describes some recent theoretical studies on four categories of positive symptoms of schizophrenia: neurodynamics, noise, disconnectivity, and Bayesian models of hallucinations. Results from simulations of these neural networks as well as the potential alterations leading to aberrant experiences are presented and discussed.01/2013: pages 289-313;